Medical technology research advances day by day. Yet, for most people it’s often hard to see these advancements. How many of us spend our time researching the most recent scientific articles, reading them and understanding them? Well, we do. As we work in the field of experimental medicine, it is crucial for us to be up-to-date not only on cryonics, but on many topics connected to what we want to achieve: the possibility for each person to decide how long they want to live. If you too are interested in recent scientific articles regarding cryopreservation, have a look at our summary!
Where do we stand on the development of cryopreservation
Let’s start from the beginning. The term “cryopreservation” refers to the process of storing biological material at low temperatures. Cells, tissues, embryos, semen, organs and complete organisms can be cryopreserved. Biostasis (aka cryonics) companies offer a service of human cryopreservation. Since humans are made out of cells, tissues, embryos (or semen) and organs, discoveries concerning any of these could consequently influence the biostasis field. Likewise, breakthroughs in human cryopreservation would possibly help the developments of connected fields. So, how far have researchers come in developing cryopreservation and rewarming techniques?
Winter is coming: the future of cryopreservation
If you are looking for a recent overview of the subject, its current applications and prospects, “Winter is coming: the future of cryopreservation” is the article for you. Published in April 2021 by Bojic, S., Murray, A., Bentley, B.L. et al. , this work is the perfect tool to understand cryopreservation as an “interdisciplinary endeavour between medicine, biology, bioinformatics, chemistry and physics ”.
Cryopreservation is a relatively niche field of study and it’s only around 70 years since the dedicated field of cryobiology was founded. In that short time, it has made remarkable progress. In the past, researchers were only able to freeze spermatozoa that is on average about 50 micrometers in size (5/100.000 of a meter). Today, using complex multi-component solutions, we can vitrify tissues, small organs and whole organisms as complex as human beings.
But what exactly do we need cryopreservation for?
- Organ and tissue preservation could facilitate the transplantation process and solve the problems connected to the shortage of organ donors - by allowing the creation of an organ bank. The need for such a solution is high. In fact, in 2010 only 10% of the worldwide need for organ transplantation was met.
- Fertility preservation (eggs, sperm, or reproductive tissue) is a field that has grown exponentially, with great results. Since the first birth following in vitro fertilization (IVF) in 1978, at least 8 million babies have been produced with the help of medically assisted reproduction.
- Drug discovery, development and testing could also benefit from the availability of large quantities of cryopreserved tissues and cells. Pharmaco-toxicological research could utilize tissue slices of human organ material. This would lead to more effective results and a decrease of laboratory animal use.
- Stem cells represent highly promising resources for application in cell therapy and regenerative medicine. Their commercial and clinical applications, presently, depend on cryopreservation - the only available long-term storage option.
- Finally, human cryopreservation could completely revolutionize the field of emergency medicine. The use of very low temperatures to save lives is still in its infancy. Moderate states of hypothermia have recently become a common practice to gain crucial time in emergency situations. Depth hypothermia and vitrification are less common, yet promising fields.
Finally, the article offers technical but not too complex explanations of fundamental aspects such as freezing and vitrification, the different cryoprotectant agents and their toxicity, thawing and warming. Concluding the work on a very promising note: there are still many opportunities that lie ahead, from short-term improvements in transplantation biology, to ambitions that may once have been viewed as science fiction, such as the building of organ banks or long-term suspended animation.
New approaches to cryopreservation of cells, tissues, and organs
If you are interested in cryonics, you probably already had some knowledge of the topics discussed in the first article. This second article instead outlines a variety of new approaches for both preservation at low temperatures and warming. It’s title is “New approaches to cryopreservation of cells, tissues and organs” and it was published in June 2019 by Taylor MJ, Weegman BP, Baicu SC, Giwa SE.
The purpose of the study is clear. Development of an organ and tissue supply chain that can meet the healthcare demands of the 21st century means overcoming twin challenges of (1) having enough of these lifesaving resources and (2) having the means to store and transport them for a variety of applications .
Let’s focus on this second challenge. With today's technologies, about 60% of donated hearts and lungs have to be thrown away. This is because the person in need is often located at a distance that is more than a few hours away (the amount of time these tissues can survive outside the body). To solve this problem, researchers are studying ways to preserve tissues and organs. Short term preservation can be achieved with the use of temperatures a few degrees above the freezing point. Because there is no ice formation, the successive thawing procedure is, in most cases, rather simple. Yet, in most cases, we need to store the biological material for a longer period of time. Lower temperatures become necessary. With lower temperatures comes the problem of ice formation (that would damage the tissues). To avoid ice formation and improve the quality of the cryopreservation, researchers utilize anti-freeze cryoprotectant solution inducing a process called vitrification. But with these solutions comes the problem of toxicity while thawing. And for this problem, medical technology hasn’t found a solution yet.
Let’s have a look at some of the different approaches the article presents.
- Supercooling. Many species in nature can sustain subfreezing body temperatures for weeks or longer, supercooling/hibernating to avoid ice formation. Supercooling could be artificially induced in human organs through the application of low-molecular-weight cryoprotectants and synthetic ice blockers.
