Effects of Osthole on Progesterone Secretion in Chicken Preovulatory Follicles Granulosa Cells

Dietary supplementation of osthole and icariin improves the production performance of laying hens by promoting follicular development

Osthole (Ost) and icariin (Ica) are extracted from traditional Chinese medicine Cnidium monnieri and Epimedii Folium, respectively, and both exhibit estrogen-like biological activity. This study aimed to determine the efficacy and safety of combining Ost with Ica on the production performance of laying hens and to explore their possible mechanisms. The production performance, egg quality, residues of Ost and Ica in eggs, serum reproductive hormone levels, expression of ovarian reproductive hormone receptor, proliferation of granulosa cells in small yellow follicles (SYF), and progesterone secretion in large yellow follicles (LYF) related genes and proteins expression were detected. The results showed that adding 2 mg/kg Ost + 2 mg/kg Ica to the feed increased the laying rate, average egg weight, Haugh unit, and protein height of laying hens. Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), and progesterone (P4) levels increased, and the expression of ovarian estrogen receptor (ER), follicle-stimulating hormone receptor (FSHR), and progesterone receptor (PGR) mRNA was up-regulated. Additionally, the mRNA and protein levels of steroidogenesis acute regulatory protein (StAR), cytochrome P450 side-chain cleavage (P450scc), and 3β-hydroxysteroid dehydrogenase (3β-HSD) increased in LYF. Furthermore, mRNA and protein levels of proliferating cell nuclear antigen (PCNA), cyclin E1, and cyclin A2 were up-regulated in SYF. The residues of Ost and Ica in egg samples were not detected by high-performance liquid chromatography (HPLC). In conclusion, dietary supplementation of Ost and Ica increased granulosa cells proliferation in SYF and increased P4 secretion in granulosa cells of LYF, ultimately improving the production performance of laying hens.

MFN2 regulates progesterone biosynthesis and proliferation of granulosa cells during follicle selection in hens

Follicle selection in hens refers to a biological process that only one small yellow follicle (SYF) is selected daily or near-daily for following hierarchical development (from F5/F6 to F1) until ovulation. MFN2 is a kind of GTPases located on the mitochondrial outer membrane, which plays a crucial role in mitochondrial fusion. This study aimed to elucidate the role of MFN2 in proliferation and progesterone biosynthesis of granulosa cells (GCs) during follicle selection in hens. The results showed that GCs began to produce progesterone (P4) after follicle selection, accompanied with changes from multi-layer with flat cells to single layer with cubic cells. MFN2 was detected in GCs of follicles from SYF to F1. After follicle selection, the expression level of MFN2 in GCs upregulated significantly, accompanied with increases in P4 biosynthesis, ATP production, mitochondrial DNA (mtDNA) copy numbers of granulosa cells. FSH (80 ng/mL) facilitated the effects of P4 biosynthesis and secretion, ATP production, mtDNA copy numbers, cell proliferation and the MFN2 transcription of granulosa cells from F5 (F5G) in vitro. However, FSH treatment did not promote P4 secretion in granulosa cells from SYF (SYFG) in vitro. Meanwhile, we observed that change fold of MFN2 transcription, ATP production, mtDNA copy numbers and cell proliferation rate in F5G after treatment with FSH were greater than those in SYFG. Furthermore, expression levels of MFN2 protein and messenger RNA in F5G were significantly higher than those in SYFG after treatment with FSH. P4 biosynthesis, ATP production, mtDNA copy numbers as well as cell proliferation reduced significantly in F5G with MFN2 knockdown. Oppositely, P4 biosynthesis, ATP production, mtDNA copy numbers and cell proliferation increased significantly in SYFG after the overexpression of MFN2. Our results suggest that the upregulation of MFN2 may be involved in the initiation of P4 biosynthesis, and promotion of GCs proliferation during follicle selection.

Effect of Heat Stress on Egg Production, Steroid Hormone Synthesis, and Related Gene Expression in Chicken Preovulatory Follicular Granulosa Cells

Simple Summary

The debilitating effects of heat stress on poultry production have been well documented. Heat stress already results in severe economic loss worldwide. Regarding the decline in the reproductive performance of heat-stressed hens, the exact mechanisms involved are still unknown. The present study was conducted to elucidate the molecular mechanisms underlying heat-stress-induced abnormal egg production in laying hens. Our results confirmed that laying hens reared under heat stress had impaired laying performance. Follicular granulosa cells cultured in vitro are sensitive to the effects of heat stress, showing an increase in apoptosis and cellular ultrastructural changes. These effects appeared in the form of heat-stress-elevated progesterone, with the increased expression of steroidogenic acute regulatory protein, cytochrome P450 family 11 subfamily A member 1, and 3b-hydroxysteroid dehydrogenase, along with inhibited estradiol synthesis through the decreased expression of follicle-stimulating hormone receptor and the cytochrome P450 family 19 subfamily A member 1. Collectively, laying hens exposed to high temperatures showed damage to granulosa cells that brought about a decline in egg production. This study provides a molecular mechanism for the abnormal laying performance of hens subjected to heat stress, which may help when developing novel strategies to reverse the adverse impact.

Abstract

This study was conducted to elucidate the molecular mechanisms underlying heat stress (HS)-induced abnormal egg-laying in laying hens. Hy-Line brown laying hens were exposed to HS at 32 °C or maintained at 22 °C (control) for 14 days. In addition, granulosa cells (GCs) from preovulatory follicles were subjected to normal (37 °C) or high (41 °C or 43 °C) temperatures in vitro. Proliferation, apoptosis, and steroidogenesis were investigated, and the expression of estrogen and progesterone synthesis-related genes was detected. The results confirmed that laying hens reared under HS had impaired laying performance. HS inhibited proliferation, increased apoptosis, and altered the GC ultrastructure. HS also elevated progesterone secretion by increasing the expression of steroidogenic acute regulatory protein (StAR), cytochrome P450 family 11 subfamily A member 1 (CYP11A1), and 3b-hydroxysteroid dehydrogenase (3β-HSD). In addition, HS inhibited estrogen synthesis in GCs by decreasing the expression of the follicle-stimulating hormone receptor (FSHR) and cytochrome P450 family 19 subfamily A member 1 (CYP19A1). The upregulation of heat shock 70 kDa protein (HSP70) under HS was also observed. Collectively, laying hens exposed to high temperatures experienced damage to follicular GCs and steroidogenesis dysfunction, which reduced their laying performance. This study provides a molecular mechanism for the abnormal laying performance of hens subjected to HS.