BackgroundOur aim was to differentiate human (h) embryonic stem (ES) cells into lung epithelial lineage-specific cells [i.e., alveolar epithelial type I (AEI) and type II (AEII) cells and Clara cells] as the first step in the development of cell-based strategies to repair lung injury in the bleomycin mouse model of idiopathic pulmonary fibrosis (IPF). A heterogeneous population of non-ciliated lung lineage-specific cells was derived by a novel method of embryoid body (EB) differentiation. This differentiated human cell population was used to modulate the profibrotic phenotype in transplanted animals.Methodology and Principal FindingsOmission or inclusion of one or more components in the differentiation medium skewed differentiation of H7 hES cells into varying proportions of AEI, AEII, and Clara cells. ICG-001, a small molecule inhibitor of Wnt/β-catenin/Creb-binding protein (CBP) transcription, changed marker expression of the differentiated ES cells from an AEII-like phenotype to a predominantly AEI-like phenotype. The differentiated cells were used in xenograft transplantation studies in bleomycin-treated Rag2γC−/− mice. Human cells were detected in lungs of the transplanted groups receiving differentiated ES cells treated with or without ICG-001. The increased lung collagen content found in bleomycin-treated mice receiving saline was significantly reduced by transplantation with the lung-lineage specific epithelial cells differentiated from ES cells. A significant increase in progenitor number was observed in the airways of bleomycin-treated mice after transplantation of differentiated hES cells.ConclusionsThis study indicates that ES cell-based therapy may be a powerful novel approach to ameliorate lung fibrosis.

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OBJECTIVE-Leukocyte recruitment to inflammatory sites is a prominent feature of acute and chronic inflammation. Instrumental in this process is the coordinated upregulation of leukocyte integrins (among which α4β1 and β2 integrins are major players) and their cognate receptors in inflamed tissues. To avoid the ambiguity of previous short-term antibody-based studies and to allow for long-term observation, we used genetically deficient mice to compare roles of α4 and β2 integrins in leukocyte trafficking.METHODS-Aseptic peritonitis was induced in α4 or β2 integrin-deficient (conditional and conventional knockouts, respectively) and control mice, and recruitment of major leukocyte subsets to the inflamed peritoneum was followed for up to 4 days. RESULTS-Despite normal chemokine levels in the peritoneum and adequate numbers, optimal recruitment of myeloid cells was impaired in both α4-and β2-deficient mice. Furthermore, clearance of recruited neutrophils and macrophages was delayed in these mice. Lymphocyte migration to the peritoneum in the absence of α4 integrins was drastically decreased, both at steady state and during inflammation, a finding consistent with impaired lymphocyte in vitro adhesion and signaling. By contrast, in the absence of β2 integrins, defects in lymphocyte recruitment were only evident when peritonitis was established.CONCLUSIONS-Our data with concurrent use of genetic models of integrin deficiency reveal non-redundant functions of α4 integrins in lymphocyte migration to the peritoneum and further refine specific roles of α4 and β2 integrins concerning trafficking and clearance of other leukocyte subsets at homeostasis and during inflammation.

Objective Chronic asthma is characterized by ongoing recruitment of inflammatory cells and airway hyperresponsiveness leading to structural airway remodeling. Although α4β1 and β2 integrins regulate leukocyte migration in inflammatory diseases and play decisive roles in acute asthma, their role has not been explored under the chronic asthma setting. To extend our earlier studies with α4Δ/Δ and β2−/− mice, which showed that both a4 and b2 integrins have nonredundant regulatory roles in acute ovalbumin (OVA)-induced asthma, we explored to what extent these molecular pathways control development of structural airway remodeling in chronic asthma. Materials and Methods Control, α4Δ/Δ, and β2−/−mouse groups, sensitized by intraperitoneal OVA as allergen, received intratracheal OVA periodically over days 8 to 55 to induce a chronic asthma phenotype. Post-OVA assessment of inflammation and pulmonary function (airway hyperresponsiveness), together with airway modeling measured by goblet cell metaplasia, collagen content of lung, and transforming growth factor β1 expression in lung homogenates, were evaluated. Results In contrast to control and β2−/− mice, α4Δ/Δ mice failed to develop and maintain the composite chronic asthma phenotype evaluated as mentioned and subepithelial collagen content was comparable to baseline. These data indicate that β2 integrins, although required for inflammatory migration in acute asthma, are dispensable for structural remodeling in chronic asthma. Conclusion α4 integrins appear to have a regulatory role in directing transforming growth factor β-induced collagen deposition and structural alterations in lung architecture likely through interactions of Th2 cells, eosinophils, or mast cells with endothelium, resident airway cells, and/or extracellular matrix.