Bone Morphogenetic Protein 15 (BMP-15) Improves In Vitro Mouse Folliculogenesis

SIMPLE SUMMARY: Multilayered secondary follicles were encapsulated and cultured for 12 days in a 3D culture system by using alginate supplemented with bone morphogenetic protein 15 (BMP-15). Alginate is used in in vitro culture systems to mimic the natural ovarian environment by maintaining the 3D follicular architecture, cell–cell interactions, and paracrine signals underlying direct follicle development. Typically employed for follicle culture, alginate prepared at a concentration of 0.5% w/v led to considerable developmental competence and steroidogenesis. BMP-15 is a member of the superfamily of transforming growth factor-beta (TGF-β), a protein that is necessary for ovarian follicular growth. This protein functions primarily by attaching to its receptor on the surface of granulosa cells, which are also essential for the development of ovarian follicles. Regarding observations of follicle growth, in vitro culture using 0.5% alginate supplemented with 15 ng/mL BMP-15 can promote the production of mature oocytes and increase steroidogenesis. However, mature oocytes retrieved in vitro were subject to hypoxia conditions. ABSTRACT: Multilayered secondary follicles were encapsulated in a 0.5% alginate matrix and cultured in a 3D culture system supplemented with bone morphogenetic protein 15 (BMP-15; 15 ng/mL) for 12 days. The in vitro development of ovarian follicles was evaluated. On day 12, the follicle diameter, follicle survival rate, and antrum formation rate were significantly higher for follicles cultured in BMP-15-supplemented medium than those cultured in regular medium. The percentage of ovulated metaphase II oocytes retrieved from follicles cultured in BMP-15-supplemented medium was greater than that of oocytes retrieved from follicles cultured in regular medium. The secretion of P4 was significantly higher on days 6, 8, and 10 in follicles cultured in BMP-15-supplemented medium. The result for E2 tended toward significance on day 12. Intracellular reactive oxygen species levels were higher and glutathione levels were lower in mature oocytes from the in vitro culture than in mature oocytes from an in vivo control. A 3D culture system using an alginate matrix and supplemented with BMP-15 effectively improves the outcomes of in vitro ovarian follicle culture.