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Introduction: Adaptive angiogenesis can drive repair or underlie the pathogenesis of tissue remodeling. Pulmonary vascular dysfunction is a major manifestation of chronic lung disease (CLD) but the role of angiogenesis in CLD is not well defined. Microvascular capillaries are the vessels most affected by pruning and remodeling in the lung resulting in reduced capillary length and density. Our lab has previously demonstrated that microvascular progenitors (ABCG2 + MVPCs) drive adaptive angiogenesis or loss of tissue structure downstream of the Wnt or mTOR signaling pathways. Therefore, we hypothesize that visualization of the pulmonary microvasculature and MVPC-driven adaptive angiogenesis in three-dimensions is essential to define the role of MVPC-driven adaptive angiogenesis during repair or the pathogenesis of CLD. Methods: To evaluate the contribution of Wnt activated MVPCs to angiogenesis in three-dimensions during injury repair, we crossed ABCG2-Cre ERT2 mice to a BOE strain (flΔex3) with stabilized β-catenin expression and a fluorescent membrane eGFP reporter strain to facilitate lineage tracing. The development and resolution of fibrosis were induced in vivo via aspiration of bleomycin sulfate (0.05U). Mice were retro-orbitally perfused with fluorescently conjugated tomato lectin. Lung tissue was inflated with agarose and up to 500μm thickness precision cut lung slices (PCLS) were mounted for imaging. PCLS were imaged on the Zeiss LSM900 and Z-stacks were obtained. Imaris software (Oxford Instruments) was used for three-dimensional reconstruction and FIJI and Wimasis Image Analysis (Onimagin Technologies) were utilized to segment vessels, quantitate vessel density, volume, diameter, and length. Results: Following perfusion, vascular staining of both the lung and kidney was observed, suggesting successful systemic perfusion and labeling. The pulmonary microvasculature was visualized to a diameter of 1-3μm in high fidelity. We observed a significant reduction in vessel density in mice treated with bleomycin compared to mice treated with a vehicle control. In our three-dimensional reconstructions we observed increased density of ABCG2 + MVPC-derived de novo angiogenic structures in areas of fibrosis. Conclusion: De novo angiogenesis driven by ABCG2 + MVPCs likely plays a role in tissue repair following bleomycin induced lung injury. In addition, we have developed a simple and reliable perfusion technique allowing for the visualization and quantitation of the pulmonary microvasculature in three-dimensions. This tool will allow the quantitation of microvessel remodeling underlying pathogenesis and repair in multiple lung injury models. Thus, this methodology will further support the study and understanding of angiogenesis during CLD and repair following injury. This approach may be utilized in various organ systems to visualize microvasculature structure and its role in disease. NIA RAG073317 NHLBI 1R35HL161238. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Lundberg et al. (2024) studied this question.