Assessment of the in vitro function of human stem cell-derived β cells

Abstract

Insulin-producing human embryonic stem cell-derived β (SC-β) cells are a promising cell source for diabetes cell replacement therapy. We have recently reported a differentiation strategy that produces SC-β cells in islet organoids that not only undergo glucose-stimulated insulin secretion but also have an islet-like dynamic insulin release profile, displaying both first and second phase insulin secretion. The goal of this study was to further characterize the functional profile of these SC-β cells in vitro. We utilized a Seahorse extracellular flux analyzer to measure mitochondrial respiration of SC-β cells at low and high glucose. We also used photolithography to fabricate a microfluidic device containing microwells to immobilize SC-β cells for perfusional analysis, monitoring cytoplasmic calcium using Fluo-4 AM at low and high glucose. Here we find that in addition to increased insulin secretion, SC-β cells have increased cellular respiration and cytoplasmic calcium ion concentration in response to a high glucose stimulation. Our results indicate that SC-β cells have similar function to that reported for islets, providing further performance characterization that could help with eventual development for diabetes cell therapy and drug screening.3 Diabetes Mellitus (DM) is a group of metabolic disorders that leads to the inability of the body to regulate blood glucose levels. Type 1 diabetes (T1D) involves the autoimmunemediated destruction of the insulin-producing pancreatic β cells located in the islets of Langerhans, leading to insulin deficiency and hyperglycemia. T1D is typically managed by injection of exogenous insulin. However, this clinical intervention does not emulate the normal behavior of the native β cells, making patients at risk for many long term complications 1 . An alternative therapy for T1D is the transplantation of cadaveric human islets, with the hope of reducing hyper-and hypoglycemic episodes. Some patients who were transplanted with islets have remained insulin independent for several years 2 . A major limitation of this approach, however, is the scarcity and quality of islets sourced from cadavers, limiting the widespread application of this therapy. Differentiation of human embryonic stem cells (hESCs) to insulinproducing β (SC-β) cells in islet organoids could serve as an unlimited supply of cells to treat millions of patients 3 , particularly if combined with transplantation strategies that vascularization, allow retrievability, and/or protect the cells from immune attack 4-8 .We recently reported a strategy for making large numbers of SC-β cells from hESCs 9 . This protocol is highly efficient, generating an almost pure population of pancreatic endocrine, of which most cells express insulin. These cells are highly functional, capable of undergoing glucose-stimulated insulin secretion. These cells were capable of restoring glucose tolerance when transplanted into streptozotocin-treated mice. Of particular note was the ability of these cells to display first and second phase insulin s...