piR-27222 alleviates dexamethasone-induced osteoporosis by inhibiting ferroptosis through modulating WWP1

Glucocorticoid-induced osteoporosis (GIOP) is the most common cause of secondary osteoporosis. Piwi-interacting RNA (piRNA) represents a novel class of small non-coding RNAs. However, the role and potential mechanism of piRNA in GIOP remain unclear. Differentially expressed genes (DEGs) during the chondrogenic and osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) and in osteoblasts treated with dexamethasone were screened. Osteogenic differentiation and adipogenic differentiation of hBMSCs were induced, and a rat GOIP model was constructed. qRT-PCR was used to screen the differentially expressed piRNAs (piR-27222). MiRDB and TargetRank databases were used to screen the potential target genes of piR-27222, and the key target gene was further screened by topological analysis based on protein-protein interaction network. The potential binding sites of piR-27222 and WW domain-containing protein 1 (WWP1) were predicted using miRanda database, which were verified by Dual-luciferase reporter gene assay. The piR-27222 was then selectively modulated in hBMSCs via transfection, and the piR-rno-27222 antagonist was injected into GIOP rats through the tail vein. The viability of hBMSCs was detected using CCK-8 and colony formation assay. Alizarin red staining and oil red O staining were respectively used to evaluate the osteogenic and adipogenic differentiation of hBMSCs. The bone formation area of GIOP rats was detected by H&E staining. The contents of glutathione, malonaldehyde and Fe2+ were detected using the corresponding kits. The expression of piRNAs was detected by qRT-PCR, and the expression levels of osteogenic differentiation markers runt-related transcription factor 2 and osteopontine, WWP1, as well as ferroptosis-related proteins were detected by Western blot. piR-27222 was significantly down-regulated in the GIOP rat model and significantly up-regulated during the osteogenic differentiation of hBMSCs. Overexpression of piR-27222 could significantly promote the proliferation and viability of hBMSCs, and piR-27222 inhibitors could significantly inhibit the proliferation and viability of hBMSCs. Overexpression of piR-27222 could also significantly promote osteogenic differentiation of hBMSCs and inhibit adipogenic differentiation. In addition, piR-27222 could significantly inhibit ferroptosis of hBMSCs and GIOP rat models. WWP1 was identified as a target gene of piR-27222, and negatively regulated by it. piR-27222 inhibits ferroptosis by repressing WWP1, promotes osteogenic differentiation and suppresses adipogenic differentiation, and thereby alleviates dexamethasone-induced osteoporosis.