1α,25-Dihydroxyvitamin D Regulates microRNA Packaging in Extracellular Matrix Vesicles and Their Release in the Matrix.

Growth plate chondrocytes are regulated by numerous factors and hormones as they mature during endochondral bone formation, including transforming growth factor beta-1 (TGFb1), bone morphogenetic protein 2 (BMP2), insulin-like growth factor-1 (IFG1), parathyroid hormone and parathyroid hormone related peptide (PTH, PTHrP), and Indian hedgehog (IHH). Chondrocytes in the growth plate's growth zone (GC) produce and export matrix vesicles (MVs) under the regulation of 1α,25-dihydroxyvitamin D [1α,25(OH)D]. 1α,25(OH)D regulates MV enzyme composition genomically and 1α,25(OH)D secreted by the cells acts on the MV membrane nongenomically, destabilizing it and releasing MV enzymes. This study examined the regulatory role 1α,25(OH)D has over production and packaging of microRNA (miRNA) into MVs by GC cells and the release of miRNA by direct action on MVs. Costochondral cartilage GC cells were treated with 1α,25(OH)D and the miRNA in the cells and MVs sequenced. We also treated MVs with 1α,25(OH)D and determined if the miRNA was released. To assess whether MVs can act directly with chondrocytes and if this is regulated by 1α,25(OH)D, we stained MVs with a membrane dye and treated GC cells with them. 1α,25(OH)D regulated production and packaging of a unique population of miRNA into MVs compared to the vehicle control population. 1α,25(OH)D treatment of MVs did not release miRNA. Stained MVs were endocytosed by GC cells and this was increased with 1α,25(OH)D treatment. This study adds new regulatory roles for 1α,25(OH)D with respect to packaging and transport of MV miRNAs.