*Purpose: Regenerative therapy for type I Diabetes Mellitus has been expected to be a promising treatment. A subcutaneous site is an ideal candidate for stem cell-derived β-cells/islet transplantation site because of being able to reduce procedure risk and explant the graft if necessary. However, the site is poor vascularity for the tissue engraftment. Recently, we have established a cell coating technique that enables the cell surface to be coated with extracellular matrix (fibronectin and gelatin) based on the concept of a layer-by-layer (LbL) assembly to construct functional three-dimensional tissues (Sasaki et al. Biomaterials. 2017, Fukuda et al. Biomaterials. 2018). Here, we investigated the construction of functional vascularized β-cells tissues using mouse β-cell line (MIN6) or human iPSC-derived β-cells (iPSCβ) by LbL technique.

*Methods: MIN6 or iPSCβ (Cellartis hiPS Beta Cells), human umbilical vein endothelial cells (HUVEC), and normal human dermal fibroblasts (NHDF) were used to construct the vascularized β-cell tissues. The β-cell spheroids by LbL cell coating technique, HUVEC and NHDF were seeded into the cell culture insert. After three days of incubation, three-dimensional β-cell tissues with blood capillary networks were fabricated. The function of insulin secretion between vascularized/non-vascularized β-cells spheroid/single β-cells was compared.

*Results: In the morphological analysis, insulin-positive β-cells spheroids were able to be embedded in the well-structured three-dimensional tissue composed of fibroblasts with CD31 positive vascular network using each β-cells. In the functional analysis, the vascularized β-cells spheroid had significantly greater insulin secretion ability with increased expression of the insulin genes (compared to non-vascularized β-cells spheroid and vascularized/non-vascularized single β-cells) using MIN6. Using iPSCβ, there was no significant difference in the amount of insulin secretion between vascularized/non-vascularized β-cells spheroid; however, the vascularized β-cells spheroid had a significantly greater amount of insulin secretion than vascularized single β-cells. We constructed the three-dimensional vascularized functional β-cells tissues using MIN6 or iPSCβ as a β-cell source by LbL cell coating technique.

*Conclusions: The constructed tissues would be clinically applicable to subcutaneous transplantation. Further experiments using three-dimensional vascularized β-cells tissues are now in progress to prove the long-term survival of the graft for in vivo application.

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