Vitrification and nanowarming enable long-term organ cryopreservation and life-sustaining kidney transplantation in a rat model
Published in Vitrification.
Zonghu Han, Joseph Sushil Rao, Lakshya Gangwar, Bat-Erdene Namsrai, Jacqueline L. Pasek-Allen, Michael L. Etheridge, Susan M. Wolf, Timothy L. Pruett, John C. Bischof & Erik B. Finger
Banking cryopreserved organs could transform transplantation into a planned procedure that more equitably reaches patients regardless of geographical and time constraints. Previous organ cryopreservation attempts have failed primarily due to ice formation, but a promising alternative is vitrification, or the rapid cooling of organs to a stable, ice-free, glass-like state. However, rewarming of vitrified organs can similarly fail due to ice crystallization if rewarming is too slow or cracking from thermal stress if rewarming is not uniform. Here we use “nanowarming,” which employs alternating magnetic fields to heat nanoparticles within the organ vasculature, to achieve both rapid and uniform warming, after which the nanoparticles are removed by perfusion. We show that vitrified kidneys can be cryogenically stored (up to 100 days) and successfully recovered by nanowarming to allow transplantation and restore life-sustaining full renal function in nephrectomized recipients in a male rat model. Scaling this technology may one day enable organ banking for improved transplantation.
The ability to intentionally and reproducibly cryopreserve living biological systems, including cells, tissues, organs, and even whole organisms, began in 1949 with the preservation of fowl sperm using glycerol, a cryoprotective agent (CPA) that protected the sperm cells during freezing1. That work was followed by important proof-of-principle cryopreservation of mammalian blood and embryos with other CPAs2,3. These and other studies also demonstrated that injury from ice crystallization during freezing limited success, especially in larger systems4,5,6,7,8,9. Efforts to address this barrier led to “vitrification,” an approach using higher concentrations of CPAs and faster rates of cooling that avoided crystallization entirely by forming a glassy state during cooling, as demonstrated in both embryos10 and even whole rabbit kidneys11. By avoiding crystallization during both cooling and rewarming, mammalian embryo cryopreservation became a reality and transformed the field of reproductive technology. However, preventing crystallization during rewarming in larger bulk systems, like whole kidneys, remains elusive due to the inability of conventional convective rewarming (i.e., surface warming) to provide rapid and uniform heating rates across these larger scales. Indeed, vitrification followed by long-term transplant success with a kidney (or any organ) has never been reproducibly achieved.