Selective enrichment of microRNAs in extracellular matrix vesicles produced by growth plate chondrocytes

• RNA is present in matrix vesicles (MVs) secreted by chondrocytes, in which small RNA is enriched.
• MV RNA is well-protected from degradation by the lipid membrane.
• Enrichment of specific miRNAs is consistently observed, suggesting selective packaging.
• MV-enriched miRNAs are related to major bone formation and metabolic signaling pathways.
• MVs as “matrisomes” are involved in cell–cell communication in cartilage and bone development.

Matrix vesicles (MVs) are membrane organelles found in the extracellular matrix of calcifying cells, which contain matrix processing enzymes and regulate the extracellular environment via action of these enzymes. It is unknown whether MVs are also exosomic mediators of cell–cell communication via transfer of RNA material, and specifically, microRNA (miRNA). We investigated the presence of RNA in MVs isolated from cultures of costochondral growth zone chondrocytes. Our results showed that the average yield of MV RNA was 1.93 ± 0.78 ng RNA/104 cells, which was approximately 0.1% of the parent cell's total RNA. MV RNA was well-protected from RNase by the lipid membrane and was highly enriched in small RNA molecules compared to cells. Moreover, coding and non-coding small RNAs in MVs were in proportions that differed from parent cells. Enrichment of specific miRNAs was consistently observed in all three miRNA detection platforms that we used, suggesting that miRNAs are selectively packaged into MVs. MV-enriched miRNAs were related to different signaling pathways associated with bone formation. This study suggests a significant role for MVs as “matrisomes” in cell–cell communication in cartilage and bone development via transfer of specific miRNAs.