Porcine Ovarian piRNA Dynamics: A Comparative Study During Follicular Atresia

Follicular atresia is a natural process of follicular degeneration in mammal ovaries, significantly impacting female reproductive potential. However, the underlying regulatory mechanisms remain underexplored, particularly those involving non-coding RNAs like PIWI-interacting RNAs (piRNAs). In this study, we collected single antral follicles from the ovaries of 180-day-old commercial sows, classified them as healthy (HF) and atretic (AF) based on morphological and biochemical criteria, and sequenced the RNA samples using the Illumina Hiseq 3000 system (San Diego, CA, USA). piRNAs were identified using three algorithms, and the differential expression was compared and validated by qPCR. The target genes of differentially expressed piRNAs were predicted and subjected to functional analysis. A total of 452 piRNAs were identified across all samples, with 103 showing differential expression between HFs and AFs. Among the top 12 piRNAs with the most significant expression differences validated by qPCR, 5 (piR-23, piR-27, piR-64, piR-65, and piR-76) exhibited statistically significant differences. Pathway analysis showed that these piRNAs primarily targeted genes involved in cell apoptosis regulation, inflammation and oxidative stress response, substance transport and signal transduction, and cellular structural integrity maintenance. Our study provides the first comprehensive profile of piRNAs in porcine ovarian follicles during atresia and reveals underlying potential regulatory mechanisms. These findings enhance our understanding of piRNA functions during the early follicular atresia process and offer insights for further functional studies and biomarker development in ovarian pathology.