Long-term survival and functional recovery of cryopreserved vascularized groin flap and below-the-knee rat limb transplants

Effective cryopreservation of large tissues, limbs and organs has the potential to revolutionize medical post-trauma reconstruction options and organ preservation and transplantation procedures. To date, vitrification and directional freezing are the only viable methods for long-term organ or tissue preservation but are of limited clinical relevance. This work aimed to develop a vitrification-based approach that will enable the long-term survival and functional recovery of large tissues and limbs following transplantation. The presented novel two-stage cooling process involves rapid specimen cooling to subzero temperatures, followed by gradual cooling to the vitrification solution and tissue glass transition temperature. Flap cooling and storage was only feasible at temperatures equal to or slightly lower than the VS Tg (i.e. -135 0C). Vascularized rat groin flaps and below-the knee (BTK) hind limb transplants cryopreserved using this approach exhibited long-term survival (>30 days) following transplantation to rats. BTK-limb recovery included hair regrowth, normal peripheral blood flow, and normal skin, fat and muscle histology. Above all, BTK-limbs were reinnervated, enabling rats to sense pain in the cryopreserved limb. These findings provide a strong foundation for the development of a long-term large-tissue, limb and organ preservation protocol for clinical use.