PARTIAL CLONING OF RAT CD34 CDNA AND EXPRESSION DURING STEM CELL-DEPENDENT LIVER-REGENERATION IN THE ADULT-RAT

The sialomucin CD34 is expressed on human and mouse hematopoietic stem cells and is used as an important marker for isolating the hematopoie tic stem/progenitor cells, The involvement of hepatic stem cells in li ver regeneration under certain conditions in adult rats is now well su pported. The objective of the present research was to explore the idea that CD34 might also be expressed on hepatic stem cell progeny, Polym erase chain reaction (PCR)-based cloning of rat CD34 was partially acc omplished. During the hepatic stem cell activation (2-acetylaminofluor ene/partial hepatectomy [AAF/PH] model), the CD34 transcripts were inc reased and reached the peak level between 9 and 12 days after partial hepatectomy when the progenitor cells (e.g., oval cells, early hepatoc ytes in basophilic foci, and intestinal type of cells) are most abunda nt, Both in situ hybridization and immunohistochemistry, using anti-mo use CD34 antibody, which recognizes the cytoplasmic domain, clearly sh owed the expression of CD34 on oval cells as well as on endothelial ce lls of large hepatic vessels, In addition, bile ductular epithelial (B DE) cells both in the AAF/PH model and in normal liver expressed CD34, suggesting a close relationship between BDE cells and the hepatic ste m-cell compartment, Taken-together, the data indicate that CD34 would, similar to its role in the hematopoietic system, be an important prob e for characterizing the cellular biology of the hepatic stem-cell com partment.