Tag: Cryobiology

Annotated bibliography of cryoprotectant toxicity

Introduction

Cryoprotectant toxicity should be distinguished from other mechanisms of cryopreservation injury such as chilling injury (injury produced by too low temperatures as such) and cold shock  (injury produced by rapid cooling). Cryoprotectant toxicity itself can again be divided into general cryoprotectant toxicity and specific cryoprotectant toxicity. General cryoprotectant toxicity involves concentration (water substitution) effects of cryoprotectants and specific cryoprotectant toxicity involves the effects of individual compounds on cellular viability. General cryoprotectant toxicity presents a formidable obstacle for cryopreservation methods that require very high concentrations of cryoprotectant agents (such as vitrification).

Another mechanism of injury that is rarely discussed in the cryobiology literature but that can complicate cryopreservation of complex organs is “non-specific” dehydration injury. In light of the fact that the current generation of vitrification agents are delivered in hypertonic carrier solutions and contain non-penatrating cryoprotective agents which do not cross the blood brain barrier, this form of damage may be especially important in cryopreservation of the brain.

Systemic reviews of cryoprotectant toxicity are rare but some mechanisms for (specific) cryoprotectant toxicity have been proposed including, but not limited to, protein denaturation, modification of biomolecules, membrane injury, destabilization of the cytoskeleton, oxidative damage, and ATP depletion. It is important to stress that some of the mechanisms may be downstream effects of other mechanisms. For example, ATP depletion can cause oxidative damage. And as Gregory Fahy has pointed out, cryoprotectant toxicity should be distinguished from injury associated with the method of introduction and washout of the cryoprotectant. In 2004, Fahy, Wowk et al., proposed a compositional variable to predict general cryoprotectant toxicity.

Cryoprotectant toxicity can also vary by species and organ type. Cryoprotectants that are moderately toxic in one species can be highly toxic in others. Similarly, cryoprotectants that are moderately toxic in one organ can be highly toxic in others (or even between different types of cells within organs). This raises the question of whether universal non-toxic cryoprotective agents are attainable (a requirement for reversible vitrification in complex organisms).

Cryoprotectant toxicty can be investigated by cryopreserving an organ (or cell) and measuring its viability after rewarming and washout of the cryoprotective agent. To eliminate the influence of other mechanisms of injury associated with cryopreservation (such as ice formation), a cell can just be loaded and unloaded with the cryoprotectant without cryopreservation. The effects of hypothermia on viability can be eliminated altogether by normothermic perfusion of the organ. This, of course,  introduces a challenge for hypoxia sensitive organs such as the heart and the brain because cryoprotective agents may not be good oxygen carriers.

Papers

Baxter SJ, Lathe GH (1971). Biochemical effects of kidney of exposure to high concentrations of dimethyl sulphoxide.
Biochemical Pharmacology. Jun; 20(6): 1079-91.

Baxter and Lathe investigated the effect of high concentrations of DMSO on kidney preparations. In a series of illuminating experiments, the investigators established that anaerobic glycolysis was reduced in slices and homogenates as a result of increased activation of the gluconeogenesis enzyme Fructose 1,6-diphosphatase (FDPase). DMSO-induced activation of FDPase can be inhibited by adding an amide or lysine to DMSO. The finding that a combination of DMSO and an amide allows for less toxic cryoprotectants formed the basis of subsequent investigations of GM Fahy for potent vitrification solutions.

Fahy GM (1983). Cryoprotectant Toxicity Neutralizers Reduce Freezing Damage.
Cryo-Letters 4: 309-314.

In this paper GM Fahy reports the ability of toxicity neutralizers urea, formamide, and acetamide (all amides) to reduce injury of cryopreserved renal cortical slices with DMSO. In later research papers Fahy will establish that DMSO neutralizes the toxicity of formamide, and not the other way around.

Fahy GM (1984). Cryoprotectant toxicity: biochemical or osmotic?
Cryo-Letters 5: 79-90.

If osmotic stress is an important cause of injury during introduction and removal of cryoprotectant agents, improved viability can be obtained by reducing the rate of cryoprotective agent introduction and removal. Fahy reviews the literature and presents data obtained in renal cortical slices that indicate that substantial hypertonic osmotic stress does not produce major changes in viability. Conversely, reducing exposure time to higher concentrations of the cryoprotectant can contribute to improved viability. These results suggest that biochemical toxicity, not osmotic stress, is the major factor in cryoprotectant-induced injury.

Fahy GM (1984). Cryoprotectant toxicity: specific or non-specific?
Cryo-Letters 5: 287-294

Fahy reviews the argument (Morris, Cryoletters 4, 339-340, 1983) that the lower toxity of cryoprotectant solutions that contain DMSO and amides can be entirely explained by the lower absolute concentration of DMSO. Fahy points out that the original Bexter and Lathe experiments demonstrated that solutions with the same absolute amount of DMSO (4.6 M) but with or without amides had different effects on glucose utilization. The author also presents data showing that “simple substitution (“dilution”) of one agent for another strikingly fails to reduce overall toxicity over a very critical range of DMSO concentration.” Also briefly discussed is the possibility of mutual toxicity neutralization between DMSO and amides, a topic that would be further explored by Fahy in future research.

Fahy GM, MacFarlane DR, Angell CA, Meryman HT (1984). Vitrification as an approach to cryopreservation.
Cryobiology.  Aug ; 21(4): 407-26.

In this paper on vitrification as an alternative to conventional cryoprotection, Fahy et al., list a number of methods for reducing cryoprotectant toxicity:

Primary (direct) methods:

  1. Maintain temperature as low as possible;
  2. Select an appropriate carrier solution;
  3. Keep exposure time at higher concentrations to a minimum;
  4. When possible, employ specific cryoprotectant toxicity neutralizers.

Secondary (indirect) methods:

  1. Avoid osmotic injury;
  2. Mutual dilution of cryoprotectants may be helpful in some instances;
  3. Use extracellular cryoprotectant to reduce exposure to intracellular cryoprotectant when possible.

The most important insights, some of which are still maintained in the current generation of vitrification solutions, concern toxicity neutralization, the choice of an appropriate carrier solution, and the use of extracellular cryoprotectants.

Fahy GM (1986). The relevance of cryoprotectant “toxicity” to cryobiology.
Cryobiology. Feb; 23(1) :1-13.

Fahy presents evidence that cryoprotectants themselves can present a source of injury. As a consequence, the advantages of higher concentrations of the cryoprotective agents does not necessarily produce higher viability after freezing, even when this allows for greater ice inhibition. He reviews data on “cryoprotectant-associated freezing injury” for DMSO, ethylene glycol, methanol, ethanol, and glycerol.  Because vitrification requires very high concentrations of cryoprotective agents, toxicity is the key limiting factor in reversible vitrification of organs.

