[Cell sources of liver development].

The work is devoted to consequent expression of different cell types' protein markers such as vimentin, desmin, cytokeratins 7, 18, 19, stem cell markers CD34 and Bcl-2 at early stages of human prenatal development. Desmin was revealed in sinusoidal liver cells on 3.5-12 weeks of gestation, in mesenchymal cells of ventral mesentery and hepatoblasts on the 4-7 accordingly. During hepatic period of blood formation such desmin positive sinusoidal cells were found to be located close to blood cells. So called "cholangio-" cytokeratins 7 and 19 showed different expression, the first one was found only in cholangiocytes, while cytokeratin 19 existed in hepatoblasts as well until week 15-16 of prenatal development. Mesenchymal cells of ventral mesentery are positive for cytokeratins 18 and 19 even brighter than hepatoblasts in the 4-7 weeks of gestation. Bcl-2 expression was seen in the same periods in most sinusoidal and mesenchymal cells of ventral mesentery. CD34 positive cells are strongly depicted in liver sinusoids from 4th until 9th weeks of gestation, but probably they are not a source of hepatocytes' development in embryonic ontogenesis. Ventral mesentery mesenchyme was negative for this very marker. These results let us suppose that hepatocytes and cholangiocytes may develop from quite different embryonic sources: cholangyocytes grow exceptionally from duodenum epithelial cells, while there is a strong possibility that hepatoblasts formation occurs with participation of mesenchymal cells.