Transcriptomic profiling confirms microRNA-140 is more functional in joint development than in disease

To investigate the distinct roles of microRNA-140 (miR-140) in skeletal development and osteoarthritis (OA), and to identify novel miR-140-5p targets using advanced transcriptomic profiling.

A global Mir140-null mouse model was generated using CRISPR-Cas9 for phenotyping and histological analysis of skeletal development. For OA studies, mice underwent destabilisation of the medial meniscus (DMM) surgery, with cartilage damage and osteophyte formation evaluated histologically, complemented with transcriptomic profiling of medial epiphyseal tissue. To pinpoint miR-140-5p role in development, RNA sequencing of costal chondrocytes and spatial transcriptomics of hind limb growth plates from 7-day-old mice were employed to provide zonal resolution of gene expression changes.

Mir140-null mice exhibited skeletal defects, including reduced long bones and craniofacial abnormalities, consistent with previous studies. Transcriptomic analysis of growth plate chondrocytes revealed a significant enrichment of upregulated predicted miR-140-5p targets, impacting relevant pathways. Spatial transcriptomics uniquely revealed miR-140-5p's most pronounced functional role to resting chondrocytes and, unexpectedly, the perichondrium. In contrast, following DMM, Mir140-null mice showed only a modest increase in cartilage damage compared to controls, with no significant enrichment of predicted miR-140-5p within the upregulated differentially expressed genes. However, osteophyte formation was altered, with evidence of delayed development in null mice.

miR-140-5p is indispensable for skeletal development, orchestrating endochondral ossification through regulation of chondrocyte proliferation and differentiation, with distinct activity in resting zone chondrocytes and the perichondrium identified by spatial transcriptomics. In contrast, its influence on post-traumatic OA is modest, with limited impact on cartilage degeneration but a role in modulating osteophyte formation.