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Different approaches have investigated the effects of different extracellular matrices (ECMs) and three-dimensional (3D) culture on islet function, showing encouraging results. Ideally, the proper scaffold should mimic the biochemical composition of the native tissue as it drives numerous signaling pathways involved in tissue homeostasis and functionality. Tissue-derived decellularized biomaterials can preserve the ECM composition of the native tissue making it an ideal scaffold for 3D tissue engineering applications. However, the decellularization process may affect the retention of specific components, and the choice of a proper detergent is fundamental in preserving the native ECM composition. In this study, we evaluated the effect of different decellularization protocols on the mechanical properties and biochemical composition of pancreatic ECM (pECM) hydrogels. Fresh porcine pancreas tissue was harvested, cut into small pieces, rinsed in water, and treated with two different detergents (sodium dodecyl sulfate [SDS] or Triton X-100) for 1 day followed by 3 days in water. Effective decellularization was confirmed by PicoGreen assay, Hoescht, and H&E staining, showing no differences among groups. Use of a protease inhibitor (PI) was also evaluated. Effective decellularization was confirmed by PicoGreen assay and hematoxylin and eosin (H&E) staining, showing no differences among groups. Triton-treated samples were able to form a firm hydrogel under appropriate conditions, while the use of SDS had detrimental effects on the gelation properties of the hydrogels. ECM biochemical composition was characterized both in the fresh porcine pancreas and all decellularized pECM hydrogels by quantitative mass spectrometry analysis. Fibrillar collagen was the major ECM component in all groups, with all generated hydrogels having a higher amount compared with fresh pancreas. This effect was more pronounced in the SDS-treated hydrogels when compared with the Triton groups, showing very little retention of other ECM molecules. Conversely, basement membrane and matricellular proteins were better retained when the tissue was pretreated with a PI and decellularized in Triton X-100, making the hydrogel more similar to the native tissue. In conclusion, we showed that all the protocols evaluated in the study showed effective tissue decellularization, but only when the tissue was pretreated with a PI and decellularized in Triton detergent, the biochemical composition of the hydrogel was closer to the native tissue ECM.

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference.

Blood vessels play a critical role in pancreatic islet health and function, yet current culture methods to generate islet organoids from human pluripotent stem cells (SC-islets) lack a vascular component. Here, we engineered 3D vascularized SC-islet organoids by assembling SC-islet cells, human primary endothelial cells (ECs) and fibroblasts both in a non-perfused model and a microfluidic device with perfused vessels. Vasculature improved stimulus-dependent Ca2+ influx into SC-β-cells, a hallmark of β-cell function that is blunted in non-vascularized SC-islets. We show that an islet-like basement membrane is formed by vasculature and contributes to the functional improvement of SC-β-cells. Furthermore, cell-cell communication networks based on scRNA-seq data predicted BMP2/4-BMPR2 signaling from ECs to SC-β-cells. Correspondingly, BMP4 augmented the SC-β-cell Ca2+ response and insulin secretion. These vascularized SC-islet models will enable further studies of crosstalk between β-cells and ECs and can serve as in vivo-mimicking platforms for disease modeling and therapeutic testing. Competing Interest Statement C.C.W.H. and S.C.G. are founders and shareholders of Aracari Biosciences, Inc, which is commercializing the microfluidics technology used in this manuscript. R.H.F.B. is a shareholder of Aracari Biosciences, Inc. All work was performed with the full knowledge and approval of the UCI and UCD Conflict of Interest committees.

Neural stem cells (NSCs) give rise to all the major cell types in the brain, including neurons, oligodendrocytes, and astrocytes. However, the intracellular signaling pathways that govern brain NSC proliferation and differentiation have been incompletely characterized to date. Since several neurodevelopmental brain disorders (i.e., Costello syndrome, Noonan syndrome) are caused by germline mutations in the RAS genes, Ras small GTPases are likely critical regulators of brain NSC function. In the mammalian brain, Ras exists as three distinct molecules (H-Ras, K-Ras, and N-Ras), each with different subcellular localizations, downstream signaling effectors, and biological effects. Leveraging a novel series of conditional Ras molecule-expressing genetically-engineered mouse strains, we demonstrate that K-Ras, but not H-Ras or N-Ras, hyperactivation increases brain NSC growth in a Raf-dependent, but Mek-independent, manner. Moreover, we show that K-Ras regulation of brain NSC proliferation requires Raf binding and suppression of retinoblastoma (Rb) function. Collectively, these observations establish tissue-specific differences in Ras molecule regulation of brain cell growth that operate through a non-canonical mechanism.

Insulin is an essential regulator of blood glucose homeostasis that is produced exclusively by β cells within the pancreatic islets of healthy individuals. In those affected by diabetes, immune inflammation, damage, and destruction of islet β cells leads to insulin deficiency and hyperglycemia. Current efforts to understand the mechanisms underlying β cell damage in diabetes rely on in vitro-cultured cadaveric islets. However, isolation of these islets involves removal of crucial matrix and vasculature that supports islets in the intact pancreas. Unsurprisingly, these islets demonstrate reduced functionality over time in standard culture conditions, thereby limiting their value for understanding native islet biology. Leveraging a novel, vascularized micro-organ (VMO) approach, we have recapitulated elements of the native pancreas by incorporating isolated human islets within a three-dimensional matrix nourished by living, perfusable blood vessels. Importantly, these islets show long-term viability and maintain robust glucose-stimulated insulin responses. Furthermore, vessel-mediated delivery of immune cells to these tissues provides a model to assess islet-immune cell interactions and subsequent islet killing -- key steps in type 1 diabetes pathogenesis. Together, these results establish the islet-VMO as a novel, ex vivo platform for studying human islet biology in both health and disease. Competing Interest Statement C.C.W.H. and S.C.G. are co-founders and shareholders of Aracari Biosciences Inc., a biotechnology start-up company focused on commercializing the core VMO technology described here. R.H.F.B is a part-time employee of Aracari Biosciences Inc. and receives stock and financial compensation. The terms of these arrangements have been reviewed and approved by the University of California, Irvine in accordance with its conflict-of-interest policies.