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Humbert MV, Spalluto CM, Bell J, Blume C, Conforti F, Davies ER, Dean LSN, Elkington P, Haitchi HM, Jackson C, Jones MG, Loxham M, Lucas JS, Morgan H, Polak M, Staples KJ, Swindle EJ, Tezera L, Watson A, Wilkinson TMA. Towards an artificial human lung: modelling organ-like complexity to aid mechanistic understanding. Eur Respir J 2022; 60:2200455. [PMID: 35777774 DOI: 10.1183/13993003.00455-2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 06/11/2022] [Indexed: 11/05/2022]
Abstract
Respiratory diseases account for over 5 million deaths yearly and are a huge burden to healthcare systems worldwide. Murine models have been of paramount importance to decode human lung biology in vivo, but their genetic, anatomical, physiological and immunological differences with humans significantly hamper successful translation of research into clinical practice. Thus, to clearly understand human lung physiology, development, homeostasis and mechanistic dysregulation that may lead to disease, it is essential to develop models that accurately recreate the extraordinary complexity of the human pulmonary architecture and biology. Recent advances in micro-engineering technology and tissue engineering have allowed the development of more sophisticated models intending to bridge the gap between the native lung and its replicates in vitro Alongside advanced culture techniques, remarkable technological growth in downstream analyses has significantly increased the predictive power of human biology-based in vitro models by allowing capture and quantification of complex signals. Refined integrated multi-omics readouts could lead to an acceleration of the translational pipeline from in vitro experimental settings to drug development and clinical testing in the future. This review highlights the range and complexity of state-of-the-art lung models for different areas of the respiratory system, from nasal to large airways, small airways and alveoli, with consideration of various aspects of disease states and their potential applications, including pre-clinical drug testing. We explore how development of optimised physiologically relevant in vitro human lung models could accelerate the identification of novel therapeutics with increased potential to translate successfully from the bench to the patient's bedside.
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Affiliation(s)
- Maria Victoria Humbert
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
- Department of Medicine, University of Cambridge, Cambridge, UK
| | - Cosma Mirella Spalluto
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
- M.V. Humbert and C.M. Spalluto are co-first authors and contributed equally to this work
| | - Joseph Bell
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
| | - Cornelia Blume
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
- Institute for Life Sciences, University of Southampton, Southampton, UK
- School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK
| | - Franco Conforti
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
| | - Elizabeth R Davies
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, UK
| | - Lareb S N Dean
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
| | - Paul Elkington
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
- Institute for Life Sciences, University of Southampton, Southampton, UK
| | - Hans Michael Haitchi
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
- Institute for Life Sciences, University of Southampton, Southampton, UK
| | - Claire Jackson
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
| | - Mark G Jones
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
| | - Matthew Loxham
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
- Institute for Life Sciences, University of Southampton, Southampton, UK
| | - Jane S Lucas
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
| | - Hywel Morgan
- Institute for Life Sciences, University of Southampton, Southampton, UK
- Electronics and Computer Science, Faculty of Physical Sciences and Engineering, University of Southampton, Southampton, UK
| | - Marta Polak
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
- Institute for Life Sciences, University of Southampton, Southampton, UK
| | - Karl J Staples
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
| | - Emily J Swindle
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
- Institute for Life Sciences, University of Southampton, Southampton, UK
| | - Liku Tezera
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- Department of Infection and Immunity, Faculty of Medicine, University College London, London, UK
| | - Alastair Watson
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
- College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
- School of Clinical Medicine, University of Cambridge, Cambridge, UK
- Department of Medicine, University of Cambridge, Cambridge, UK
| | - Tom M A Wilkinson
- School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, UK
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Hamvas A, Feng R, Bi Y, Wang F, Bhattacharya S, Mereness J, Kaushal M, Cotten CM, Ballard PL, Mariani TJ. Exome sequencing identifies gene variants and networks associated with extreme respiratory outcomes following preterm birth. BMC Genet 2018; 19:94. [PMID: 30342483 PMCID: PMC6195962 DOI: 10.1186/s12863-018-0679-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 10/01/2018] [Indexed: 12/28/2022] Open
Abstract
Background Previous studies have identified genetic variants associated with bronchopulmonary dysplasia (BPD) in extremely preterm infants. However, findings with genome-wide significance have been rare, and not replicated. We hypothesized that whole exome sequencing (WES) of premature subjects with extremely divergent phenotypic outcomes could facilitate the identification of genetic variants or gene networks contributing disease risk. Results The Prematurity and Respiratory Outcomes Program (PROP) recruited a cohort of > 765 extremely preterm infants for the identification of markers of respiratory morbidity. We completed WES on 146 PROP subjects (85 affected, 61 unaffected) representing extreme phenotypes of early respiratory morbidity. We tested for association between disease status and individual common variants, screened for rare variants exclusive to either affected or unaffected subjects, and tested the combined association of variants across gene loci. Pathway analysis was performed and disease-related expression patterns were assessed. Marginal association with BPD was observed for numerous common and rare variants. We identified 345 genes with variants unique to BPD-affected preterm subjects, and 292 genes with variants unique to our unaffected preterm subjects. Of these unique variants, 28 (19 in the affected cohort and 9 in unaffected cohort) replicate a prior WES study of BPD-associated variants. Pathway analysis of sets of variants, informed by disease-related gene expression, implicated protein kinase A, MAPK and Neuregulin/epidermal growth factor receptor signaling. Conclusions We identified novel genes and associated pathways that may play an important role in susceptibility/resilience for the development of lung disease in preterm infants. Electronic supplementary material The online version of this article (10.1186/s12863-018-0679-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Aaron Hamvas
- Department of Pediatrics, Northwestern University, Chicago, IL, USA. .,Ann and Robert H. Lurie Children's Hospital of Chicago and Northwestern University, Chicago, IL, USA.
