Vascular dysfunction by myofibroblast activation in patients with idiopathic pulmonary fibrosis and prognostic significance

Antibody-mediated depletion of CCR10+EphA3+ cells ameliorates fibrosis in IPF

Idiopathic pulmonary fibrosis (IPF) is characterized by aberrant repair that diminishes lung function via mechanisms that remain poorly understood. CC chemokine receptor (CCR10) and its ligand CCL28 were both elevated in IPF compared with normal donors. CCR10 was highly expressed by various cells from IPF lungs, most notably stage-specific embryonic antigen-4-positive mesenchymal progenitor cells (MPCs). In vitro, CCL28 promoted the proliferation of CCR10+ MPCs while CRISPR/Cas9-mediated targeting of CCR10 resulted in the death of MPCs. Following the intravenous injection of various cells from IPF lungs into immunodeficient (NOD/SCID-γ, NSG) mice, human CCR10+ cells initiated and maintained fibrosis in NSG mice. Eph receptor A3 (EphA3) was among the highest expressed receptor tyrosine kinases detected on IPF CCR10+ cells. Ifabotuzumab-targeted killing of EphA3+ cells significantly reduced the numbers of CCR10+ cells and ameliorated pulmonary fibrosis in humanized NSG mice. Thus, human CCR10+ cells promote pulmonary fibrosis, and EphA3 mAb-directed elimination of these cells inhibits lung fibrosis.

Development of Lymphatic Capillary Network Along the Alveolar Walls of Autopsied Human Lungs with Pneumonia

BACKGROUND

Limited information is available regarding the lymphatic vasculature during pneumonia.

OBJECTIVE

To characterize lymphatic vasculatures in autopsied cadavers with pneumonia.

METHODS

Paraffin-embedded lung tissues obtained from 20 autopsied cadavers with complicated pneumonia and 10 control cadavers without pneumonia were used for immunohistochemical analyses using primary antibodies against podoplanin, vascular endothelial growth factor receptor-3 (VEGFR-3), CD34, vascular endothelial growth factor (VEGF)-C, VEGF-D, CD73, and CD163.

RESULTS

There was no difference in the vascular density of podoplanin⁺ usual lymphatics between the individuals with and without pneumonia. In half of the cadavers with pneumonia, however, a network of podoplanin⁺ cells lying together in a side-by-side bead-like arrangement appeared along the alveolar septa; however, this was absent in the control cadavers. The podoplanin⁺ cells in the network were characterized by a weaker expression of podoplanin, relative to usual lymphatics, and the occasional presence of ductal structures. Although podoplanin⁺ cells were not coexpressed with VEGFR-3, a part of the network was connected to CD73⁺ afferent lymphatics. The network showed an intertwined relationship with CD34⁺ capillaries, suggesting that the network represents lymphatic capillaries. The number of CD163⁺ macrophages was significantly increased in individuals with the network than those without the network, while a significant decrease in neutrophils was observed. VEGF-C expressed in CD163⁺ macrophages and type II epithelial cells was observed in the cadavers with the network.

CONCLUSION

The development of lymphatic capillary networks along the alveolar septa rather than the usual lymphangiogenesis was noted in autopsied individuals with pneumonia.

Radiation-induced impairment in lung lymphatic vasculature

BACKGROUND

The lymphatic vasculature has been shown to play important roles in lung injury and repair, particularly in lung fibrosis. The effects of ionizing radiation on lung lymphatic vasculature have not been previously reported.

METHODS AND RESULTS

C57Bl/6 mice were immobilized in a lead shield exposing only the thoracic cavity, and were irradiated with a single dose of 14 Gy. Animals were sacrificed and lungs collected at different time points (1, 4, 8, and 16 weeks) following radiation. To identify lymphatic vessels in lung tissue sections, we used antibodies that are specific for lymphatic vessel endothelial receptor 1 (LYVE-1), a marker of lymphatic endothelial cells (LEC). To evaluate LEC cell death and oxidative damage, lung tissue sections were stained for LYVE-1 and with TUNEL staining, or 8-oxo-dG respectively. Images were imported into ImageJ v1.36b and analyzed. Compared to a non-irradiated control group, we observed a durable and progressive decrease in the density, perimeter, and area of lymphatic vessels over the study period. The decline in the density of lymphatic vessels was observed in both subpleural and interstitial lymphatics. Histopathologically discernible pulmonary fibrosis was not apparent until 16 weeks after irradiation. Furthermore, there was significantly increased LEC apoptosis and oxidative damage at one week post-irradiation that persisted at 16 weeks.

CONCLUSIONS

There is impairment of lymphatic vasculature after a single dose of ionizing radiation that precedes architectural distortion and fibrosis, suggesting important roles for the lymphatic circulation in the pathogenesis of the radiation-induced lung injury.

Plasticity of airway lymphatics in development and disease

The dynamic nature of lymphatic vessels is reflected by structural and functional modifications that coincide with changes in their environment. Lymphatics in the respiratory tract undergo rapid changes around birth, during adaptation to air breathing, when lymphatic endothelial cells develop button-like intercellular junctions specialized for efficient fluid uptake and transport. In inflammatory conditions, lymphatic vessels proliferate and undergo remodeling to accommodate greater plasma leakage and immune cell trafficking. However, the newly formed lymphatics are abnormal, and resolution of inflammation is not accompanied by complete reversal of the lymphatic vessel changes back to the baseline. As the understanding of lymphatic plasticity advances, approaches for eliminating the abnormal vessels and improving the functionality of those that remain move closer to reality. This chapter provides an overview of what is known about lymphatic vessel growth, remodeling, and other forms of plasticity that occur during development or inflammation, with an emphasis on the respiratory tract. Also addressed is the limited reversibility of changes in lymphatics during the resolution of inflammation.