Normothermic Machine Perfusion Combined With Modified Small Interfering RNA Targeting Beta-2-microglobulin and Class II Major Histocompatibility Complex Transactivator Mitigates Acute Rejection of Renal Allograft

Abstract

Background: Acute rejection (AR) remains a major determinant of renal allograft outcomes, with the major histocompatibility complex (MHC) playing a pivotal role in its pathogenesis. Although immunosuppressive therapies have advanced, their reliance on high doses and lifelong administration increases the risks of infections, malignancies, and other serious complications. Normothermic machine perfusion (NMP) has emerged as a valuable tool in clinical transplantation, enabling organ preservation, functional assessment, and therapeutic intervention. Integrating NMP with genetic engineering approaches to modulate donor kidney MHC expression may offer a novel strategy for preventing AR.

Methods: We synthesized cholesterol-modified small interfering RNA targeting B2m and Ciita (si B2m -Chol and siCiita -Chol) and set cholesterol-modified negative control small interfering RNA (siNC-Chol) as control. Interfering with MHC expression in transplanted kidneys using NMP combined with siB2m-Chol and siCiita-Chol pretreatment of donor kidneys to prevent AR of posttransplant allografts, we evaluated the efficacy of this approach by assessing postoperative survival, renal function, histological features, and inflammatory responses.

Results: NMP combined with siB2m-Chol and siCiita-Chol significantly reduced MHC expression on postoperative day 3, improved allograft function, and prolonged recipient survival. By postoperative day 7, pathological damage was reduced, and T cells, macrophages, B cells, donor-specific antibodies, and inflammatory cytokine production were markedly lower in treated grafts compared with the siNC-Chol control group.

Conclusions: These findings demonstrate that ex vivo NMP effectively delivers cholesterol-modified small interfering RNA to renal grafts, substantially downregulating both MHC class I and II expression and consequently attenuating AR.