Tiam Mana Saffari

108 CHAPTER 6 ABSTRACT Background A well-vascularized bed for nerve grafts may diminish nerve rejection by altering the microenvironment and intricate paracrine mechanisms that control local cellular pathways. The purpose of this study was to determine how surgical angiogenesis alters the cellular environment of processed nerve allografts in a rat sciatic nerve defect model. Materials and Methods Unilateral sciatic nerve defects of Lewis rats (N=39) were repairedwith (i) autografts, (ii) decellularized processed nerve allografts, or (iii) allografts wrapped with a superficial inferior epigastric fascial (SIEF) flap to provide vascularization. Animals were evaluated at two weeks (N=5/group) for flow cytometry and gene expression profiles, and at 12 and 16 weeks (N=4/group/time point) for immunohistochemistry. Gene expression was quantified by quantitative polymerase chain reaction (qPCR) analysis of representative biomarkers, including angiogenic, neurotrophic, immunotrophic and extracellular matrix (ECM) genes. Results Flow cytometry revealed a significant increase in T helper population (CD4) in SIEF rats, compared to baseline, untreated rats (P=0.02) after one week. Expression of several angiogenic markers, including Cd34, Pecam1/Cd31, Vegfa andMmp2 (P<0.05 compared to autograft), as well as extracellular matrix proteins such as collagen type I (Col1A1) and type III (Col3A1) (P<0.01, compared to allograft) was significantly increased in SIEF samples and confirmed by immunohistochemistry. Conclusions Surgical angiogenesis of processed nerve allografts alters the cellular environment confirmed with immune cells obtained from peripheral blood, gene expression profiles and immunohistochemical staining. These immunological and angiogenic changes may enhance short- and long-term outcomes of nerve regenerative strategies.