MicroRNA engineered umbilical cord stem cell-derived exosomes direct tendon regeneration by mTOR signaling

Zhixiao Yao,Shikun Wang,Xingyu Ouyang,Yun Qian,Cunyi Fan,Hao Xiong,Jiexin Ning,Juehong Li,Haomin Cui

doi:10.1186/s12951-021-00906-4

Abstract

BackgroundExosomes are extracellular vesicles of nano-structures and represent an emerging nano-scale acellular therapy in recent years. Tendon regeneration is a sophisticated process in the field of microsurgery due to its poor natural healing ability. To date, no successful long-term solution has been provided for the healing of tendon injuries. Functional recovery requires advanced treatment strategies. Human umbilical cord mesenchymal stem cell-derived exosomes (HUMSC-Exos) are considered as promising cell-free therapeutic agents. However, few studies reported their potential in the tendon repair previously. In this study, we explored the roles and underlying mechanisms of HUMSC-Exos in the tendon regeneration.ResultsExpression of tendon‐specific markers in, and collagen deposition by, tendon-derived stem cells (TDSCs) treated with HUMSC-Exos increased in vitro. In a rat Achilles tendon injury model, treatment with HUMSC-Exos improved the histological structure, enhanced tendon-specific matrix components, and optimized biomechanical properties of the Achilles tendon. Findings in miRNA sequencing indicated a significant increase in miR-29a-3p in HUMSC-Exo-treated Achilles tendons. Next, luciferase assay in combination with western blot identified phosphatase and tensin homolog (PTEN) as the specific target of miR-29a-3p. Furthermore, we applied a miR-29a-3p-specific agonist to engineer HUMSC-Exos. These HUMSC-Exos overexpressing miR-29a-3p amplified the gain effects of HUMSC-Exos on tendon healing in vivo. To explore the underlying mechanisms, a transforming growth factor-β1 (TGF-β1) inhibitor (SB-431542), mTOR inhibitor (rapamycin), and engineered HUMSC-Exos were employed. The results showed that TGF-β1 and mTOR signaling were involved in the beneficial effects of HUMSC-Exos on tendon regeneration.ConclusionThe findings in our study suggest that PTEN/mTOR/TGF-β1 signaling cascades may be a potential pathway for HUMSC-Exos to deliver miR-29a-3p for tendon healing and implicate a novel therapeutic strategy for tendon regeneration via engineered stem cell-derived exosomes.Graphic abstract

Highlights

Tendon injuries including tendon rupture are common in sports and workplaces
We pleasantly revealed that Human umbilical cord mesenchymal stem cell (HUMSC)-Exos overexpress miR-29a-3p amplified the effect of tendon healing by regulating the phosphatase and tensin homolog (PTEN) /mTOR/transforming growth factor-β1 (TGF-β1) signaling pathway
The nanoparticle tracking analysis (NTA) indicated an abundance of HUMSC-derived vesicles with an average diameter of 137.6 nm (Fig. 1B), further, the western blot analysis showed that exosomal specific markers including CD9, CD63, and Alix were positive (Fig. 1C)

Summary

Introduction

The hypocellular and hypovascular nature of tendon makes the healing a slow and inefficient process. The impaired motor function and shortened service life reduced the prognosis for tendon injuries due to compromised mechanical property of the poorly regenerated tendon [1, 2]. Yao et al J Nanobiotechnol (2021) 19:169 in understanding the pathogenesis of tendon development and tendon injury have hampered the advances in clinical treatments. Tendon regeneration is a sophisticated process in the field of microsurgery due to its poor natural healing ability. No successful long-term solution has been provided for the healing of tendon injuries. We explored the roles and underlying mechanisms of HUMSC-Exos in the tendon regeneration

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Discussion

Conclusion