Comparison of the Effects of Recombinant and Native Prolactin on the Proliferation and Apoptosis of Goose Granulosa Cells

In poultry, prolactin (PRL) plays a key role in the regulation of incubation behavior, hormone secretion, and reproductive activities. However, previous in vitro studies have focused on the actions of PRL in ovarian follicles of poultry, relying on the use of exogenous or recombinant PRL, and the true role of PRL in regulating ovarian granulosa cell (GC) functions in poultry awaits a further investigation using endogenous native PRL. Therefore, in this study, we first isolated and purified recombinant goose PRL protein (rPRL) and native goose PRL protein (nPRL) using Ni-affinity chromatography and rabbit anti-rPRL antibodies-filled immunoaffinity chromatography, respectively. Then, we analyzed and compared the effects of rPRL and nPRL at different concentrations (0, 3, 30, or 300 ng/mL) on the proliferation and apoptosis of both GCs isolated from goose ovarian pre-hierarchical follicles (phGCs) and from hierarchical follicles (hGCs). Our results show that rPRL at lower concentrations increased the viability and proliferation of both phGCs and hGCs, while it exerted anti-apoptotic effects in phGCs by upregulating the expression of Bcl-2. On the other hand, nPRL increased the apoptosis of phGCs in a concentration-dependent manner by upregulating the expressions of caspase-3 and Fas and downregulating the expressions of Bcl-2 and Becn-1. In conclusion, this study not only obtained a highly pure nPRL for the first time, but also suggested a dual role of PRL in regulating the proliferation and apoptosis of goose GCs, depending on its concentration and the stage of follicle development. The data presented here can be helpful in purifying native proteins of poultry and enabling a better understanding of the roles of PRL during the ovarian follicle development in poultry.