Estrogen Enhances Endothelial Differentiation and Angiogenic Function of Adipose-Derived Stromal Cells to Improve Therapeutic Outcomes in Critical Limb Ischemia

Background: Aging, especially after menopause, reduces the quantity and function of adult stem cells. Estrogen deficiency impairs proliferation, differentiation, and regenerative capacity. This study evaluated whether estrogen enhances endothelial differentiation of adipose-derived stromal cells (ADSCs) and improves therapeutic efficacy in critical limb ischemia (CLI). Methods: Male-derived ADSCs were assessed in vitro for endothelial differentiation using flow cytometry, biochemical assays, and angiogenesis analyses. Therapeutic effects were tested in a rat CLI model using endothelial-differentiated ADSCs (ED-ADSCs) with or without 17β-estradiol (E2). An ovariectomized (OVX) model examined estrogen deficiency and supplementation in vivo. Results: E2 promoted endothelial differentiation, increasing ERα/ERβ expression and activating PI3K/Akt/eNOS and MAPK signaling. This led to elevated VEGF expression, enhanced tube formation, and increased CD34⁺, KDR⁺, and CD31⁺ cell populations. In vivo, E2-pretreated ED-ADSCs significantly improved blood flow recovery. Estrogen deficiency reduced endothelial progenitor populations, which were restored by E2 supplementation. Conclusions: Estrogen modulates endothelial-associated characteristics and angiogenesis-related responses of ADSCs via ER-associated signaling, and may contribute to improved functional outcomes in ischemic conditions. E2 preconditioning may represent a potential strategy for stem cell-based therapy in estrogen-deficient settings.