Encapsulation of ovarian allograft precludes immune rejection and promotes restoration of endocrine function in immune-competent ovariectomized mice

Premature ovarian insufficiency (POI) is a significant complication of cytotoxic treatments due to extreme ovarian sensitivity to chemotherapy and radiation. POI is particularly devastating for young girls reaching puberty, because it irreversibly affects their physical and cognitive development. Changes occurring during puberty determine their height, bone health, insulin responsiveness, lipid metabolism, cardiovascular health and cognition. The only available treatment for POI during puberty is hormone replacement therapy (HRT), which delivers non-physiological levels of estrogen, lacks other ovarian hormones and pulsatility, and is not responsive to feedback regulation. Here we report that ovarian allografts encapsulated in a hydrogel-based capsule and implanted in ovariectomized mice restore ovarian endocrine function in immune competent mice. Ovarian tissue from BALB/c mice was encapsulated in poly(ethylene-glycol) (PEG) hydrogels, with a proteolytically degradable core and a non-degradable shell. The dual capsules were implanted subcutaneously in immune competent ovariectomized C57BL/6 mice for a period of 60 days. As expected, non-encapsulated ovarian allografts implanted in a control group sensitized the recipients as confirmed with donor-specific IgG in the serum, which increased 26-fold in the 3 weeks following transplantation (p = 0.02) and infiltration of the graft with CD8 T cells consistent with allo-immunity. In contrast, encapsulation in the Dual PEG capsules prevented sensitization to the allograft in all the recipients with no evidence of lymphocytic infiltration. In summary, the approach of hydrogel-based immunoisolation presents a minimally invasive and robust cell-therapy to restore hormonal balance in ovarian insufficiency. This report is the first to demonstrate the application of a tunable PEG-based hydrogel as an immunoisolator of allogeneic ovarian tissue to restore endocrine function in ovariectomized mice and prevent cell-mediated immune rejection in immune competent mice.