miR-324 mediates bone homeostasis through the regulation of osteoblast and osteoclast differentiation and activity

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.10.548366v1?rss=1 Authors: Hayman, D. J., Lin, H., Prior, A., Charlesworth, G., Johnson de Sousa Brito, F. M., Hao, Y., Patel, K., Soul, J., Clark, I. M., Pirog, K. A., Barter, M. J., van 't Hof, R. J., Young, D. A. Abstract: microRNAs (miRNAs) are non-coding RNAs which modulate the expression of other RNA molecules. One miRNA can target many transcripts, allowing each miRNA to play key roles in many biological pathways. miR-324 is a miRNA previously implicated in bone and cartilage maintenance, defects of which result in common age-related diseases, such as osteoporosis or osteoarthritis (OA). In global miR-324-null mice cartilage damage was increased in both surgically and ageing-induced OA, despite minimal changes to the cartilage transcriptome, with few predicted miR-324 targets dysregulated. However, micro-computed tomography and histology demonstrated that global miR-324-null the mice had an increase in bone mineral density, trabecular thickness and cortical thickness, with many parameters increasing with age. The bone marrow of miR-324-null mice also had reduced lipid content while and in vivo TRAP staining revealed a decrease in osteoclasts, with histomorphometry demonstrating an increased rate of bone formation in miR-324-null mice. Ex vivo assays revealed that the high bone mass phenotype of the miR-324-null mice resulted from increased osteoblast activity and decreased osteoclastogenesis. RNA-seq and qRT-PCR followed by miR-324 target prediction and validation in osteoblasts, osteoclasts and bone marrow macrophages identified the osteoclast fusion regulator Pin1 as a miR-324 target in the osteoclast lineage and the master osteogenic regulator Runx2 as a target of miR-324-5p in osteoblasts, the in vitro overexpression of which recapitulated the increased osteogenesis and decreased adipogenesis phenotype observed in vivo. These data point to important roles of miR-324 in skeletal biology with altered bone homeostasis in miR-324-null mice potentially causal for the increased cartilage damage observed during OA and ageing. Elucidation of pathways regulated by miR-324 offer promise for the treatment of bone diseases such as osteoporosis. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC