Molecular determinants of islet-specific endothelium for regulation of beta-cell homeostasis - ABSTRACT Islet transplantation is a promising treatment for type 1 diabetes but suffers from significant islet loss with the standard intraportal liver infusion, consequently requiring large numbers of costly islets, often multiple transplants, and suboptimal achievement of long-term insulin independence. This is because islet isolation protocols result in regression of islet-specific endothelial cells (ISECs), with the loss of the critical, supportive islet vascular niche resulting in islet death. Furthermore, strategies to achieve islet engraftment in an extrahepatic site have been stymied by poor vascularization and lack of knowledge of how β-cell interaction with ISECs contributes to β-cell homeostasis. The overall goal of this project is to engineer ISECs to uncover the cellular cross-talk between -cells and their specialized vascular niche, to ultimately augment transplanted islet engraftment in the subcutaneous space. Each organ is vascularized by unique, specialized endothelial cells (ECs) that provide a tissue-specific vascular niche that supplies angiocrine factors key in choreographing organ homeostasis and repair. Indeed, there is growing evidence that a functional and physical interplay exists between specialized ISECs and -cells. Employing single cell analyses, we obtained a molecular signature of ISECs, identifying the novel transcription factor NKX2-3. This proposal will explore if vascularization of islets with NKX2-3+ ECs will facilitate engraftment, function, and survival of subcutaneously transplanted islets. ISECs have the additional critical feature of modulating the expression and migration of immune mediators, with macrophages being the most abundant pancreatic immune cell. In turn, these macrophages supply growth and immunomodulatory factors to sustain the integrity of -cells. Therefore, we hypothesize that induction of NKX2-3 in ECs confers these cells with the specialized properties of ISECs which, by supplying defined angiocrine factors and proper polarization of pro-reparative macrophages, support islet function. Accordingly, we will test the hypothesis that NKX2-3 is necessary for the specification of ISECs, which have the capacity to support islets in vitro and in vivo, through the following aims: Aim 1: Assess the impact on islet function of selective and conditional loss of NKX2-3 in pancreatic ECs. Aim 2: Examine the efficacy of enforced NKX2-3 expression in human umbilical vein endothelial cells in augmenting durable subcutaneous engraftment of transplanted islets. Aim 3: Decipher the mechanism by which NKX2-3, through macrophage polarization, coordinates pro-regenerative and anti-fibrotic islet innate inflammatory responses within the pancreas. The proposed training will guide and enhance my development in core competencies, including immunology, bioinformatics, and stem cell-derived islets, that will enable me to transition to research independence as a surgeon-scientist dedicated to improving islet transplantation outcomes. Weill Cornell Medicine is an ideal environment to execute this training plan due to its outstanding physical resources and its robust intellectual community of researchers with strong records of mentorship of early-stage investigators.
