Delta-cell-specific expression of hedgehog pathway Ptch1 receptor in murine and human endocrine pancreas

Hedgehog pathway plays an important role during pancreas development, when its inactivation is crucial to assure expression of pancreatic marker genes involved in the organ formation and to assure an appropriate organogenesis. Patched1 (Ptch1) is a transmembrane receptor of hedgehog pathway which has a key role in this process. In fact, heterozygous Ptch1 mutant (ptc+/-) mice are affected by an impaired glucose tolerance accompanied by reduced islet function. In the light that the cell distribution of Ptch1 receptor within the endocrine pancreas has not yet been established, we aimed at identifying the pancreatic endocrine cell subset(s) expressing such molecule.

Double immunostaining for Ptch1 and pancreatic hormones insulin, glucagon and somatostatin on pancreatic paraffin sections of C57BL/6J mice and human non-diabetic multiorgan donors was performed and analysed using confocal microscopy. In addition, diabetes was experimentally induced in mice by intraperitoneal injection of streptozotocin. Quantitative real-time polymerase chain reaction after laser-capture microdissection of different islets from frozen pancreatic murine tissue sections was also performed.

Ptch1 receptor was detected only in somatostatin-positive delta cells both in mice and in human pancreas; in mice its expression was not affected by streptozotocin treatment. A significant increase of Ptch1 mRNA expression levels in the islet periphery versus the islet core was observed by quantitative real-time polymerase chain reaction, in accord with immunohistochemical observations.

Our data show a delta-cell-specific expression of Ptch1 receptor in murine and human pancreas.