Wilms' tumor 1 (Wt1) regulates pleural mesothelial cell plasticity and transition into myofibroblasts in idiopathic pulmonary fibrosis.

Pleural mesothelial cells (PMCs), which are derived from the mesoderm, exhibit an extraordinary capacity to undergo phenotypic changes during development and disease. PMC transformation and trafficking has a newly defined role in idiopathic pulmonary fibrosis (IPF); however, the contribution of Wilms' tumor 1 (Wt1)-positive PMCs to the generation of pathognomonic myofibroblasts remains unclear. PMCs were obtained from IPF lung explants and healthy donor lungs that were not used for transplantation. Short hairpin Wt1-knockdown PMCs (sh Wt1) were generated with Wt1 shRNA, and morphologic and functional assays were performed in vitro. Loss of Wt1 abrogated the PMC phenotype and showed evidence of mesothelial-to-mesenchymal transition (MMT), with a reduced expression of E-cadherin and an increase in the profibrotic markers α-smooth muscle actin (α-SMA) and fibronectin, along with increased migration and contractility, compared with that of the control. Migration of PMCs in response to active transforming growth factor (TGF)-ß1 was assessed by live-cell imaging with 2-photon microscopy and 3D imaging, of Wt1-EGFP transgenic mice. Lineage-tracing experiments to map the fate of Wt1(+) PMCs in mouse lung in response to TGF-ß1 were also performed by using a Cre-loxP system. Our results, for the first time, demonstrate that Wt1 is necessary for the morphologic integrity of pleural membrane and that loss of Wt1 contributes to IPF via MMT of PMCs into a myofibroblast phenotype.

Pleural mesothelial cell differentiation and invasion in fibrogenic lung injury.

The origin of the myofibroblast in fibrotic lung disease is uncertain, and no effective medical therapy for fibrosis exists. We have previously demonstrated that transforming growth factor-ß1 (TGF-ß1) induces pleural mesothelial cell (PMC) transformation into myofibroblasts and haptotactic migration in vitro. Whether PMC differentiation and migration occurs in vivo, and whether this response can be modulated for therapeutic benefit, is unknown. Here, using mice recombinant for green fluorescent protein (GFP) driven by the Wilms tumor-1 (WT-1) promoter, we demonstrate PMC trafficking into the lung and differentiation into myofibroblasts. Carbon monoxide or the induction of heme oxygenase-1 (HO-1) inhibited the expression of myofibroblast markers, contractility, and haptotaxis in PMCs treated with TGF-ß1. Intrapleural HO-1 induction inhibited PMC migration after intratracheal fibrogenic injury. PMCs from patients with idiopathic pulmonary fibrosis (IPF) exhibited increased expression of myofibroblast markers and enhanced contractility and haptotaxis, compared with normal PMCs. Carbon monoxide reversed this IPF PMC profibrotic phenotype. WT-1-expressing cells were present within fibrotic regions of the lungs in IPF subjects, supporting a role for PMC differentiation and trafficking as contributors to the myofibroblast population in lung fibrosis. Our findings also support a potential role for pleural-based therapies to modulate pleural mesothelial activation and parenchymal fibrosis progression.

Idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease of unknown cause characterized by progressive scarring of the lung parenchyma and relentless loss of lung function. The diagnosis depends on close collaboration between clinicians, radiologists, and pathologists. No therapies approved by the Food and Drug Administration are available for IPF, and an analysis of completed clinical trials has demonstrated that the clinical course of IPF is largely unpredictable. Until therapies that improve survival become available, measures to preserve function and quality of life should be considered, and gastroesophageal reflux should be treated aggressively.

Heme oxygenase-1 promotes granuloma development and protects against dissemination of mycobacteria.

Non-tuberculous mycobacterial (NTM) infections occur in both immunocompromised and immunocompetent hosts and are an increasingly recognized cause of morbidity and mortality. The hallmark of pulmonary mycobacterial infections is the formation of granuloma in the lung. Our study focuses on the role of heme oxygenase-1 (HO-1), a cytoprotective enzyme, in the regulation of granuloma development and maturation following infection with Mycobacterium avium. We examined the role of HO-1 in regulating monocyte chemoattractant protein-1 (MCP-1) and chemokine receptor 2 (CCR2), two molecules involved in monocyte-macrophage cell trafficking after infection. We showed that RAW 264.7 mouse monocytes exposed to M. avium expressed HO-1 and MCP-1. Inhibition of HO by zinc protoporphyrin-IX led to inhibition of MCP-1 and increased expression of CCR2, its cognate receptor. HO-1⁻/⁻ mice did not develop organized granuloma in their lungs, had higher lung colony forming unit of M. avium when infected with intratracheal M. avium, and had loose collections of inflammatory cells in the lung parenchyma. Mycobacteria were found only inside defined granulomas but not outside granuloma in the lungs of HO-1⁺/⁺ mice. In HO-1⁻/⁻ mice, mycobacteria were also found in the liver and spleen and showed increased mortality. Peripheral blood monocytes isolated from GFP⁺ mice and given intravenously to HO-1⁺/⁺ mice localized into tight granulomas, while in HO-1⁻/⁻ mice they remained diffusely scattered in areas of parenchymal inflammation. Higher MCP-1 levels were found in bronchoalveolar lavage fluid of M. avium infected HO-1(-/-) mice and CCR2 expression was higher in HO-1⁻/⁻ alveolar macrophages when compared with HO-1⁺/⁺ mice. CCR2 expression localized to granuloma in HO-1⁺/⁺ mice but not in the HO-1⁻/⁻ mice. These findings strongly suggest that HO-1 plays a protective role in the control of M. avium infection.

Lung transplantation in patients 60 years and older: results, complications, and outcomes.

BACKGROUND: Advanced recipient age is reported to negatively affect survival after lung transplantation (LTX). We hypothesized that LTX in patients aged > or = 60 years could be performed with acceptable outcomes. METHODS: We identified 182 consecutive LTX recipients from 1995 to 2005. Outcomes were analyzed and survival compared with results in recipients aged < 60, as well as with United Network for Organ Sharing (UNOS) registry outcomes for the same age and study period. Actuarial survivals were calculated by the Kaplan-Meier method. RESULTS: During the study period, 29% (52/182) of LTX recipients were > or = 60 years old (range, 60 to 69 years). Median follow-up was 2.9 years (range, 0 to 10 years). All patients but one received a single lung. Indications included chronic obstructive pulmonary disease in 63% (33/52), idiopathic pulmonary fibrosis in 27% (14/52), and other in 10% (5/52). In-hospital mortality was 12% (6/52) for those aged > or = 60 compared with 7% (9/130) for those aged < 60 (p = NS). Complications included reoperation in 10% (5/52), requirement for extracorporeal membrane oxygenation in 6% (3/52), renal failure in 12% (6/52), and stroke in 4% (2/52). Actuarial survivals at 30 days, and 1, 3, and 5 years were 90% (82, 98), 86% (76, 96), 71% (56, 85), and 55% (37, 73), respectively. No significant difference in survival was observed between age cohorts for our institutional data by Kaplan-Meier analysis (p = 0.34) or by Cox proportional hazard model (p = 0.15). A significant survival advantage was noted for our institution compared with UNOS for this cohort (p = 0.018). CONCLUSIONS: In carefully selected recipients > or = 60 years of age, LTX offers acceptable outcomes and survival.