Thymopentin alleviates premature ovarian failure in mice by activating YY2/Lin28A and inhibiting the expression of let-7 family microRNAs

Objective: Thymopentin (5TP) significantly improved typical murine premature ovarian failure (POF) symptoms induced by a high-fat and high-sugar (HFHS) diet. However, its effect and mechanism remain unclear.

Materials and methods: RNA-Seq was used to detect the differentially expressed genes among each group. HFHS-induced POF mouse model was generated and injected with siRNA using Poly (lactic-co-glycolic acid) (PLGA) as a carrier.

Results: RNA-Seq suggested that 5TP promoted the expression of Yin Yang 2 (YY2) in mouse ovarian granulosa cell (mOGC) of HFHS-POF mice. Luciferase reporter assay indicated that 5TP promoted the binding of YY2 to the specific sequence C(C/T)AT(G/C)(G/T) on the Lin28A promoter and promoted Lin28A transcription and expression. We continuously injected PLGA-cross-linked siRNA nanoparticles targeting YY2 into HFHS-POF mice (siYY2@PLGA), which significantly reduced the therapeutic effect of 5TP. siYY2@PLGA injection also significantly attenuated the upregulation of Lin28a expression in mOGCs induced by 5TP and enhanced the expression of let-7 family MicroRNAs, thereby inhibiting the proliferation and division of mOGCs. qPCR results showed that there was a significant difference in the expression levels of exosome-derived Yy2 mRNAs between POF patients and normal women, and that there was a specific correlation between the expression level of exosome-derived Yy2 and the peripheral concentrations of the blood Hormones pregnenolone, progesterone and oestradiol.

Conclusions: Thymopentin promotes the transcriptional activation of Lin28A via stimulating transcription factor YY2 expression, inhibits the activity of let-7 family MicroRNAs and alleviates the ageing of ovarian granulosa cells, ultimately achieving a therapeutic effect on POF in mice.