Inverse relationship between connexin43 and desmin expression in cultured porcine aortic smooth muscle cells

Our previous work has shown that in vascular tissues the elastic medial reg ions express high levels of the gap junctional protein, connexin43, but low levels of desmin, while the muscular medial regions express low levels of connexin43 but high levels of desmin, It is uncertain, however, whether thi s regional difference at the tissue level extends down to the level of the individual cell, or reflects an averaged relationship of groups of cells of different connexin43 and desmin expression. The present study has addresse d this question using cultured porcine aortic smooth muscle cells. Immunoco nfocal microscopic analysis of single-labeled cells showed that while smoot h muscle a-actin, calponin and vimentin were positively labeled in the majo rity of medial smooth muscle cells both in intact porcine aorta and corresp onding cultured cells, desmin and connexin43 labeling was highly heterogene ous. In the cultured cells, 0.3-0.5 % of cells mere found to be desmin-posi tive, and quantitative analysis after double labeling for desmin and connex in43 revealed that the desmin-positive cells were smaller, and contained si gnificantly lower numbers and smaller sizes of connexin43 gap-junctional sp ots than did desmin-negative cells. Our findings demonstrate that an invers e expression pattern of connexin43 and desmin holds true at the level of th e individual cell. This suggests a close relationship between intrinsic phe notypic control and the regulation of connexin43 expression in the arterial smooth muscle cell.