(770c) Biomaterial Based Engineering of Vascularized Pancreatic Islet Organoids Derived from Human Pluripotent Stem Cells (hPSCs)

Organoids are 3D engineered constructs comprising multiple organ specific cell populations capable of recapitulating an in vivo organ systemâ??s specific structure and function in an in vitro setting. Development of such systems requires an organ specific parenchyma cell source and a platform for self-organization and lineage specific induction of the chosen cell types. Human and murine hPSCs, unique in their abilities for self-renewal and capacity to differentiate into organ specific cell types, have been used to produce organoids representing all three germ layers. In addition to the necessary organ specific cell populations, attaining functional vasculature is a critical component, vital for maintaining nutrient supply and appropriate organ function. This is particularly critical for pancreatic islet organoid development, since generating a specialized, fenestrated vasculature is crucial for glucose delivery and insulin response. Recent success in generating pancreatic b-cells from hPSCs has set the ultimate stage for engineering vascularized islet organoids from a regenerative cell source.

We have thus developed a novel hydrogel promoting spontaneous aggregation of pre- differentiated hESC derived pancreatic progenitor cells (hESC-PPs) into a 3D organoid when cultured directly on the hydrogel surface without embedment. The resulting spheroids are amenable for size and cellular composition tuning. Following 3D organoid formation, the hESC- PP cells exhibited enhanced PP gene and protein expression throughout the cell population. Furthermore, using isolated microvessel elements from adipose, a new microvasculature was integrated within the hESC-PPs organoids during initial seeding and spheroid formation. Additionally, inclusion of a supporting mesenchyme within the organoid promoted microvascular expansion and vascular specification within the organoid in 4 days. Upon continued culture, the gene expression of key pancreatic maturation markers (NKX6.1, PDX1, and INS) was enhanced in the vascularized organoids even in the absence of specific chemical induction. Moreover, the intra-organoid vasculature demonstrated an increase in islet endothelial specific API gene expression and PLVAP, a marker noted for increased endothelial diaphragm and fenestration. In conclusion, we believe the results represent a major step in the in vitro production of hPSC islet organoids with further microvasculature, a development indirectly extendable to other organ-specific applications.