The roles of the microrna 29 family in cartilage homeostasis and osteoarthritis

TLDR: The miR-29 family was found to be the negative regulator in both human and murine chondrogenesis, and was also found to involve in murine limb development.

Abstract: MicroRNAs are short endogenous non-coding RNA molecules, typically 19-25 nucleotides in length, which negatively regulate gene expression. In osteoarthritis (OA), several genes necessary for cartilage homeostasis are aberrantly expressed, with a number of miRNAs implicated in this process. However, our knowledge of the earliest stages of OA, prior to the onset of irreversible changes, remains limited. The purpose of this study was to identify miRNAs involved across the time-course of OA using both a murine model and human cartilage, and to define their function. Expression profile of miRNAs (Exiqon) and mRNAs (Illumina) on total RNA purified from whole knee joints taken from mice which underwent destabilisation of the medial meniscus (DMM) surgery at day 1, 3 and 7 post-surgery showed: the miRNA expression in whole mouse joints post DMM surgery increased over 7 days; at day 1 and 3, the expression of only 4 miRNAs altered significantly; at day 7, 19 miRNAs were upregulated and 15 downregulated. Among the modulated miRNAs, the miR-29b was the most interesting and was chosen to further investigate since integrating analysis of the miRNA and mRNA expression array data showed the inverse correlation between miR-29b and its potential targets. In end-stage human OA cartilage and in murine injury model, the miR-29 family was found to increase expression. Moreover, the miR-29 family was found to be the negative regulator in both human and murine chondrogenesis, and was also found to involve in murine limb development. Expression of the miR-29 family was found to suppress by SOX9 at least in part through directly binding to the promoter of the primary miR-29a/b1. Also, TGFβ1/3 decreased expression of the miR-29 family whilst Wnt3a did not have any effect. Lipopolysaccharide suppressed the miR-29 family expression in part through NFκB signalling pathway while the IL-1 strongly induced its expression partly through P38 MAKP signalling. Using luciferase reporter assay, the miR-29 family was showed to suppress the TGFβ, NFκB, and WNT/β-catenin signalling pathways. Gene expression profiles of gain- and-loss-of-function revealed regulation of a large number of previously recognised extracellular matrix-associated genes as well as an additional subset of protease and Wnt signalling pathway-related genes. Among these genes, ADAMTS6, ADAMTS10, ADAMTS14, ADAMTS17, ADAMTS19, FZD3, DVL3, FRAT2, CK2A2 were experimentally validated as direct targets of the miR-29 family.