MAP hydrogel promotes revascularization of human ovarian graft and integration with the hypothalamic-pituitary axis in a mouse model of primary ovarian insufficiency

Ovarian tissue cryopreservation and autotransplantation (OTCT) is a crucial fertility preservation strategy for patients facing gonadotoxic cancer treatments, but its clinical success is hampered by ischemic injury and follicle loss following transplantation. This study aimed to enhance OTCT outcomes by employing microporous annealed particle (MAP) hydrogels to promote human ovarian graft revascularization. Unlike non-encapsulated tissue grafts, which exhibited early but transient and disorganized host vascular infiltration followed by regression, tissue grafts encapsulated in MAP hydrogels (OvaMAPs) demonstrated delayed yet organized and stable, long-term revascularization. OvaMAPs had significantly greater mouse CD31 ⁺ tissue area and vessel length after 3 and 6 weeks post-transplantation in ovariectomized immunodeficient mice compared to non-encapsulated grafts. By 20 weeks, both groups restored physiological estradiol levels (with OvaMAPs reaching 158 pg/mL) and suppressed follicle-stimulating hormone, confirming integration of the grafts with the hosts' hypothalamic-pituitary axes. Notably, OvaMAPs achieved comparable endocrine function restoration with reduced estradiol variability, indicating more consistent graft function. In conclusion, MAP hydrogel encapsulation promoted long-term graft revascularization and vascular stability after OTCT, ultimately supporting consistent endocrine integration with host physiology.