TGF-β1 derived from macrophages contributes to load-induced tendon-bone healing in the murine rotator cuff repair model by promoting chondrogenesis. Issue 3 (10th March 2023)

• Record Type: Journal Article
• Authors: Wang, Linfeng; Li, Shengcan; Xiao, Han; Zhang, Tao; Liu, Yuqian; Hu, Jianzhong; Xu, Daqi; Lu, Hongbin
• Is Part Of: Bone & joint research. Volume 12:Issue 3(2023)
• Page Start: 219
• Page End: 230
• Publication Date: 2023-03-10
• Subjects: Musculoskeletal system -- Periodicals; 573.705
• DOI: 10.1302/2046-3758.123.BJR-2022-0368.R1
• Languages: English
• ISSNs: 2046-3758

Abstract

Abstract : Aims: It has been established that mechanical stimulation benefits tendon-bone (T-B) healing, and macrophage phenotype can be regulated by mechanical cues; moreover, the interaction between macrophages and mesenchymal stem cells (MSCs) plays a fundamental role in tissue repair. This study aimed to investigate the role of macrophage-mediated MSC chondrogenesis in load-induced T-B healing in depth. Methods: C57BL/6 mice rotator cuff (RC) repair model was established to explore the effects of mechanical stimulation on macrophage polarization, transforming growth factor (TGF)-β1 generation, and MSC chondrogenesis within T-B enthesis by immunofluorescence and enzyme-linked immunosorbent assay (ELISA). Macrophage depletion was performed by clodronate liposomes, and T-B healing quality was evaluated by histology and biomechanics. In vitro, bone marrow-derived macrophages (BMDMs) were stretched with CELLOAD-300 load system and macrophage polarization was identified by flow cytometry and quantitative real-time polymerase chain reaction (qRT-PCR). MSC chondrogenic differentiation was measured by histochemical analysis and qRT-PCR. ELISA and qRT-PCR were performed to screen the candidate molecules that mediated the pro-chondrogenic function of mechanical stimulated BMDMs. Results: Mechanical stimulation promoted macrophage M2 polarization in vivo and in vitro. The conditioned media from mechanically stimulated BMDMs (MS-CM) enhanced MSC chondrogenic differentiation, and mechanically stimulated BMDMs generated more TGF-β1. Further, neutralizing TGF-β1 in MS-CM can attenuate its pro-chondrogenic effect. In vivo, mechanical stimulation promoted TGF-β1 generation, MSC chondrogenesis, and T-B healing, which were abolished following macrophage depletion. Conclusion: Macrophages subjected to appropriate mechanical stimulation could polarize toward the M2 phenotype and secrete TGF-β1 to promote MSC chondrogenesis, which subsequently augments T-B healing. Cite this article: Bone Joint Res 2023;12(3):219–230.