In vitro drug screening for type 1 diabetes therapies has largely been conducted on human organ donor islets for proof of efficacy. While native islets are the ultimate target of these drugs (either in situ or for transplantation), significant benefit can be difficult to ascertain due to the highly heterogeneous nature of individual donors and the overall scarcity of human islets for research. We present an in vitro coculture model based on immortalized insulin-producing beta-cell lines with human endothelial cells in 3D spheroids that aims to recapitulate the islet morphology in an effort towards developing a standardized cell model for in vitro diabetes research. Human insulin-producing immortalized EndoC-βH5 cells are cocultured with human endothelial cells in varying ratios to evaluate 3D cell culture models for type 1 diabetes research. Insulin secretion, metabolic activity, live cell fluorescence staining, and gene expression assays were used to compare the viability and functionality of spheroids composed of 100 beta-cells, 1:1 beta-cell/endothelial, and 1:3 beta-cell/endothelial. Monoculture and βH5/HUVEC cocultures formed compact spheroids within 7 days, with average diameter 140μm. This pilot study indicated that stimulated insulin release from 0 to 20mM glucose increased from 8-fold for monoculture and 1:1 coculture spheroids to over 20-fold for 1:3 EndoC-βH5/HUVEC spheroids. Metabolic activity was also 12 higher in the 1:3 EndoC-βH5/HUVEC group compared to other groups. Stimulating monoculture beta-cell spheroids with 20mM glucose +1μg/mL glycine-modified INGAP-P increased the insulin stimulation index 2-fold compared to glucose alone. Considering their availability and consistent phenotype, EndoC-βH5-based spheroids present a useful 3D cell model for in vitro testing and drug screening applications.

Islet transplantation is a curative treatment for patients suffering from type 1 diabetes and has the potential to replace current treatment strategies involving the exogenous administration of insulin. Despite this potential, there are many hurdles in achieving successful long‐term graft survival due to autoimmune and foreign body reactions leading to graft rejection coupled with donor shortage and potential adverse effects from the need for long‐term administration of immunosuppressive drugs. As a result, various approaches have been proposed to increase the viability and function of islet grafts during isolation and ex vivo culture with the use of growth factors, hormones, and other therapeutic agents. In addition, other strategies have addressed how to enhance or maintain islet graft performance after implantation with improvements on immunosuppressive drug regimens and the use of biomaterials to encapsulate and protect the cells from graft rejection. This review focuses on the recent advances in strategies to improve islet viability and function with the addition of exogenous compounds and the implementation of conformal coating as a promising tool for immunoprotection of islet transplants.

Three-dimensional (3D) cell culture models are widely used to provide a more physiologically relevant microenvironment in which to host and study desired cell types. These models vary in complexity and cost, ranging from simple and inexpensive to highly sophisticated and costly systems. In this study, we introduce a novel translucent multi-compartmentalized stacked multilayered nanocellulose scaffold and describe its fabrication, characterization, and potential application for co-culturing multiple cell types. The scaffold consists of bacterial nanocellulose (BNC) layers separated by interlayers of a lower density of nanocellulose fibers. Using this system, we co-cultured the MDA-MB-231 cell line with two tumor-associated cell types, namely BC-CAFs and M2 macrophages, to simulate the tumor microenvironment (TME). Cells remained viable and metabolically active for up to 15 days. Confocal microscopy showed no signs of cell invasion. However, BC-CAFs and MDA-MB-231 cells were frequently observed within the same layer. The expression of breast cancer-related genes was analyzed to assess the downstream functionality of the cells. We found that the E-cadherin expression was 20% lower in cancer cells co-cultured in the multi-compartmentalized scaffold than in those cultured in 2D plates. Since E-cadherin plays a critical role in preventing the initial dissociation of epithelial cells from the primary tumor mass and is often downregulated in the tumor microenvironment in vivo, this finding suggests that our scaffold more effectively recapitulates the complexity of a tumor microenvironment.

Conformal coating is a promising encapsulation approach to reduce the immunogenicity of islet transplants in the treatment of type 1 diabetes (T1D). The primary objective of this work was to investigate a combination of non-immunogenic polyelectrolytes, tetrahydropyran triazole phenyl-alginate (TZ-AL) and quaternized phosphocholine-chitosan (PC-QCH), to create a nano-thin film onto the surface of human donor islets and assess its potential for clinical translation. To evaluate the coating materials, spheroids made from human-derived proliferative EndoC-βH1 and non-proliferative βH5 beta cell lines as pseudo-islet models was used as complementary models before applying the coating onto human islets. Coating formation and biocompatibility were first validated with spheroids and then applied to human islets. The results indicated formation of the desired coating morphology on both spheroids and human islets. In addition, both coated spheroids and human islets cultured for 7 days in vitro maintained cell viability, metabolic activity, and glucose stimulated insulin secretion compared to non-coated control groups. Gene expression of islet/beta cell markers (INS, GCG, PDX1, and MAFA) also remained similar, suggesting no significant impact on coated spheroid and islet cell function. Lastly, transplantation of coated human islets in diabetic mice restored normoglycemia for up to 30 days. These findings suggest that this conformal coating can maintain human islet cell function and thus, it can be a promising candidate towards clinical application of nanoencapsulation for T1D cell therapy.