Fahy GM, Lilley TH, Linsdell H, Douglas MS, Meryman HT (1990). Cryoprotectant toxicity and cryoprotectant toxicity reduction: in search of molecular mechanisms.
Cryobiology. Jun; 27(3): 247-68.

Fah,y et al., delineate 6 criteria that must all be met simultaneously in order for a putative mechanism of cryoprotectant toxicity to be implicated:

  1. The relationship between observed biochemical alteration and cellular viability must be clear or easily plausible;
  2. The maginitude of the cryoprotectant effect must be large enough to be significant;
  3. The effect must be irreversible over a reasonable time span after removal of the cryoprotectant;
  4. The time course of the observed effect must be consistent with the time course of observed injury;
  5. The cryoprotectant effect must be possible under conditions that could reasonably be encountered inside a living cell being prepared for freezing or being subjected to freezing and thawing itself;
  6. The cryoprotectant effect must be due to the cryoprotectant itself and not due to the technique of introduction and washout.

The authors investigate the proposed mechanisms for the biochemical effects of DMSO toxicity in the 1971 Baxter study and find that a) the effect of DMSO on FDPase activation is too small to affect the normal respiration of the cell and therefore fails to meet criterion 2 to be a significant mechanism of cryoprotectant toxicity; b) the presence of formamide does not affect the interaction between DMSO and lysine; and c) toxicity is not consistently reduced by blocking alteration of FDPase rather than substituting those compounds for DMSO.

The authors further present results that do not support the theory that generalized  protein denaturation is related to cryoprotectant toxicity.  The article ends with a referenced list of phenomena possibly related to mechanisms of cryoprotectant toxicity.

Fahy GM, da Mouta C, Tsonev L, Khirabadi BS, Mehl P,  Meryman HT (1995). Cellular injury associated with organ cryopreservation: Chemical toxicity and cooling injury.
Editors: John J. Lemasters, Constance Oliver. Cell Biology of Trauma, CRC Press

Fahy, et al., review different mechanisms of cryoprotectant toxicity with a particular focus on DMSO-medicated chemical injury. Mechanisms discussed include fructose-1,6-bisphosphatase activation, sulfhydryl oxidation, activation of extracellular proteinases and endothelial cell detachment and death. The article lists a number of interventions that do not change CPA-medicated injury such as inhibition calcium mediated injury or protein denaturation. The authors also report how the toxicity of formamide can be completely reversed by addition of DMSO.

Bakaltcheva IB,  Odeyale CO, Spargo BJ (1996). Effects of alkanols, alkanediols and glycerol on red blood cell shape and hemolysis.
Biochimica et Biophysica Acta. 1280: 73-80

In this elegant and thoughtful paper, the authors use the human red blood cell to study cryoprotectant toxicity. Morphological observations, quantification of hemolysis, measurements of the dielectric constant of the incubation medium (Ds) and the dielectric constant of the erythrocyte membrane in the presence of organic solutes (Dm), are used to investigate cryoprotectant toxicity in a series of alkanols, alkanediols, and glycerol. The authors propose that toxicity of a cryoprotectant is related to its ability to change the ratio of Ds/Dm. Changes in this ratio reflect changes in the difference between hydrophobicity of the solution and the membrane, with decreases in this ratio leading to increased exposure of membrane surface area and vesiculation, and increases in this ratio leading to decreased exposure of membrane surface area and cell fusion. The authors suggest that the design of less toxic cryoprotective agents should involve the maintenance of dielectric homeostasis of the medium and the membrane. Their findings also throw light on the observation that combinations of various cryoprotectant agents (such as DMSO and formamide) can reduce the overall toxicity of a solution.

Fahy GM, Wowk B, Wu J, Paynter S (2004). Improved vitrification solutions based on the predictability of vitrification solution toxicity.
Cryobiology. Feb; 48(1): 22-35.

This seminal paper on non-specific cryoprotectant toxicity represents a major contribution to the cryobiology literature in general, and enabled the authors to formulate less toxic vitrification solutions for the cryopreservation of whole organs. In the paper the authors propose a new compositional variable that reflects the strength of water-cryoprotectant hydrogen bonding called qv*. Contrary to the cryobiology wisdom to date, the authors found that weaker glass formers favor higher viability. As a consequence, vitrification agents with higher concentrations of cryoprotective agents are not necessarily more toxic. Although qv* is not helpful in predicting specific cryoprotectant toxicity, this paper, and the research that is reflected in it, suggests that non-specific cryoprotectant toxicity is mediated through the effects of penetrating cryoprotectant agents on the hydration of biomolecules.

The 2011 Cryobiology Conference

July 24-27 I attended the 2011 annual Society for Cryobiology conference in Corvallis, Oregon.

A number of the first presentations were concerned with means to *avoid* cryopreservation. Room temperature storage is much less expensive and troublesome, and improves ease of transport, especially in remote areas. One such technology “shrink wrapped” DNA in a glass  and another used trehalose to protect lipid membranes in a similar manner. Applied to cells, such technologies are viewed as a form of room-temperature vitrification.

Another researcher had successfully freeze-dried hematopoietic stem cells using trehalose and other additives without losing the ability of the stem cells to differentiate. Stress proteins in combination with trehalose allowed for desiccation of mammalian embryonic kidney cells without loss of viability. Late Embryogenesis Abundant (LEA) proteins also assist trehalose in dehydration tolerance.

Christoph Stoll showed that depleting red blood cell membranes of cholesterol can increase
trehalose uptake, but when I asked him in person about it, he said that the uptake was not enough to make much difference. Depleting cell membranes of cholesterol makes them more vulnerable to chilling injury, so I don’t think cholesterol depletion is a very good idea.

Masakazu Matsumoto spoke about some of the interesting anomalous properties of water.

Andrew Brooks spoke about the largest University cell and DNA repository in the world at Rutgers University.  They store DNA by plunging in liquid nitrogen.  He told me that 10 freezings and thawings does not impair DNA quality. That is encouraging for CI’s tissue/DNA storage program, because we plunge our samples into liquid nitrogen. Brooks gave data  showing that RNA is much less hardy in liquid nitrogen than DNA.

David Denlinger noted that HSP70 RNAi can block cold tolerance in insects. He also mentioned a Czech study which found that insect larva fed proline could survive liquid nitrogen. Perhaps we should be feeding proline to terminal cryonics patients.

