Radiosensitivity and sublethal damage repair in human umbilical cord vein endothelial cells

The assessment of the comparative radiosensitivity of different parenchymal cells is potentially of great importance in clinical radiotherapy. Previous studies from various laboratories using vessel regeneration techniques have demonstrated that endothelial cells are quite radioresistant, having a Do in excess of 250 rads. The present studies were undertaken to investigate the radiosensitivity of human endothelial cells obtained from umbilical cord veins (HEC) using "colony formation" as an endpoint, and to evaluate their ability to repair sublethal radiation damage (SLD). The endothelial origin of the cells in the surviving colonies was demonstrated by their positive staining for factor VIII antigen. The survival curve for HEC has a Do of about 165 rads, with a moderate initial shoulder. Dose fractionation studies demonstrate a moderate capability to repair SLD, comparable to other human cells studied including fibroblasts and other normal diploid cells in vitro. These studies indicate that HEC, being a terminally differentiated cell type with various differentiated markers, may prove useful in radiobiological and radiocarcinogenesis studies.