Epithelial-Mesenchymal Interactions in the Developing Lung

Shannon, John M.; Hyatt, Brian A.

doi:10.1146/annurev.physiol.66.032102.135749

Cited by 305 publications

(231 citation statements)

References 111 publications

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“…In addition to the positive effects of Dex on LPCAT expression, we found that treating fetal lung explants with SU5402, which blocks signaling through FGF receptors, totally abrogated the endogenous increase in LPCAT expression. FGF family members play important roles in several aspects of lung growth and differentiation (25). Therefore, in the fetal lung, LPCAT is regulated like other components of the surfactant system, which supports the concept that this enzyme is important for DPPC synthesis in surfactant.…”

Section: Discussionsupporting

confidence: 58%

Identification and characterization of a lysophosphatidylcholine acyltransferase in alveolar type II cells

Chen

Hyatt

Mucenski

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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176

187

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Pulmonary surfactant is a complex of lipids and proteins produced and secreted by alveolar type II cells that provides the low surface tension at the air-liquid interface. The phospholipid most responsible for providing the low surface tension in the lung is dipalmitoylphosphatidylcholine. Dipalmitoylphosphatidylcholine is synthesized in large part by phosphatidylcholine (PC) remodeling, and a lysophosphatidylcholine (lysoPC) acyltransferase is thought to play a critical role in its synthesis. However, this acyltransferase has not yet been identified. We have cloned full-length rat and mouse cDNAs coding for a lysoPC acyltransferase (LPCAT). LPCAT encodes a 535-aa protein of Ϸ59 kDa that contains a transmembrane domain and a putative acyltransferase domain. When transfected into COS-7 cells and HEK293 cells, LPCAT significantly increased lysoPC acyltransferase activity. LPCAT preferred lysoPC as a substrate over lysoPA, lysoPI, lysoPS, lysoPE, or lysoPG and prefers palmitoyl-CoA to oleoyl-CoA as the acyl donor. This LPCAT was preferentially expressed in the lung, specifically within alveolar type II cells. Expression in the fetal lung and in rat type II cells correlated with the expression of the surfactant proteins. LPCAT expression in fetal lung explants was sensitive to dexamethasone and FGFs. KGF was a potent stimulator of LPCAT expression in cultured adult type II cells. We hypothesize that LPCAT plays a critical role in regulating surfactant phospholipid biosynthesis and suggest that understanding the regulation of LPCAT will offer important insight into surfactant phospholipid biosynthesis.biochemistry ͉ lung ͉ surfactant ͉ phosphatidylcholine

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Section: Discussionsupporting

confidence: 58%

Identification and characterization of a lysophosphatidylcholine acyltransferase in alveolar type II cells

Chen

Hyatt

Mucenski

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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176

187

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“…29). Thus distal lung mesenchyme is able to induce growth and branching of the tracheal epithelium and to reorient its differentiation toward an alveolar phenotype (31).…”

Section: Discussionmentioning

confidence: 99%

Effects of vascular endothelial growth factor on isolated fetal alveolar type II cells

Raoul¹,

Chailley‐Heu²,

Barlier-Mur³

et al. 2004

American Journal of Physiology-Lung Cellular and Molecular Phys

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Previous investigations gained from in vivo or lung explant studies suggested that VEGF is an autocrine proliferation and maturation factor for developing alveolar type II cells. The objective of this work was to determine whether VEGF exerted its growth and maturation effects directly on isolated type II cells. These were isolated from 19-day fetal rat lung and cultured in defined medium. The presence of VEGF receptor-2 was assessed in cultured cells at the pre- and posttranslational levels. Recombinant VEGF165, formerly found to be active on lung explants, failed to enhance type II cell proliferation estimated by thymidine and 5-bromo-2′-deoxy-uridine incorporation. It increased choline incorporation in saturated phosphatidylcholine by 27% but did not increase phospholipid surfactant pool size. VEGF (100 ng/ml) left unchanged the transcript level of surfactant proteins (SP)-A, SP-C, and SP-D but increased SP-B transcripts to four times the control steady-state level. VEGF slightly retarded, but did not prevent, the in vitro transdifferentiation of type II into type I cells, as assessed by immunolabeling of the type I cell marker T1α. We conclude that, with the exception of SP-B expression, which appears to be controlled directly, the previously observed effects of this VEGF isoform on type II cells are likely to be exerted indirectly through reciprocal paracrine interactions involving other lung cell types.

