Novel Complement C5 Small-interfering RNA Lipid Nanoparticle Prolongs Graft Survival in a Hypersensitized Rat Kidney Transplant Model

Prophylaxis of antibody-mediated rejection (AMR) caused by donor-specific antibodies remains challenging. Given the critical roles of complement activity in antibody-mediated graft injury, we developed a lipid nanoparticle (LNP) formulation of small-interfering RNA against complement C5 (C5 siRNA-LNP) and investigated whether C5 siRNA-LNP could downregulate the complement activity and act as an effective treatment for AMR.Lewis recipient rats were sensitized by skin grafting from Brown Norway donor rats. Kidney transplantation was performed at 4 wk post-skin grafting.C5 siRNA- or control siRNA-LNP was administered intravenously, and the weekly injections were continued until the study's conclusion. Cyclosporin (CsA) and/or deoxyspergualin (DSG) were used as adjunctive immunosuppressants. Complement activity was evaluated using hemolysis assays. The deposition of C5b9 in the grafts was evaluated using immunohistochemical analysis on day 7 posttransplantation.C5 siRNA-LNP completely suppressed C5 expression and complement activity (hemolytic activity ≤ 20%) 7 d postadministration. C5 siRNA-LNP in combination with CsA and DSG (median survival time: 56.0 d) prolonged graft survival compared with control siRNA-LNP in combination with CsA and DSG (median survival time: 21.0 d; P = 0.0012; log-rank test). Immunohistochemical analysis of the grafts revealed that downregulation of C5 expression was associated with a reduction in C5b9-positive area (P = 0.0141, Steel-Dwass test).C5 siRNA-LNP combined with immunosuppressants CsA and DSG downregulated C5 activity and significantly prolonged graft survival compared with control siRNA-LNP with CsA and DSG. Downregulation of C5 expression using C5 siRNA-LNP may be an effective therapeutic approach for AMR.