PDGF-AA promotes gap junction intercellular communication in chondrocytes via the PI3K/Akt pathway.

Background: Gap junction intercellular communication (GJIC) plays an important role in cell growth, development and homeostasis. Connexin 43 (Cx43) is an important half-channel protein responsible for gap junction formation. Platelet-derived growth factor AA (PDGF-AA) regulates the proliferation, migration, metabolism, apoptosis and cell cycle of chondrocytes. However, the role of PDGF-AA in gap junction intercellular communication in chondrocytes is not fully understood. In the current study, we performed experiments to explore the effect of PDGF-AA on GJIC and its underlying biomechanical mechanism.

Methods: qPCR was performed to determine the expression of PDGF, PDGFR and connexin family genes in chondrocytes and/or cartilage. A scrape loading/dye transfer assay was used to determine GJIC. Western blot analysis was applied to detect the expression of Cx43 and PI3K/Akt signaling pathway proteins. Immunofluorescence staining was utilized to examine protein distribution. Scanning electron microscopy was used to delineate the morphology of chondrocytes.

Results: Expression of PDGF-A mRNA was highest among the PDGF family in chondrocytes and cartilage tissues. PDGF-AA promoted functional GJIC formation in chondrocytes by upregulating the expression of Cx43. Enhanced functional GJIC formation in chondrocytes induced by PDGF-AA occurred through the activation of PI3K/Akt signaling and its nuclear accumulation.

Conclusion: For the first time, this study provides evidence demonstrating the role of PDGF-AA in cell-to-cell communication in chondrocytes through mediating Cx43 expression.