Type 1 diabetes (T1D) results from autoimmune insulitis destruction of insulin-secreting β cells. β cell senescence with upregulated expression of P21 has been observed in the adult NOD mice and new-onset patients. However, it remains unclear whether the beta cell senescence is an outcome of persistent insulitis, and the factors trigger insulitis remains unclear.

The initial infiltration in the islets of 3-week-old infant NOD mice was predominantly Mθ, but the mechanisms for the initial Mθ infiltration remain unclear. A recent report (Sturmlechner et al., Science2021) demonstrate that P21 activation not only results in cell-cycle arrest but also activate a large collection of genes that encoding chemokines (i.e., CXCL14) and cytokines (i.e., IL-6), called P21-activated secretory phenotype (PASP), which attract Mθ and other cell infiltration to exert immunosurveillance. It is well recognized that abnormal immune surveillance could lead to autoimmune diseases, although the mechanisms remain largely unknown. Our preliminary data with RNA-seq analysis and in vitro culture of CD45+ hematopoietic stem cell-derived immunocytes and CD45- parenchymal stem cell-derived fibroblast reticular cells (FRCs) and β cells from 3-week-old infant NOD, insulitis-resistant NOR, and non-autoimmune C57BL/6 (B6) mice indicate that exaggerated P21-activated PASP in fibroblast reticular cells (FRCs) and immunocytes (i.e., macrophages) intiates peri-insulitis and insulitis, leading to β cell senescence and destruction and full blown T1D.

Imaging mass cytometry (IMC), a powerful novel technology, allows us to analyze in situ tissue cells with more than 30 markers on the cell surface, intracellularly, and in the nucleus, and can identify cell subsets with different intracellular cytokine and chemokine profiles as well as intracellular signaling pathways and spatial cell distribution. We have developed IMC techniques in our lab and have applied IMC to study of GVHD target tissues (Kong et al: Blood, 2013) and pancreatic islet cellular analysis of murine and human islets (see preliminary data). In the current studies, we will analyze murine and human islets with IMC in couple with other functional studies to test whether exaggerated P21-activated PASP exists in the islets of new-onset T1D patients. If successful, the proposed studies will help establish a paradigm-shift concept of T1D pathogenesis.