Synthesis and expression of smooth muscle phenotype markers in primary culture of rabbit aortic smooth muscle cells: influence of seeding density and media and relation to cell contractility.

Rabbit aortic smooth muscle cells (SMC) were seeded at moderate or high densities and grown either in the presence of serum or in the serum-substitution formula Monomed. Expression and synthesis of marker proteins caldesmon, calponin, smooth muscle myosin, and vinculin were monitored during SMC cultivation. Contractility was tested by the ability of cultured SMC to deform silicone membranes following ionomycin treatment. The results show that cells of moderate density grown in Monomed, as opposed to those grown in 5% serum, have the smooth muscle isoform of caldesmon 1.6-fold higher, calponin 1.4-fold and smooth muscle myosin 1.4-fold higher on Day 14 of cultivation. Synthesis of these proteins corresponded to their expression in SMC. The metavinculin:vinculin ratio slightly decreased over the first days with a following reestablishment on Day 8. Contraction was observed until Day 13, compared with Day 7 for cells grown in the presence of serum. High seeding density also prevented a decrease in the expression of smooth muscle markers with the exception of smooth muscle caldesmon whose content in the high density SMC culture was not significantly different from that in the moderate density culture. The period of contractility of SMC in the high density culture was also similar to that in the moderate density culture in the presence of serum. We conclude that cultivation of primary SMC in Monomed allows the maintenance of cells in the contractile phenotype more effectively than high initial seeding density.