In preparation for this conference, I had done a lot of reading on the subject of chilling injury and was hoping to question researchers on the subject. Steve Mullen showed a video of meiotic spindles dissociating at low temperature.

Spindles are a form of microtubules. Microtubules are known to dissociate at low temperature, but can spontaneously re-associate upon rewarming. But that would not be so beneficial when the microtubules are functioning as centrosomes because the reassembly would not be a reconstruction of the original structure. This is probably why cell division often  stops at low temperature.

Tiantian Zhang is one of the two candidates to become the new Society for Cryobiology President. Her field of study is cryopreservation of fish embryos and oocytes, which are especially vulnerable to chilling injury.

Fish are useful scientific models because they have a much simpler genome than mammals. 50% of endangered species are fish, but fish don’t get anywhere near the concern that pandas do. In both her lecture, and when I spoke to her in person, Dr. Zhang had apparently not learned any more than what was in her 2009 paper.

Why does reducing yolk content reduce chilling injury? Why is methanol the most non-toxic cryoprotectant for fish embryos, and so protective? If microtubule dissociation were a mechanism of chilling injury, it is indeed ironic that a 2006 Society of Cryobiology meeting presentation found that methanol causes proteolysis.

Kevin Brockbank spoke on the oxygenated hypothermic machine perfusion that he used to preserve pig livers at 4-6deg C for 12 hours. As a somewhat off-the-wall question, I asked him if he had assayed for chilling injury. This was off-the-wall because I have never heard of anyone assaying chilling injury. He responded that he had not, but that there were plans to use gene arrays to assay for chilling injury. This is like gene arrays to assay for aging — it requires deeper analysis, especially if chilling injury — like aging — is due to multiple mechanisms, the mechanisms are controversial, and no one mechanism is dominant. Northern wood frogs, arctic insects, and polar fish don’t have problems with chilling injury, although their adaptations include heat shock proteins and highly unsaturated cell membranes.

Much to my frustration, I have not had a good conversation with Peter Mazur (the uncrowned guru of cryobiology) since he got me to tell him I am a cryonicist several years ago. I have repeatedly asked him questions, and he has repeatedly been rude and dismissive. This year was different, for some reason. When I asked him about frozen water expansion contributing to mechanical damage he noted that cells could tolerate a 9% expansion without lysis even if freezing was intracellular. When I asked him how much dehydration cells could tolerate without damage, he said cells could lose all of the osmotic water (90% of cell water), and could lose more in freeze-drying with proper protectants (like trehalose). I was somewhat stunned by this answer, which takes no account of intracellular electolyte concentration increasing on dehydration. Next year I will be more optimistic about the possibility of talking with him, and I will prepare questions more carefully.

I spoke to Society for Cryobiology President John Crowe about his negative remarks concerning trehalose, in light of the fact that he is very aware of many of its benefits. John told me that a new method of manufacturing trehalose from starch is making trehalose as inexpensive as sucrose. If trehalose is used on bakery sugar, the sugar will not melt and run after a couple of days, as happens with sucrose. I mentioned to John that Robert Ettinger had just died. I had imagined that he might ask me to say a few words about the matter to the cryobiologists at their business meeting, but John treated the matter as a non-event, and I got the distinct impression that he would have preferred that I had not mentioned it.

At the business meeting it was noted that membership has dropped from close to 300 in 2008 and 2009 to just above 200 in 2011. There is concern that web access to the journal
CRYOBIOLOGY is becoming so easy that the incentives for membership have dropped. Or the global financial crisis is taking its toll on Society for Cryobiology membership. CRYOBIOLOGY journal impact factor has fallen to 1.830 from a high of 2.044 in 2002.

I appreciate being able to attend the business meetings, but one of the vehemently anti-cryonics cryobiologists gives me dirty looks. I have not been kicked-out yet, though, and decreasingly worry that I will be. A similar thought goes through my head as when I attend an Alcor meeting: “Spy in the House of Love.” But I really want the Society to prosper and grow, not be harmed, because I appreciate their good work (as with Alcor), even if they view me as a threat.

I had a brief chat with the cryonics-friendly Treasurer, who asked me when I think a cryonics patient will be reanimated. When I told him not less than 50 years, he said that a lot of surprising things can happen in 20 years. He is a more optimistic cryonicist than I am! At least as remarkable is that he is currently working with biotechnologists who are engineering scaffolds that can be used for growing organs from stem cells. That is a very cryonics-relevant project!

Every year I exchange a few words with Arthur Rowe (the cryobiologist who repeatedly compares cryonics to restoring a cow from hamburger — as he did in “Death in the Deep Freeze” – a comparison which probably originated with Peter Mazur). This year Arthur spent a lot of time hanging out with John G. Baust (the man who compared publishing cryonics science research with publishing Nazi hypothermia experiments). At the end of the conference I lost patience trying to catch Arthur alone, so I approached Arthur to say “hi”. Arthur said that he had seen on TV that Robert Ettinger had just died. He asked me about Robert’s educational credentials, and about my taking Robert’s place as CI President. Then he introduced me to John Baust. John was politely quiet, and said very little.

As with the 2010 Cryobiology Conference, I felt decreasingly paranoid as the meeting proceeded, but my level of paranoia was nonetheless very high near the beginning of this meeting. Overall, the amount by which I “came out” as a cryonicist was modest this year, and my softening of the hostility of cryobiologists to cryonics was modest this year compared to the previous one. The 2012 Society for Cryobiology Conference is scheduled to be held in Argentina.

Gerald Feinberg on physics and life extension

Gerald Feinberg, a Columbia university physicist who, among other things, hypothesized the existence of the muon neutrino, had a strong interest in the future of science and life extension. In 1966 he published the article “Physics and Life Prolongation” in Physics Today in which he reviews cryobiology research with the aim of realizing medical time travel. Unlike most of his scientific colleagues, Feinberg recognized that it might be possible for people dying today to benefit from future advances in science in the absence of perfected techniques:

For the living it is necessary to await successful completion of freezing research before attempting to freeze them. For the newly dead this consideration is irrelevant since the dead have nothing to lose by being frozen, even by imperfect methods…

He doubts, however, whether “the primitive freezing techniques now available” would be good enough to permit successful resuscitation in the future.  Although his article ends in endorsing cryonics as a procedure, Feinberg did not make cryopreservation arrangements himself, despite his familiarity with molecular nanotechnology and his association with the Foresight Institute.

