Bone marrow-derived pancreatic stellate cells in rats

Origin and fate of pancreatic stellate cells （PSCs） before, during and after pancreatic injury are a matter of de- bate. The crucial role of PSCs in the pathogenesis of pancreatic fibrosis is generally accepted. However, the turnover of the cells remains obscure. The present study addressed the issue of a potential bone marrow （BM） origin of PSCs. We used a model of stable hematopoietic chimerism by grafting enhanced green fluorescence protein （eGFP）-express- ing BM cells after irradiation of acceptor rats. Chimerism was detected by FACS analysis of eGFP-positive cells in the peripheral blood. Dibutyltin dichloride （DBTC） was used to induce acute pancreatic inflammation with subse- quent recovery over 4 weeks. Investigations have been focused on isolated cells to detect the resting PSC population. The incidence of eGFP-positive PSC obtained from the pancreas of chimeric rats was approximately 7% in healthy pancreatic tissue and increased significantly to a mean of 18% in the restored pancreas 4 weeks after DBTC-induced acute inflammation. Our results suggest that BM-derived progenitor cells represent a source of renewable stellate cells in the pancreas. Increased numbers of resting PSCs after regeneration point toward enhanced recruitment of BM-derived cells to the pancreas and/or re-acquisition of a quiescent state after inflammation-induced activation.

Cis-hydroxyproline-induced inhibition of pancreatic cancer cell growth is mediated by endoplasmic reticulum stress

AIM： To investigate the biological effects of cishydroxyproline （CHP） on the rat pancreatic carcinoma cell line DSL6A, and to examine the underlying molecular mechanisms. METHODS： The effect of CHP on DSL6A cell proliferation was assessed by using BrdU incorporation. The expression of focal adhesion kinase （FAK） was characterized by Western blotting and immunofluorescence. Induction of endoplasmic reticulum （ER） stress was investigated by using RT-PCR and Western blotting for the glucose-related protein-78 （GRP78） and growth arrest and DNA inducible gene （GADD153）. Cell viability was determined through measuring the metabolic activity based on the reduction potential of DSL6A cells. Apoptosis was analyzed by detection of caspase-3 activation and cleavage of poly（ADP-ribose） polymerase （PARP） as well as DNA laddering. RESULTS： In addition to inhibition of proliferation, incubation with CHP induced proteolytic cleavage of FAK and a delocalisation of the enzyme from focal adhesions, followed by a loss of cell adherence. Simultaneously, we could show an increased expression of GRP78 and GADD153, indicating a CHP-mediated activation of the ER stress cascade in the DSL6A cell line. Prolonged incubation of DSL6A cells with CHP finally resulted in apoptotic cell death. Beside L-proline, the inhibition of intracellular proteolysis by addition of a broad spectrum protease inhibitor could abolish the effects of CHP on cellular functions and the molecular processes. In contrast, impeding the activity of apoptosis-executing caspases had no influence on CHP-mediated cell damage.CONCLUSION： Our data suggest that the initiation of ER stress machinery by CliP leads to an activation of intracellular proteolytic processes, including caspaseindependent FAK degradation, resulting in damaging pancreatic carcinoma cells.