INTIMAL PROLIFERATION IN AN ORGAN-CULTURE OF HUMAN INTERNAL MAMMARY ARTERY

Objective: Intimal smooth muscle cell proliferation is an early feature of atherosclerosis. Its progression is difficult to monitor in humans and previous studies have mostly relied on necropsy material. The aim of this study was therefore to establish whether intimal proliferation occurred in an organ culture of human internal mammary artery. Methods: Segments of freshly isolated internal mammary artery were maintained in standard tissue culture medium containing 30% calf serum for 14 d. Tissue viability (measured by ATP concentration) was maintained during processing and throughout the culture period [22(SEM 28) nmol ATP.g-1 wet weight on d 1 v 208(27) on d 14]. Results: Histological transverse sections of cultured internal mammary artery showed the development of a neointima containing smooth muscle cells identified by immunocytochemistry for alpha actin. Pulse labelling of cultures with [H-3]-thymidine showed proliferating cells predominantly in a neointimal layer with few dividing cells in the media. Cultured de-endothelialised vessels showed less neointimal thickening than cultured freshly isolated vessels [16(3) v 36(5) mum, p<0.0025] as well as a reduced number of dividing cells per mm of neointimal length [3.1(0.6) v 5.5(l.1), p<0.05]. Conclusions: Intimal proliferation occurred in organ culture of internal mammary artery. There is evidence for a factor derived from the endothelium, which may be important in the development of intimal proliferation.