Histological and developmental study of prehierarchical follicles in geese.

The development of the follicular wall and apoptosis of corresponding cells are dependent upon the stage of follicle growth and levels of endogenous hormones. However, the development and apoptosis of prehierarchical follicles in geese is insufficiently known. In order to obtain an understanding about the microstructure, development and apoptosis of prehierarchical follicles in geese, firstly, a histological method was used to investigate the morphological structure of prehierarchical follicles. Results showed that the thickness of granulosa cell layers of the follicular wall increased first, then decreased to the lowest when follicles grew to 9-10 mm in diameter, and the theca layers also thinned to the lowest thickness at the same stage. Moreover, the expression of follicle-stimulating hormone receptor (FSHR) mRNA and the enzyme activity of caspase-3 were analyzed and the results showed that the expression of FSHR was highest when follicles grew to 8-9 mm in diameter (p < 0.05); the enzyme activity of caspae-3 was the highest when follicles grew to 6-8 mm in diameter (p < 0.05). These collective findings suggested that follicles 6-10 mm in diameter were especially significant, and perhaps represent a turning point from growing follicles to dominant follicles to be selected into a hierarchical sequence or to other follicles to be degenerated during prehierarchical follicle development.