Adhesion Characteristics of Human Pancreatic Islets, Duct Epithelial Cells, and Acinar Cells to a Polymer Scaffold

3D evaluation of the extracellular matrix of hypoxic pancreatic islets using light sheet fluorescence microscopy

Pancreatic islet transplantation is a promising treatment for type 1 diabetes, but the survival and function of transplanted islets are hindered by the loss of extracellular matrix (ECM) during islet isolation and by low oxygenation upon implantation. This study aimed to evaluate the impact of hypoxia on ECM using a cutting-edge imaging approach based on tissue clearing and 3D microscopy. Human and rat islets were cultured under normoxic (O2 21%) or hypoxic (O2 1%) conditions. Immunofluorescence staining targeting insulin, glucagon, CA9 (a hypoxia marker), ECM proteins (collagen 4, fibronectin, laminin), and E-cadherin (intercellular adhesion protein) was performed on fixed whole islets. The cleared islets were imaged using Light Sheet Fluorescence Microscopy (LSFM) and digitally analyzed. The volumetric analysis of target proteins did not show significant differences in abundance between the experimental groups. However, 3D projections revealed distinct morphological features that differentiated normoxic and hypoxic islets. Under normoxic conditions, ECM could be found throughout the islets. Hypoxic islets exhibited areas of scattered nuclei and central clusters of ECM proteins, indicating central necrosis. E-cadherin was absent in these areas. Our results, demonstrating a diminution of islets' functional mass in hypoxia, align with the functional decline observed in transplanted islets experiencing low oxygenation after grafting. This study provides a methodology combining tissue clearing, multiplex immunofluorescence, Light Sheet Fluorescence Microscopy, and digital image analysis to investigate pancreatic islet morphology. This 3D approach allowed us to highlight ECM organizational changes during hypoxia from a morphological perspective.

ECM Proteins Nidogen-1 and Decorin Restore Functionality of Human Islets of Langerhans upon Hypoxic Conditions

Transplantation of donor islets of Langerhans is a potential therapeutic approach for patients with diabetes mellitus; however, its success is limited by islet death and dysfunction during the initial hypoxic conditions at the transplantation site. This highlights the need to support the donor islets in the days post-transplantation until the site is vascularized. It was previously demonstrated that the extracellular matrix (ECM) proteins nidogen-1 (NID1) and decorin (DCN) improve the functionality and survival of the β-cell line, EndoC-βH3, and the viability of human islets post-isolation. To advance the use of these ECM proteins toward a clinical application and elucidate the mechanisms of action in primary islets, the study assesses the effects of ECM proteins NID1 and DCN on isolated human donor islets cultured in normoxic and hypoxic conditions. NID1- and DCN-treatment restore β-cell functionality of human donor islets in a hypoxic environment through upregulation of genes involved in glycolytic pathways and reducing DNA fragmentation in hypoxic conditions comparable to normoxic control islets. The results demonstrate that the utilization of NID1 or DCN with islets of Langerhans may have the potential to overcome the hypoxia-induced cell death observed post-transplantation and improve transplant outcomes.