1a,25-Dihydroxyvitamin D3 Regulates Packaging of microRNAs within 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. Chondrocytes in the growth plate's growth zone (GC cells) produce and export matrix vesicles (MVs) under the regulation of 1a,25-dihydroxyvitamin D3 [1a,25(OH)2D3]. 1a,25(OH)2D3 secreted by the cells acts on the MV membrane, releasing its contents. This study examined the regulatory role 1a,25(OH)2D3 has over the production and packaging of microRNA into MVs by GC cells and the ability to release microRNA from MVs once produced. We treated GC cells with 1a,25(OH)2D3 and then sequenced the microRNA in the cells and MVs. We also treated MVs with 1a,25(OH)2D3 and determined if the microRNA was released. To assess whether MVs can act directly with chondrocytes and if this is regulated by 1a,25(OH)2D3, we stained MVs with a membrane dye and treated GC cells with them. 1a,25(OH)2D3 regulated the production and packaging of microRNA into matrix vesicles. MVs did not release microRNA when treated with 1a,25(OH)2D3, indicating a heterogeneous MV population or a protective factor. Stained MVs were endocytosed by GC cells and this was increased with 1a,25(OH)2D3 treatment. This study adds new regulatory roles for 1a,25(OH)2D3 with respect to packaging and transport of MV microRNAs. Overall design: miRNA expression profiles of growth zone chondrocyte cells and matrix vesicles with either 24 hour vehicle (EtOH) or 1a,25-dihydroxyvitamin D3 treatment