The Role of Connexins and Pannexins in the Cell Communications of Bone Cells

Connexins and Pannexins play important roles in osteocytes and osteoblasts differentiation, intracellular signal transduction, maintenance of bone balance, and bone regeneration. This article reviews the progress and limitations of Connexins-mediated gap junctions and Pannexins mediated hemichannel in bone. Current research has shown that these molecules, in the form of gap junctions or separate hemichannels, deliver external stimuli to the skeletal system. However, little is known about the role of other cell types in bone development and homeostasis, such as pre-osteoblasts and bone marrow mesenchymal stem cells, in maintaining normality. In addition, at present, the most well-studied member of the Connexins family is Connexin43 (Cx43), while the roles and mechanisms of other members in bone development are still behind the veil. Gene-edited animal models provide basic information on the role of Connexins and Pannexins in the skeletal system, but the similarities and differences between Connexins and Pannexins remain to be discovered. Targeting a specific function of Connexins or Pannexins for bone stimulation and bone disease remains a challenge, with pharmacological selective overlap between channels, compensation of other subtypes, differences in methods for assessing channel function, and genetic changes associated with transgenic mouse models. Therefore, better tools and research pathways are needed to understand the role of these pathways in bone and cartilage. An essential task for future research will be to identify specific compounds that regulate Connexins or Pannexins subtypes to enable them to be used as pharmaceutical agents in the treatment of bone diseases, providing the possibility to develop new therapeutic strategies for improving bone health and treating diseases of the skeletal system.