Type 1 diabetes is a chronic autoimmune disease in which the pancreas produces little or no insulin. Insulin is a hormone needed to allow sugar (glucose) to enter cells to produce energy. The exact cause of type 1 diabetes is unknown. Usually, the body’s own immune system mistakenly destroys the insulin-producing cells (called beta cells) in the islets of Langerhans of the pancreas.
Dr. Teresa Rodriguez-Calvo is a junior group leader at the Institute of Diabetes Research (Helmholtz Zentrum München) in Germany.
She runs a lab focused on increasing our understanding of the immunopathogenesis of human type 1 diabetes in order to develop novel therapies aimed at increasing insulin secretion and stopping the autoimmune attack.
We spoke with Dr. Rodriguez-Calvo about her recent publication investigating interferon sensors in the islets of Langerhans and the importance of whole slide imaging for the study and analysis of pancreas pathology.
What new discoveries did you present in your recent publication?
We observed that the interferon sensors MxA, PKR and HLA-I are expressed in the islets of Langerhans in type 1 diabetic subjects and at risk-individuals. An interesting observation is that in diabetic individuals, these interferon sensors are predominantly detected in islets that still contain insulin, but their expression is associated with the downregulation of multiple genes in the insulin secretion pathway, indicating a potential functional defect of the remaining insulin-producing beta cells. The expression of these interferon sensors is also more abundant in islets with high immune infiltration, suggesting that they are contributing to the inflammatory environment of the islet and they might exacerbate the immune response.
Representative immunofluorescence images from the islets of Langerhans from a non-diabetic donor showing normal HLA-I expression (top), and a type 1 diabetic donor with high expression of HLA-I (bottom). Scale bars, 100 μm. Image collected using automated whole slide scanning.
We also observed a positive correlation of these sensors with the presence of a protein from the capsid of enteroviruses, which suggest that they might be induced in response to viral infections, as we would expect for interferon responses. For this reason, we believe that our study highlights the importance of interventions that prevent or eliminate viral infections and also supports the use of therapeutic agents that could diminish interferon-induced inflammation in individuals with type 1 diabetes. One of our future goals is to further characterize these innate immune responses and to study how the immune system recognizes viral as well as self-antigens during the course of type 1 diabetes.
How do you use digital whole slide imaging in your research?
One of the biggest challenges in the study and analysis of pancreas pathology is the heterogeneity of the human pancreas, which is evident at multiple levels.
In our recent publication, we scanned whole tissue sections using a ZEISS slide scanner. The numbers of insulin- and glucagon-positive islets, as well as the presence of interferon-associated molecules like HLA-I, MxA, PKR, and dsRNA, were assessed manually. The analysis was performed by researchers blinded to the study groups. Two different operators evaluated the expression of every marker and islet independently and blinded. Then, a third operator combined and revised all the analysis. Next, results from consecutive sections stained for the different markers were combined into a single image using the annotation tools from the ZEISS Zen software.
For other parts of the project, we used an open-source software for digital pathology and whole-slide image analysis as described by Bankhead et al. (2017). We have recently published an article describing how we perform whole-slide imaging analysis of the pancreas using a ZEISS slide scanner and QuPath (Apaolaza et al. (2021)).
A whole pancreatic tissue section. Each positive islet was assigned a colored circle based on the number of expressed interferon response markers as follows: red for the expression of one marker, yellow for two markers, purple for three markers, and blue for four markers. Scale bar, 290 μm. Image collected using automated whole slide scanning.
See image slider below for detailed, inset images.
Overall, whole-slide imaging is essential for the study of the pancreas and of type 1 diabetes. Understanding and characterizing the large heterogeneity and the changes that we observe in the pancreas during disease progression, even within an individual, is greatly needed in order to move towards successful therapeutic and preventive strategies in diabetes.