The expression and localization of leptin and its receptor in goat ovarian follicles

Leptin, a hormone that was originally identified in adipocytes, has been implicated in the regulation of ovarian folliculogenesis through endocrine, autocrine and/or paracrine mechanisms. The aim of this study was to investigate the expression patterns of leptin (LEP) and its receptor (LEPRb) in different types of ovarian follicular cells from goats. In small follicles, the expression levels of LEP were higher (P<0.001) in granulosa cells than in theca cells, cumulus cells and oocytes. The expression of LEP in granulosa cells was higher (P<0.001) in small follicles than in large follicles. In large follicles, the expression of LEPRb was higher (P<0.05) in granulosa cells than in theca cells, cumulus cells and oocytes. Higher expression (P<0.05) of LEPRb was detected in granulosa cells isolated from large follicles than in granulosa cells isolated from small follicles. Immunohistochemical analyses revealed the presence of the LEP and LEPR proteins in follicles at all stages of development. The most intense staining for LEP and LEPR was observed in the cytoplasm of oocytes and the surrounding granulosa cells. In conclusion, it was demonstrated that leptin and its receptor are expressed at both the mRNA and protein levels in goat ovarian follicles. Furthermore, the presence of a leptin signaling system in the caprine ovary suggests a potential regulatory role for leptin in follicular development and the maturation of goat oocytes.