Recipient-driven metabolic and epigenetic remodeling of donor hematopoietic cells after transplantation in Fanconi Anemia.

Background Haematopoietic cell transplantation (HCT) restores donor-derived haematopoiesis in Fanconi anaemia (FA) but leaves recipient stromal and other non-haematopoietic cells genetically uncorrected. We investigated to what extent the persistent FA recipient environment influences the metabolic, redox, inflammatory and epigenetic phenotype of donor-derived haematopoietic cells after HCT. Methods Peripheral blood and, when available, bone marrow samples were analysed from healthy donors, patients with FA before and after HCT, and severe aplastic anaemia (SAA) patients after HCT as transplant controls. Mitochondrial function, cellular energy status, oxidative damage, antioxidant responses and circulating cytokines were assessed. Healthy donor mononuclear cells were exposed to conditioned media from FANCA-deficient mesenchymal stromal cells or FA fibroblasts, with FANCA-corrected fibroblasts as controls. DNA methylation profiling, acute inflammatory stimulation and pharmacological targeting of inflammatory pathways or mitochondrial oxidative stress were also performed. Results Despite stable full donor chimerism, FA recipients retained a pro-inflammatory and pro-oxidative circulating environment after HCT that was not observed in SAA transplant controls. Donor-derived mononuclear cells exposed to this environment acquired a distinct dysfunctional phenotype characterized by impaired mitochondrial oxidative phosphorylation and energy homeostasis, compensatory antioxidant and stress-response activation, and persistent lipid and protein oxidation. These alterations remained detectable after 96 h of ex vivo culture, suggesting relatively stable cellular remodelling, and were accompanied by a DNA methylation profile that, although globally shifted toward the donor state, retained an intermediate FA-associated episignature. Mechanistically, conditioned media from FANCA-deficient stromal cells and FA fibroblasts reproduced mitochondrial and oxidative abnormalities in healthy donor cells, whereas FANCA-corrected fibroblasts did not. Pharmacological targeting of inflammatory pathways or mitochondrial oxidative stress improved energy homeostasis and reduced oxidative damage, supporting a contributory role for chronic inflammation and oxidative stress in the microenvironment-driven phenotype acquired by donor-derived cells. Conclusions HCT corrects FA haematopoiesis without fully normalising the recipient environment. Persistent exposure to the FA milieu promotes metabolic, redox, signalling and epigenetic remodelling of donor-derived haematopoietic cells after transplantation. These findings identify the recipient environment as a determinant of post-HCT cell biology and highlight chronic inflammation and oxidative stress as mechanisms contributing to donor-cell remodelling in FA.