Identification of the connective tissues synthesized by the venous and arterial endothelia of the human umbilical cord: a comparative study.

Immunocytochemistry has been used to identify endothelial cells in sections of human umbilical cord and in cultures of the venous and arterial endothelium, using Factor VIII and Ulex europaeus as endothelial markers. The connective tissue components, including various collagen types, fibronectin and laminin, were identified and localized in the cord and in both venous and arterial cultured endothelium. Interstitial collagens synthesized by the cultured cells were isolated and quantified. Angiogenic ability was examined. The effect of a noxious stimulus, 24 h hypoxia, was quantified in cultured venous endothelium. The results showed that cultured arterial endothelium possesses a vacuolated cytoplasm which is absent in venous endothelium. The major collagens observed in venous culture were types III and V; the latter was found mainly in the cell layer. Venous endothelium was angiogenic. It responded to hypoxia by producing fewer cells, more protein/10(6) cells but less collagen, both in absolute terms and as a percentage of protein/10(6) cells, thus behaving like cultured porcine and bovine aortic endothelium. Fibronectin was the major 'glue' associated with endothelium. We conclude that culture can reveal the synthetic potential of endothelium which the cord itself does not often show; moreover culture appears essential to demonstrate that arterial and venous endothelium behave differently from each other.