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Project Abstracts - CBDS

Discovery and Investigation of Noninvasive Diagnostic Potential of Circulating Pancreatic Islet Beta Cell Exosomes as Biomarkers of Beta Cell Injury

Contact PI: Prashanth Vallabhajosyula, MD

Abstract

Exosomes are tissue specific microvesicles containing protein and RNA cargoes; they are released by many cell types into bodily fluids including peripheral blood. Exosomes comprise a central mechanism of intercellular communication, both at the paracrine and systemic levels. Exosome quantitative and cargo profiles are dynamic, reflecting conditionspecific changes imposed on their cellular counterparts. Therefore, plasma tissue specific exosome profiles have the potential to serve as a “liquid biopsy” of tissue of interest. Work in our laboratory has shown that islet β cells release insulin-containing exosomes into their environment. We have discovered that a β cell specific surface protein, FXYD2A, is also expressed on β cell exosome surface, and can be utilized for purification and noninvasive characterization of β cell exosomes from peripheral blood. Our studies have demonstrated that plasma FXYD2A enriched exosomes, representing β cell exosomes, are altered in condition-specific manner based on stimulation or injury imposed on β cell mass. Based on these findings, we hypothesize that characterization of plasma β cell specific exosome platform has translational potential in the field of T1D diagnostics. We propose to study the following aims to investigate this novel concept.

1) Study quantitative and cargo profiles of β cell exosomes enriched from supernatant medium of cultured human islets harvested from pancreata of donor subjects with stage 1/2 T1D, stage 3 T1D versus age-matched controls.

Preliminary work in our laboratory demonstrated that β cell exosomes released into supernatant medium by cultured human islets from T1D donors (n=3) are markedly altered compared to age-matched controls (n=5). We will utilize the supernatant medium available from human islet isolations performed by the Human Pancreas Analysis Program (HPAP). Supernatant medium from cultured human islets from 5 donor subjects with > stage 3 T1D and low C peptide levels (between 0.2 to 0.7 ng/ml), 5 donors with stage1/ 2 T1D (> 2 autoantibody positive, asymptomatic hyperglycemia or no hyperglycemia), and 5 age-matched normal controls (within 5 years) will be analyzed to understand T1D specific changes in β cell exosome cargoes.

2) Investigate the noninvasive diagnostic potential of plasma β cell exosomes to prognosticate and differentiate progressive β cell stress/ injury in subjects with newly diagnosed T1D (stage 2 T1D) compared to age-matched controls

In this pilot feasibility study, we will recruit 10 subjects with newly diagnosed stage 2 T1D (within 3 months of diagnosis), and characterize their circulating β cell exosome profiles at 6-month intervals over a follow-up of 2 years (n=4 samples per subject). Age and gender matched normal subjects without T1D or positive autoantibody status will serve as controls. We will investigate for changes in quantitative and cargo profiles of plasma β cell exosomes to understand the feasibility of this platform to reliably characterize β cell specific exosomes in T1D and control subjects over the follow-up period. Differences in profiles between the 2 groups will be characterized to assess whether a β cell exosome signature can be developed that enables noninvasive, time sensitive, and accurate reflection of progressive β cell stress in T1D development. This signature will be correlated with immunologic (autoantibodies) and metabolic (hemoglobin A1c, OGTT, C-peptide, fasting glucose) data to understand its diagnostic potential compared to current clinical standards.