Enhancing the Neuromuscular Regenerative Potential of Replanted Extremities Using Ex Situ Hypothermic Perfusion.

• Applicant: Dr. Lioba Huelsboemer
• Subject Area: Orthopaedics, Traumatology, Reconstructive Surgery
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 508239629

Limb amputation due to high velocity accidents, severe infection or oncologic disease is a life-changing event, often associated with devastating psychological, social and economic effects. Prosthetic fittings are unable to fully compensate for the functional deficit of losing a limb. Vascularized composite allotransplantation (VCA) is a novel and yet nonstandard procedure that uses healthy limbs procured from organ donors to restore the anatomy and sensomotoric functions. However, limb transplantation is facing the same limitations that are challenging solid organ transplantation. One such limitation is known as ischemia-reperfusion injury (IRI). IRI occurs when the limb is separated from its oxygen supply for transportation and the course of transplantation (i.e. it becomes ischemic), which is initiating a deleterious chain of events such as formation of oxygen radicals.To shorten ischemia times, the team of Dr. Pomahac developed a portable, lightweight perfusion system that uses an acellular perfusate for extracorporal limb preservation for up to 12 hours. This project aims to further develop the existing extracorporal preservation system: we will preserve oxygen supply by combining machine perfusion with engineered smart polymeric microbubbles loaded with oxygen that spontaneously dissolve following contact with physiological fluids. This allows one to titrate the intravascular oxygen delivery.Hydrogen gas (H2), a potent antioxidant, will be used in addition to scavenge and neutralize reactive oxygen species. We hypothesize that normothermic perfusion of the VCA with artificial O2 (dioxygen) microcarriers and dissolved H2 will mimic near physiological conditions from procurement to transplantation.Therefore, we want to determine if microbubble perfusates improve limb viability and nerve regeneration and whether ex vivo perfusion with optimized perfusates improves functional outcomes in an orthotopic syngeneic hindlimb ex vivo perfusion model.This will result in minimizing IRI, improving long-term neuromuscular VCA function and extending the allowable ischemia time to 24 h.The overarching goal is to develop an inexpensive, easy to transport and store perfusion system that would deliver an adequate amount of oxygen to tissues thus minimizing IRI.If successful, this project may redefine limb preservation protocols and improve long-term limb function.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Dr. Bohdan Pomahac