Regulation of bone marrow homing by hematopoietic stem cell vesicles

/ABSTRACT The goal of the proposed five-year training plan is the development of my independent research career as an academic hematopathology physician-scientist studying hematopoietic stem and progenitor cell (HSPC) crosstalk and transplantation. I am currently a research fellow at the Children’s Hospital of Philadelphia (CHOP) and attending physician in the Division of Hematopathology at the University of Pennsylvania (UPenn). I am specifically seeking to develop and refine skills required for my successful career as an independent investigator, including expertise in HSPC transplantation and microscopy, miRNA mimic and inhibitor screening, lipid nanoparticle delivery, and bioinformatics. My overarching goal is to improve HSPC transplantation outcomes through study of key mechanisms of HSPC-niche cell crosstalk. My mentor for this award is Dr. Peter Kurre, a recognized leader in hematopoietic stem cell biology and bone marrow (BM) failure syndromes. To further add to my scientific and career guidance, I have assembled a mentoring committee composed of scientists and physician-scientists from complementary research fields. I will have the full resources and support of UPenn and CHOP available for the completion of my research and career development goals. This proposal outlines experimental plans to define mechanisms of cellular crosstalk between HSPCs and BM ECs that will inform potential strategies for improving HSPC transplantation. Graft success after transplantation requires initial homing of donor HSPCs to the bone marrow niche, a specialized vascular microenvironment that supports long-term blood cell and immune system reconstitution. BM migration is a dynamic process involving various adhesion and signaling molecules that are not completely defined. My preliminary data have elucidated a novel mechanism of crosstalk between HSPCs and ECs that initiates from cargo trafficked by secreted extracellular vesicles (EVs). Specifically, HSPC EVs promote remodeling of ECs and lead to reciprocal CCR2 receptor-ligand interactions that likely interact with CXCR4 to drive HSPC migration. This proposal will define the molecular mechanisms underlying EC remodeling and HSPC migration, and investigate innovative pre- conditioning strategies to recapitulate and exploit physiologic mechanisms with the goal of improving HSPC transplantation outcomes. These objectives will be achieved via three specific aims: to elucidate key signaling pathways driving EC remodeling, to define CCR2 cooperativity in BM homing, and to test pre-conditioning strategies to induce EC CCR2 ligand upregulation and enhance HSPC engraftment. The outcome of these studies will deepen our understanding of HSPC-niche crosstalk and unveil new therapeutic strategies to optimize HSPC transplantation. Completion of these aims will consolidate my experience in models of murine HSPC transplantation and EV-mediated signal transduction, further my training in nanoparticle-based in vivo delivery, and provide the basis for a future R01 funding proposal, leaving me uniquely prepared for an independent career as a physician-scientist with a focus on HSPC transplantation. Project Number: 1K08HL175130-01A1 | Fiscal Year: 2025 | NIH Institute/Center: National Heart Lung and Blood Institute (NHLBI) | Principal Investigator: Stephanie Hurwitz | Institution: INDIANA UNIVERSITY INDIANAPOLIS, INDIANAPOLIS, IN | Award Amount: $153,117 | Activity Code: K08 | Study Section: NHLBI Mentored Clinical and Basic Science Study Section[MCBS (JA)] View on NIH RePORTER: https://reporter.nih.gov/project-details/1K08HL17513001A1