CTGF facilitates cell-cell communication in chondrocytes via PI3K/Akt signalling pathway

Gap junction intercellular communication (GJIC) is essential for articular cartilage to respond appropriately to physical or biological stimuli and maintain homeostasis. Connective tissue growth factor (CTGF), identified as an endochondral ossification genetic factor, plays a vital role in cell proliferation, migration and adhesion. However, how CTGF regulates GJIC in chondrocytes is still unknown. This study aims to explore the effects of CTGF on GJIC in chondrocytes and its potential biomechanism.

qPCR was performed to determine the expression of gene profile in the CCN family in chondrocytes. After CTGF treatment, CCK-8 assay and scratch assay were performed to explore cell proliferation and migration. A scrape loading/dye transfer assay was adopted to visualize GJIC in living chondrocytes. Western blot analysis was done to detect the expression of Cx43 and PI3K/Akt signalling. Immunofluorescence staining was used to show protein distribution. siRNA targeting CTGF was used to detect the influence on cell-cell communication.

The CTGF (CCN2) was shown to be the highest expressed member of the CCN family in chondrocytes. CTGF facilitated functional gap junction intercellular communication in chondrocytes through up-regulation of Cx43 expressions. CTGF activated PI3K/Akt signalling to promote Akt phosphorylation and translocation. Suppressing CTGF also reduced the expression of Cx43. The inhibition of PI3K/Akt signalling decreased the expressions of Cx43 and thus impaired gap junction intercellular communication enhanced by CTGF.

For the first time, we provide evidence to show CTGF facilitates cell communication in chondrocytes via PI3K/Akt signalling pathway.