Periodic Reporting for period 3 - BreakingBarriers (Targeting endothelial barriers to combat disease)
Período documentado: 2022-07-01 hasta 2023-12-31
Tissue homeostasis requires coordinated barrier function in blood and lymphatic vessels. Opening of junctions between endothelial cells (ECs) lining blood vessels leads to tissue fluid accumulation that is drained by lymphatic vessels. A pathological increase in blood vessel permeability or lack or malfunction of lymphatic vessels leads to edema and associated defects in macromolecule and immune cell clearance. Unbalanced barrier function between blood and lymphatic vessels contributes to neurodegeneration, chronic inflammation, and cardiovascular disease. In this proposal, we seek to gain mechanistic understanding into coordination of barrier function between blood and lymphatic vessels, how this process is altered in disease models and how it can be manipulated for therapeutic purposes. We will focus on two critical barriers with diametrically opposing functions, the blood-brain barrier (BBB) and the lymphatic capillary barrier (LCB). ECs of the BBB form very tight junctions that restrict paracellular access to the brain. In contrast, open junctions of the LCB ensure uptake of extravasated fluid, macromolecules and immune cells, as well as lipid in the gut. Using selective genetic manipulation in blood and lymphatic endothelium, respectively, of novel effectors of BBB and LCB junctions that we have identified, we will determine how function of the BBB and the LCB in adult homeostasis and in disease models is coordinated. Progress made during the initial grant period includes i) approaches to prevent neuroinflammation associated with BBB defects that develop in the face of a brain tumor, ii) identification of novel molecular approaches to manipulate the BBB, and iii) imaging of cranial lymphatic outflow in human patients using MRI. These pioneering studies promise to open up new opportunities for research and treatment of neurovascular and cardiovascular disease.
Research performed under WP1 has led to the following achievements. 1. We characterized blood brain barrier (BBB) permeability defects and associated neuroinflammation in mouse orthotopic glioma tumor models, and in human glioma patient-derived xenografts. We also identified molecular approaches to prevent tumor supportive macrophage polarization that prolong survival of glioma tumor-bearing mice (Geraldo et al, JCI 2021). 2. We identified a novel critical ligand-receptor pathway that regulates maintenance of BBB integrity in adult mice, using genetic models of ligand and receptor inactivation and monoclonal antibodies that block ligand binding to the receptor (Boye et al, Nat Comm 2022). Going forward, we aim to test if antibody-mediated BBB opening can increase chemotherapy delivery into the brain of tumor-bearing mice. In work that sets the stage for WP2, we have optimized single cell sequencing and obtained single cell RNA seq data of mouse retinas (Zarkada et al, Dev Cell 21). Going forward, we will apply this technology to brain endothelium from BBB mutant mice and controls, with the goal to identify effectors of BBB permeability downstream of the receptor. Work under Aim3 has led to the identification of meningeal lymphatic drainage pathways that are conserved between mice and humans (Jacob et al, under revision). WP4 experiments will be initiated in the coming year.
Significant achievement 1 prompts us to develop monoclonal antibodies blocking tumor-supportive macrophage polarization that could be combined with existing chemotherapy-immunotherapy to combat glioblastoma tumor progression, which remains a major unmet medical need. Furthermore, significant achievement 2 synergizes with these efforts, as antibody-mediated BBB opening could enhance chemotherapy delivery into the tumor-bearing brain. Testing efficacy and potential toxicity of such antibodies is required to justify this conclusion and could lead to translation into the clinic. Finally, our MRI protocol allows, for the first time, the visualization of cranial lymphatic drainage and will likely become a standard in medical practice, as abnormal cranial lymphatic drainage is suspected to contribute significantly to the aggravation of neurological disease in patients with various conditions such as idopathic intracranial hypertension, multiple sclerosis, Alzheimer's disease and glioma progression.