From this analysis comparing the PCOS and control groups, we chose ten piRNAs with significantly upregulated expression (pir-36441, pir-57942, pir-54998, pir-34896, pir-33221, pir-51671, pir-33226, pir-43997, pir-33405, and pir-36040) and ten piRNAs with significantly downregulated expression (pir-43772, pir-35414, pir-43771, pir-35413, pir-35469, pir-33065, pir-35463, pir-35468, pir-35467, and pir-33387) for further study, as shown in Fig. 4B. The gene discussed is PIR; the disease is polycystic ovary syndrome.