Affinity-Binding Cytokine Platforms to Promote the In Vitro Maturation of Ovarian Primordial Follicles

In-vitro maturation (IVM) of early stage 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. One strategy is the co-cultivation of the primordial follicles with ovarian stromal cells within macroporous alginate scaffolds supplemented with growth factors/cytokines, presented as affinity-bound to the matrix. The affinity binding of the growth factors/cytokines to the alginate matrix has been achieved via their interactions with alginate-sulfate or hyaluronan-sulfate. Surface Plasmon Resonance (SPR) analysis proved the affinity binding of the sulfated polysaccharides to cytokines critical for folliculogenesis, such as the binding of sulfated HA to BMP-4 (KD=33.6 nM) and BMP-15 (KD=12.5 μM). Macroporous alginate scaffolds impregnated with the sulfated polysaccharides promoted the maturation of porcine primordial follicles. This was demonstrated by a dramatic increase (Over 400%) in follicular diameters (reaching up to 130 μm) and formation of visible cuboidal multi-layered granulosa cell support. These results lay the basis to utilize the affinity binding platform for the delivery and presentation of cytokines and growth factors important for follicle maturation, which may hold a great promise for the preservation of female fertility.