MicroRNAs in cartilage development, homeostasis, and disease.

microRNAs (miRNAs) regulate gene expression mainly at the posttranscriptional level. Many different miRNAs are expressed in chondrocytes, and each individual miRNA can regulate hundreds of target genes, creating a complex gene regulatory network. Experimental evidence suggests that miRNAs play significant roles in various aspects of cartilage development, homeostasis, and pathology. The possibility that miRNAs can be novel therapeutic targets for cartilage diseases led to vigorous investigations to understand the role of individual miRNAs in skeletal tissues. Here, we summarize our current understanding of miRNAs in chondrocytes and cartilage. In the first part, we discuss roles of miRNAs in growth plate development and chondrocyte differentiation. In the second part, we put a particular focus on articular cartilage and discuss the significance of variety of findings in the context of osteoarthritis, the most common degenerative joint disease.