Tailored apoptotic vesicles promote bone regeneration by releasing the osteoinductive brake

Abstract

Accumulating evidence has demonstrated that apoptotic vesicles (apoVs) derived from mesenchymal stem cells (MSCs) play a vital role in bone regeneration, and possess superior capabilities compared to MSCs and other extracellular vesicles derived from MSCs (like exosomes). The osteoinductive effect of MSC-apoVs is attributed to their diverse contents, especially enriched proteins or microRNAs (miRNAs). To optimize their osteoinductive capacity, it is indispensable to determine the unique cargo profiles of MSC-apoVs. In our previous study, we established the protein landscape and identified the specific proteins of MSC-apoVs. However, the features and functions of miRNAs enriched in MSC-apoVs remain elusive. In this study, we compared MSCs, MSC-apoVs, and MSC-exosomes from two different types of MSCs. We established a unique miRNA map of MSC-apoVs and identified 7 miRNAs specifically enriched in apoVs compared to MSCs and MSC-exosomes, which can be used as apoV-specific miRNAs. Among these 7 specific miRNAs, hsa-miR-4485-3p is the most abundant and stable miRNA. Then, we explored whether it is the main motive force responsible for apoV osteoinductive function. Unexpectedly, hsa-miR-4485-3p enriched in apoVs is proven to inhibit osteogenesis but promote adipogenesis by targeting the AKT pathway. Tailored apoVs by downregulating hsa-miR-4485-3p exhibited a more powerful effect in bone regeneration than normal apoVs. Like releasing the brake, we acquired more powerful osteoinductive apoVs. In summary, we determined miRNA cargo, identified the specific miRNAs of MSC-apoVs, and constructed an optimized tailored apoVs with excellent osteo-inductivity which is promising in apoV-based therapy for bone regeneration.