Abstract

BACKGROUND
Preadipocyte factor-1/Delta-like 1(Pref-1/Dlk1) is a type I membrane protein that has six epidermal growth factor (EGF)-like repeats in its extracellular and a short cytoplasmic domain. It is widely expressed in embryonic tissues, whereas its expressions were limited in adult and postnatal stage. To characterize the Pref-1 expressing cells during pancreas development and regeneration after birth, we analyzed Pref-1 expression in embryonic and adult partial pancreatectomized rat pancreas, and primary cultured neonatal pig pancreatic cells. METHODS: Whole fetuses or pieces of rat pancreas were obtained at E20. 90% partial pancreatectomy (Px) and sham operation were done using 5 week-old Sprague-Dawley rats. Experimental animals were divided into 11 groups by time of killing after surgery; 0, 1, 3, 6 and 12 hours, 1, 2, 3, 5, 7, and 14 days. All tissues were immunostained with Pref-1 and analysed by reverse transcriptase (RT)-PCR. Porcine neonatal pancreas cell clusters (NPCCs) were prepared from neonatal pigs aged 1-2 days. Cells were harvested on day 0, 3, 4, 5, 6, and 7 after dispersion. All cells were immunostained with Pref-1 and other specific cell markers such as Pan-cytokeratin (Pan-CK), vimentin (VT) and islet hormones, and confirmed by Western blot, RT-PCR and fluorescence activated cell sorting (FACS) analysis. RESULTS: In the rat embryonic pancreas at E20, Pref-1 expression was restricted only in the small branching ductules. In adult rat pancreas, Pref-1 was not expressed at all. Whereas, Pref-1 transiently expressed in the small regenerating duct cells located in foci of regeneration in Px model, then completely disappeared at day 7. The Pref-1 mRNA measured by RT-PCR was peaked at day 3 after Px and then gradually disappeared. Pref-1 expression pattern was also reproduced in monolayer cultured NPCCs. In NPCCs, protein levels of Pref-1 were peaked at day 0 to day 4 then gradually disappeared until day 7 by western blot. Most of Pref-1 expressing cells were co-stained with cytokeratin. The proportion of Pref-1 expressing cells in dispersed NPCCs were counted and isolated by FACS at 3 days after culture were 25% and then decreased over time during 7 days culture period. CONCLUSIONS: Pref-1 expression was regained in adult pancreatic cells during regeneration in vivo and in vitro and Pref-1 might be a useful marker for the pancreatic protodifferentiated cells.

• Keywords: Pref-1;Pancreatic duct cell;Cytokeratin;Vimentin;Protodifferentiation;Panc- reatic precursor cell;