PRRX1/miR-143-3p signaling regulates homeostasis of antler reserve mesenchymal cells

The molecular regulation mechanisms for maintaining the homeostasis of mesenchymal stem cells still remains poorly defined. Antler reserve mesenchymal cells (RM cells) persist through the whole rapid antler growth stage as a reserved stem cell population capable of division and differentiation, that makes the RM cells a unique model in stem cell regulation and cancer mechanism studies. Herein, we sequenced and analyzed the extracellular vesicles (EVs) of RM cells in the growth center of antler, and identified a high expression level of miR-143-3p and its target genes IGF1R, TGF(31, BMP2, etc. The upstream positive regulatory factor PRRX1 of miR-143-3p was identified through ATAC and CUT-taq analysis, combined with dual luciferase assay. We showed that PRRX1 overexpression resulted in a decreased proliferation of RM cells and induced a higher expression of miR-143-3p. miR-143-3p enriched EVs derived from PRRX1 overexpression RM cells had an inhibitory effect on RM cells, osteosarcoma 143B cells (considered as excessive proliferation model for RM cells) and in vivo in osteosarcoma bearing mice, and the mRNA and protein levels of IGF1R were significantly reduced. We confirmed that miR143-3p enriched EVs inhibited 3D culture induced chondrogenic differentiation of RM cells and xenogeneic antler chondrogenesis through targeting TGF(31 and BMP2. Together, PRRX1 was identified as an activator of miR-143-3p, and higher amounts of miR-143-3p in EVs of RM cells could inhibit excessive proliferation, and help maintain the undifferentiated state of RM cells. We conclude that PRRX1/miR-143-3p signaling was a regulator of homeostasis of antler RM cells and was a potential regulator of osteosarcoma. Our findings are essential for advancing medical and biological sciences, providing new theoretical foundations and strategies for cancer treatment and tissue regeneration.