Using Bioinspired Next-Generation Cryoprotectants to Advance Ex Vivo Preservation of Vascularized Composite Allografts at High Subzero Temperature
Tessa Muss*1, Yi-nan Guo1, Yichuan Zhang1, Amanda Loftin1, Emma Rowley1, Amy Bodine1, Arthi Shridhar2, Xiaoxi Wei2, Mark Kline2, Byoung Chol Oh1, Gerald Brandacher1
1Plastic and Reconstructive Surgery, Johns Hopkins University, Baltimore, MD; 2X-Therma Inc., Richmond, CA
Vascularized composite allotransplantation (VCA) can restore form and function to patients with upper limb loss, but its use is limited by a short cold ischemia time (CIT) of 6 hours at 4°C. Subzero storage is a promising solution to prolong the CIT, but a cryopreservative is needed to prevent ice damage. As such, a novel biopreservative, XT-ViVo (XTV), was developed to preserve tissue at -5°C in an ice-free state. This study aims to show that storing VCAs at high subzero temperatures with XTV will extend the CIT to increase graft availability for transplant.
Male Lewis rat forelimbs were procured. Limbs were perfused with University of Wisconsin (UW) solution and stored at 4°C or perfused with XTV and stored at -5°C for CITs of 6, 24, 48, or 72 hours. Groups were named according to the assigned solution and CIT (e.g. UW6). Limbs were then orthotopically transplanted to syngeneic rats. Images, serum, and grip strength were collected postoperatively. Grafts were harvested on postoperative day (POD) 30 for analysis.
28 recipient rats were transplanted: UW6 (n=5), UW24 (n=4), UW48 (n=3), UW72 (n=5), XTV24 (n=4), XTV48 (n=4), XTV72 (n=3). XTV limbs reperfused faster on average than UW counterparts: 18.3 vs 20.7 seconds (24hr CIT), 7.7 vs 20 seconds (48hr CIT), 15 vs 30 seconds (72hr CIT). All paws remained well perfused until POD30, but skin necrosis positively correlated with CIT. At 24 and 48hr CIT, both UW and XTV groups had peri-incisional skin necrosis as soon as POD5 down to the mid-humerus, whereas necrosis began as soon as POD3 and extended past the elbow at 72hr CIT. Functionally, all groups could form fists for grip strength testing, but there were no significant differences at 4 weeks. Median nerves showed histologic evidence of regeneration in all groups.
Preliminary findings indicate that preserving forelimbs in XTV for up to 72 hours at subzero conditions is feasible, as grafts can maintain perfusion for 30 days and nerves can regenerate and reinnervate muscle. This builds a foundation to further optimize this technology for prolonged preservation of VCAs.
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