In the June 1992 issue of Cryonics magazine, Mike Perry writes:

Only a few days ago, as I write this, Gerald Feinberg, aged 58, died of cancer.  He was not frozen.  It appears  that he didn’t lack the means to make the arrangements, nor the time. Somehow, he was just not interested enough.  Friends or acquaintances I’ve talked to could give little in the way of definite reasons for the lack of  interest, but I get the impression that, when all was said and done, the  interest he did show was mainly academic after all.  Another factor may  have been hostility from colleagues and family members.  Apparently he was well criticized for the Physics Today article on the prolongation of life, though not for something really scientifically daring, like the tachyon  theory.

Human cryopreservation procedures have changed considerably since 1992 and cryonics researcher Mike Darwin has composed an ambitious article to answer the question whether current cryopreservation techniques can preserve identity. One of the most important observations in this article is that we do not need to wait until the future to get a better understanding of how good our current procedures are in this regard.

As long as we keep in mind that the absence of ultrastructural evidence for the preservation of identity-critical information does not necessarily mean the absence of this information as such (after all, future imaging and data gathering technologies may be more powerful than today’s) it is very important for cryonics advocates to recognize that preliminary work to infer the original structure of the brain from (3D) images of ischemic and cryopreserved tissue can start right now. Even in the absence of physical technologies to restore those structures to their native state, demonstrating that we can infer the original state, and visually reconstruct it, can be another argument in favor of human cryopreservation.

Further reading: Gerald Feinberg – Physics and Life Prolongation

Neural cryobiology and the legal recognition of cryonics

It has been said that if you want to persuade someone, you need to find common ground. But one of the defining characteristics of cryonics is that proponents and opponents cannot even seem to agree on the criteria that should be employed in discussing cryonics. The cryonics skeptic will argue that the idea of cryonics is dead on arrival because cryonics patients are dead. The response of the cryonics advocate is that death is not a state but a process and there is good reason to believe that a person who is considered dead today may not be considered dead by a future physician. In essence, the cryonics advocate is arguing that his skeptical opponent would agree with him if he would just embrace his conception of death….

Cryonicists have named their favorite conception of death “information-theoretic death.” In a nutshell, a person is said to be dead in the information-theoretic sense of the word if no future technologies are capable of inferring the original state of the brain that encodes the person’s memories and identity. There are a lot of good things to be said about substituting this more rigorous criterion of death for our current definitions of death. However, in this brief paper I will argue that our best response does not necessarily need to depend on skeptics embracing such alternative definitions of death and that we may be able to argue that opponents of cryonics should support legal protection for cryonics patients or risk contradicting conventional definitions of death.

In contemporary medicine, death can be pronounced using two distinct criteria; cardiorespiratory arrest or brain death. A lot of ink has been spilled over the co-existence of those criteria and its bioethical implications but I think that most people would agree that the practice of medicine requires this kind of flexibility. What is interesting for us is that clinical brain death (or brain stem death) is defined as “the stage at which all functions of the brain have permanently and irreversibly ceased.” There are a number of ways how such a diagnosis can be made, but in this context I want to focus on the absence of organized electrical activity in the brain.

We first should note the use of the word “irreversible.” After all, if a patient is cooled down to a low core temperature to permit complicated neurosurgical procedures most of us would not say that this person is “temporarily brain dead.” As a matter of fact, one could argue that cryonics is just an experimental extension of clinical hypothermic circulatory arrest in which there is a temporal separation of stabilization and treatment. Now, we could argue that what may be irreversible by today’s standards may not be irreversible by future standards but then, again, we are trying to persuade the other person to accept our view of future medicine. It would be much better, and I hope much easier, to argue that contemporary cryopreservation techniques can preserve organized electrical activity in the brain. The advantage of this approach is obvious. Instead of arguing in favor of our own criterion of death we can argue that, according to mainstream criteria for determination of death, cryonics patients are not dead. This is an interesting case in which a scientist (i.e., a cryobiologist) may be able to make a major contribution to the legal recognition and protection of cryonics patients.

So where are we standing right now? How good are our preservation techniques? If we aim for reversible whole brain cryopreservation a cryoprotective agent should have two properties: (1) elimination of ice formation, and (2) negligible toxicity. In the early days of cryonics, we were not able to satisfy both criteria at once. Using just a little bit of glycerol would not be toxic but it would still allow massive ice formation. Using a lot of a strong glass former such as DMSO would eliminate ice formation but at the price of severe toxicity. Mostly due to the groundbreaking work of cryobiologists Gregory Fahy and Brian Wowk, in the year 2000 the Alcor Life Extension Foundation introduced a vitrification agent called B2C that eliminated ice formation and had a more favorable toxicity profile. In the year 2005, the separation between the state of the art in experimental cryobiology and cryonics practice was further narrowed when Alcor introduced M22 as their new vitrification agent. M22 is the least toxic vitrification agent in the academic cryobiology literature that permits vitrification of complex mammalian organs at a realistic cooling rate.

M22 and other solutions derived from the same cryobiological principles have been validated in the brain as well. Former Cryonics Institute researcher Yuri Pichugin and collaborators used a related vitrification solution for the preservation of rat hippocampal brain slices without loss of viability after vitrification and rewarming. At a cryonics conference in 2007, 21st Century Medicine announced that the use of M22-based solutions permitted the maintenance of organized electrical activity in rabbit brain slices. So, at this stage we can argue that our existing vitrification solutions have a reasonable chance of maintaining organized electrical activity in brain slices. The next challenge is to demonstrate this property in whole brains.

Whole brain cryopreservation is not just the cryopreservation of a great number of individual brain slices. Brain slices can be cryopreserved by (step-wise) immersion in the vitrification solution. Vitrification of whole brains (even small brains such as rodent brains) requires the introduction of the vitrification solution through the circulatory system. This aspect of whole brain vitrification presents a number of technical challenges. Electron micrographs of vitrified tissue from whole brains, however, indicate that these challenges can be overcome. The current research objective is to perfect perfusion techniques and optimize vitrification solutions to maintain organized electrical activity in whole brains. We know that this objective is possible in principle because the famous surgeon Robert White demonstrated retention of electrical activity in whole isolated brains after cooling them to ~2-3°C. Isolated brain perfusion is a complicated surgical procedure, but the current writer and cryobiologist Brian Wowk have recognized that validation of whole brain activity is also feasible in situ.

Reversible cryopreservation of the whole brain without losing organized electrical activity is not a trivial research objective but it should be easier to achieve than reversible cryopreservation of the whole body and, perhaps, some other organs. If and when we accomplish this, we will no longer be dependent on “rationalist” arguments that appeal to logic and optimism about the future. We can argue that our patients should not be considered dead by the most rigorous criterion for determination of death in current medical practice. We can then even mount some smart legal challenges to seek better protection for cryonics patients. If we can make this step forward we should also aim at improved protection of existing cryonics patients, which will allow them, among other things, to own assets and bank accounts. This is how science can be employed in legal strategies for asset preservation.

