(176p) Islet-Mimetic Organoid Vascularization Utilizing Microvascular Fragments

Authors: 
Wiegand, C. - Presenter, University of Pittsburgh
Candiello, J. E., University of Pittsburgh
Kumta, P., University of Pittsburgh
Hoying, J., University of Louisville
Banerjee, I., University of Pittsburgh
Islets of Langerhans are vital for the maintenance of the body’s glucose levels through the functionality of the insulin secreting beta cells. Diabetes forms when the beta cells are unable to produce enough insulin, whether through beta cell destruction (type 1 diabetes) or insulin resistance (type 2 diabetes). The leading long-term solution for improving endogenous insulin production is transplanting primary human islets, which has limitations due to donor scarcity. Alternatively, islet mimetic organoids could be used for implantation. Organoids are in vitro synthesized tissue that mimics the structure and functionality of in vivo organ systems. Primary islets are constructed of endocrine cells, stromal cells, and a dense vascular network. The aim of the current project is to form an islet-mimetic organoid that maintains glucagon and insulin secretion while integrating an intra-islet vascular network. Since beta cells reside near vasculature in vivo, we hypothesize that the resulting organoid will replicate the structure and functionality of primary human islets.

A crucial step for islet organoid engineering is the controlled aggregation of the varying cell types into a 3-D spheroid morphology. Our lab has developed methods for controlling heterotypic (different cell types), spheroid aggregation of human pluripotent stem cell (hPSC) -derived pancreatic endocrine cells and endothelial cells. Additionally, we have had promising results in forming an intra-vascular network in the hPSC derived cells. The intra-vascular network was reproduced by aggregating hPSC derived pancreatic endocrine cells, adipose-derived microvascular fragments, and stromal cells. During this experimentation, the formation of the neo-vascular network has found to be sensitive to the phenotype of the hPSC-derived cell population and the culture media, wherein media was adjusted to promote angiogenesis while maintaining endocrine differentiation. The resulting vascularized organoids demonstrated higher gene expression of maturing pancreatic beta cell markers (NKX, PDX1, and Insulin), an islet specific endothelial gene (API), and an endothelial diaphragm fenestration indicator (PLVAP) compared to homotypic aggregates of hPSC-derived pancreatic endocrine cells and initial microvascular fragments. With enhanced pancreatic phenotype and vascular network, these organoids will be highly applicable in regenerative therapy for diabetes and incorporated into microphysiology system models for disease modeling.