The role of macrophage polarization in organ transplantation: research progress on impact on graft injury, repair, and fibrosis.

Organ transplantation is a life-saving therapy for patients with end-stage organ failure. However, post-transplant graft injury, immune rejection, and chronic fibrosis severely compromise the long-term survival of recipients and graft function. Macrophages, as core components of innate immunity, possess remarkable plasticity and can polarize into pro-inflammatory M1 or anti-inflammatory/reparative M2 phenotypes in response to microenvironmental signals, thereby deeply participating in the post-transplant immune response and tissue remodeling processes. This review systematically explores the regulatory network of macrophage polarization after transplantation and thoroughly analyzes the complex and often paradoxical roles of different polarization phenotypes in ischemia-reperfusion injury, acute and chronic rejection, graft repair, and progressive fibrosis. Based on current research progress, this article further envisions the therapeutic potential of precisely regulating macrophage polarization phenotypes to intervene in transplant-related pathological processes, aiming to provide innovative theoretical foundations and strategic directions for improving long-term graft survival and function.