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Dengue virus (DENV) represents a major public health concern globally and in Vietnam, where an estimated 1.6 million cases occur each year (1). Clinical manifestations range from fever to severe [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2006.03.032 Byline: Nguyet M. Nguyen (a), Robert M. Senior (a)(b) Keywords: Basement membrane; Laminin; Lung development; Lung epithelial cell differentiation Abbreviations: BM, basement membrane; Lama, laminin [alpha]; Lamb, laminin [beta]; Lamc, laminin [gamma] Abstract: Laminins are a major component of basement membranes. Each laminin molecule is a heterotrimeric glycoprotein composed of one [alpha], one [beta], and one [gamma] chain. Fifteen laminin isoforms exist, assembled from various combinations of 5[alpha], 3[beta], and 3[gamma] chains. The embryonic lung has abundant laminin isoforms. Increasing evidence suggests that different laminin isoforms have unique functions in lung development. Studies of embryonic lung explants and organotypic co-cultures show that laminin [alpha]1 and laminin 111 are important for epithelial branching morphogenesis and that laminin [alpha]2 and laminin 211 have a role in smooth muscle cell differentiation. In vivo studies of laminin [alpha]5-deficient mice indicate that this laminin chain, found in laminins 511 and 521, is essential for normal lobar septation in early lung development and normal alveolization and distal epithelial cell differentiation and maturation in late lung development. However, not all of the laminin chains present in the developing lung appear to be necessary for normal lung development since laminin [alpha]4 null mice do not have obvious lung abnormalities and laminin [gamma]2 null mice have only minimal changes in lung development. The mechanisms responsible for the lung phenotypes in mice with laminin mutations are unknown, but it is clear that multiple laminin isoforms are crucial for lung development and that different laminin isoforms exhibit specific, non-overlapping functions. Author Affiliation: (a) Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA (b) Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA Article History: Received 21 January 2006; Revised 16 March 2006; Accepted 27 March 2006

Laminin [alpha]5 is prominent in the basement membrane of alveolar walls, airways, and pleura in developing and adult lung. Targeted deletion of laminin [alpha]5 in mice causes developmental defects in multiple organs, but embryonic lethality has precluded examination of the latter stages of lung development. To identify roles for laminin [alpha]5 in lung development, we have generated an inducible lung epithelial cell-specific Lama5 null (SP-Clama[5.sup.fl/-]) mouse through use of the Cre/loxP system, the human surfactant protein C promoter, and the reverse tetracycline transactivator. SP-Clama[5.sup.fl/-] embryos exposed to doxycycline from E6.5 died a few hours after birth. Compared to control littermates, SP-Clama[5.sup.fl/-] lungs had dilated, enlarged distal airspaces, but basement membrane ultrastructure was preserved. Distal epithelial cell differentiation was perturbed, with a marked reduction of alveolar type II cells and a virtual absence of type I cells. Cell proliferation was reduced and apoptosis was increased. Capillary density was diminished, and this was associated with a decrease in total lung VEGF production. Overall, these findings indicate that epithelial laminin [alpha]5, independent of its structural function, is necessary for murine lung development, and suggest a role for laminin [alpha]5 in signaling pathways that promote alveolar epithelial cell differentiation and VEGF expression. Keywords: Laminin; Lung development; Basement membrane; Alveolar epithelial cell; Differentiation; VEGF

Laminin [alpha/beta/gamma] heterotrimers are the major noncollagenous components of all basement membranes. To date, five [alpha], three [beta], and three [gamma] chains have been identified. Laminin [alpha]5 is expressed early in lung development and colocalizes with laminin [alpha]l. While laminin [alpha]1 expression in the lung is restricted to the embryonic period, laminin [alpha]5 expression persists throughout embryogenesis and adulthood. Targeted mutation of the mouse laminin [alpha]5 gene Lama5 causes embryonic lethality at E14-E17 associated with exencephaly, syndactyly, placentopathy, and kidney defects, all attributable to abnormal basement membranes. In this investigation, lung development in Lama[5.sup.-/-] mice up to E16.5 was examined. We observed normal lung branching morphogenesis and vasculogenesis, but incomplete lobar septation and absence of the visceral pleura basement membrane. Preservation of branching morphogenesis was associated with ectopic deposition of laminin [alpha]4 in the airway basement membrane. Perturbation of pleural basement membrane formation and right lung septation correlated with absence of laminin [alpha]5, which was found to be the only laminin [alpha] chain present in the normal visceral pleura basement membrane. Our finding of normal lung branching morphogenesis with abnormal lobar septation demonstrates that these processes are not obligatorily linked. Key Words: laminin; lung development; basement membrane; visceral pleura; lobar septation.

