Cellular mechanisms involved in the recapitulation of endocrine development in the duct ligated pancreas

[摘要] ENGLISH ABSTRACT: Diabetes mellitus is amongst the leading causes of morbidity and mortality in the world, affectingyoung, adult and old people. Beta cell replacement therapy for insulin delivery remains the ultimateremedy for diabetes. However, insufficient donor pancreas and the use of immunosuppressive drugsprevent the wide-spread of this therapy. Other avenues of self generated beta cells within the organitself need to be explored. Therefore, understanding the chronobiology of cellular mechanisms inthe lineage of beta cell induced neogenesis is a valuable tool in improving beta cell replacement inpatients with diabetes. The aim of this study was to induce recapitulation of the morpho-geneticsequence of endocrine cells development in the pancreas of rats after the pancreatic duct ligation(PDL) procedure. Serial sections of PDL tissues of the pancreas were obtained from 78 Sprague-Dawley rats and were assessed morphologically. The immunofluorescent tissues were statisticallyanalysed using a computerized morphometry technique. The protein expression indices ofCaspase3, Insulin, Pdx1, Ngn3, NeuroD and Pax6 were quantified. The efficiency levels of coexpressionof these homeodomain proteins separately with insulin were defined by the ratio of themean value of insulin expression to the mean value of their respective protein expression. Themorphological changes were characterized by the appearance of granulated acinar cells at 6 hourspost-PDL and the proliferation of endocrine tissues from 84 hours through to 120 hours. Themorpho-immunofluorescent evaluation showed the highest immunoreactivity of Caspase3 and Pdx1at 6 hours, Ngn3 at 36 hours, Pax6 and insulin at 84 hours while NeuroD expression was at 120hours. The immunohistofluorescent analysis showed that caspase3 and Pdx1 were the first to beexpressed at 6 hours while the insulin and NeuroD expression appeared later at 84 hours and 120hours, respectively. However, Pax6 expression was continuous across time periods post-PDL, whileNgn3 expression showed a peak at 36 hours. The efficiency (highest and earliest expression) of co-expression of all these homeodomain proteins with insulin was restricted between 12 hours and 24hours. The optimal efficiency was at 12 hours by Ngn3 with insulin. A good efficiency was shownfor Pdx1 with insulin, NeuroD with insulin and Pax6 with insulin at 12 hours and 24 hours,respectively. A low efficiency was observed for insulin and caspase3 co-expression at 24 hours.This study suggests that for transplantation, PDL tissues harvested at an early time post-PDL(between 12 and 24 hours) could yield a higher success rate; the study also provides evidence for aconnection between morphological changes in the PDL pancreas and the protein synthesisnecessary for the lineage of endocrine cell development.

[发布机构] Stellenbosch University