Morphological study of endothelial cells in the human fetus during early period of gestation.

During the formation of blood vessels, proliferation and migration of endothelial cells (ECs) are one of the most important mechanisms. The development of the vessels involves two different mechanisms: vasculogenesis i.e. differentiation of ECs in situ from mesenchymal precursors, and angiogenesis i.e. sprouting of ECs from pre-existing vessels. The frontal lobes from 20 brains of human fetuses ranging from 8 to 17 weeks of gestation (GW) were subjected to correlative light and electron microscopic studies. Our observations demonstrate the sprouting of ECs from pre-existing vessels in leptomeninges (angiogenesis) during the formation of a capillary network of the fetal human brain. In addition, the study did not reveal after the 8th GW the mitotic proliferation of ECs in examined specimens which allows to underline the importance of sprouting and elongation of ECs channels for this phase of vascularization of cerebral hemispheres.