Engineering a biomimetic matrix to promote development of human ovarian follicles in vitro

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The long-term goal of the proposed research is to establish a broad fertility preservation option for women undergoing gonadotoxic anticancer treatments and facing infertility. The overall objective of this proposal in working towards the presented goal and mitigating the risks associated with autotransplantation is to create a biomimetic environment that promotes human follicle development from the primordial stage in vitro. The low success rates of small follicle culture are largely attributed to the complex and poorly understood paracrine, autocrine and endocrine signaling between follicular cells, neighboring follicles, and stromal cells. The central hypothesis is that transcriptional profiling of human follicles will reveal mechanisms driving development and recreating the ovarian microenvironment through design of a biomimetic hydrogel which retains cell-secreted extracellular matrix (ECM) will support human follicle development in vitro. The rationale for the proposed work is that by deciphering the mechanisms driving follicle activation and early development, and recapitulating the natural ovarian microenvironment in an ECM-sequestering hydrogel, future culture systems can be translated to the clinic for maturation of cryopreserved ovarian follicles and subsequent fertilization and pregnancy. In the first aim, single cell RNA sequencing will be used to profile human ovarian follicles and supportive stromal cells. In the second aim, ECM-sequestering peptides will be incorporated in a biomimetic poly (ethylene glycol) (PEG) hydrogel system using Michael-type addition chemistry to promote deposition of ECM components and mimic the native ovarian tissue. The follicle’s basement membrane is composed of ECM proteins and it functions as structural support for follicular cells, a selective barrier for molecules entering the follicle, and a scaffold for retaining soluble growth factors and cytokines. It is continuously remodeled during follicle development, but cell- secreted ECM molecules are unable to adhere to unmodified PEG for self-assembly. By integrating ECM- sequestering peptides in the PEG hydrogels, the structural and biological roles of ECM can be restored for in vitro follicle development. The contribution of this work will be a single cell atlas of the reproductive-age ovary highlighting mechanisms driving follicle development and stromal cells’ supportive roles in folliculogenesis and a novel in vitro follicle culture system that supports human follicle development. The contribution of this work will be significant because it will guide the development of a standardized in vitro culture for maturation of human follicles and a safe fertility preservation option for patients unable to produce mature eggs as a result of gonadotoxic treatments. The proposed work is innovative in that it will be the first single cell dataset from healthy reproductive aged women and the first instance of human follicle culture in a synthetic ECM-sequestering matrix.