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, co nnexin37 (Cx37), Cx40 and Cx43 will contribute to adaptive arteriogenesis w as tested in growing coronary collateral vessels (CV) of the do:: heart by immunoconfocal microscopy and transmission electron microscopy (TEM). We fo und that: (1) in the normal coronary system Cx37 and Cx40 H ere only expres sed in endothelial cells (EC) from artery to capillary: (2) during collater al growth Cx37; was significantly induced in smooth muscle cells (SMC) from small-large arteries to precapillary arterioles (circle divide =15 mum), w hile Cx4() was still only present in EC: (3) both homogeneous and heterogen eous distribution of Cx37 M as observed in normal vessels (NV) and growing vessels (GV): (4) in mature vessels (MV), Cx3; was downregulated, similar t o NV: (5) dual immunostaining revealed an inverse correlation between expre ssion of Cs 3; and desmin in GV occurring prior to downregulation of x-smoo th actin and calponin: (h) Cx43 was undetectable in any vascular cells, bot h in NV and GV: (7) GJ were not found ill SMC by TEM. Our data for the firs t lime show the profile of connexin expression in the coronary system and p rovide evidence For existence of CI proteins in capillaries, it is a novel finding that an altered expression of Cx37 is characteristic of adaptive ar teriogenesis in the dog heart and may be used as a marker of vascular growt h. Induced Cx3; may be an early signal indicating that SMC are responding t o haemodynamic changes, i.e. increased shear stress. (C) 2001 Academic Pres s.