Basement membranes have a critical role in alveolar structure and function. Alveolar type II cells make basement membrane constituents, including laminin, but relatively little is known about the production of basement membrane proteins by murine alveolar type II cells and a convenient system is not available to study basement membrane production by murine alveolar type II cells. To facilitate study of basement membrane production, with particular focus on laminin chains, we examined transformed murine distal respiratory epithelial cells (MLE-15), which have many structural and biochemical features of alveolar type II cells. We found that MLE-15 cells produce laminin[alpha]5, a trace amount of laminin-[alpha]3, laminins-[beta]1 and -[gamma]1, type IV collagen, and perlecan. Transforming growth factor-[beta]l significantly induces expression of laminin-[alpha]l. When grown on a fibroblast-embedded collagen gel, MLE-15 cells assemble a basement membrane-like layer containing laminin-[alpha]5. These findings indicate that MLE-15 cells will be useful in modeling basement membrane production and assembly by alveolar type II cells. murine alveolar type II cells; transforming growth factor-[beta]; extracellular matrix

Abstract Background Laminin γ2 (Lamc2), one of the polypeptides in laminin-332 (laminin-5), is prominent in the basement membrane of alveolar walls and airways of developing and adult lung. Laminins are important for lung morphogenesis and based on its localization, a function for laminin γ2 in lung development has been hypothesized. Targeted deletion of the laminin γ2 gene in mice results in skin blistering and neonatal death at 3–5 days after birth due to failure to thrive. Methods Examination of lung development in Lamc2-/- mice through 1–2 days postnatal was accomplished by morphometric analysis, lung bud culture, electron microscopy, immunohistochemical and immunofluorescence staining. Results Compared to littermate controls, Lamc2-/- lungs were similar in morphology during embryonic life. At post-natal day 1–2, distal saccules were mildly dilated by chord length measurements. Epithelial differentiation as evaluated by immunohistochemical staining for markers of ciliated cells, Clara cells, alveolar type I cells and alveolar type II cells did not reveal a difference between Lamc2-/- and littermate control lungs. Likewise, vascular development, smooth muscle cell differentiation, and elastic fiber formation looked similar, as did airway basement membrane ultrastructure. Branching morphogenesis by lung bud culture was similar in Lamc2-/- and littermate control lungs. Since laminin-332 is important for hemidesmosome formation, we examined the structure of tracheal hemidesmosomes by transmission electron microscopy. Compared to littermate controls, Lamc2-/- tracheal hemidesmosomes were less organized and lacked the increased electron density associated with the basement membrane abutting the hemidesmosome. Conclusion These findings indicate that laminin γ2 and laminin-332, despite their prominence in the lung, have a minimal role in lung development through the saccular stage.

Presents a study which performed electrochemical and spectroscopic measurements to characterize the electrochromic behavior of sputtered vanadium pentoxide films. Experimental procedures; Results and discussion; Conclusions.

The article discusses a study to implement a magnetic resonance imaging-based lung morphometry to assess pulmonary diseases in mice. It focuses on the reliability of the information on the geometry and microstructure of airways. It explains the potential of the technique as a noninvasive procedure in the diagnosis and treatment of lung diseases.

