A Novel Scoring System to Assess Vascularized Composite Allograft Preservation with Adipose Stem Cell Media

BACKGROUND: Vascularized composite allografts (VCAs) offer a promising solution for complex reconstructive procedures. However, their clinical application is constrained by a narrow preservation window, with prolonged ischemia hindering graft viability and post-transplant longevity. The University of Wisconsin (UW) preservation solution, the gold standard perfusate, extends viability by reducing cellular edema and scavenging for free radicals. However, its efficacy declines beyond the conventional 4–6-hour storage window, a significant drawback for muscle tissue, which is highly susceptible to ischemia. Muscle viability in VCAs, partly defined by structural characteristics, is difficult to assess due to the lack of a dedicated histological scoring system. Considering these challenges, adipose-derived stem cell-conditioned media (ADSC-CM), enriched with numerous growth factors and cytokines may mitigate ischemic damage. We therefore propose supplementing UW with ADSC-CM, creating UW-CM, to improve graft preservation, with evaluation using a novel histopathological injury scoring system (HISS). METHODS: Rat osteomyocutaneous grafts, comprising a superficial inferior epigastric artery skin flap, vascularized muscle, and femur, were perfused with and stored in one of three conditions: 1) saline, 2) UW, or 3) UW-CM. We evaluated graft muscle viability using hematoxylin and eosin (H&E) staining and a histological scoring system that categorized muscle integrity based on endomysium and fiber appearance (1 = normal, 2 = mild/moderate degradation, 3 = severe degradation). We performed pairwise comparisons using the Mann-Whitney U test where sample size allowed. Furthermore, inter-rater reliability was evaluated using Cohen’s Kappa. Two independent raters analyzed a total of 84 regions of interest (ROIs) across 21 flaps. RESULTS: At 6 hours, the saline group exhibited the highest mean score for endomysium and fiber injury (2.38 ± 0.48), indicating moderate to severe muscle degradation. In comparison, UW-treated grafts achieved a mean score of 1.50 ± 0.13, while UW-CM-treated grafts reached a mean score of 1.81 ± 0.17, suggesting that both UW and UW-CM reduce the degree of histological injury relative to saline. At 24 hours, UW-CM-treated samples recorded a lower mean injury score (1.88 ± 0.63) compared to both UW (2.39 ± 0.48) and saline (2.38 ± 0.95). By 48 hours, UW-CM maintained a numerically lower mean score (2.20 ± 0.39) relative to UW (2.53 ± 0.33). Although the Mann-Whitney U test did not reach statistical significance at 48 hours (p = 0.234), these findings suggest that UW-CM may still offer slight improvements in preserving muscle integrity. Additionally, inter-rater reliability analysis showed substantial agreement (Cohen’s Kappa = 0.691). CONCLUSION: These findings indicate that supplementing UW with ADSC-CM may improve graft preservation by enhancing muscle integrity during extended storage. While UW alone provides consistent protection at early time points (6 hours), the addition of ADSC-CM appears to confer additional benefits at 24 and 48 hours. However, the lack of statistically significant differences at 48 hours highlights the need for further studies with larger sample sizes and optimized ADSC-CM concentrations. Overall, ADSC-CM shows promise as a supplement to extend VCA viability and improve reconstructive outcomes. Additionally, the scoring system provides a simple, useful tool for evaluating graft viability.