Fight Aging!

Another step forward for the magnetic nanoparticle approach to thawing vitrified tissues was recently reported. Vitrification for low-temperature storage is a fairly well established technique, at least for organs. The challenge lies in thawing vitrified organ tissue without causing so much damage that it becomes non-viable for transplantation. Researchers have now managed to make this work for rat kidneys, albeit just barely. The kidneys were damaged, and it remains the case that scaling up to human organs will have its challenges. A greater volume of tissue makes cryopreservation and later thawing much harder, but success will greatly improve the economics and logistics of organ transplantation and tissue engineering, allowing tissues to be stored indefinitely.

For decades bringing organs back from a deep freeze without injury and with full function has remained a frustrating problem for the field. Researchers have already vitrified and revived human, mouse, and pig pancreas islet cells, and vitrified and rewarmed rat hearts and livers. When vitrifying, scientists first infuse the organ or tissue with magnetic nanoparticles and safeguarding chemicals called cryoprotective agents that serve as a kind of antifreeze. Afterward, they cool it quickly - 24 degrees Celsius per minute - to bypass the formation of cell-shredding ice crystals and directly enter a glass-like state.

Researchers have spent years developing technology that can rewarm vitrified materials fast enough to avoid ice-crystal formation in the physical transition back from glass. This rewarming, critically, also must be uniform, to avoid an organ cracking and splitting from its outside surfaces being too different a temperature from its core - like an ice cube in a glass of room-temperature water. Their solution is a technique called nanowarming, which utilizes a radio-frequency copper coil to create a magnetic field that excites iron nanoparticles throughout the organ all at once, similar to a microwave oven, but more uniform.

The experimental thawed rat kidneys produced urine within 45 minutes of transplantation into young rats, compared to a few minutes for their fresh counterparts. And for the first days after surgery, they were slower to clear out creatinine, a chemical waste product that kidneys remove from the body. "The biggest issue is that the kidneys were, in fact, badly damaged. The function of those kidneys was cut in about half. These were kidneys in the peak of life, in perfect health - and they barely made it." On the other hand, the degree to which the kidneys did heal and recover was "remarkable and encouraging." The researchers also noted that because they ended the study 30 days post-transplant, they weren't able to assess longer-term survival.

Researchers said they plan to spend the next six months attempting to scale their cryopreservation method up to pig organs - a size change, kidney-wise, from a large grape (in rats) to about a pear (in pigs). As they go, they will continue to study whether rewarmed animal organs recover their original physiological, chemical, and electrical properties. Down the line, if all goes well, the future might hold living banks where organs, skin, nerves, blood vessels, cartilage, and stem cells are preserved in liquid nitrogen for years until they're matched with the right patients.

Link: https://www.statnews.com/2023/06/21/cryogenic-organ-preservation-transplants/