Mesenchymal stem cell exosomes regulate TGFβ/Smad3 by decreasing the METTL3-NEAT1 axis to inhibit scar progression after breast surgery.

BACKGROUND

Scars are traces of tissue loss left behind by connective tissue overgrowth and repair. Studies in recent years have shown that mesenchymal stem cell exosomes (MSC-Exo) have the ability to inhibit and repair cutaneous scarring, but their specific role in post-breast surgery scar formation and the mechanisms behind it remain enigmatic.

METHODS

Extraction and characterization of exosomes from mesenchymal stem cells (MSCs). Western Blot and RT-qPCR were used to evaluate the expression of fibrillar protein and TGF-β/Smad3 in mammary hypertrophic scar fibroblasts (MHSFs) stimulated with MSC-Exo, sh-METTL3, sh-NEAT1 and their negative controls. Construction of a mouse model of proliferative scar formation using mechanical tension and detection of fibronectin and pathway protein expression using Western Blot and RT-qPCR. Pathologic changes of mammary scarring in mice using HE staining, Masson staining and immunofluorescence.

RESULTS

Both in vitro and in vivo, MSC-Exo, sh-METTL3 and sh-NEAT1 were shown to decrease the expression of COL1A1, COL3A1, α-SMA, fibronectin, TGF-β, p-Smad2/Smad2, p-Smad3/Smad3, by Western Blot and RT-qPCR. In addition, improved lesions and reduced collagen deposition were observed in mice by HE and Masson assays.

CONCLUSIONS

In summary, our study revealed that exosomes of MSCs function through the m6A methyltransferase METTL3, which regulates the NEAT1/TGF-β/Smad3 axis to slow down the rate of scar formation after breast surgery.