miRNA profiling reveals that gga-let-7i/COL1A2 axis induces cell cycle arrest and triggers cellular senescence to accelerate ovarian aging in laying hens by suppressing the PI3K/AKT/MDM2 pathway.

Reproductive senescence in laying hens, characterized by a progressive decline in egg production, represents a major challenge for the poultry industry. Although microRNAs (miRNAs) are recognized as important regulators of aging, their specific roles and mechanisms in ovarian aging of hens remain largely unclear. This study was designed to comprehensively analyze miRNA expression patterns during ovarian aging in laying hens. The objectives of this study were to identify key functional miRNAs and to elucidate their molecular regulatory mechanisms. Specifically, this study evaluated ovarian senescence in hens at 350, 500 and 700 days of age, observing a decline in egg production, increased follicular atresia, and p53 upregulation. miRNA sequencing analysis identified 44 differentially expressed miRNAs (DEMs), among which gga-let-7i exhibited the highest abundance and showed progressive upregulation during aging. Functional assays revealed that gga-let-7i induces cell cycle arrest and promotes cellular senescence in ovarian follicle granulosa cells (GCs). Mechanistically, collagen type I alpha 2 chain (COL1A2) was confirmed as a direct target of gga-let-7i, and it has been demonstrated that gga-let-7i accelerates senescence by inhibiting the COL1A2/PI3K/AKT/MDM2 pathway, resulting in p53 accumulation and the downstream cellular senescence signaling pathways activation. These results uncover a novel gga-let-7i/COL1A2 regulatory axis involved in ovarian aging and suggest potential targets for extending reproductive longevity in laying hens.