Clusterin expression in porcine endocrine cells during islet development.

Clusterin is a well-known glycoprotein expressed by many cell types involved in multiple physiological functions. In rat pancreatic tissue it is expressed along with islet cell development and found to be involved in regeneration of pancreatic endocrine cells after various types of tissue injuries. These results led us to propose that clusterin might play a crucial role in organization and assembling processes of islet cells during pre- and postnatal development. Therefore, the aim of this study was to find out whether and in which cell type clusterin is expressed during islet cell organization in the porcine species which could play a future role in the field of xenotransplantation. For this purpose we examined the expression pattern of clusterin at different developing stages in the porcine pancreas by double-immunostaining with antibodies against chromogranin A and clusterin, and clarified whether distinct islet hormones were coexpressed with clusterin. Further, we checked by RT-PCR whether clusterin was locally expressed or possibly locally bound to the corresponding receptor. In newborn and up to 3-month-old animals clusterin was found to be expressed in a special cell type which is closely associated and intermingled with other endocrine cells. In fully developed adult islets clusterin-cells then reorganize and were found to be mainly localized in the mantle area of Langerhans islets. Double-immunostaining with antibodies against clusterin and different islet hormones such as insulin, glucagon, and somatostatin clearly demonstrate that clusterin expression was found in an own special cell type and it is also present in a subset of glucagon producing A-cells. Taken together, our results show that clusterin expression in porcine species is found in an own, as yet unidentified cell type during postnatal developmental stages, and probably labels immature precursor cells in adult animals, which finally have the potential to differentiate into glucagon-expressing cells.

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