This article is a slightly revised version of a paper that accompanied a recent presentation on neural cryobiology and the legal recognition of  cryonics at the 5th Asset Preservation Meeting in Benicia, California.

At last, a sure-cold way to sell cryonics with guaranteed success!

A humorous romp through a promising new technique in aesthetic medicine from one cryonicist’s (warped) point of view.

Figure 1: Before cryopreservation (L) and after cryopreservation (R).

As everyone involved in cryonics for more than a fortnight is sadly aware, cryonics doesn’t sell. Indeed, if we were pitching a poke in the eye with a sharp stick, we’d more than likely have more takers than we’ve had trying to ‘market’ cryonics to the public. To see evidence that this is so, you need only wander around a shopping mall on a weekend and observe all the (painfully) stainless steel lacerated and brightly colored needle-pierced flesh sported by the young and trendy and increasing by the old and worn, as well.

Yes, it’s clear; we misread the market, to our lasting detriment.

It’s true that we’ve tried the ‘you’ll be rich when you wake you up line,’ and heaven knows we’ve beaten the ‘you’ll be young and beautiful forever’ line, well, virtually beaten it to death. And while people are certainly interested in great fortune and youth, both of these things share the same unfortunate shortcoming, namely that they are things that people either don’t have but want, or do have and don’t want to lose. As anyone who is really savvy at marketing will tell you, the best way to sell something is to promise (and preferably be able to deliver) that you can get rid of something that people have and really don’t want – something that is ruining the quality of their life, destroying their health, draining their pocketbook and, worst of all, making them really, really ugly.

So, it turns out that for onto 50 years now, we’ve missed the real selling point of cryonics that’s been there all along: IT WILL MAKE YOU THIN! Guaranteed!

Can such a claim be true? Well, surprisingly, the answer would seem to be an almost unqualified, “Yes!”

Recently it’s been discovered that adipocytes, the cells responsible not only for making you fat, but for making you hungry, as well, are particularly susceptible to a phenomenon in cryobiology that has proved a nettlesome (and only recently (partially) overcome) barrier to solid organ cryopreservation: chilling injury. Quite apart from freezing damage due to ice crystals forming, adipocytes are selectively vulnerable to something called ‘chilling injury.’ 1-5 Chilling injury occurs when tissues are cooled to a temperature where the saturated fats that comprise their cell membranes (external and internal) freeze. You see, saturated fat, which is the predominant type of fat in us humans, freezes well above the temperature of water – in fact, it freezes at just below room temperature. That’s why that big gash of fat on the edge of your T-bone steak is stiff and waxy when it is simply refrigerated, and not frozen.

Figure 2: Chilling injury is thought to result from crystallization of cell membrane lipids.

Chilling injury isn’t really well understood. In the days before both cryobiology and indoor heating, humans used to experience a very painful manifestation of it in the form of chilblains – tender swelling and inflammation of the skin due to prolonged cold exposure (without freezing haven taken place). In the realm of organ preservation it is currently thought that chilling injury occurs when cell membranes are exposed to high subzero temperatures (-5oC to -20oC), again, in the absence of freezing.

There is evidence that the lipids (fats) that make up the smooth, lamellar cell membranes undergo crystallization when cells are cooled much below 0 deg C. Since the crystals are hexagonal in shape and have a hole in the middle, this has the effect of creating a pore or hole in the membrane. Cells don’t like that – those holes let all kinds of ions important to cells keeping their proper volume and carrying on their proper metabolic functions leak in and out, as the case may be. This isn’t merely an inconvenience for cells, it’s downright lethal. Without boring you with technical details, it is possible to partially address this state of affairs in organ preservation by adjusting the ‘tonicity’ of the solution bathing the cells: oversimplifying even more, this means by increasing  the concentration of salts to a concentration higher than would normally be present

Figure 3: Contouring of the skin in a pig subjected to brief, subzero cooling of subcutaneous fat.

But, to return to our chilled adipocytes and the promise not only of weight loss, but of a fat-free future; adipocytes are killed, en masse, when their temperature is dropped to between 0 and -7oC. Within a few days of exposure to such temperatures they undergo programmed cell death (apoptosis) and within a couple of months they are phagocytized by the body; and all that ugly and unwanted fat is carted off to be used as fuel by the liver. Now the rub would seem to be that this effect is most pronounced when the temperature of the tissue is cooled to below the freezing point of water and held there – preferably for a period of 10 minutes or longer.

That sounds dire, doesn’t it? What about the skin, the fascia, blood vessels, and the other subcutaneous tissues that will FREEZE (in the very conventional sense of having lots and lots of ice form in them)? Well, the answer, as any long-time experimental cryobiologist will know (even if he won’t tell you) is: pretty much nothing. Way back in the middle of the previous century, a scientist named Audrey Smith and her colleagues at Mill Hill, England found that you could freeze hamsters ‘solid’ – freeze 70+% of the water in their skin and 50% of the water in their bodies – and they would recover from this procedure none the worse for wear. Similarly, those of us who have carelessly handled dry ice for a good part of our lives will tell you that we see parts of our fingertips turn into stiff chalky islands of ice all the time, with the only side effect being a bit of temporary numbness that resolves in a few days to a week – certainly a side effect well worth it to avoid the considerable inconvenience of rummaging around to find a pair of protective gloves.

Figure 4: The Zeltiq Cool Sculpting Cryolipolysis device.

But alas, we scientists (most of us, anyway) are not a very entrepreneurial lot, and so we never thought either of inventing the ZeltiqTM cryolipolysis system, or using ‘the thin-new-you’ as a marketing tool for cryonics.

Yes, that’s right; some very clever folks have found a way to make a huge asset out of a colossal liability – to organ preservationists, anyway. Around 2004 a Minneapolis dermatologist named Brian Zellickson, MD, who specialized in laser and ultrasonic skin rejuvenating procedures, made a not so obvious connection. Both laser and skin ‘face-lifting’ and skin ‘rejuvenation’ procedures rely on the subcutaneous delivery of injuring thermal energy to the tissues of the face, or other treated parts of the body (cellulite of the buttocks and thighs are two other common areas for treatment). These energy sources actually inflict a second degree burn in a patchy and well defined way to the subdermal tissues.

