Changes in extracellular matrix stiffness affect pancreatic islet function

Abstract

In the pancreas, the islet is surrounded by a specialized protein scaffold known as the extracellular matrix (ECM) that regulates cell survival and insulin secretion. Little is known about how the properties of the pancreas microenvironment, like matrix stiffness, regulate islet function in health and disease. Previous studies have shown that tissue stiffness in muscle cells regulates phosphofructokinase (PFK) activity. The mechanisms underlying mechanotransduction regulation of insulin secretion have not been well studied in the β-cell and a connection between metabolism and mechanotransduction has never been studied in intact islets. We hypothesize that increasing matrix stiffness will increase islet glucose sensitivity by increasing PFK activity. Our lab has developed a 3D reverse thermal gel (RTG) system that allows us to mimic the islet microenvironment and to investigate how the environment affects islet function. To determine the effect of changes in ECM stiffness on islet function we encapsulated mouse islets in the RTG with increasing stiffness as determined by rheological analysis. Glucose-stimulated insulin secretion, PFK activity, and PFK expression was measured after 24 hours of culture. We found that increasing RTG wt% yielded increasing stiffness at 40°C. Insulin secretion increased as the matrix stiffness increased in basal and high glucose conditions. Insulin secretion at high glucose normalized to low glucose (stimulation index) decreases with matrix stiffness indicating dysfunction to insulin secretion. PFK activity increased in islets encapsulated in stiffer RTGs. Our results provide insight into how changes in ECM stiffness contribute to islet dysfunction.