Ovary

Activin and Follicle-Stimulating Hormone Signaling Are Required for Long-Term Culture of Functionally Differentiated Primary Granulosa Cells from the Chicken Ovary

Abstract

FSH, activin A and TGF- are important regulators of chicken granulosa cell (cGC) function. Hence, we aimed to test whether these growth factors are useful for establishing a suitable in vitro cell culture model system of primary cGC. Although cGC are easily isolated from distinct follicular stages, a long-term cGC culture system for in vitro studies has been unavailable as yet. We here report a novel long-term cell culture system that allows for cGC proliferation in vitro, while maintaining the epithelial phenotype granulosa cells exhibit in vivo. cGC rapidly lose their epithelial morphology and acquire a mesenchymal or fibroblastoid phenotype when cultured in the absence of activin A. This process is strongly enhanced by transforming growth factor alpha (TGF-), a well-known granulosa cell mitogen. However, FSH stimulates cGC proliferation without enhancing morphological changes and de-differentiation. Interestingly, a combination of both activin A and FSH stimulates cGC proliferation and supports maintenance of differentiated epithelial morphology. Furthermore, activin A and FSH synergistically induce granulosa cell-specific differentiation markers such as inhibin- and chicken zona pellucida protein C (chZPC), suggesting that cultured cGC resemble functionally differentiated granulosa cells. Our data demonstrate that activin signaling is necessary to sustain a morphologically differentiated phenotype of cGC in vitro. The results also suggest a pivotal importance of activin signaling for granulosa cell function in vivo.