Hematopoietic cells are a source of nidogen-1 and nidogen-2 during mouse liver development

Nidogen-1 and -2 are key components of basement membranes (BMs). Despite the presence of nidogen molecules in the parenchyma of the developing liver, no BMs are formed therein. This suggests that, in the liver, nidogens may also have functions other than BM formation. As a first step toward the elucidation of the possible cell biological functions of nidogens in the developing liver, we aimed to study their cellular origin. We localized expression of nidogen-1 and nidogen-2 on prenatal days 12, 14, and 16 in the developing mouse liver using in situ hybridization at the light and electron microscopic level and light microscopic immunohistochemistry. Our results show that nidogens are produced both in portal anlagen and in the parenchyma during liver development. In the parenchyma, transcripts can be found in hepatocytes, precursors of stellate cells, endothelial cells and, most interestingly, hematopoietic cells. Using real-time PCR, we found that the gene expression for both proteins shows a decrease from day 14 to day 16 concomitant with a decrease in the hepatic hematopoiesis. We suggest that nidogens may, to some extent, take part in the regulation of hepatic hematopoiesis.