Exosomal MATN3 of Urine-Derived Stem Cells Ameliorates Intervertebral Disc Degeneration by Antisenescence Effects and Promotes NPC Proliferation and ECM Synthesis by Activating TGF- β

Our study suggests that reduced MATN3 can be considered a characteristic of intervertebral disc degeneration. USC-exos may represent a potentially effective agent for alleviating intervertebral disc degeneration by promoting NPC proliferation and ECM synthesis by transferring the MATN3 protein.

Low back pain (LBP) is one of the top three causes of disability in developed countries, and intervertebral disc degeneration (IDD) is a major contributor to LBP. In the process of IDD, there is a gradual decrease in nucleus pulposus cells (NPCs) and extracellular matrix (ECM). Exosomes are important exocrine mediators of stem cells that can act directly on cells for tissue repair and regeneration. In this study, we determined the antisenescence, cell proliferation promotion, and ECM modulation effects of human urine-derived stem cell (USC) exosomes (USC-exos) on degenerated intervertebral discs and explored the underlying mechanism.

The flow cytometry results showed that USCs were positive for CD29, CD44, and CD73, which are USC surface-specific markers, but negative for CD34 and CD45. In addition, USCs showed osteogenic, adipogenic, and chondrogenic differentiation potential. USC-exos exhibited a cup-shaped morphology, with a mean diameter of 49.7 ± 7.3 nm, and were positive for CD63 and TSG101 and negative for calnexin. USC-exos could promote NPC proliferation and ECM synthesis. The protein content of the matrilin family was significantly reduced in degenerative intervertebral discs, and the decrease in MATN3 was the most significant. USC-exos were found to be rich in MATN3 protein, and exosomal MATN3 was required for USC-exos-induced promotion of NPC proliferation and ECM synthesis, as well as alleviation of intervertebral disc degeneration in IVD rats. In addition, the effects of MATN3 in USC-exos were demonstrated to be achieved by activating TGF-β, which elevated the phosphorylation level of SMAD and AKT. Conclusions: Our study suggests that reduced MATN3 can be considered a characteristic of intervertebral disc degeneration. USC-exos may represent a potentially effective agent for alleviating intervertebral disc degeneration by promoting NPC proliferation and ECM synthesis by transferring the MATN3 protein.