Small extracellular vesicles with LncRNA H19 "overload": YAP Regulation as a Tendon Repair Therapeutic Tactic.

Functional healing of tendon injuries remains a great challenge. Small extracellular vesicles (sEVs) have received attention as pro-regenerative agents. H19 overexpression could bring tendon regenerative ability, but the mechanism is still not fully elucidated, and reliable method for delivery of long non-coding RNAs (LncRNAs) was demanded. We identified the downstream mechanism of H19, the activation of yes-associated protein (YAP) via the H19-PP1-YAP axis. We established tendon stem/progenitor cells (TSPCs) stably overexpressing H19 with CRISPR-dCas9-based hnRNP A2/B1 activation (H19-CP-TSPCs). H19-OL-sEVs (H19 "overloading" sEVs) could be produced effectively from H19-CP-TSPCs. Only H19-OL-sEVs were able to significantly load large amounts of H19 rather than other competitors, and the potential of H19-OL-sEVs to promote tendon healing was far better than that of other competitors. Our study established a relatively reliable method for enrichment of LncRNAs into sEVs, providing new hints for modularized sEV-based therapies, and modularized sEVs represented a potential strategy for tendon regeneration.