Abstract. Extracellular vesicles and particles (EVPs) are a group of heterogeneous nanoparticles that are secreted into the extracellular milieu by many types of cells. EVPs have emerged as important mediators in cell-to-cell communications within organs. Recent studies have suggested that EVPs might be involved in β cell-immune cell interaction and β cell dysfunction and survival in type 1 diabetes (T1D). However, many of these studies were performed using mouse models and not focused on human samples. Hence, there is a unmet need to understand the contribution of human islet/pancreas-associated EVPs in T1D progression. Here, we have assembled an interdisciplinary team, including experts in islet biology (Chen, Liu), EVP biology (Lyden), vascular biology (Rafii), and T1D patient care (Antal), to test the hypothesis that abnormal EVPs of pathogenic human islets and pancreatic tissues disrupt human islet function and survival and trigger T1D progression. We have performed extensive proteomics analyses of EVPs derived from human β cell lines cultured in T1D conditions. In addition, by comparing the plasma membrane protein profiles of human β cell line and primary human islet-derived EVPs with an EVP proteomic database containing 426 human samples, we have identified several plasma membrane protein candidates to isolate β cell-specific EVPs. Here, we will use multiple platforms, including primary human islets from healthy, pre-T1D, and T1D donors, human pluripotent stem cell (hPSC)-derived islet organoids, perfusable microfluidic devices containing vascularized islets, and pancreatic slice culture to systematically examine the role of human islet/pancreas-associated EVPs in islet cell function and survival during T1D progression. In this proposal, we expect to identify membrane-bound EVP protein panels to purify EVPs from human α, β cells, islets, and pancreatic tissue. We will define the EVP protein and RNA profiles and identify signature molecules associated with islet status during T1D progression. Moreover, we will systemically dissect the roles of human islet/pancreas EVPs in human β cell function and survival, as well as their role in the crosstalk between β cells and peri-islet cell niche. Overall, this study will facilitate the identification of novel “biomarkers” for T1D diagnosis and guide the development of new therapeutic strategies to treat and prevent the progression of T1D.