Gap junction-mediated cell-to-cell communication in oral development and oral diseases: a concise review of research progress

Homoeostasis depends on the close connection and intimate molecular exchange between extracellular, intracellular and intercellular networks. Intercellular communication is largely mediated by gap junctions(GJs), a type of specialized membrane contact composed of variable number of channels that enable direct communication between cells by allowing small molecules to pass directly into the cytoplasm of neighbouring cells. Although considerable evidence indicates that gap junctions contribute to the functions of many organs, such as the bone, intestine, kidney, heart, brain and nerve, less is known about their role in oral development and disease. In this review, the current progress in understanding the background of connexins and the functions of gap junctions in oral development and diseases is discussed. The homoeostasis of tooth and periodontal tissues, normal tooth and maxillofacial development, saliva secretion and the integrity of the oral mucosa depend on the proper function of gap junctions.Knowledge of this pattern of cell–cell communication is required for a better understanding of oral diseases. With the everincreasing understanding of connexins in oral diseases, therapeutic strategies could be developed to target these membrane channels in various oral diseases and maxillofacial dysplasia.

Transforming growth factor-β1-induced N-cadherin drives cell–cell communication through connexin43 in osteoblast lineage

Gap junction(GJ)has been indicated to have an intimate correlation with adhesion junction.However,the direct interaction between them partially remains elusive.In the current study,we aimed to elucidate the role of N-cadherin,one of the core components in adhesion junction,in mediating connexin 43,one of the functional constituents in gap junction,via transforming growth factor-β1(TGF-β1)induction in osteoblasts.We first elucidated the expressions of N-cadherin induced by TGF-β1 and also confirmed the upregulation of Cx43,and the enhancement of functional gap junctional intercellular communication(GJIC)triggered by TGF-β1 in both primary osteoblasts and MC3T3 cell line.Colocalization analysis and Co-IP experimentation showed that N-cadherin interacts with Cx43 at the site of cell–cell contact.Knockdown of N-cadherin by siRNA interference decreased the Cx43 expression and abolished the promoting effect of TGF-β1 on Cx43.Functional GJICs in living primary osteoblasts and MC3T3 cell line were also reduced.TGF-β1-induced increase in N-cadherin and Cx43 was via Smad3 activation,whereas knockdown of Smad3 signaling by using siRNA decreased the expressions of both N-cadherin and Cx43.Overall,these data indicate the direct interactions between N-cadherin and Cx43,and reveal the intervention of adhesion junction in functional gap junction in living osteoblasts.