LIPUS-mediated mechanotransduction activates the YAP/TAZ/SCX axis and enhances tenogenesis-associated responses in tendon stem cells.

Tendon healing is frequently accompanied by fibrosis, scar formation and incomplete functional recovery. Tendon stem cells (TSCs) are central to tendon regeneration; however, the molecular basis by which low-intensity pulsed ultrasound (LIPUS) regulates their tenogenesis-associated behavior through mechanotransduction remains incompletely understood. In the present study, it was investigated whether LIPUS enhances tenogenesis-associated responses and matrix-related gene expression in rat TSCs through the YAP/TAZ/SCX signaling axis. Public transcriptomic data from the Gene Expression Omnibus database (GSE273466) were analyzed to identify differentially expressed genes and enriched pathways associated with LIPUS exposure. Primary rat Achilles tendon-derived TSCs were isolated, expanded and characterized by morphology and flow cytometry. Passage-3 TSCs were assigned to the Control, LIPUS and LIPUS + Verteporfin (VP) groups. Cell migratory behavior was evaluated using a scratch assay. Immunofluorescence staining, western blotting and reverse transcription-quantitative PCR were performed to assess the expression of YAP, TAZ, SCX, COL I and TNMD. Transcriptomic analysis indicated that LIPUS enriched mechanotransduction-related, cytoskeleton-associated, and YAP/TAZ-related signaling programs, together with enhanced SCX-associated signatures. Cultured cells exhibited a typical TSC phenotype, characterized by positive expression of CD90, CD105 and CD146 and negative expression of CD11b, CD34 and CD45. LIPUS increased scratch closure at 24 and 48 h and upregulated YAP, TAZ, SCX, COL I and TNMD at the protein and/or mRNA level. These effects were attenuated by VP treatment. In conclusion, LIPUS enhances a tenogenesis-associated molecular phenotype in TSCs and promotes matrix-related gene expression, at least in part through mechanotransduction-dependent activation of YAP/TAZ signaling and upregulation of SCX. These findings provide mechanistic support for further investigation of LIPUS as a strategy for tendon regeneration.