AFFINITY-BOUND GROWTH FACTOR PLATFORMS TO PROMOTE THE IN VITRO MATURATION OF OVARIAN PRIMORDIAL FOLLICLES

In-vitro maturation (IVM) of early stage ovarian follicles has been a challenging task. Up to now, most efforts in this field have been focused on cultivation of secondary follicles in various hydrogels as a strategy for promoting maturation. Primordial follicles, the most infant, yet abundant follicular population, hold a great potential for women fertility preservation. Therefore, we are devising strategies to promote their maturation to fully functional follicles. We hypothesized that co-cultivation of primordial follicles with ovarian stromal cells in macroporous alginate scaffolds, supplemented with affinity-bound growth factors (GFs) would promote maturation of primordial follicles to functional follicles in vitro. Sulfation of alginate enabled affinity binding of GFs essential for primordial follicle maturation, such as growth and differentiation factor-9 (GDF-9, K_D = 76.6n ) and bone morphogenetic protein-7 (BMP-7, K_D=187.9 nM). We observed that alginate-sulfate (alg-S) and GFs co-assemble to nanoparticles (NPs). Impregnating the scaffolds with GF/alg-S NPs led to a dramatic increase in follicle diameters (up to 200µm), formation of developed three dimensional structure, significant increase in AMH and GDF-9 gene expression and elevated estradiol secretion, in comparison to when GFs are provided as soluble to pristine alginate scaffolds. We conclude that affinity binding of GFs to scaffolds presents the factors in a more natural way and sustained manner, thus contributing to their better effect on maturation of primordial follicles in vitro.