Pilot 14 – Hyalouronan and hlyaladherins in the pathogenesis of cystic fibrosis related diabetes

P.I.: Marika Bogdani, PhD
Staff Scientist, Matrix Biology
Benaroya Research Institute

This proposal seeks to determine the contributions of hyaluronan (HA), a major component of islet extracellular matrix (ECM) and HA-binding molecules, hyaladherins, to islet pathology and β-cell loss in cystic fibrosis (CF)- related diabetes (CFRD). CFRD has become the most common co-morbidity in CF, but its causes and pathophysiology remain largely unknown. CFRD is a unique form of diabetes, nevertheless, the islet histopathology in CFRD shows some characteristic features of islet damage observed in type 1 and type 2 diabetes. Our recent studies in human diabetic pancreata suggested that altered islet HA and hyaladherins contribute to islet inflammation and diabetes pathogenesis. We hypothesize that the amount and distribution of these specific islet ECM components are altered in CFRD, leading to formation of an abnormal islet ECM, which contributes to chronic islet inflammation and β-cell damage in CFRD. We will address the following two Specific Aims: In Aim 1, we will determine the kinetics of changes in the amount and distribution of HA and hyaladherins that take place in human islets in CF and CFRD. These changes will be correlated with the extent of β-cell loss and islet immune cell infiltrations. For these studies, we will examine autopsy pancreas sections from CFRD patients, CF patients without diabetes, and age-matched controls. Tissues from patients with type 1 diabetes and appropriately-matched individuals without diabetes or any other pancreas disease will serve as positive and negative controls for the measurements of interest. We anticipate that tissues from CFRD patients will show extensive deposits of islet HA and hyaladherins versican and IαI, together with a decrease in β-cell area, reduced insulin expression, and presence of islet immune cell infiltrates. In Aim 2, we will determine whether similar changes in islet ECM take place in the pancreas tissues of CFTR-knockout pigs and ferrets with altered glucose metabolism, two animal models used to study human CFRD. We will examine whether islets from CFTRknockout ferrets and pigs display altered HA and hyaladherins during the course of development of hyperglycemia in these animals. We will initially establish the staining protocols for HA and hyaladherins in the normal pig and ferret pancreas. Pancreas tissues from just born (birth to 3 days), one month old, and young adult CFTR-knockout animals will then be examined for changes in the amount and distribution of these ECM molecules in correlation with the decrease in relative β-cell areas, islet inflammation, and metabolic parameters of blood glucose levels, impaired glucose tolerance, and insulin secretion. We will study novel aspects of islet pathology in CF prior to the development of CFRD and in CFRD. The contribution of islet ECM in islet lesion and CFRD pathogenesis is unknown. Therefore, these studies will provide new insight into our understanding of the process leading to β-cell damage in CFRD, and ultimately, will lead to the identification of molecules key to the islet pathogenic process, which can serve as potential molecular targets for therapeutic interventions to prevent β-cell damage in CFRD. The goals of this grant proposal are, thus, directly relevant to the mission of the NIDDK.