Differentiation of acute versus chronic skin rejection in a rodent model of vascularized composite allotransplantation

This study validates the application of the updated Banff classification in rat VCA rejection models, highlighting overlapping and distinct features of acute and chronic rejection patterns. Clear differentiation between acute and chronic rejection remains challenging, as no single criterion provides absolute diagnostic certainty and multiple pathways with transitional forms are involved. In our cohort, allograft vasculopathy, loss of rete ridges, and band-like lymphohistiocytic infiltrates were the most distinctive features, underscoring the need for an integrative diagnostic approach. The findings reflect patterns seen in human chronic active rejection and underscore the need for further research to better understand the mechanisms driving sustained inflammation and tissue remodeling in VCA rejection.