CONNEXIN43 GAP JUNCTION LEVELS DURING DEVELOPMENT OF THE THORACIC AORTA ARE TEMPORALLY CORRELATED WITH ELASTIC LAMINAE DEPOSITION AND INCREASED BLOOD-PRESSURE

A characteristic property of the vascular smooth muscle cell is its ab ility to modulate between a contractile phenotype, responsible for con trol of vascular tone and tension, through to a synthetic phenotype, c apable of migration and synthesis of extracellular matrix molecules. S mooth muscle cells are coupled by gap junctions, the membrane structur es which permit direct intercellular passage of ions and small molecul es, and which play a role both in electrical coupling and intercellula r communication during patterning and development. We have previously found that connexin43 type gap junction expression is upregulated in t he synthetic phenotype smooth muscle cell in vitro and during atherosc lerotic plaque formation in human coronary arteries. On the basis of i mmunohistochemical labelling, confocal laser scanning microscopy and d igital image analysis, we now report that relatively high levels of co nnexin43 are expressed during development of the rat thoracic aorta, t emporally correlating with reported periods of smooth muscle cell prol iferation and secretion of elastic laminae. A major peak in expression occurs at seven days post-natal, with a second less pronounced peak a t 72 days post-natal. The principal peak in gap junction levels appear s to coincide with increased post-natal blood pressure and aorta media thickening. The amount of gap junction labelling falls off to normal adult levels as the smooth muscle cells modulate towards the contracti le phenotype and growth is completed. The results indicate an associat ion between direct cell-to-cell communication and synthetic phenotype smooth muscle cell activity during aortic growth and patterning. (C) 1 997 Academic Press Limited.