Cultured aortic smooth muscle cells from newborn and adult rats show distinct cytoskeletal features

It is well known that arterial smooth muscle cells (SMC) of adult rats, cultured in a medium containing fetal calf serum (FCS), replicate actively and lose the expression of differentiation markers, such as desmin, smooth muscle (SM) myosin and alpha-SM actin. We report here that compared to freshly isolated cells, primary cultures of SMC from newborn animals show no change in the number of alpha-SM actin containing cells and a less important decrease in the number of desmin and SM myosin containing cells than that seen in primary cultures of SMC from adult animals; moreover, contrary to what is seen in SMC cultured from adult animals, they show an increase of alpha-SM actin mRNA level, alpha-SM actin synthesis and expression per cell. These features are partially maintained at the 5th passage, when the cytoskeletal equipment of adult SMC has further evolved toward dedifferentiation. Cloned newborn rat SMC continue to express alpha-SM actin, desmin and SM myosin at the 5th passage. Thus, newborn SMC maintain, at least in part, the potential to express differentiated features in culture. Heparin has been proposed to control proliferation and differentiation of arterial SMC. When cultured in the presence of heparin, newborn SMC show an increase of alpha-SM actin synthesis and content but no modification of the proportion of alpha-SM actin total (measured by Northern blots) and functional (measured by in vitro translation in a reticulocyte lysate) mRNAs compared to control cells cultured for the same time in FCS containing medium. This suggests that heparin action is exerted at a translational or post-translational level. Cultured newborn rat aortic SMC furnish an in vitro model for the study of several aspects of SMC differentiation and possibly of mechanisms leading to the establishment and prevention of atheromatous plaques.     

Astrocytoma derived short-term cell cultures retain molecular signatures characteristic of the tumour in situ

The heterogeneity of tumours and uncertainties surrounding derived short-term cell cultures and established cell lines fundamentally challenge the research and understanding of tumour growth and development. When tumour cells are cultured, changes are inevitably induced due to the artificial growth conditions. Several recent studies have questioned how representative established cell lines or derived short-term cell cultures are of the tumour in situ. We have characterised gene expression changes induced by short-term culture in astrocytoma in order to determine whether derived short-term cell cultures are representative of the tumour in situ. In comparison to the majority of studies, paired biopsies and derived short-term cultures were investigated to reduce the effects of long-term culture and inter-tumour variability when comparing biopsies and derived cultures from tumours with the same histology from different individuals. We have used the Affymetrix GeneChip^® U133A to generate gene expression profiles of 6 paediatric pilocytic astrocytoma (PA) biopsies and derived short-term cell cultures and 3 adult glioblastoma multiforme (GBM) biopsies and derived short-term cultures. Significant differential gene expression is induced by short-term culture. However, when the biopsy and derived short-term cell culture samples were grouped according to tumour type (PA and GBM) a molecular signature of 608 genes showed significant differential expression between the groups. This gene cohort can distinguish PA and GBM tumours, regardless of the sample source, suggesting that astrocytoma derived short-term cultures do retain key aspects of the global tumour expression profile and are representative of the tumour in situ. Furthermore, these genes are involved in pathways and functions characteristic of adult GBM including VEGF signalling, hypoxia and TP53 signalling.