Pancreatic regeneration in chronic pancreatitis requires activation of the Notch signalling pathway
Peter Buechler, Yun Su, Amiq Gazdhar, Markus W. Buechler, Helmut Friess; General Surgery, University of Heidelberg, Heidelberg, Germany
Introduction: Chronic pancreatitis is a continuous inflammatory and fibrosing process of the pancreas characterized by irreversible morphological changes, permanent endocrine and exocrine dysfunction and pain for unknown reasons. Pancreatic regeneration, inflammation and likely cancer development are closely related processes. During pancreatic regeneration an embryonic genetic program is reinstated including re-activation of Notch signalling pathway (Notch-1/4, Jagged-1/2, Delta-1/2). This pathway governs development of exocrine, endocrine and neuronal tissue as well as early neoplastic transformation in the pancreas. The current study analyzed this pathway in chronic pancreatitis, and characterized its influence on pain, fibrogenesis and neoplastic transformation. Material and Methods: Real time quantitative PCR was used to quantify mRNA expression in human CP specimens. Immunohistochemistry was used to localize protein expression within tissue specimens. Recombinant activation of the Notch signalling was done by transfection of NIH 3T3 cells and one pancreatic cell line with a constitutive active Notch-1 mutant (Notch-IC). Over expression of Jagged and Delta was achieved by retroviral transfection of full length cDNA. Notch activation was determined by a specific Luciferase-HES-1-reporter constructs after cell transfection and stimulation insulin, glucagon, somatostatin, steroids, glucose and bile acids. Results: Notch-2, Notch-3 and Notch-4 mRNA were significantly overexpressed in human chronic pancreatitis specimens. Among the ligands Jagged-1, Jagged -2 and Delta were highly overexpressed. Immunopositivity of Jagged-1, Delta, Notch-1 and Notch-4 were seen in nerves and regenerating exocrine cells as well as in the endocrine compartment. The correlation between pain and reactivation of Notch gene members was conducted for all six factors. Cell transfection studies revealed a strong activation of Notch activation upon cell stimulation with glucose, steroids and bile acids. High glucose levels were further associated with increased collagen I production which was revertible upon addition a Notch inhibitor. Conclusion: The embryological active Notch pathway is reactivated in chronic pancreatitis in exocrine cells, neuronal structures and islet regeneration. These findings indicate that the Notch pathway mediates the regenerative potential in the inflamed pancreas. Among the stimuli activating the Notch pathway are steroids, high glucose levels and bile acids. This study provides insides in mechanisms of pancreatic tissue regeneration.
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