TGFβ signaling in lung epithelium regulates bleomycin-induced alveolar injury and fibroblast recruitment

The response of alveolar epithelial cells (AECs) to lung injury plays a central role in the pathogenesis of pulmonary fibrosis, but the mechanisms by which AECs regulate fibrotic processes are not well defined. We aimed to elucidate how transforming growth factor-β (TGFβ) signaling in lung epithelium impacts lung fibrosis in the intratracheal bleomycin model. Mice with selective deficiency of TGFβ receptor 2 (TGFβR2) in lung epithelium were generated and crossed to cell fate reporter mice that express β-galactosidase (β-gal) in cells of lung epithelial lineage. Mice were given intratracheal bleomycin (0.08 U), and the following parameters were assessed: AEC death by terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling assay, inflammation by total and differential cell counts from bronchoalveolar lavage, fibrosis by scoring of trichrome-stained lung sections, and total lung collagen content. Mice with lung epithelial deficiency of TGFβR2 had improved AEC survival, despite greater lung inflammation, after bleomycin administration. At 3 wk after bleomycin administration, mice with epithelial TGFβR2 deficiency showed a significantly attenuated fibrotic response in the lungs, as determined by semiquantitatve scoring and total collagen content. The reduction in lung fibrosis in these mice was associated with a marked decrease in the lung fibroblast population, both total lung fibroblasts and epithelial-to-mesenchymal transition-derived (S100A4(+)/β-gal(+)) fibroblasts. Attenuation of TGFβ signaling in lung epithelium provides protection from bleomycin-induced fibrosis, indicating a critical role for the epithelium in transducing the profibrotic effects of this cytokine.     

Targeted immunomodulation of the NF-kappaB pathway in airway epithelium impacts host defense against Pseudomonas aeruginosa

We investigated the impact of inflammatory signaling in airway epithelial cells on host defense against Pseudomonas aeruginosa, a major cause of nosocomial pneumonia. In mice, airway instillation of P. aeruginosa resulted in NF-kappaB activation in the lungs that was primarily localized to the bronchial epithelium at 4 h, but was present in a variety of cell types by 24 h. We modulated NF-kappaB activity in airway epithelium by intratracheal delivery of adenoviral vectors expressing RelA (AdRelA) or a dominant inhibitor of NF-kappaB before P. aeruginosa infection. Bacterial clearance was enhanced by up-regulation of NF-kappaB activity following AdRelA administration and was impaired by treatment with a dominant inhibitor of NF-kappaB. The TNF-alpha concentration in lung lavage was increased by AdRelA treatment and beneficial effects of NF-kappaB up-regulation were abrogated in TNF-alpha-deficient mice. In contrast, NF-kappaB inhibition reduced MIP-2 expression and neutrophil influx following P. aeruginosa infection. Therefore, inflammatory signaling through the NF-kappaB pathway in airway epithelial cells critically regulates the innate immune response to P. aeruginosa.     

Species variation in BrdUrd-induced sister-chromatid exchanges.

Peripheral blood lymphocytes from cattle, pigs, sheep and humans were cultured in the presence of 0.5, 1, 2, 5, 10 or 20 micrograms/ml of BrdUrd. Sister-chromatid exchanges were scored in 25 second-division metaphases from each donor at each level of the chemical. Dose--response curves for all 4 species increased steeply to 2 micrograms/ml; above this level, SCE numbers increased less rapidly but maintained a linear relationship to increasing BrdUrd concentration. Comparisons of the straight-line portions of the dose--response curves showed human cells to be significantly more sensitive to increasing BrdUrd level than cow or pig cells and different from sheep at the 10% level of confidence.     

Bone marrow derived mesenchymal stem cells incorporate into the prostate during regrowth

Background

Prostate cancer recurrence involves increased growth of cancer epithelial cells, as androgen dependent prostate cancer progresses to castrate resistant prostate cancer (CRPC) following initial therapy. Understanding CRPC prostate regrowth will provide opportunities for new cancer therapies to treat advanced disease.

Methodology/Principal Findings

Elevated chemokine expression in the prostate stroma of a castrate resistant mouse model, Tgfbr2^fspKO, prompted us to look at the involvement of bone marrow derived cells (BMDCs) in prostate regrowth. We identified bone marrow cells recruited to the prostate in GFP-chimeric mice. A dramatic increase in BMDC recruitment for prostate regrowth occurred three days after exogenous testosterone implantation. Recruitment led to incorporation of BMDCs within the prostate epithelia. Immunofluorescence staining suggested BMDCs in the prostate coexpressed androgen receptor; p63, a basal epithelial marker; and cytokeratin 8, a luminal epithelial marker. A subset of the BMDC population, mesenchymal stem cells (MSCs), were specifically found to be incorporated in the prostate at its greatest time of remodeling. Rosa26 expressing MSCs injected into GFP mice supported MSC fusion with resident prostate epithelial cells through co-localization of β-galactosidase and GFP during regrowth. In a human C4-2B xenograft model of CRPC, MSCs were specifically recruited. Injection of GFP-labeled MSCs supported C4-2B tumor progression by potentiating canonical Wnt signaling. The use of MSCs as a targeted delivery vector for the exogenously expressed Wnt antagonist, secreted frizzled related protein-2 (SFRP2), reduced tumor growth, increased apoptosis and potentiated tumor necrosis.

Conclusions/Significance

Mesenchymal stem cells fuse with prostate epithelia during the process of prostate regrowth. MSCs recruited to the regrowing prostate can be used as a vehicle for transporting genetic information with potential therapeutic effects on castrate resistant prostate cancer, for instance by antagonizing Wnt signaling through SFRP2.     

A critical role for macrophages in promotion of urethane-induced lung carcinogenesis

Macrophages have established roles in tumor growth and metastasis, but information about their role in lung tumor promotion is limited. To assess the role of macrophages in lung tumorigenesis, we developed a method of minimally invasive, long-term macrophage depletion by repetitive intratracheal instillation of liposomal clodronate. Compared with controls treated with repetitive doses of PBS-containing liposomes, long-term macrophage depletion resulted in a marked reduction in tumor number and size at 4 mo after a single i.p. injection of the carcinogen urethane. After urethane treatment, lung macrophages developed increased M1 macrophage marker expression during the first 2-3 wk, followed by increased M2 marker expression by week 6. Using a strategy to reduce alveolar macrophages during tumor initiation and early promotion stages (weeks 1-2) or during late promotion and progression stages (weeks 4-16), we found significantly fewer and smaller lung tumors in both groups compared with controls. Late-stage macrophage depletion reduced VEGF expression and impaired vascular growth in tumors. In contrast, early-stage depletion of alveolar macrophages impaired urethane-induced NF-κB activation in the lungs and reduced the development of premalignant atypical adenomatous hyperplasia lesions at 6 wk after urethane injection. Together, these studies elucidate an important role for macrophages in lung tumor promotion and indicate that these cells have distinct roles during different stages of lung carcinogenesis.