# BMSC‐Exosomes Combined With TGF‐β1 Enhance Meniscal Fibrochondrocyte Function: Implications for Cartilage Repair

## TL;DR

Combining exosomes from bone marrow stem cells with TGF-β1 improves the function of meniscal cells, offering a new treatment for cartilage injuries.

## Contribution

The novel contribution is demonstrating the synergistic effect of BMSC-Exos and TGF-β1 on enhancing meniscal fibrochondrocyte function.

## Key findings

- BMSC-Exos are crescent-shaped with an average size of 118 nm and express TSG101 protein.
- BMSC-Exos combined with TGF-β1 significantly enhance proliferation, migration, and DNA content in meniscal fibrochondrocytes.
- Fluorescently labeled BMSC-Exos are aggregated in meniscus fibrocartilage cells.

## Abstract

Meniscal healing is often limited because adult meniscal fibrochondrocytes (MFCs) possess inherently low proliferative and reparative capacities. Bone marrow mesenchymal stem cell‐derived exosomes (BMSC‐Exos) have recently emerged as promising cell‐free therapeutics with regenerative potential, whereas transforming growth factor‐β1 (TGF‐β1) is a well‐established chondrogenic factor. In this study, we investigated the potential synergistic effects of BMSC‐Exos and TGF‐β1 on MFC proliferation, migration, and extracellular matrix synthesis in vitro.

To explore the effects of BMSC‐Exos combined with TGF‐β1 on MFCs and to investigate new approaches for treating meniscus injuries.

BMSC‐Exos were extracted by differential centrifugation and identified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blotting. The meniscus fibrochondrocytes were treated with BMSC‐Exos, TGF‐β1, and BMSC‐Exos + TGF‐β1 for 24 h. The distribution of fluorescently labeled BMSC‐Exos in meniscus fibrochondrocytes was observed by fluorescence microscopy. The effects of BMSC‐Exos, TGF‐β1, and BMSC‐Exos + TGF‐β1 on the proliferation and migration of meniscus fibrochondrocytes were evaluated by CCK‐8 assay, DNA quantification, cell migration assay, and cell scratch assay.

(1) BMSC‐Exos are crescent‐shaped, with an average particle size of approximately 118 nm, and express the specific protein TSG101. (2) The results of immunofluorescence staining showed that BMSC‐Exos were aggregated in the fibrocartilage cells of the meniscus. (3) Compared with the blank control group (CON group), the proliferation and migration abilities of the fibrocartilage cells of the meniscus in the three experimental groups were all enhanced, among which the BMSC‐Exos + TGF‐β1 group had the most significant effect. (4) The DNA content of the cells in the three experimental groups was all higher than that of the CON group, and the DNA content of the cells in the BMSC‐Exos + TGF‐β1 group was the highest (p < 0.001).

The combined application of BMSC‐Exos and TGF‐β1 can more effectively promote the proliferation and migration of meniscus fibrocartilage cells, and holds promise as a new approach for the treatment of meniscus injuries.