- Controlled, Partial-Ice Freezing. There are at least 45 animals that can survive long periods of time at high-subzero temperatures in a state of biostasis. Researchers are studying low-molecular-weight CPAs that could help reproducing this ability in humans.
- Nanowarming. In order to accomplish both rapid and uniform warming after cryopreservation, we could use heat transfer methods capable of warming tissue from within rather than through surface conduction alone. Nanowarming technology could do so by biocompatible magnetic nanoparticles perfused with the vitrification solutions. Through radiofrequency fields we could excite these nanoparticles, causing a rapid and uniform warming.
Vitrification and Nanowarming of Kidneys
Considering the importance of nanowarming for thawing and future revival, let's see how far research has progressed in this field. The article “Vitrification and Nanowarming of Kidneys” showcases a successful experiment of nanowarming on a rat kidney. Published in August 2021 by Sharma A, Rao JS, Han Z, et al., this work suggests that this method holds tremendous promise for transplantation.
During the experiment, the researchers perfused rat kidneys via the renal artery with a cryoprotective cocktail (CPA) and silica-coated iron oxide nanoparticles (sIONPs). After cooling down the kidneys to −40 °C, they verified the distribution of the sIONPs and the vitrified state of the kidneys through the use of microcomputed tomography (µCT) imaging. Once it was established that the solutions had been perfused correctly, the nanoparticles were excited by applying a radiofrequency field. The vitrified kidneys were nanowarmed successfully: modeling shows the avoidance of both ice crystallization and cracking during these processes. The experiment showed a predominant preservation of vascular integrity (flow rates, low pressure, and low resistance), and such measures are important indicators of organ quality in current clinical practice. On the other hand, researchers noticed damages caused by the toxicity of the cryoprotectant solutions utilized. To tackle this issue, there will be the need to develop less toxic and more stable vitrification solutions.
As the article concludes: combining the enabling studies reported here with continually evolving perfusion and cryoprotection technology holds the promise of fully successful organ cryopreservation in the foreseeable future, with potentially revolutionary implications for the future of organ transplantation .
Cryopreservation of a human brain and its experimental correlate in rats
Finally, the last article we recommend focuses on understanding how successful current cryopreservation procedures are in storing the brain and memories of a living being. Published in December 2020 by Canatelli-Mallat M, Lascaray F, Entraigues-Abramson M, et al., “Cryopreservation of a human brain and its experimental correlate in rats” shows exciting results.
As stated in the article, the idea that human cryopreservation is “an unrealistic or even utopic endeavor has been progressively changing in recent years ”. NASA, for example, is currently sponsoring suspended animation research projects. This technology is considered essential for interstellar or even interplanetary travel - and feasible with the necessary amount of investment and research.
This study compares the cryopreserved brain of a woman (who donated her body to science) to the brains of three different groups of rat brains, cryopreserved with different solutions. Three groups of rats were perfused with either fixative but not frozen (reference group), vitrification solution VM1 (control group) or the cryoprotection solution used in the patient (experimental group). After being stored at -80ºC the brains of both the woman and the rats were thawed. The researchers found no histological evidence of ice formation. When ice forms in a cryopreserved brain and subsequently melts, the ice crystals leave cavities in the tissue. No such cavities were found. Additionally, they compared specific neurons - NeuN neurons, Hippocampal SYN immunostaining, Hippocampal DCX and dopaminergic neurons. The cryoprotective procedures didn’t have any adverse impact on hippocampal or cortical thickness (necessary for remembering). However, the immature (DCX positive) neurons of the hippocampus showed an unfavorable impact.
Citing the discussion of the article: Perhaps the more encouraging finding of the present study is that the density of hippocampal synapses (SYN immunoreactive area) was affected by neither of the cryoprotective protocols. If future studies show that brain synaptic density is not affected by cryoprotection procedures, this would suggest that the connectome retains an acceptable integrity after vitrification, which would let us expect that cryopreserved brains keep a substantial proportion of the information present in the nervous system at the time of death .
Medical technology hasn’t been able to tackle all aspects connected with cryopreservation yet. However, day after day we are getting closer to possibly achieving revival. Through human cryopreservation, we could in the (maybe not too far) future treat people’s diseases and save their lives. It may be a long way but definitely not an impossible one.
 Bojic S, Murray A, Bentley BL, et al. Winter is coming: the future of cryopreservation. BMC Biol. 2021;19(1):56. Published 2021 Mar 24. doi:10.1186/s12915-021-00976-8
 Taylor MJ, Weegman BP, Baicu SC, Giwa SE. New Approaches to Cryopreservation of Cells, Tissues, and Organs. Transfus Med Hemother. 2019;46(3):197-215. doi:10.1159/000499453
 Sharma A, Rao JS, Han Z, et al. Vitrification and Nanowarming of Kidneys. Adv Sci (Weinh). 2021;8(19):e2101691. doi:10.1002/advs.202101691
 Canatelli-Mallat M, Lascaray F, Entraigues-Abramson M, et al. Cryopreservation of a Human Brain and Its Experimental Correlate in Rats. Rejuvenation Res. 2020;23(6):516-525. doi:10.1089/rej.2019.2245
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