Connexin37, not Cx40 and Cx43, is induced in vascular smooth muscle cells during coronary arteriogenesis

The hypothesis that an altered expression of gap junction (GJ) proteins, connexin37 (Cx37), Cx40 and Cx43 will contribute to adaptive arteriogenesis was tested in growing coronary collateral vessels (CV) of the do:: heart by immunoconfocal microscopy and transmission electron microscopy (TEM). We found that: (1) in the normal coronary system Cx37 and Cx40 H ere only expressed in endothelial cells (EC) from artery to capillary: (2) during collateral growth Cx37; was significantly induced in smooth muscle cells (SMC) from small-large arteries to precapillary arterioles (circle divide =15 mum), while Cx4() was still only present in EC: (3) both homogeneous and heterogeneous distribution of Cx37 M as observed in normal vessels (NV) and growing vessels (GV): (4) in mature vessels (MV), Cx3; was downregulated, similar to NV: (5) dual immunostaining revealed an inverse correlation between expression of Cs 3; and desmin in GV occurring prior to downregulation of x-smooth actin and calponin: (h) Cx43 was undetectable in any vascular cells, both in NV and GV: (7) GJ were not found ill SMC by TEM. Our data for the first lime show the profile of connexin expression in the coronary system and provide evidence For existence of CI proteins in capillaries, it is a novel finding that an altered expression of Cx37 is characteristic of adaptive arteriogenesis in the dog heart and may be used as a marker of vascular growth. Induced Cx3; may be an early signal indicating that SMC are responding to haemodynamic changes, i.e. increased shear stress. (C) 2001 Academic Press.