A vascularized 3D model of the human pancreatic islet for ex vivo study of immune cell-islet interaction

Abstract

Insulin is an essential regulator of blood glucose homeostasis that is produced exclusively by β cells within the pancreatic islets of healthy individuals. In those affected by diabetes, immune inflammation, damage, and destruction of islet β cells leads to insulin deficiency and hyperglycemia. Current efforts to understand the mechanisms underlying β cell damage in diabetes rely on in vitro-cultured cadaveric islets. However, isolation of these islets involves removal of crucial matrix and vasculature that supports islets in the intact pancreas. Unsurprisingly, these islets demonstrate reduced functionality over time in standard culture conditions, thereby limiting their value for understanding native islet biology. Leveraging a novel, vascularized micro-organ (VMO) approach, we have recapitulated elements of the native pancreas by incorporating isolated human islets within a three-dimensional matrix nourished by living, perfusable blood vessels. Importantly, these islets show long-term viability and maintain robust glucose-stimulated insulin responses. Furthermore, vessel-mediated delivery of immune cells to these tissues provides a model to assess islet-immune cell interactions and subsequent islet killing -- key steps in type 1 diabetes pathogenesis. Together, these results establish the islet-VMO as a novel, ex vivo platform for studying human islet biology in both health and disease.

The Foundation for Engineering a Pancreatic Islet Niche

“…As an easily cell-degradable material, fibrin may also be suitable for providing a dynamic environment for islets to remodel within a 3D space ( 171 ). In addition, fibrin is a common material used to support the formation of in vitro vascular networks, which could be combined with islets to form vascular structures around these spheriods ( 172 , 173 ). Combinatory ECM-based hydrogels can also be made to provide further customization ( e.g.…”

Engineered vasculature induces functional maturation of pluripotent stem cell-derived islet organoids

“…Under physiological conditions, the endothelium is exposed to continuous shear stress due to interstitial and pulsatile blood flow, which has been shown to stimulate vascular network formation [24] and islet function [25]. To introduce vessel flow into vasculature surrounding SC-islets, we adapted a vascularized micro-organ microfluidic system, in which ECs and FBs are seeded to form a network of perfused microvessels in a microfluidic device [25][26][27]. In this system, the shear of interstitial flow induces formation of a vascular network that is perfused through the microfluidic channels (Fig.…”

“…Microfluidic device used in the study was fabricated using standard soft lithography techniques as previously described [26]. The PDMS (Sylgard 184, Dow Corning) device consists of two straight microfluidic channels (upper channel as arteriole and lower channel as venule) separated by a tissue chamber (channel height, 200 µm).…”

“…All devices were subsequently sterilized by autoclaving at 120 °C before use. We followed the method for loading cells into microfluidic channels and forming vessels as previously described [26]. Briefly, to prepare fibrin gels for device loading, the filtered fibrinogen solution in EBM at 5 mg/ml was supplemented with 0.15 U/ml Aprotinin (Sigma-Aldrich) at the ratio of 1:100 (v/v), then mixed with 0.2 mg/ml fibronectin at the ratio of 1:4 (v/v).…”

Using single‐cell multi‐omics screening of human fetal pancreas to identify novel players in human beta cell development

“…In an adult pancreas only approximately 1%–2% of the cells are endocrine, contained within the islets of Langerhans, and the remaining cells are mainly acinar, with lesser amounts of other cell types including ductal, mesenchymal and endothelial cells. It is known that co‐ordinated interactions between multiple cell types such as mesenchyme, pericytes, endothelial cells and macrophages within the islet microenvironment regulate mouse beta cell development and maturity, 50‐53 and the islet cellular environment must be replicated to produce functional beta cells in vitro 54,55 . During pancreas development, the endocrine progenitors are specified in the presence of other pancreatic cell types, and since the cellular microenvironment plays a crucial role in determining cell fate, an improved understanding of how other cell types influence endocrine progenitor specification and differentiation will be useful in improving protocols for generating beta cells in vitro.…”