lncRNA NEAT1 affects granulosa cell apoptosis and steroid biosynthesis via the miR-204-5p/ESR1 axis in ovarian aging

Long non-coding RNAs (lncRNAs) play an important role in ovarian aging by affecting the biological functions of granulosa cells (GCs) through multiple mechanisms. The lncRNA NEAT1 is significantly downregulated in aging ovaries; however, the exact regulatory mechanism has not been elucidated. In the current study, we aimed to investigate the effects of the lncRNA NEAT1 in GC functions during ovarian aging and explore its therapeutic potential. We observed that NEAT1 expression is downregulated in GCs of older patients with diminished ovarian reserve (DOR), which is closely associated with ovarian reserve function and assisted reproductive cycle outcomes. Functional assays revealed that NEAT1 promotes KGN cell proliferation by increasing the proportion of S-phase cells and inhibiting apoptosis. Bioinformatics analysis and a dual-luciferase reporter assay confirmed that NEAT1 acts as a miR-204-5p sponge and identified ESR1 as a miR-204-5p target gene, both of which were significantly differentially expressed in the GCs of older patients with DOR. Mechanistic experiments demonstrated that NEAT1 acts as a competitive endogenous RNA and adsorbs miR-204-5p through molecular sponging, which in turn promotes the expression of ESR1 and upregulates the expression of key enzymes (steroidogenic acute regulatory protein and cytochrome P450 family 19 subfamily A member 1) involved in steroid hormone synthesis. This induces estradiol biosynthesis and activates the downstream mitogen-activated protein kinase (MAPK) signaling pathway to promote the phosphorylation of extracellular signaling-related kinase and cyclic adenosine monophosphate response element binding protein, which affects the cell cycle and results in the promotion of proliferation and inhibition of apoptosis of KGN cells. Our results suggest that NEAT1 activates the downstream MAPK pathway through the miR-204-5p/ESR1 axis; regulates GC proliferation, apoptosis, and the cell cycle; and affects steroid biosynthesis. Therefore, NEAT1 represents a potential therapeutic target to delay ovarian aging.