Project Grant R01DK137221

THE ROLE OF THE PANCREAS MICROENVIRONMENT IN REGULATING ISLET FUNCTION AND SURVIVAL IN TYPE 1 DIABETES - PROJECT SUMMARY: TYPE 1 DIABETES (T1D) IS CHARACTERIZED BY THE IMMUNE-MEDIATED LOSS OF INSULIN-PRODUCING B-CELLS IN THE ISLET. LOSS OF THE PERI-ISLET ECM HAS BEEN WELL DOCUMENTED IN RECENTLY DIAGNOSED PATIENTS WITH T1D AND IS ASSOCIATED WITH INCREASED INSULITIS AND B-CELL DEATH. IN PRE-SYMPTOMATIC T1D, B-CELL DYSFUNCTION AND ER STRESS OCCUR PRIOR TO SIGNIFICANT IMMUNE CELL INFILTRATION. OUR PRELIMINARY RESULTS INDICATE THAT CYTOKINE-STRESSED B- CELLS EXPRESS ECM DEGRADING ENZYMES (INCLUDING MMPS) THAT MAY CONTRIBUTE TO LOSS OF THE PERI-ISLET ECM PRIOR TO THE ONSET OF INSULITIS AND MAY FACILITATE INFILTRATION OF AUTOREACTIVE IMMUNE CELLS AND B-CELL DEATH. IN THE EARLY STAGES OF T1D, ISLET INFILTRATION CORRELATES WITH LOSS OF PERI-ISLET LAMININ-10. OUR PRELIMINARY DATA SUGGESTS THAT LOSS OF ISLET INTERACTIONS WITH LAMININ-10 INCREASES CYTOKINE-INDUCED DEATH AND INCREASES THE ACTIVITY OF PROTEIN KINASE C D (PKCD), WHERE WE HAVE RECENTLY IDENTIFIED INCREASES IN PKCD ACTIVITY AS A CRITICAL MEDIATOR OF B-CELL DEATH. ADDITIONALLY, PREVIOUS STUDIES HAVE SHOWN THAT ISLET INTERACTIONS WITH LAMININ INCREASE GLUCOSE STIMULATED INSULIN SECRETION (GSIS) VIA INCREASED EXPRESSION OF GLYCOLYTIC ENZYMES AND MEDIATE MITOCHONDRIAL MORPHOLOGY AND FUNCTION. TAKEN ALL TOGETHER, THIS SUPPORTS A ROLE FOR LOSS OF PERI-ISLET LAMININ-10 IN CONTRIBUTING TO T1D PATHOGENESIS. WE HYPOTHESIZE THAT CYTOKINE-STRESSED B-CELLS CONTRIBUTE TO LOSS OF THE PERI-ISLET ECM IN EARLY T1D LEADING TO DECREASES IN B-CELL FUNCTION AND SURVIVAL. WE PROPOSE THE FOLLOWING 2 AIMS: 1) DETERMINE IF CYTOKINE-STRESSED B-CELLS DEGRADE THE PERI-ISLET ECM IN EARLY T1D, AND 2) DETERMINE IF LOSS OF LAMININ-10 INTERACTIONS REGULATES ISLET SURVIVAL AND FUNCTION IN EARLY T1D. EXPERIMENTS FOR BOTH AIMS WILL UTILIZE MOUSE AND HUMAN ISLETS ENCAPSULATED IN A NOVEL 3D BIOMIMETIC SCAFFOLD WITH LAMININ-10, AS WELL AS HUMAN PANCREAS SECTIONS FROM THE NPOD PROGRAM. AIM 1 WILL DETERMINE IF B-CELL MEDIATED DEGRADATION OF THE PERI-ISLET ECM PRECEDES THE ONSET OF T1D. AIM 2 WILL DETERMINE THE MOLECULAR MECHANISMS UNDERLYING ISLET DYSFUNCTION AND DEATH WITH LOSS OF PERI-ISLET LAMININ-10 IN T1D. THE SUCCESSFUL COMPLETION OF THIS PROJECT WILL DEFINE A NEW ROLE FOR THE B-CELL IN DEGRADING THE PERI-ISLET ECM IN EARLY T1D THAT CONTRIBUTES TO ALTERED ISLET FUNCTION AND SURVIVAL. OUR RESULTS WILL CHALLENGE THE CURRENT PARADIGM THAT B-CELLS ARE INNOCENT BYSTANDERS IN T1D ONSET AND WILL PROVIDE NOVEL THERAPEUTIC TARGETS TO HALT IMMUNE INFILTRATION OF THE ISLET AND IMPROVE ISLET FUNCTION AND SURVIVAL.