Abstract
Rationale: Pancreatic islet transplantation is a promising cell-based therapy for replacing damaged β-cells and helping restore insulin independence in Type 1 diabetes (T1D) patients. However, the challenges associated with transplant rejection and islet viability hinder long-term islet graft function. A key obstacle is islet-induced inflammation, especially macrophage (MΦ)-associated inflammation in the early stages, contributing to islet graft mass loss. Understanding and mitigating this inflammation through an in vitro model is crucial for improving islet transplantation outcomes.
Approach: To address these questions, a novel microfluidic-based Islet-MΦ-Inflammation-on-chip (IMI) platform was developed and utilized. The platform, coupled with brightfield and fluorescence live-cell imaging, allowed for a systematic investigation of inflammation reactions and their spatiotemporally distinct interactions, specifically targeting the native inflammatory microenvironment of islet transplantation and islet graft properties. The platform allowed for the assessment of interactions, morphology, functionality, and inflammatory responses between mouse islets and MΦ, as well as under various stress stimuli, such as hypoxia and hyperglycemia that were two important microenvironmental factors for islet grafts. Additionally, the integration of a 3D bioprinting technique enabled the development of multiscale porous scaffolds composed of interconnected yet distinguishable bio-ink hydrogel particles, advancing in encapsulating human pancreatic islets for islet transplantation without immunosuppressant.
Results: The study revealed notable findings in the dynamics of islet-MΦ interactions and the effects of stress conditions on islet functionality and inflammation. In IMI platform, the interaction between islets and MΦ led to increased cytokine production, particularly TNF-α, G-CSF, and IL-1α. Under hypoxic stress, there was a marked elevation in the production of TNF-α, G-CSF, IL-1α, and IL-6. Similarly, high glucose stress further escalated cytokine production. The study also highlighted the impact of these stress conditions on gene expression, islet physiological functionality, and insulin secretion. Changes in MΦ morphology and activities were observed under stress conditions, particularly in response to hyperglycemia. Additionally, the in vitro platform was explored to study therapeutic strategies like etanercept and metformin in order to alleviate inflammation. Both etanercept and metformin showed anti-inflammatory effects, reducing TNF-α and IL-6 production. Additionally, the development of multiscale porous scaffolds hydrogel particles proved effective in encapsulating pancreatic islets, enhancing their insulin release in response to glucose.
Conclusion: We designed, fabricated, and applied an islet-MΦ-inflammation-on-chip, the first of kind in islet transplantation. The studies reveal the critical role of MΦ-islet interactions in islet inflammation and offer significant insights for optimizing islet transplantation procedures. Incorporating innovative techniques like multiscale porous scaffolds serves as a sophisticated platform for analyzing complex interactions in the islet transplantation microenvironment. This study contributes significantly to the field of T1D research, paving the way for future studies on transplantation outcomes and the development of novel therapeutic strategies.
