Immortalized functional endothelial progenitor cell lines from umbilical cord blood for vascular tissue engineering.

Endothelial progenitor cells (EPCs) play a significant role in multiple biological processes such as vascular homeostasis, regeneration, and tumor angiogenesis. This makes them a promising cell of choice for studying a variety of biological processes, toxicity assays, biomaterial-cell interaction studies, as well as in tissue-engineering applications. In this study, we report the generation of two clones of SV40-immortalized EPCs from umbilical cord blood. These cells retained most of the functional features of mature endothelial cells and showed no indication of senescence after repeated culture for more than 240 days. Extensive functional characterization of the immortalized cells by western blot, flow cytometry, and immunofluorescence studies substantiated that these cells retained their ability to synthesize nitric oxide, von Willebrand factor, P-Selectin etc. These cells achieved unlimited proliferation potential subsequent to inactivation of the cyclin-dependent kinase inhibitor p21, but failed to form colonies on soft agar. We also show their enhanced growth and survival on vascular biomaterials compared to parental cultures in late population doubling. These immortalized EPCs can be used as a cellular model system for studying the biology of these cells, gene manipulation experiments, cell-biomaterial interactions, as well as a variety of tissue-engineering applications.