Now this may seem a very counterintuitive thing to do if you are trying to induce ‘rejuvenation’ or ‘lift’ a sagging face. But if you think about it, it makes a great deal of sense. As any burn victim will tell you, one of the most difficult (and painful) parts of recovery is stretching the highly contracted scar tissue that has formed as a result of the burn injury. Indeed, for many patients with serious burns over much of their body, the waxy, rubbery and very constricting scar tissue prevents the return of normal movement, and can lock fingers and even limbs into a very limited range of motion. Many burn victims must do painful stretching exercises on a daily basis to avoid the return of this paralyzing skin (scar) contracture.

And it must be remembered that aged skin – even the skin of the very old – can still do one thing, despite the many abilities it has lost with age, and that thing is to form scar tissue in response to injury. Thus, laser and ultrasonic heating of normal (but aged) skin induces collagen proliferation and large-scale remodeling of the skin. For all the bad things said about scar tissue it is still a remarkable achievement in that it does constitute regenerated tissue. Regenerated tissue which does the minimum that normal skin must do to keep us alive: provide a durable covering that excludes microbial invasion, and prevents loss of body fluids. By injuring the tissue just below the complexly differentiated layer of the dermis (with its hair follicles, sweat glands and highly ordered pigmentation cells) much of the benefit of ‘scarring’ is obtained without the usual downsides.

The injured tissues respond by releasing collagen building cytokines as well as cytokines that result in angiogenesis (new blood vessel formation) and widespread tissue remodeling. And all that newly laid down collagen contracts over time, tightening and lifting the skin – and the face it is embedded in. These techniques may justly be considered much safer versions of the old fashioned chemical face peel, which could be quite effective at erasing wrinkles and achieving facial ‘rejuvenation,’ but was not titrateable and was occasionally highly unpredictable: every once in awhile the result was disastrous burning and accompanying long term scarring and disfiguration of the patient’s face.

St some point Dr. Zellickson seems to have realized that the selective vulnerability of adipocytes to chilling offered the perfect opportunity for a truly non-invasive approach to ‘liposuctioning’ by using the body’s own internal suctioning apparatuses, the phagocytes, to do the job with vastly greater elegance and panache than any surgeon with a trocar and a suction machine could ever hope to do. Thus was invented the Zeltiq Cool SculptTM cryolipolysis machine.6

Figure 5: The cooling head of the Zeltiq devive equipped with ultrasonic imaging equipment and a suction device to induce regional ischemia and hold the tissue against the cooling surface.

The beauty of cryolipolysis is that it is highly titrateable, seems never to result to in excessive injury to, or necrosis of the overlying skin, and yields a smooth and aesthetically pleasing result. Not unjustifiably for this reason it is marketed under the name Cool SculptingTM. The mechanics of the technique are the essence of simplicity. The desired area of superficial tissue to be remodeled is entrained by vacuum in a cooling head equipped with temperature sensors, an ultrasonic imaging device, and a mechanical vibrator. The tissue in the cooling head is sucked against a conductive surface (made evenly conductive by the application of a gel or gel-like dressing to the skin) where heat is extracted from it. The tissue is cooled to a temperature sufficient to induce apoptosis in the adipocytes, while at the same time leaving the overlying skin untouched. The depth of cooling/freezing is monitored by ultrasound imaging and controlled automatically by the Zeltiq device.  At the appropriate point in the cooling process the tissue is subjected to a 5 minute period of mechanical agitation (massage) which helps to exacerbate the chilling injury, perhaps by nucleating the unfrozen fat causing it to freeze.7 When the treatment is over, the device pages an attendant to return to the treatment room and remove it.

The tissue under vacuum is also made ischemic – blood ceases to flow, and this has the dual advantage of speeding the course of the treatment by preventing the blood borne delivery of unwanted heat – and more importantly, by making the cooling more uniform, predictable and reproducible. It also has the effect of superimposing ischemic injury on top of the chilling injury which is something that seems to enhance adipocyte apoptosis. The whole treatment, in terms of actual cooling time, takes about 60 minutes. In the pig work which served as the basis for the human clinical treatments, the duration of treatment was only 10 minutes: but the cooling temperature was also an ‘unnerving’ -7oC. The degree of temporary and fully reversible peripheral nerve damage (that temporary numbness us ‘dry ice handlers’ know so well) was more severe at this temperature, although it resolved in days to a week or two, without exception.

As previously noted, cryolipolysis causes apoptosis of adipocytes and this results in their subsequently being targeted by macrophages that engulf and digest them. This takes time, and immediately after treatment there are no visible changes in the subcutaneous fat. However, three days after treatment, there is microscopic evidence that an inflammatory process initiated by the apoptosis of the adipocytes is underway, as evidenced by an influx of inflammatory cells into the fat of the treated tissues. This inflammatory process matures between seven and fourteen days after treatment; and between fourteen and thirty days post-treatment, phagocytosis of lipids is well underway. Thirty days after treatment the inflammatory process has begun to decline, and by 60 days, the thickness of interlobular septa in the fat tissue has increased. This last effect is very important because it is weakness, or failure of the interlobular fat septae that is responsible for the ugly ‘cottage cheese’ bulging that is cellulite. Three months after the treatment you get the effect you see below on the ‘love handles’ of this fit, and otherwise trim fellow. Thus, it is fair to say that Cool SculptingTM is in no way a misnomer.

Figure 6: Art left is a healthy, fit young male who has persistent accumulation of fat in the form of ‘love handles’ that are resistant to diet and exercise and the same man 3 months after cryolipolysis.

Does cryolipolysis really work? The answer is that it works extremely well for regional remodeling or sculpting of adipose tissue – those pesky love handles, that belly bulge around the navel, that too plump bum, or those cellulite marred thighs. So far it has not been used to try and ablate large masses of fat – although there seems no reason, in principal, why this could not be done using invasive techniques such as pincushioning the fat pannus with chilling probes, as is done with cryoablation in prostate surgery. However, this would be invasive, vastly more expensive, and likely to result in serious side effects.

And that was one of the really interesting things about the research leading up to FDA approval of cryolipolysis: it seems to cause no perturbation in blood lipids, no disturbance of liver function (the organ that has to process all that suddenly available fat) and no global alterations in immune function. It seems to be safe and largely adverse effect free. There is some localized numbness (as is the case in freezing of skin resulting from handling dry ice) but it resolves without incident with a few weeks of the procedure.8

So, all of this makes me wonder, since human tissues tolerate ice formation and respond to it in much the same way as they do to laser or ultrasound ‘rejuvenation’ (depending upon the degree of damage) a logical question is, “would it be possible to use partial freezing of the skin – just enough to provoke the remodeling response – as a method of facial rejuvenation?” It should be safer than a chemical people and it is, like laser and ultrasound therapy, titrateable.

