Enhancement of connexin 43 expression increases proliferation and differentiation of an osteoblast-like cell line

Bone cells form a functional syncytium as they are coupled by gap junctions composed mainly of connexin 43 (Cx43). To further understand the role of C x43 in bone cell growth and differentiation, we stably transfected Car45-ex pressing UMR 106-01 cells with Cx43 using an expression vector containing r at Cx43 cDNA Three stably transfected clones were analyzed, all of which sh owed altered expression of Cx43 and/or Cx45 as was obvious from immunocytoc hemistry and Northern blotting. Double whole-cell patch clamping revealed s ingle-channel conductances of 20 (Cx45) and 60 pS (Cx43). The overexpressio n of Cx43 led to an increase in dye coupling concomitant with elevated gap- junctional conductance. The phenotype of the transfected clones was charact erized by an increased proliferation (4- to 7-fold) compared to controls. M oreover, a transfectant clone with 10- to 12-fold enhanced Cx43 expression showed a significantly increased calcium content of the extracellular matri x and enlarged mineralization nodules, while alkaline phosphatase was moder ately increased. We conclude that enhanced gap-junctional coupling via Cx43 significantly promotes proliferation and differentiation of UMR cells. (C) 2001 Academic Press.