Studying the role of Sirtuin-1 in the maintenance of mouse intestinal epithelium

Iqbal, M. S. (Handledare)

Aktivitet: ExaminationstyperHandledning av annat kunskapsprov (pro gradu, licentiatavhandling)

Beskrivning

Sirtuin-1 (Sirt-1), an NAD+-dependent deacetylase, maintains energy homeostasis upon stress-induced decline in energy levels. Sirt-1 possesses many other functions ranging from regulating cellular proliferation and apoptosis to maintaining glucose and lipid metabolism. By deacetylating its target proteins, Sirt-1 can also increase the lifespan of lower organisms such as yeast, flies, and worms. However, lifespan-prolonging ability of Sirt-1 in rodent models and human subjects has been investigated, exhibiting only partially promising results.

Contrary to its role in increasing lifespan in rodents and humans, Sirt-1 has exhibited positive results on prolonging the health-span of these model organisms by delaying or inhibiting the development of diseases and disorders that present themselves with increasing age. Drug mediated Sirt-1 activation via resveratrol and Sirt-1 activation through calorie restriction were shown to bring a healthy balance to glucose and lipid metabolism especially in rodents fed on high-fat diet. Currently, Sirt-1 is investigated as a target gene for the treatment of Type-2 Diabetes in multiple clinical trials.

In this study, we investigated the role of the Sirtuin-1 in the maintenance of intestinal epithelium. In our study, we utilized intestinal organoid models grown from isolated crypts of mouse small intestine. We performed knockdown of Sirt-1 at mRNA level via lentiviral shRNA. Additionally, we targeted Sirt-1 activity by applying resveratrol to the culture media of mouse intestinal organoids. Our main aim was to address how manipulations of Sirt-1 expression or activity would affect the function of intestinal stem cells and Paneth cells located in the crypt tips of intestinal organ-oids. Furthermore, we were interested in how these changes would alter organoid viability and crypt regeneration.

In this study, we demonstrate that Sirt-1 is a fundamental gene for mouse intestinal organoid viability as well as organoid crypt regeneration. We also show that Sirt-1 controls crypt regeneration by regulating Paneth cell differentiation and thus intestinal stem cell niche conditions in the crypt bottoms of mouse intestinal organoids.

Activation of Sirt-1 by resveratrol decreases total Paneth cell number in a crypt bottom leading to the relative retardation of crypt regeneration as well as the reduction in crypt size. High concentrations of resveratrol resulted in death of intestinal organoids, probably due to complete loss of Paneth cells.
Period2 jun 2015
ExaminandEmir Cansu
Examination vidUniversity of Helsinki