Extracorporeal photopheresis preserves fertility in a GVHD mouse model by remodeling the testicular immune microenvironment.

BACKGROUND: Graft-versus-host disease (GVHD) is a major complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Although male infertility is frequently observed in survivors, the direct role of GVHD in testicular injury and reproductive impairment remains poorly understood.

METHODS: We employed mouse models of syngeneic and allogeneic bone marrow transplantation to investigate the impact of acute GVHD (aGVHD) on testicular function and fertility. Comprehensive assessments included testicular histopathology, seminiferous tubule structural integrity, sperm count, serum reproductive hormone profiling (testosterone, LH, FSH), and fertility analysis through mating trials. The testicular immune microenvironment was characterized by flow cytometric analysis of immune cell populations, along with measurements of inflammatory cytokines (IL-1β, IL-6) and oxidative stress markers (MDA, GSSG, GSSG/GSH). Extracorporeal photopheresis (ECP) was administered to evaluate its fertility-preserving effects in aGVHD mice.

RESULTS: In the aGVHD model, we observed severe testicular atrophy, disrupted spermatogenesis and infertility. Mechanistically, aGVHD disturbed testicular immune homeostasis, evidenced by a reduction in regulatory T cells (Tregs) and M2 macrophages, a shift toward M1 polarization, elevated pro-inflammatory cytokines and increased oxidative stress. These alterations were associated with germ cell nuclear pyknosis, necrosis and subsequent spermatogenic failure. Treatment with ECP improved survival rates and clinical symptoms and reversed the testicular damage by restoring Treg populations and M2-like macrophage polarization, attenuating local inflammation and oxidative damage, and ultimately preserving sperm count and male fertility in mice with established aGVHD.

CONCLUSIONS: Our study demonstrates that aGVHD directly targets the testis and disrupts its immune-privileged microenvironment, leading to functional impairment and infertility, independently of conditioning-related injury. Furthermore, we provide evidence that ECP, a clinically available immunomodulatory therapy, improves testicular function and may preserve male fertility in a murine model of aGVHD.