Integrated analysis of transcriptome and metabolomic uncover molecular mechanisms of ovarian aging in laying hens

Ovarian aging shortens the productive lifespan and diminishes economic value of poultry, yet its mechanisms are unclear. This study investigated ovarian aging using transcriptomics and metabolomics. Result suggested that the number of primitive, primary, and secondary follicles significantly reduced in aged hens, while atretic follicles increased. Ovaries showed fibrosis with increased collagen deposition, and the thickness of follicle granulosa cell layers was remarkably reduced, exhibiting a disorganized and loose structure. The mitochondria of granulosa cells in aged hens exhibited vacuolation and sparse cristae. Additionally, antioxidant (GSH-Px, SOD) and reproductive hormone (AMH, E2) levels were significantly lower in aged hens (p < 0.05). Transcriptomic analysis revealed altered pathways including PPAR, ECM-receptor interaction, and cytokine-cytokine receptor interaction in aging ovaries. Metabolomic profiling further implicated biosynthesis of unsaturated fatty acids and purine metabolism pathways in aging ovaries. Integrated analysis revealed that FABP4 was a critical mediator linking lipid metabolism and inflammation, and it showed a negative correlation with conjugated linoleic acids (CLA) and cis-4,7,10,13,16,19-docosahexaenoic acid (DHA), suggesting therapeutic potential of their dietary supplementation. To understand how lipid metabolism dysregulation induced ovarian aging, the expression of key genes was assessed by qRT-PCR. The expression of senescence markers (p16, p21, p53), apoptosis-related genes (Bax/Bcl-2) (p < 0.001), autophagy-related gene (p62) (p < 0.01) and inflammation-related genes (IL6, TNFα, NOS2) (p < 0.01) in aged hens signifficantly increased, while the expression of autophagy-related genes (LC3B/LC3A) decreased (p < 0.05). This work provides a theoretical basis for strategies to delay ovarian aging and improve reproductive efficiency.