Functional Outcome After Dynamic Hypothermic Ex-situ Perfusion on Rat Hindlimb Allografts
Nathan Lawera, Emre Gok, Carrie Kubiak, Erin Guy, Alvaro Rojas-Pena, Robert Bartlett, Paul Cederna, Stephen W. Kemp, Kagan Ozer.
University of Michigan, Ann Arbor, MI, USA.
PURPOSE: The standard of care for preservation of vascularized composite tissue allografts (VCA) prior to transplantation is static cold storage (SCS). A dynamic hypothermic ex-situ perfusion system reduces the metabolic rate of muscle cells, and removes toxic metabolytes from the circulation. The use of such a system as an alternative to SCS may prolong allograft survival and function in the long-term. The primary purpose of this study was to determine the effect of dynamic hypothermic ex-situ limb perfusion on the survival and long-term function of VCAs using a rat hind-limb allograft transplantation model.
METHODS: Thirty-five male Lewis rats (250±25g) were divided into 4 experimental groups. Group 1 was a denervartion control group (no repair). In group 2, 5 hind limbs were immediately transplanted to the recipient (isograft control) without dynamic perfusion. In group 3, five donor limbs were preserved at 4°C using HTK solution for 6 hours and transplanted (SCS group). In group 4 using the same preservative solution, five limbs were continuously perfused at 10-15°C for 6 hours and transplanted. Sciatic nerves were repaired in all groups. Muscle injury and function were assessed using sciatic function index (SFI), EMG, muscle force, muscle histology, and metabolomics analysis at 3 months
RESULTS: All recipients in groups 1 and 2 survived, while groups 3 and 4 had 40% and 20% mortality rates at an early postoperative period. The average SFI for groups 2, 3 and 4 were -54.5±4.2, -84.3±5.9, and -66.4±3.9, respectively. The average muscle injury score of group 2, 3 and group 4 were 40.1±9.2, 89.3±8.9, and 47.7±5.6, respectively (p<0.05). The average twitch muscle force for groups 2, 3, and 4 were 369.9+24.85, 218+28, 287.6+10.14 respectively. Maximum tetanic force values were 1870+67.58, 862+16.42, and 781.8+58.26 for groups 2-4.
CONCLUSION: Static cold storage is unable to protect muscle viability and function at 6 hours. Dynamic hypothermic ex-situ perfusion appears to provide with better viability and function in this model. Less than optimum preservation using static cold storage demonstrates the need to re-think the way we preserve vascularized composite tissue allograft prior to transplantation. Future directions include prolongation of ex-situ limb support for 24 h, and subsequent transplantation of these limbs.
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