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“…To form a ramified network, the initial tubular geometry is molded by a series of branching events, patterned in both space and time (1)(2)(3). In most cases, branching involves reciprocal signaling between adjacent tissues (4,5), but it remains unclear how the locations of new branches are determined.…”

mentioning

confidence: 99%

Mechanically patterning the embryonic airway epithelium

Varner

Gleghorn

Miller

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

108

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Collections of cells must be patterned spatially during embryonic development to generate the intricate architectures of mature tissues. In several cases, including the formation of the branched airways of the lung, reciprocal signaling between an epithelium and its surrounding mesenchyme helps generate these spatial patterns. Several molecular signals are thought to interact via reactiondiffusion kinetics to create distinct biochemical patterns, which act as molecular precursors to actual, physical patterns of biological structure and function. Here, however, we show that purely physical mechanisms can drive spatial patterning within embryonic epithelia. Specifically, we find that a growth-induced physical instability defines the relative locations of branches within the developing murine airway epithelium in the absence of mesenchyme. The dominant wavelength of this instability determines the branching pattern and is controlled by epithelial growth rates. These data suggest that physical mechanisms can create the biological patterns that underlie tissue morphogenesis in the embryo.buckling | instability | mechanical stress | morphodynamics | morphogenesis S pace-filling, branched networks form the basic architecture of several organs, including the lung, kidney, and mammary gland. In the developing embryo, these complex structures originate as simple epithelial tubes. To form a ramified network, the initial tubular geometry is molded by a series of branching events, patterned in both space and time (1-3). In most cases, branching involves reciprocal signaling between adjacent tissues (4, 5), but it remains unclear how the locations of new branches are determined.Airway branching is highly stereotyped in the developing mouse lung (6) and regulated in part by fibroblast growth factors (FGFs) (7). New epithelial branches are thought to emerge at locations adjacent to a prepattern of focal expression of FGF10 in the neighboring mesenchyme (8, 9) (Fig. 1A), a molecular mechanism with remarkable similarity to the induction of Drosophila tracheal branching by the FGF homolog Branchless (10). Moreover, the prepattern of FGF10 is regulated by reciprocal feedback between core signaling pathways, including those downstream of sonic hedgehog, bone morphogenetic protein, Wnt, and Notch (5, 11-13). These molecular signals are thought to interact via a reaction-diffusion mechanism (14, 15) to generate the spatial template of FGF10 (16) and are typically assumed to be sufficient to pattern branch locations along the airway epithelium (5, 10). This rich molecular description, however, overlooks the role that mechanical cues might play in establishing biological patterns. The pattern of villi in the developing gut, for instance, is determined by physical buckling (17,18).When the mesenchyme is removed, thus disrupting reciprocal signaling, isolated epithelia still branch in response to FGF1 or FGF10 (19,20). In these culture models, the exogenous growth factors are present ubiquitously, with no apparent spatial pattern (Fig. 1...

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Epithelial-Mesenchymal Interactions in the Developing Lung

Cited by 305 publications

References 111 publications

Identification and characterization of a lysophosphatidylcholine acyltransferase in alveolar type II cells

Identification and characterization of a lysophosphatidylcholine acyltransferase in alveolar type II cells

Effects of vascular endothelial growth factor on isolated fetal alveolar type II cells

Mechanically patterning the embryonic airway epithelium

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