Figure 7: “Gad darn it, this shiny gold stuff keeps getting into the silt I’m tryin to git out of this here river!”

Which returns me to the whole subject of cryonics: fat is very poorly perfused and it seems unlikely that things done to moderate or abolish chilling injury will be nearly so effective for the adipocytes in fat (if it they are effective at all). That means that we might well all come back from our cryogenic naps not only young, via the magic of nanotechnology and stem cell medicine, and rich via the miracle of compound interest (which none other than Albert Einstein once remarked was “the most powerful force in the universe”), but also THIN! For all these years organ cryopreservationists, like Fahy and Wowk, have been panning for the mundane silt of a way around a chilling injury9 all the while discarding the gleaming nuggets of gold that were persistently clogging up their pans.

We cryonicists should not repeat their error and should realize a good thing when we see it. Now, for the first time, we can credibly claim that if you get cryopreserved you’ll come back not only young and rich, but young and rich and beautiful and thin!

Methinks there must be very few in the Western World today, man woman or child, who can resist a product that has all that to offer – and which, by the way, bestows practical immortality in the bargain.

Ok, Ok, maybe we shouldn’t mention that last part about immortality; it might scare the children.

REFERENCES:

1)     Wiandrowski TP, Marshman G. Subcutaneous fat necrosis of the newborn following hypothermia and complicated by pain and hypercalcaemia. Australas J Dermatol 2001;42:207–10.

2)     Diamantis S, Bastek T, Groben P, Morrell D. Subcutaneous fat necrosis in a newborn following icebag application for treatment of supraventricular tachycardia. J Perinatol 2006;26:518–

3)     Lidagoster MI, Cinelli PB, Levee´ EM, Sian CS. Comparison of autologous fat transfer in fresh, refrigerated, and frozen specimens: an animal model. Ann Plast Surg 2000;44:512–5.

4)      Wolter TP, von Heimburg D, Stoffels I, et al. Cryopreservation of mature human adipocytes: in vitro measurement of viability. Ann Plast Surg 2005;55:408–13.

5)      Manstein D, Laubach H, Watanabe K, Farinelli W, Zurakowski D, Anderson RR. Selective cryolysis: a nivel method of noninvasive fat removal. Lasers Surg Med 2008;40:595–604.

6)     Avram MM, Harry RS. Cryolipolysis for subcutaneous fat layer reduction. Lasers Surg Med. 2009 Dec;41(10):703-8. Review. PubMed PMID: 20014262.

7)     Zelickson B, Egbert BM, Preciado J, Allison J, Springer K, Rhoades RW, Manstein D. Cryolipolysis for noninvasive fat cell destruction: initial results from a pig model. Dermatol Surg. 2009 Oct;35(10):1462-70. Epub 2009 Jul 13. PubMed PMID: 19614940.

8)     Coleman SR, Sachdeva K, Egbert BM, Preciado J, Allison J. Clinical efficacy of noninvasive cryolipolysis and its effects on peripheral nerves. Aesthetic Plast Surg. 2009 ul;33(4):482-8. Epub 2009 Mar 19. PubMed PMID: 19296153.

9)     Fahy GM, Wowk B, Wu J, Phan J, Rasch C, Chang A, Zendejas E. Cryopreservation of organs by vitrification: perspectives and recent advances. Cryobiology. 2004 Apr;48(2):157-78.

Robert Ettinger on cryonics and research

One of the most common criticisms of cryonics is to argue that cryonics can only be a legitimate endeavor when there is (peer reviewed) demonstration of whole body suspended animation. Advocates of cryonics  point out that this is an unreasonable position because it sets a standard for rational decision making (certainty) that is rarely encountered, if ever, in real life. People make decisions under conditions of uncertainty all the time. Why should cryonics be held to higher standards?

Like many other arguments against cryonics, this line of criticism is addressed by Robert Ettinger in his book Man into Superman (1972):

There is one more foible of many scientists and physicians important enough for separate attention: the notion that we should spend our money on research, not on cryonic suspension. This is nonsense on its face, and on the record.

To begin with, as repeatedly emphasized, those now dying cannot wait for more research, but must be given the benefit of whatever chance current methods offer. Most of us, if we are in our right minds, have limited interest in abstract humanity or remote posterity; we are primarily concerned with those near us, and cannot forego their probable physical benefit and certain psychological benefit. But even on their own terms, those who complain that research should come first are wrong.

Cryonics does not divert money from research, but channels money into research, and it is the only likely source of such funds in large amounts. Those who speak of using the funds for research “instead” of cryonics are out of touch with reality: these are not the alternatives. This is scarcely even arguable; it is a matter of record. Cryobiology has always been ill-supported, and in recent years support seems actually to have dwindled, partly because of a cutback in NASA funds. And private efforts to raise research money have had very little success. In contrast, organizations growing directly out of the cryonics program have donated money to cryobiological research without the help of a single big name: these include the Cryonics Societies of America, the Harlan Lane Foundation, and the Bedford Foundation. The sums involved have so far been very modest, but they will grow with the Societies. Note, for example, that Professor James Bedford, not a very wealthy man, left $100,000 of his estate for research in cryobiology and related areas, because he was planning cryonic suspension for himself. Does it require much imagination to see how this research will fare when people are being frozen by the thousands or by the millions?

Robert Ettinger makes another important point. Cryonics does not compete with resources for cryobiology research. If anything, it makes more money available to engage in such research. What better incentive to fund research than your own life being at stake? It is not a coincidence that the field of vitrification of complex organs has received great support from cryonics advocates. This funding has culminated in the identification of the least toxic vitrification agent known in the peer reviewed cryobiology literature and the maintenance of long-term potentiation (LTP) in vitrified brain slices.

So the idea that money should be allocated to research instead of cryonics is nonsense indeed. People can have rational reasons for choosing cryonics before suspended animation has been perfected. And when they make cryonics arrangements they have a stronger incentive to contribute to research that will benefit the science and practice of human cryopreservation.

The case for cryonics

The biology-of-aging blog Ouroboros has posted a skeptical post about cryonics that is highly representative of how most biological scientists respond to questions about cryonics. The discussion of cryonics is largely reduced to a discussion of the technical feasibility of suspended animation and resuscitation requirements. But suspended animation is not cryonics. Cryonics should be discussed in the broader context of decision making under uncertainty. People who have made cryonics arrangements are more than aware that contemporary science is not able to vitrify and resuscitate a complex organism. To them the central question is whether we can reasonably expect that future technologies will be able to repair the injury that is produced by contemporary cryopreservation technologies and rejuvenate the patient. That is the “probabilistic” side of the issue. On the utility side of the equation is nothing less than personal survival.

