Transcriptional profiling and growth kinetics of endothelium reveals differences between cells derived from porcine aorta versus aortic valve.

Abstract

Valvular tissue and aorta calcify at different rates when placed as fresh homografts or cryopreserved allografts. Furthermore, differences between valvular endothelial cells and aortic endothelial cells are not well appreciated. We established primary cultures of valve and aortic endothelial cells derived from swine and tested transcriptional and proliferative differences on various extracellular matrices. Transcriptional profiling was performed on primary cultures of porcine valve and aortic endothelial cells. We extracted total RNA from both cell types and created cDNA libraries. We scored for 847 genes important in signal transduction pathways, and measured their expression on valve and aortic endothelial cells. To determine if there were functional differences between aortic and valvular cells, their growth rate was determined by cell counting on various extracellular matrices. Of 847 genes investigated, 69 (8.1%) were transcriptionally active on aortic endothelial cells and 89 (10.5%) on valve endothelial cells. Common to both cell types were 55 genes, which represents 79.7% (55/69) of activated genes on aortic endothelial cells and 61.8% (55/89) of those in valve endothelial cells. Remarkable features of the analysis included Ephrin ligand and receptor specificity for cell type, a potential fibroblast growth factor autocrine loop in both cell types, as well as upregulation of the platelet-derived growth factor receptor in valvular cells. Aortic endothelial cells were noteworthy of upregulation of vascular endothelial cell growth factor-B and vascular cell adhesion molecule. Proliferation analysis revealed that valve endothelial cells grew more rapidly (12-fold over control) than aortic endothelial cells (3-fold over control). Furthermore, valve endothelial cells proliferated most rapidly on gelatin or collagen, whereas aortic endothelial cells were most proliferative on lysine or laminin. Valve and aortic endothelial cells have different transcriptional and proliferative profiles. The knowledge of these differences may be an exploitable strategy in the future rational design of artificially engineered valve surfaces and in the study of the valve antigenicity, immunogenicity and structural failure.