Follicle dynamics and granulosa cell differentiation in the turkey hen ovary

Abstract

Similar to the domestic hen ovary, entry of a follicle into the preovulatory hierarchy in the turkey hen represents a process in which a single follicle initiates rapid growth and final maturation prior to ovulation. Published data derived from the laying hen support the proposal that differentiation of the follicle granulosa cell (GC) layer begins coincident with entry into the rapid growth phase and is characterized by the initial capacity for follicle stimulating hormone (FSH)-mediated cell signaling. The present studies were conducted with photostimulated B.U.T. Big 6 turkey hens to compare follicle dynamics and cellular mechanisms to those in the laying hen. The measurement and weights of turkey ovarian follicles greater than 1 mm in diameter revealed a discrete size hierarchy that was maintained throughout follicle development. GC layers collected from the single follicle initiating rapid growth (at the 11 to 13 mm stage of development) and incubated, in vitro, for 3 h with recombinant human (rh) FSH (10 ng/mL) responded with significantly increased steroidogenic acute regulatory protein (STAR) mRNA expression and progesterone production. The same treatment induced minimal STAR expression and no significant progesterone accumulation in GCs from 8 to 9 mm follicles (prior to the rapid growth phase). By comparison, dispersed GCs from 8 to 9 mm follicles pre-cultured for 18 h followed by a 3 h challenge with rhFSH resulted in significantly increased STAR expression plus progesterone production. Significantly, such cultured GCs pretreated for 15 min with transforming growth factor alpha (TGFα; 10 ng/mL) completely prevented both rhFSH-induced STAR expression and progesterone production. Culture of GCs from 8 to 9 mm follicles for 21 h with Bone Morphogenetic Protein 6 (BMP6) increased both cholesterol side-chain cleavage enzyme (CYP11A1) and FSH receptor mRNA (FSHR) expression. BMP6 also enhanced rhFSH-induced STAR expression, and this effect was blocked by TGFα. Collectively, these results support a conservation of mechanisms that maintain a hierarchy of follicles throughout development plus initiate FSH-responsiveness and GC differentiation as the recruited follicle enters the rapid growth phase in these closely related species.

Characterization of reproductive hormones and related gene expression in the hypothalamus and pituitary gland in the egg-laying interval in White King pigeon

“…Maximal FSH and FSHR levels in the early stages of development may be essential for folliculogenesis ( Allan et al, 2006 ; Lei et al,2010 ). The upregulation of FSHR expression on the preovulatory follicle prompted ovulation ( Ghanem and Johnson, 2018 ), which was in accordance with our results. In addition, the ovulation in birds was induced by the stimulatory action of pituitary LH ( Mellouk et al, 2018 ).…”

Genome-Wide Gene Expression Profiles Reveal Distinct Molecular Characteristics of the Goose Granulosa Cells

“…The number of follicles in the goose was found to decrease from SWF to LYF, while the diameters and the weights increased simultaneously ( Figure 1A ), which is consistent with that of the other poultry, ( Johnson, 2015 ; Gao et al, 2019 ). These results suggested that follicle selection occurs in the pre-hierarchical follicles rather than in the hierarchical ones, and the number of hierarchical follicles instead remains unchanged suppressing the follicle selection consistent with that in other poultry, along with the increase in the follicular diameters and weight ( Ghanem and Johnson, 2018 ). Moreover, the thickness of the granulosa cell layer was found to increase and then decrease in the LYF follicles ( Figures 1C,D ), which were consistent with the findings of a previous study on the histological study of the pre-hierarchical follicles in goose ( Dong et al, 2014 ).…”

Immunohistochemistry and Expression Profile of Estrogen Receptor 2 Gene in Different Grade Size Ovarian Follicles of Leizhou Black Ducks

“…LYF is an important reserve follicle that develops into grade follicles and its development and recruitment may affect the ovulation cycle of poultry (59). In that order, the recruited SWF, LWF, SYF, and LYF have a high probability of entering the grade follicular stage (40,60,61). Therefore, ESR2 was localized in SWF, LWF, SYF, and LYF to enhance their growth and development for recruitment and selection into the hierarchical order in Leizhou black duck.…”