This does not mean that cryonics should be approached as a form of Pascal’s Wager in a vacuum. Experimental evidence from fields such as cryobiology, biogerontology and nanotechnology plays an important role in shaping our expectations about the technical feasibility of the resuscitation of cryonics patients. Many biologists, however, feel confident that they can make a case against cryonics without even bothering to examine the current state of the field. For example, how many biologists know that the latest generation of vitrification agents have low enough toxicity to permit vitrification of animal brain slices with retention of electrical activity?

The author writes:

The field could take a lesson from the dawn of modern biogerontology back in the early 1990s: Acknowledge the mind-bending complexity of the challenge. Create model systems for cryonics, using the best tools from the vast edifice of modern biological knowledge.

But that is exactly what the cryonics field has done. Millions of dollars have been devoted to identify low-toxicity vitrification agents and protocols to preserve viability after pronouncement of legal death.  Progress in the cryopreservation of complex organs (including the brain) has been so successful that the vitrification agent that is currently used by the Alcor Life Extension Foundation, 21st Century Medicine’s M22, is the least toxic vitrification agent in the peer reviewed cryobiology literature to date.

The author is correct that the project of cryonics is of “mind-bending complexity.” One major reason for this is that the resuscitation of most cryonics patients will require successful rejuvenation. As a result, cryonics advocates are quite interested in anti-aging research. But whereas modern biogerontology, not unlike macroeconomics, is still plagued by ongoing (technical) debates about even the most basic definitions employed in the field, or engaged in discussions about what constitutes the most effective approach to pursue rejuvenation, the cryonics field has moved from the practice of the crude freezing of patients to the pursuit of long term care at cryogenic temperatures without ice formation and minimal ischemic injury.

Perhaps there is good reason for this difference in success rate. As mathematician and cryonics advocate Thomas Donaldson pointed out, anti-aging research faces conceptual and methodological challenges that cryobiology research does not. Perhaps the time scale to develop and validate effective anti-aging strategies is similar to that of developing a mature technology that can manipulate matter at the molecular level. If this is the case, rejuvenation research could benefit from being pursued as a broader evolutionary bio-nanotechnology research program.

The discussion of cryonics is most fruitful where logic and empirical science meet.  We need to employ the tools of logic to guide coherent decision making and we need the results of experimental science to provide empirical weight to guide those decisions. In a world where knowledge is recognized as probabilistic, and where death is recognized as a biological process that can be halted through the use of low temperatures, the decision to make cryonics arrangements can be rational and life-affirming.

Cryonics in the media

The Detroit News features a story about cryonics that is a good illustration of the upward battle that cryonics faces in the media. First and foremost, this story reinforces the idea that cryonics concerns the practice of freezing dead people:

Preparation of the body is a five-day procedure. It begins with keeping the body as cool as possible before arriving at the facility, to slow decomposition. Upon arrival, the body is put in a sleeping bag, strapped to a backboard and put in a cooling box.

There is no mention of the practice of replacing the blood with a so called cryoprotective agent to inhibit ice formation in the text, but the practice is explained in a sidebar.

Then the inevitable “expert” (John K. Critser, president of the Society for Cryobiology) makes the predictable error of  offering his opinion on the feasibility of cryonics based on our current ability to achieve real suspended animation.  If a scientist cannot conceptually distinguish between a technology that is meant to halt decomposition to allow resuscitation efforts in the future and a technology that is able to cool down a complex organism and recover it with contemporary technology, cryonics has a serious “marketing” problem.

There has been much debate about how to persuade more people to consider cryonics. Renewed efforts should be made to end  misunderstanding about the following three basic points about cryonics:

1. Cryonics is not the freezing of dead people, but involves the attempt to halt decomposition of people that have been given up by contemporary medicine through the use of low temperatures. Legal death is not biological death.

2. The objective of cryonics is to protect critically ill patients against ice formation at cryogenic temperatures by replacing the blood with a cryoprotective agent. Vitrification solutions attempt to inhibit ice formation altogether.

3. Cryonics is not suspended animation and should not be evaluated as such. Expecting people to destroy their brains because suspended animation is not feasible yet is neither prudent nor caring. Our current burial and cremation practices reflect a simplistic view of death and a desire for instant gratification and closure.

The pursuit of cryonics as medicine

The biggest obstacle to the acceptance of cryonics is medical myopia; the idea that someone who has been pronounced dead by contemporary medical criteria will still be considered dead by future criteria. Advocates of human cryopreservation strongly argue against this. There are few things more discomforting than the idea that medical professionals of the future will look back in horror and wonder why we gave up on people who still possessed the neuroanatomical basis of their identities and memories.

But there is another kind of myopia in the public discussion of cryonics that warrants consideration. It is taken for granted by some critics of contemporary cryonics that cryonics has always been framed as a form of medicine. Nothing could be further from the truth. The history of cryonics is replete with debates between advocates of the medical model and those who believe that timely transport of the patient to a cryonics facility for low temperature storage should be adequate for future resuscitation by advanced nanotechnology. It is only because  cryonics advocates with medical and research backgrounds such as Mike Darwin and Jerry Leaf vigorously argued for adopting conventional medical techniques and protocols that today’s cryonics organizations can even be criticized  for falling short of these criteria.

There is a silver lining to a lot of the controversy that surrounds today’s cryonics . Critics now adopt the premise that cryonics is a form of medicine to make a case against practices they consider suboptimal.  It was not long ago that public critics of cryonics simply dismissed the whole idea as pseudo-science. This was never a sophisticated response but ongoing advances in cryobiology (such as vitrification of the central nervous system) and synthetic biology/nanotechnology have made this position even more of a showcase of ignorance. When people read the news about animals being cloned from straight frozen DNA they will be less receptive to tendentious claims that existing cryonics technologies are hopelessly inadequate to preserve the identity of a person.

The current development in which cryonics is being criticized from a clinical framework should have positive effects on how cryonics will be approached from a regulatory framework. It does not make sense to argue that cryonics is a pseudo-science and offering false hope but at the same time insist that cryonics organizations adopt high standards of medical care. The acceptance of the concept of “patient care” in cryonics would be incoherent without (implicitly) embracing the premise that cryonics patients have interests and deserve legal recognition of that fact. As more public information is disseminated about the quality of brain vitrification that is possible today, the need to recognize cryonics as an elective medical procedure will receive more attention from bioethicists and medical professionals.

There are those who believe that the acceptance of cryonics itself is being held back by amateurism. If this is the case there should be unexploited profit opportunities for cryonics providers that pursue the highest standards of medical care.