Objectives To compare DNA synthesis in isolated arteries of normotensive and hypertensive rats and to evaluate whether removal of the endothelium affects this process. Design Carotid and renal artery segments were isolated from normotensive Wistar, Wistar-Kyoto (WKY) and Sprague-Dawley rats, and from spontaneously hypertensive rats (SHR), transgenic Sprague-Dawley rats harbouring the mouse Ren-2 gene and from WKY rats rendered hypertensive by aortic coarctation. Methods Artery segments were exposed in vitro to serum with or without previous gentle removal of the endothelium. Nuclear incorporation of the thymidine analogue 5-bromo-2‘-deoxyuridine was visualized by immunocytochemistry and the percentage of labelled medial nuclei was determined. Results In both types of artery, obtained from 6-week-old WKY rats and from 6-week-old SHR, removal of endothelium increased the percentage of 5-bromo-2‘-deoxyuridine-labelled medial nuclei (L%). Also, in the arteries of 20-week-old Wistar rats, WKY rats and WKY rats rendered hypertensive by aortic coarctation and in vessels of 11-week-old Sprague-Dawley rats and Sprague-Dawley rats harbouring the mouse Ren-2 gene, removal of endothelium increased L%. Conversely, in the arteries of 20-week-old SHR removal of the endothelium did not alter L%. Furthermore, maximally stimulated DNA synthesis was considerably smaller in de-endothelialized arteries of adult SHR than in denuded vessels from the other strains and models. Conclusion These findings confirm that the endothelium can reduce DNA synthesis in the intact rat arterial smooth muscle. This effect is not modified by hypertension, but is selectively reduced in the arteries of adult SHR.
To evaluate whether intravascular phenomena contribute to local differences in growth responses of the arterial wall, we evaluated responses to organoid culture in a broad variety of arterial preparations. Arterial segments were isolated from adult, normotensive rats, sympathectomized, denuded from endothelium, and suspended in medium supplemented with serum. As judged from the nuclear incorporation of the thymidine analogue 5-bromo-2’-deoxyuridine (BrdUrd), this induced a transient stimulation of DNA synthesis in only a fraction of the arterial smooth muscle cells in all types of arteries. This intramedial DNA synthesis was more marked in renal arteries than in carotid arteries or aortae and was least pronounced in main pulmonary, femoral, and superior mesenteric artery and in mesenteric resistance-sized arteries. Organoid culture of isolated arteries did not increase the cross-sectional area of the media or the number of medial cells. It rather resulted in proliferation of smooth-muscle-like cells outside the media. In addition, smooth-muscle-like cells migrated out of the isolated arterial segments during culture. The rate of proliferation of these isolated cells did not differ between large arteries of different anatomical origin. However, isolated cells derived from mesenteric resistance arteries proliferated at a rate that was 4 times slower than that of large artery cells. The presence of endothelium significantly reduced medial DNA synthesis in carotid and renal artery segments, but not in mesenteric resistance-sized preparations. These data indicate that growth responses of the arterial wall differ quantitatively with the anatomical location and branching order of the vascular segment. In addition to the regional heterogeneity of endothelial effects on mitogenic responses of arterial smooth muscle, this seems to be due to regional differences in the susceptibility of arterial smooth muscle to exogenous growth factors. In this respect, we speculate that subsets of growth-resistant and growth-prone arterial smooth muscle cells could be heterogeneously distributed over the arterial tree.
Two cell lines with different in vitro growth characteristics were established from a single mucinous colonic adenocarcinoma. Epithelial cells of the line 5583-E demonstrated anchoragedependent growth while those of line 5583-S were anchorage-independent and grew as multicellular floating spheroids. Both cell lines shared common characteristics with respect to the expression of differentiation markers (secretory component, carcinoembryonic antigen), mucins and karyotype (trisomy 12 and 14, marker chromosome) but also showed consistent differences. In nude mice 5583-S cells formed moderately differentiated mucinous adenocarcinomas with high carcinoembryonic antigen and mucin production, whereas 5583-E xenografts were poorly differentiated and almost entirely failed to produce carcinoembryonic antigen and mucins. The plating efficiency of 5583-E cells appeared to be greater and doubling time shorter than those of 5583-S cells. Furthermore, 5583-E cells showed an extra isochromosome, lq. The cell lines were genotypically and phenotypically stable over a period of 2 years. Our results reemphasize that multiple cell lines with heterogeneous phenotypic and genotypic characteristics can be obtained from a single primary tumor.
