Optimizing post brain death vascularized composite graft quality through ex vivo restoration of S-nitrosothiol homeostasis

A challenge in vascularized composite allotransplantation (VCA) is mitigating tissue damage within the composite secondary to brain death (BD). Loss of central nervous system function disrupts S-nitrosothiol (SNO) homeostasis to produce systemic hypoxia and ischemic injury during the donor support phase. We reasoned that addition of an S-nitrosylating agent to the preservation solution could correct this damage during ex vivo storage. Employing a swine BD preparation, we excised VC tissues (abdominal blocks and limbs) after a 16-h period of systemic support. The composites were perfused with/without the S-nitrosylating agent ethyl nitrite (ENO) present in the preservation solution. Flow rates and resistance were recorded during the storage period; tissue hypoxia was also quantified. BD decreased circulating SNO levels and reduced tissue oxygenation and muscle protein NO content. During storage, ENO increased flow and decreased resistance within the VCs. Muscle from ENO-treated VCs had lower protein levels of inducible nitric oxide synthase and the hypoxia marker Hif1α and higher levels of the anti-apoptotic protein Bcl2, all suggestive of enhancements of tissue oxygenation. As such, ex vivo S-nitrosylation therapy may be a means to correct BD-induced impairments in SNO-status to improve the quality of composite tissue grafts prior to transplantation.