A census of the lung: CellCards from LungMAP.

The human lung plays vital roles in respiration, host defense, and basic physiology. Recent technological advancements such as single-cell RNA sequencing and genetic lineage tracing have revealed novel cell types and enriched functional properties of existing cell types in lung. The time has come to take a new census. Initiated by members of the NHLBI-funded LungMAP Consortium and aided by experts in the lung biology community, we synthesized current data into a comprehensive and practical cellular census of the lung. Identities of cell types in the normal lung are captured in individual cell cards with delineation of function, markers, developmental lineages, heterogeneity, regenerative potential, disease links, and key experimental tools. This publication will serve as the starting point of a live, up-to-date guide for lung research at https://www.lungmap.net/cell-cards/. We hope that Lung CellCards will promote the community-wide effort to establish, maintain, and restore respiratory health.

Regeneration of the pulmonary vascular endothelium after viral pneumonia requires COUP-TF2.

Acute respiratory distress syndrome is associated with a robust inflammatory response that damages the vascular endothelium, impairing gas exchange. While restoration of microcapillaries is critical to avoid mortality, therapeutic targeting of this process requires a greater understanding of endothelial repair mechanisms. Here, we demonstrate that lung endothelium possesses substantial regenerative capacity and lineage tracing reveals that native endothelium is the source of vascular repair after influenza injury. Ablation of chicken ovalbumin upstream promoter-transcription factor 2 (COUP-TF2) (Nr2f2), a transcription factor implicated in developmental angiogenesis, reduced endothelial proliferation, exacerbating viral lung injury in vivo. In vitro, COUP-TF2 regulates proliferation and migration through activation of cyclin D1 and neuropilin 1. Upon influenza injury, nuclear factor κB suppresses COUP-TF2, but surviving endothelial cells ultimately reestablish vascular homeostasis dependent on restoration of COUP-TF2. Therefore, stabilization of COUP-TF2 may represent a therapeutic strategy to enhance recovery from pathogens, including H1N1 influenza and SARS-CoV-2.

Direct reprogramming induces vascular regeneration post muscle ischemic injury.

Reprogramming non-cardiomyocytes (non-CMs) into cardiomyocyte (CM)-like cells is a promising strategy for cardiac regeneration in conditions such as ischemic heart disease. Here, we used a modified mRNA (modRNA) gene delivery platform to deliver a cocktail, termed 7G-modRNA, of four cardiac-reprogramming genes-Gata4 (G), Mef2c (M), Tbx5 (T), and Hand2 (H)-together with three reprogramming-helper genes-dominant-negative (DN)-TGFß, DN-Wnt8a, and acid ceramidase (AC)-to induce CM-like cells. We showed that 7G-modRNA reprogrammed 57% of CM-like cells in vitro. Through a lineage-tracing model, we determined that delivering the 7G-modRNA cocktail at the time of myocardial infarction reprogrammed ∼25% of CM-like cells in the scar area and significantly improved cardiac function, scar size, long-term survival, and capillary density. Mechanistically, we determined that while 7G-modRNA cannot create de novo beating CMs in vitro or in vivo, it can significantly upregulate pro-angiogenic mesenchymal stromal cells markers and transcription factors. We also demonstrated that our 7G-modRNA cocktail leads to neovascularization in ischemic-limb injury, indicating CM-like cells importance in other organs besides the heart. modRNA is currently being used around the globe for vaccination against COVID-19, and this study proves this is a safe, highly efficient gene delivery approach with therapeutic potential to treat ischemic diseases.

The Tissue Renin-Angiotensin System and Its Role in the Pathogenesis of Major Human Diseases: Quo Vadis?

Evidence has arisen in recent years suggesting that a tissue renin-angiotensin system (tRAS) is involved in the progression of various human diseases. This system contains two regulatory pathways: a pathological pro-inflammatory pathway containing the Angiotensin Converting Enzyme (ACE)/Angiotensin II (AngII)/Angiotensin II receptor type 1 (AGTR1) axis and a protective anti-inflammatory pathway involving the Angiotensin II receptor type 2 (AGTR2)/ACE2/Ang1-7/MasReceptor axis. Numerous studies reported the positive effects of pathologic tRAS pathway inhibition and protective tRAS pathway stimulation on the treatment of cardiovascular, inflammatory, and autoimmune disease and the progression of neuropathic pain. Cell senescence and aging are known to be related to RAS pathways. Further, this system directly interacts with SARS-CoV 2 and seems to be an important target of interest in the COVID-19 pandemic. This review focuses on the involvement of tRAS in the progression of the mentioned diseases from an interdisciplinary clinical perspective and highlights therapeutic strategies that might be of major clinical importance in the future.

Interleukin-1ß Modulation of the Mechanobiology of Primary Human Pulmonary Fibroblasts: Potential Implications in Lung Repair.

Pro-inflammatory cytokines like interleukin-1ß (IL-1ß) are upregulated during early responses to tissue damage and are expected to transiently compromise the mechanical microenvironment. Fibroblasts are key regulators of tissue mechanics in the lungs and other organs. However, the effects of IL-1ß on fibroblast mechanics and functions remain unclear. Here we treated human pulmonary fibroblasts from control donors with IL-1ß and used Atomic Force Microscopy to unveil that IL-1ß significantly reduces the stiffness of fibroblasts concomitantly with a downregulation of filamentous actin (F-actin) and alpha-smooth muscle (α-SMA). Likewise, COL1A1 mRNA was reduced, whereas that of collagenases MMP1 and MMP2 were upregulated, favoring a reduction of type-I collagen. These mechanobiology changes were functionally associated with reduced proliferation and enhanced migration upon IL-1ß stimulation, which could facilitate lung repair by drawing fibroblasts to sites of tissue damage. Our observations reveal that IL-1ß may reduce local tissue rigidity by acting both intracellularly and extracellularly through the downregulation of fibroblast contractility and type I collagen deposition, respectively. These IL-1ß-dependent mechanical effects may enhance lung repair further by locally increasing pulmonary tissue compliance to preserve normal lung distension and function. Moreover, our results support that IL-1ß provides innate anti-fibrotic protection that may be relevant during the early stages of lung repair.