Recently, a Sendai virus (SeV) model of chronic obstructive lung disease has demonstrated an innate immune response in mouse airways that exhibits similarities to the chronic airway inflammation in human chronic obstructive pulmonary disease (COPD) and asthma, but the effect on distal lung parenchyma has not been investigated. The aim of our study is to image the time course and regional distribution of mouse lung microstructural changes in vivo after SeV infection. (1)H and (3)He diffusion magnetic resonance imaging (MRI) were successfully performed on five groups of C57BL/6J mice. (1)H MR images provided precise anatomical localization and lung volume measurements. (3)He lung morphometry was implemented to image and quantify mouse lung geometric microstructural parameters at different time points after SeV infection. (1)H MR images detected the SeV-induced pulmonary inflammation in vivo; spatially resolved maps of acinar airway radius R, alveolar depth h, and mean linear intercept Lm were generated from (3)He diffusion images. The morphometric parameters R and Lm in the infected group were indistinguishable from PBS-treated mice at day 21, increased slightly at day 49, and were increased with statistical significance at day 77 (p = 0.02). Increases in R and Lm of infected mice imply that there is a modest increase in alveolar duct radius distal to airway inflammation, particularly in the lung periphery, indicating airspace enlargement after virus infection. Our results indicate that (3)He lung morphometry has good sensitivity in quantifying small microstructural changes in the mouse lung and that the Sendai mouse model has the potential to be a valid murine model of COPD.

Background: Laminin gamma2 (Lamc2), one of the polypeptides in laminin-332 (laminin-5), is prominent in the basement membrane of alveolar walls and airways of developing and adult lung. Laminins are important for lung morphogenesis and based on its localization, a function for laminin gamma2 in lung development has been hypothesized. Targeted deletion of the laminin gamma2 gene in mice results in skin blistering and neonatal death at 3-5 days after birth due to failure to thrive., Methods: Examination of lung development in Lamc2-/- mice through 1-2 days postnatal was accomplished by morphometric analysis, lung bud culture, electron microscopy, immunohistochemical and immunofluorescence staining., Results: Compared to littermate controls, Lamc2-/- lungs were similar in morphology during embryonic life. At post-natal day 1-2, distal saccules were mildly dilated by chord length measurements. Epithelial differentiation as evaluated by immunohistochemical staining for markers of ciliated cells, Clara cells, alveolar type I cells and alveolar type II cells did not reveal a difference between Lamc2-/- and littermate control lungs. Likewise, vascular development, smooth muscle cell differentiation, and elastic fiber formation looked similar, as did airway basement membrane ultrastructure. Branching morphogenesis by lung bud culture was similar in Lamc2-/- and littermate control lungs. Since laminin-332 is important for hemidesmosome formation, we examined the structure of tracheal hemidesmosomes by transmission electron microscopy. Compared to littermate controls, Lamc2-/- tracheal hemidesmosomes were less organized and lacked the increased electron density associated with the basement membrane abutting the hemidesmosome., Conclusion: These findings indicate that laminin gamma2 and laminin-332, despite their prominence in the lung, have a minimal role in lung development through the saccular stage.

Laminin alpha/beta/gamma heterotrimers are the major noncollagenous components of all basement membranes. To date, five alpha, three beta, and three gamma chains have been identified. Laminin alpha 5 is expressed early in lung development and colocalizes with laminin alpha1. While laminin alpha1 expression in the lung is restricted to the embryonic period, laminin alpha 5 expression persists throughout embryogenesis and adulthood. Targeted mutation of the mouse laminin alpha 5 gene Lama5 causes embryonic lethality at E14-E17 associated with exencephaly, syndactyly, placentopathy, and kidney defects, all attributable to abnormal basement membranes. In this investigation, lung development in Lama5(-/-) mice up to E16.5 was examined. We observed normal lung branching morphogenesis and vasculogenesis, but incomplete lobar septation and absence of the visceral pleura basement membrane. Preservation of branching morphogenesis was associated with ectopic deposition of laminin alpha 4 in the airway basement membrane. Perturbation of pleural basement membrane formation and right lung septation correlated with absence of laminin alpha 5, which was found to be the only laminin alpha chain present in the normal visceral pleura basement membrane. Our finding of normal lung branching morphogenesis with abnormal lobar septation demonstrates that these processes are not obligatorily linked.