(337a) Vascularization of Pancreatic Islet-Mimetic Organoids with Microvessel Fragments

Pancreatic islets produce glucagon used to digest glycogen into glucose and insulin necessary for cells to absorb sugar for energy generation. Without functioning islets, a person’s body won’t be able to process their sugar intake and diabetes will develop, requiring the monitoring of blood sugar levels and injection of insulin. Transplanting donor islets remains the leading long term treatment for diabetes, but scarcity of viable donor islets restrict this option. An emerging alternative is to engineer islet mimetic organoids from human pluripotent stem cells (hPSC). Organoids are in vitro synthesized 3-D structures that imitate organ systems in organization and function. The primary constituents of pancreatic islets are hormone producing endocrine cells, stromal cells, and a dense intra-vascular network. The current project aims to engineer an islet-organoid mimetic capable of producing glucagon and insulin with the incorporation of both alpha and beta cells, along with the integration of the intra-islet vascular network. Hence, we hypothesize the resulting islet-organoid mimetic will closely replicate the structural and functional characteristics of primary human islets.

A critical step for islet organoid engineering is the controlled synthesis of the 3-D spheroid morphology. Our lab has developed methods for engineering controlled 3-D homotypic (same cell type) and heterotypic (different cell types) aggregates from hPSC-derived cells [1]. hPSCs were differentiated towards islet lineage following the protocol reported by Melton et al. [2], which results in predominantly alpha and beta cell phenotype. Subsequently, the intra-islet vascular network were reproduced by aggregating the hPSC-derived islet-like cells with adipose-derived microvessel fragments and stromal cells. The neo-vascular network formation within the islet organoids were found to be sensitive to the culture media as well as the phenotype of the hPSC derived cell population. The resulting vascularized organoids demonstrated enhanced functionality over beta cell aggregates through the gene expression of key pancreatic maturation markers (NKX6.1, PDX1, and INS). Additionally, the intra-organoid vasculature exhibited increased expression of the islet specific endothelial gene, API, along with endothelial diaphragm fenestration indicator, PLVAP, which indicates islet-specific vascular development. With enhanced pancreatic phenotype and functioning vascular network, these organoids will be highly applicable in regenerative therapy for the treatment of type 1 diabetes. Furthermore, we are currently integrating these organoids into in-vitro body-on-chip platform for disease modeling and drug/ toxicity testing.

Ref:

[1] Candiello J, Grandhi TSP, Goh SK, Vaidya V, Lemmon-Kishi M, Kumta PN, Rege K, Banerjeea I. 3D Heterogeneous Islet Organoid Generation from Human Embryonic Stem Cells using a Novel Engineered Hydrogel Platform 2018: submitted.

[2] Pagliuca, F.W.; Millman, J.R.; Guertler, M.; Segel, M.; Dervort, A.V.; Ryu, J.H.; Peterson, Q.P.; Greiner, D.; Melton, D.A. Generation of Functional Human Pancreatic b Cells In Vitro. Cell. 2014, 159, 428-439