Periodic Reporting for period 1 - EMPAtHy (Endothelial Cell Molecular and Metabolic Heterogeneity in Pulmonary Arterial Hypertension)
Reporting period: 2019-09-01 to 2021-08-31
The main role of the lung is to support blood oxygenation while removing carbon dioxide from the body. Appropriate blood circulation through the lungs, ensured by pulmonary blood vessels (arteries, capillaries and veins), is therefore crucial to support this organ’s function. In the context of pulmonary arterial hypertension (PAH), a dramatic increase in blood pressure in the pulmonary blood vessels ultimately results in right heart hypertrophy (corresponding to an abnormal enlargement of the cardiac muscle of the right heart ventricle, which pumps the blood to the lung), and heart failure, responsible for patients’ death. This disease is associated with a dysfunction of lung endothelial cells (ECs), which compose the innermost layer of blood vessels and regulate several key functions, such as vascular tone, blood vessel permeability, inflammation, etc. In PAH, lung EC dysfunction promotes an intense pulmonary vascular remodeling, imbalanced vascular tone, and inflammation. To date, with the exception of lung transplantation, this rare disease remains incurable with limited survival. A better understanding of the lung vasculature and of molecular processes underlying this disease is therefore necessary to propose new effective therapies.
Since ECs are diverse in order to support different functions throughout the whole body and the lung vasculature, the main objective of this project was to provide an in-depth molecular characterization of the lung EC heterogeneity in health and disease, and highlight PAH-specific EC subtype(s) involved in vascular remodeling, if any. Since the host lab previously showed that EC metabolism is a cornerstone of EC function in health and disease, a second objective was to characterize the metabolic fingerprints of lung ECs and in particular of PAH-specific EC subtypes(s) associated with vascular remodeling.
Since ECs are diverse in order to support different functions throughout the whole body and the lung vasculature, the main objective of this project was to provide an in-depth molecular characterization of the lung EC heterogeneity in health and disease, and highlight PAH-specific EC subtype(s) involved in vascular remodeling, if any. Since the host lab previously showed that EC metabolism is a cornerstone of EC function in health and disease, a second objective was to characterize the metabolic fingerprints of lung ECs and in particular of PAH-specific EC subtypes(s) associated with vascular remodeling.
Different protocols were established to isolate ECs from mouse lung and 10 other organs, and downstream molecular analysis by profiling gene expression at the single cell resolution (single cell transcriptomics). Analysis of these data revealed a wide range of different EC subtypes, depending on organs, vessel types and physiologic stimuli. We showed that lung ECs, as well as lung EC subtypes showed unique molecular and metabolic features. In particular, lung ECs were enriched with immunoregulatory-related signatures, suggesting a putative role in immune surveillance. To perform a similar analysis of human lung ECs, we setup a protocol adapted to frozen tissues (biopsies). Since pulmonary hypertension has been demonstrated to be a frequent complication of COVID-19, and since there was (and still is) an urgent research need in understanding COVID-19 lung disease and in particular its effects on lung ECs, we prepared 12 human control and 7 COVID samples from lungs obtained during autopsy, in order to analyze human endothelium. We could delineate 14 distinct lung EC subtypes, present in both conditions, and described molecular changes due to the disease, including a link to PAH pathophysiology. We further analyzed lung ECs from human and mouse datasets including control and PAH samples. We didn’t identify specific EC-subtypes associated with PAH. Further analysis of PAH mouse arterial ECs (given that PAH mostly affects small pulmonary arteries), revealed significant transcriptomic changes for several metabolic pathways, in line with the already reported lung EC activation and dysfunction in this disease.
This project expanded our knowledge of lung EC physiology and pathophysiology. It provided highly valuable single cell transcriptomics resources (atlas) for the scientific community in the vascular and pneumology fields, and beyond. Advances in understanding the endothelial aspects of lung COVID-19 and PAH diseases were reached, thereby yielding novel potential therapeutic insights. Increasing the size of the PAH datasets with additional human lung samples, will be needed to further strengthen our results, as well as the functional validation of the findings.