miR-29b as an Anti-Fibrotic Therapeutic: Mechanisms, Disease Biology and Translational Opportunities

Fibrosis emerges when normally self-limiting tissue repair fails to resolve and overlapping phases of injury, stromal activation, extracellular matrix (ECM) deposition and remodelling become sustained. MicroRNAs (miRNAs) shape this transition by coordinating signalling, cell-state and matrix programmes. Functionally, pro-fibrotic fibro-miRs amplify fibrogenic pathways, whereas anti-fibrotic miRNAs restrain fibroblast activation and ECM production; the miR-29 family is a principal member of the latter group. This review examines miR-29 family organisation, the regulation of miR-29b by transforming growth factor-β (TGF-β)/Smad and additional transcriptional and inflammatory inputs, and the molecular targets through which miR-29b controls collagen synthesis, processing and crosslinking. Direct canonical targets are distinguished from experimentally supported, predicted and indirect pathway components. Evidence is evaluated across fibroblasts and myofibroblasts, epithelial and endothelial cells, and pulmonary, hepatic, renal, cardiac, dermal and ocular fibrosis models. Therapeutic translation is considered in relation to miR-29b mimics and agomirs, local and tissue-targeted delivery, pharmacokinetics, dose control, off-target repression, immune activation and long-term safety. Overall, miR-29b remains a credible network-level anti-fibrotic candidate, but successful translation requires cell- and disease-specific target validation, selective delivery and preservation of physiological wound repair.