Organ banking for transplant—kidney cryopreservation by vitrification and novel nanowarming technology

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ABSTRACT: Organ banking has the potential to revolutionize the way organs are used for transplantation. Rewarming organs such as kidneys from the vitrified state is a critical step in obtaining successful cryopreservation. This would allow improved allocation, transport, and recipient preparation prior to transplant, while simultaneously providing a missing link in the potential supply chain for other engineered tissues. Typical freezing processes cause significant damage to biomaterials through ice crystal formation and cellular dehydration. However, with the aid of cryoprotectant (CPA) solutions, biospecimens can be stabilized in the vitreous (i.e. “glass” or “amorphous”) or ice free state, allowing for long-term cryopreservation. Our collaborator and consultant Dr. Greg Fahy has been able to vitrify rabbit kidneys since the 1980s. However, successful rewarming of these vitrified kidneys has remained a challenge to translation of vitirification for organ banking. Specifically, achieving critical warming rates (tens to hundreds of oC/min) necessary to avoid devitirification (i.e. crystallization) during warming has not been possible. In addition, achieving these rates in a sufficiently uniform fashion throughout the organ is also required to avoid thermal stresses that can crack the brittle material, and so both speed and uniformity of warming are of critical importance. Here we propose to investigate the ability of radiofrequency heated magnetic nanoparticles, or “nanowarming,” to overcome this major limitation hindering further development of bulk cryopreservation of kidneys. Although electromagnetic rewarming has been tried, the direct coupling of the waves to tissue will inherently result in non-uniformity in heating, which leads to crystallization, cracking and differential viability. At lower radiofrequencies (RF < 1 MHz) alternating magnetic fields (AMFs) can uniformly penetrate tissues without attenuation and negligible dielectric coupling. Although these lower frequency fields will be unable to rapidly heat the tissue on their own, they are able to produce significant heating through coupling with magnetic (e.g. iron-oxide) nanoparticles. We have already demonstrated that this approach can generate heating rates rapid enough to avoid devitirification in most CPAs of interest (up to 200 oC/min) and should scale independent of sample size. The objective of this study is to refine this novel nanowarming technology for use in cryopreserving kidneys for transplant. To this end, in Aim 1 we will physically characterize CPA and nanoparticle mixtures to heat rabbit and larger mammalian kidneys. In Aim 2 we will demonstrate our ability to perfuse this CPA and nanoparticle combination into rabbit kidneys, vitrify and nanowarm while maintaining viability, cellular function and structural tissue integrity. Finally, in Aim 3 we will demonstate in vivo function after vitrification and nanowarming by transplant in rabbits and scaling for use in human kidneys In summary, the focus of this proposal will be to leverage our breakthrough nanowarming technology by optimizing CPA composition and nanoparticle delivery in rabbit kidneys with proof of principle work to scale up to porcine and human kidneys for eventual clinical kidney banking and transplantation.