Interaction of aortic endothelial and smooth muscle cells in culture. Effect on glycosaminoglycan levels.

Co-cultivation of various intra- and interspecific combinations of pig and rat aortic endothelial cells (AEC) and smooth muscle cells (SMC) resulted in a marked increase in hyaluronic acid (HA) levels, a smaller but significant increase in sulphated glycosaminoglycans (GAG), and an increase in the HA/sulphated GAG ratio, compared with the separate culture of the two cell types. Culture of SMC in AEC-conditioned medium produced similar changes in GAG levels whereas SMC-conditioned medium had no effect on AEC GAG levels. These results add further support for the concept that epithelial cells in general can modulate the GAG composition of adjacent connective tissue and thereby influence its morphological and physiological properties. It is suggested that the normal amounts, types and distribution of GAG in the arterial wall, and especially in the intima, may be partly dependent on interaction between the endothelium and SMC. It is further suggested that injury to endothelium, with a consequent failure in this interaction, could lead directly to changes in intimal GAG composition that contribute to lesion development.