Human Vascularized Macrophage-Islet Organoids to Model Immune-Mediated Pancreatic B Cell Pyroptosis upon Viral Infection

Infectious Diseases Endocrinology Biochemistry Life Sciences Immunology Medicine Cell Biology
vascularized macrophage islet organoids B cell pyroptosis viral infection immune-mediated

Background

Since the outbreak of the COVID-19 pandemic, SARS-CoV-2 infection has not only affected the respiratory system but has also been closely related to metabolic diseases such as diabetes. Clinical observations have found occurrences of new-onset diabetes and worsening of existing diabetes among COVID-19 patients, particularly with an increase in the incidence of Type 1 Diabetes (T1D). This has drawn researchers’ attention to explore the potential mechanisms of viral infection in pancreatic damage and the onset of diabetes.

In the field of research on immune-mediated damage related to viral infections, the lack of human models has limited a deep understanding of the mechanisms of host damage induced by viral infections. To address this, the research team led by Liuliu Yang utilized spatial multi-omics technology to analyze immune cell changes in COVID-19 pancreatic autopsy samples, establishing a human pluripotent stem cell (hPSC)-derived vascularized macrophage-islet organoid model to simulate virus-induced pyroptosis of pancreatic islet B cells. The research findings were published in the journal “Cell Stem Cell”.

Research Methods

This research utilizes a multi-step experimental design to explore the impact of SARS-CoV-2 and Coxsackievirus B4 (CVB4) infection on immune cells and pancreatic islet B cells.

Sample Analysis

Researchers first collected COVID-19 pancreatic autopsy samples, using the GeoMx spatial multi-omics platform to analyze the impact of viral infection on the immune cell composition in the islet regions. They selected multiple regions of interest (ROI) from the islet, duct, and exocrine areas and performed systematic analysis on COVID-19 samples and control group samples using morphologic markers (insulin, pan-cytokeratin, and TOTO-3 staining). Multi-omics testing revealed a significant enrichment of pro-inflammatory macrophages in the islet regions of COVID-19 patients.

Single-cell RNA Sequencing Analysis

To further analyze the impact of viral infection on islet cells, the research team employed single-cell RNA sequencing (scRNA-seq) to study human pancreatic islet samples exposed to SARS-CoV-2 or CVB4. Analysis showed that viral infection activated pro-inflammatory pathways in macrophages while inducing pyroptosis pathways in islet B cells. Additionally, autophagy, ferroptosis, and other cell death pathways were identified in the B cell clusters.

Organoid Construction

To verify whether pro-inflammatory macrophages lead to B cell pyroptosis, researchers further constructed vascularized macrophage-islet organoids (VMI). In this process, the team utilized hPSCs-derived pancreatic endocrine cells, macrophages, and vascular endothelial cells, reorganizing these cells into a 3D culture system to form VMI organoids. The cells within the organoids demonstrated superior functionality compared to separately cultured hPSC-derived cells, particularly in the expression and secretion functions of B cells and endothelial cells. Electron microscopy revealed that endothelial cells in the organoids had formed fenestrations to support intercellular material exchange.

Verification of Cell Death Mechanisms

When exposed to SARS-CoV-2 or CVB4, the research team found that macrophages within the VMI organoids would engulf damaged B cells. Further analysis indicated that pro-inflammatory macrophages in virus-exposed organoids significantly expressed pyroptosis-related genes and activated the TNFSF12-TNFRSF12A signaling pathway. To verify the pathway’s role, researchers conducted experiments by adding TNFSF12 protein and neutralizing antibodies, finding that blocking the TNFSF12 pathway significantly reduced B cell pyroptosis.

Research Results

This study systematically reveals the mechanism of B cell pyroptosis induced by viral infections. Spatial multi-omics and single-cell RNA sequencing results indicate an enrichment of pro-inflammatory macrophages in the islet regions of COVID-19 samples, with the pyroptosis pathway being activated. B cell pyroptosis is closely linked to TNFSF12 signaling in macrophages, and B cell pyroptosis can be reduced by blocking the TNFSF12 pathway. Further research also found that the combined action of IL-1β and TNFSF12 can increase the occurrence of pyroptosis, providing a new perspective for understanding pancreatic damage and diabetes onset caused by COVID-19.

Significance of the Study

The vascularized macrophage-islet organoid model developed in this study provides a powerful tool for studying immune-mediated pancreatic damage, addressing the current lack of human models. Through this model, researchers have revealed the potential link between COVID-19 and diabetes onset, particularly how immune cells induce pyroptosis of islet B cells via the TNFSF12-TNFRSF12A signaling. This offers theoretical support for further investigation of virus infection and immune cell-mediated host damage, as well as potential targets for the prevention and treatment of diabetes and its complications.

The innovation of this study is reflected in the following points:

  1. Model Construction: For the first time, a vascularized macrophage-islet organoid was constructed using hPSCs to authentically simulate interactions between immune cells and islet cells.
  2. Mechanism Exploration: Multi-omics technology revealed the molecular mechanisms by which pro-inflammatory macrophages induce B cell pyroptosis via the TNFSF12-TNFRSF12A signaling.
  3. Multi-pathway Analysis: The study also revealed roles of autophagy, ferroptosis, and multiple other cell death pathways under viral infection, providing a comprehensive perspective for understanding the complex mechanisms of islet damage.

Future Prospects

Although this study provides new explanations for pancreatic damage induced by COVID-19, due to individual differences among COVID-19 patients and the limited availability of pancreatic autopsy samples, further expansion of the sample size is needed to verify the performance of pro-inflammatory macrophages in different patients. Meanwhile, the vascularization functionality of VMI organoids is not yet fully mature, and future research can further optimize culture conditions to improve vascular structure within the organoids for better simulation of the in vivo environment. Additionally, given the observed synergistic role of IL-1β in B cell pyroptosis, future studies can delve into the interaction between IL-1β and TNFSF12 to reveal regulatory networks of the pyroptosis pathway, thereby providing more precise targeted strategies for antiviral and diabetes treatments.

This research not only made significant advancements in the study of COVID-19’s pathogenesis and diabetes onset but also demonstrated the potential application of organoid models in immune-mediated damage research, providing new directions and technical support for future studies in related fields.