Probing immunovascular mechanobiology in pneumonia-associated acute lung injury at the single capillary level

PROJECT SUMMARY/ABSTRACT Acute respiratory distress syndrome (ARDS) and its less severe form, acute lung injury (ALI), are devastating, life-threatening respiratory illnesses that can result from pneumonia. Injury to the alveolar epithelial-endothelial barrier in ARDS results in alveolar edema that mechanically impairs alveolar distensibility, hinders gas exchange, and promotes inflammation. Disruption of normal lung mechanics and biology demonstrate the need to study ARDS at the intersection of lung immunobiology and physical sciences. The importance of lung mechanobiology is reflected by current effective therapeutic interventions that target lung mechanics, such as protective mechanical ventilation and prone positioning. While ARDS edema is known to compromise alveolar mechanics, the downstream consequences on capillary mechanics, hemodynamics, and oxygen transport are not well known. As a result, it remains unknown how altered capillary function in ARDS affects the trafficking, sequestration, migration, and phagocytosis of key immune cell types, such as resident and recruited macrophages. Our understanding of ARDS microphysiology is limited by a technological gap to study lung respiratory-circulatory function at the cellular scale in real-time. Current imaging modalities such as MRI/CT and histological analyses lack the necessary spatial and temporal resolution to probe dynamic events such as vascular flow, cellular trafficking and migration, and gas exchange. To address these needs, we have developed a novel “LungEx” system that allows mechanistic probing of lung respiratory-circulatory function in real-time at the single capillary scale. LungEx is an ex vivo ventilated and perfused murine lung with preserved physics and biology near that of in vivo lungs, combined with a transparent “crystal” ribcage to allow high- resolution optical microscopy of capillary function in real-time. Combining LungEx with experimental murine models of ALI caused by pneumonia (PNA-ALI), we have preliminarily observed altered capillary function in edematous PNA-ALI regions. Here, utilizing LungEx, we will test the hypotheses that: altered alveolar mechanics in PNA-ALI impairs capillary mechanics, restricts RBC flow trafficking, and hence reduces oxygen transport on the capillary scale (Aim 1); and altered mechanics in PNA-ALI differentially impedes resident vs recruited macrophage function, promoting a mechanosensitive inflammatory profile (Aim 2). These studies will improve our understanding of the mechanobiology and mechanoimmunity underlying pneumonia-associated ARDS pathogenesis that begins on the single capillary level and how it affects key immunovascular components of the lung. As part of the pre-doctoral fellowship training towards a physician-scientist career, the proposed work will emphasize hypothesis-based experimental design, scientific communication and mentorship, integration of research with clinical practice, and will be carried out at Boston University.