Expression of vimentin, TPI and MAT2A in human dermal microvascular endothelial cells during angiogenesis in vitro.

In vitro assays of angiogenesis face immense problems considering their reproducibility based on the inhomogeneous characters of endothelial cells (ECs). It is necessary to detect influencing factors, which affect the angiogenic potency of ECs. This study aimed to analyse expression profiles of vimentin (VIM), triosephosphate isomerase (TPI) and adenosylmethionine synthetase isoform type-2 (MAT2A) during the whole angiogenic cascade in vitro. Furthermore, the impact of knocking down vimentin (VIM) on angiogenesis in vitro was evaluated, while monitoring TPI and MAT2A expression. A long-term cultivation and angiogenic stimulation of human dermal microvascular ECs was performed. Cells were characterized via VEGFR-1 and VEGFR-2 expression and a shRNA-mediated knockdown of VIM was performed. The process of angiogenesis in vitro was quantified via morphological staging and mRNA-and protein-levels of all proteins were analysed. While native cells ran through the angiogenic cascade chronologically, knockdown cells only entered beginning stages of angiogenesis and died eventually. Cell cultures showing a higher VEGFR-1 expression survived exclusively and displayed an upregulation of MAT2A and TPI expression. Native cells highly expressed VIM in early stages, MAT2A mainly in the beginning and TPI during the course of angiogenesis in vitro. VIM knockdown led to a deceleration of angiogenesis in vitro and knockdown cells displayed expressional changes in TPI and MAT2A. Cell populations with a higher number of stalk cells emerged as being more stable against manipulations and native expression profiles provided an indication of VIM and MAT2A being relevant predominantly in beginning stages and TPI during the whole angiogenic cascade in vitro.