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Updated: Feb 2, 2026

Live Cell Imaging of the TGF- β/Smad3 Signaling Pathway In Vitro and In Vivo Using an Adenovirus Reporter System
Published on: July 30, 2018
TGF-β1 promotes gap junctions formation in chondrocytes via Smad3/Smad4 signalling
Qingxuan Wang1, Chenchen Zhou1, Xiaobing Li1
1State Key Laboratory of Oral Diseases, Orthodontics Department, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
Objectives:
Connexin-mediated functional gap junction intercellular communication (GJIC) has a vital role in development, homeostasis and pathology. Transforming growth factor-β1 (TGF-β1), as one of the most vital factors in chondrocytes, promotes cartilage precursor cell differentiation and chondrocyte proliferation, migration and metabolism. However, how TGF-β1 mediates GJIC in chondrocytes remains unclear. This study aims to determine the influence of TGF-β1 on GJIC in mouse chondrocytes and its underlying mechanism.
Methods:
qPCR and mRNA microarray were used to verify the expression of genes in the TGF-β and connexin families in cartilage and chondrocytes. A scrape loading/dye transfer assay was performed to explore GJIC. Western blot analysis was used to detect connexin43 (Cx43) and Smad signalling components. Immunofluorescence staining was performed to characterize protein distribution.
Results:
The TGF-β1 mRNA was the highest expressed member of the TGFβ super family in cartilage. TGF-β1 promoted functional GJIC through increased expression of Cx43. TGF-β1-mediated GJIC required the participation of TGF-β type I receptor. TGF-β1 activated Smad3 and Smad4 signalling to facilitate their nuclear translocation. The Smad3 and Smad4 signalling proteins bound to the promoter of Gja1 and thus initiated Cx43 gene expression.
Conclusions:
For the first time, these results revealed a vital role of TGF-β1 in cell-cell communication in chondrocytes via gap junction formation. We describe the regulatory mechanism, the involvement of TGF-β type I receptor and the nuclear translocation of Smad3/4.
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