Pancreatic extracellular communication. Applications to beta cell cultures and islet amyloid polypeptide aggregation

Doctoral thesis, 2018

Diabetes mellitus (DM) is a disease with epidemic proportions due to increased incidences worldwide, persistence of undiagnosed cases, uncontrolled forms of the disease, association with cardiovascular complications, and lack of definitive treatment options. In particular, type 2 DM (T2DM) is placing an enormous financial burden on worldwide healthcare systems that will increase in the future There is a need to develop physiological assay platforms that provide functionally relevant models of diabetes in order to accelerate the discovery of new treatments. In this thesis I will focus on the biological relevance of pancreatic extracellular communication, by addressing the implications of extracellular vesicles (EVs), and the pancreatic extracellular matrix (ECM) on different in vitro models. First, I present new insights on how pancreatic EVs modulate the aggregation of the hormone amylin (also known as islet amyloid polypeptide, IAPP), which is the major component of amyloid deposits found in pancreatic islets of patients with T2DM. Here, I demonstrate that EVs secreted from healthy (but not T2DM) pancreatic islets efficiently reduced amyloid formation in vitro (Paper I). Additionally, I showed that these pancreatic EVs can regulate insulin expression in stem cell-derived pancreatic cells, differentiating in a 3D-culture system in vitro (Paper II). I further addressed the significance of pancreatic ECM for the development of complex 3D-culture systems as a mean to improve the in vitro differentiation and commitment of stem cell-derived pancreatic cells. In this work, I tested stem cell-derived pancreatic cells cultured in a pancreatic decellularized scaffold with endothelial cells (Paper III). Through a collaboration I also helped to show that 3D-culturing improved the adipogenic differentiation of adipose-derived stem cells (Paper IV). Lastly, I summarized the current knowledge of 3D-strategies used to increase the functional relevance of ex vivo primary pancreatic islets, and generation of stem cell-derived pancreatic beta cells (Paper V).