| | - Rui Feng
- Department of Biostatistics, University of Pennsylvania, Philadelphia, PA, USA
| | - Yingtao Bi
- Department of Preventive Medicine, Northwestern University, Chicago, IL, USA
| | - Fan Wang
- Department of Biostatistics, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Jared Mereness
- Department of Pediatrics, University of Rochester, Rochester, NY, USA
| | - Madhurima Kaushal
- Center for Biomedical Informatics, Washington University, St. Louis, MO, USA
| | | | - Philip L Ballard
- Department of Pediatrics, University of California, San Francisco, CA, USA
| | - Thomas J Mariani
- Department of Pediatrics, University of Rochester, Rochester, NY, USA. .,Division of Neonatology and Pediatric Molecular and Personalized Medicine Program University of Rochester Medical Center, 601 Elmwood Ave, Box 850, Rochester, NY, 14642, USA.
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Developmental Decline in the MicroRNA 199a (miR-199a)/miR-214 Cluster in Human Fetal Lung Promotes Type II Cell Differentiation by Upregulating Key Transcription Factors. Mol Cell Biol 2018; 38:MCB.00037-18. [PMID: 29507184 DOI: 10.1128/mcb.00037-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Accepted: 02/27/2018] [Indexed: 02/07/2023] Open
Abstract
The major surfactant protein, SP-A (a product of the SFTPA gene), serves as a marker of type II pneumocyte differentiation and surfactant synthesis. SFTPA expression in cultured human fetal lung (HFL) epithelial cells is upregulated by hormones that increase cyclic AMP (cAMP) and activate TTF-1/NKX2.1 and NF-κB. To further define mechanisms for type II cell differentiation and induction of SP-A, we investigated roles of microRNAs (miRNAs). Using microarray to identify differentially expressed miRNAs in HFL epithelial cells during type II cell differentiation in culture, we observed that members of the miRNA 199a (miR-199a)/miR-214 cluster were significantly downregulated during differentiation. Validated and predicted targets of miR-199a-3p/miR-199a-5p and miR-214, which serve roles in type II cell differentiation (COX-2, NF-κB p50/p65, and CREB1), and the CREB1 target, C/EBPβ, were coordinately upregulated. Accordingly, overexpression of miR-199a-5p, miR-199a-3p, or miR-214 mimics in cultured HFL epithelial cells decreased COX-2, NF-κB p50/p65, CREB1, and C/EBPβ proteins, with an associated inhibition of SP-A expression. Interestingly, overexpression of the EMT factor, ZEB1, which declines during cAMP-induced type II cell differentiation, increased pri-miR-199a and reduced the expression of the targets NF-κB/p50 and COX-2. Collectively, these findings suggest that the developmental decline in miR-199a/miR-214 in HFL causes increased expression of critical targets that enhance type II cell differentiation and SP-A expression.
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Katsirntaki K, Mauritz C, Olmer R, Schmeckebier S, Sgodda M, Puppe V, Eggenschwiler R, Duerr J, Schubert SC, Schmiedl A, Ochs M, Cantz T, Salwig I, Szibor M, Braun T, Rathert C, Martens A, Mall MA, Martin U. Bronchoalveolar sublineage specification of pluripotent stem cells: effect of dexamethasone plus cAMP-elevating agents and keratinocyte growth factor. Tissue Eng Part A 2014; 21:669-82. [PMID: 25316003 DOI: 10.1089/ten.tea.2014.0097] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Respiratory progenitors can be efficiently generated from pluripotent stem cells (PSCs). However, further targeted differentiation into bronchoalveolar sublineages is still in its infancy, and distinct specifying effects of key differentiation factors are not well explored. Focusing on airway epithelial Clara cell generation, we analyzed the effect of the glucocorticoid dexamethasone plus cAMP-elevating agents (DCI) on the differentiation of murine embryonic and induced pluripotent stem cells (iPSCs) into bronchoalveolar epithelial lineages, and whether keratinocyte growth factor (KGF) might further influence lineage decisions. We demonstrate that DCI strongly induce expression of the Clara cell marker Clara cell secretory protein (CCSP). While KGF synergistically supports the inducing effect of DCI on alveolar markers with increased expression of surfactant protein (SP)-C and SP-B, an inhibitory effect on CCSP expression was shown. In contrast, neither KGF nor DCI seem to have an inducing effect on ciliated cell markers. Furthermore, the use of iPSCs from transgenic mice with CCSP promoter-dependent lacZ expression or a knockin of a YFP reporter cassette in the CCSP locus enabled detection of derivatives with Clara cell typical features. Collectively, DCI was shown to support bronchoalveolar specification of mouse PSCs, in particular Clara-like cells, and KGF to inhibit bronchial epithelial differentiation. The targeted in vitro generation of Clara cells with their important function in airway protection and regeneration will enable the evaluation of innovative cellular therapies in animal models of lung diseases.
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Affiliation(s)
- Katherina Katsirntaki
- 1 Leibniz Research Laboratories for Biotechnology and Artificial Organs (LEBAO), Department for Cardiothoracic, Transplantation and Vascular Surgery, Hannover Medical School , Hannover, Germany
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Synergistic effect of caffeine and glucocorticoids on expression of surfactant protein B (SP-B) mRNA. PLoS One 2012; 7:e51575. [PMID: 23272120 PMCID: PMC3522739 DOI: 10.1371/journal.pone.0051575] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 11/01/2012] [Indexed: 11/19/2022] Open
Abstract
Administration of glucocorticoids and caffeine is a common therapeutic intervention in the neonatal period, but possible interactions between these substances are still unclear. The present study investigated the effect of caffeine and different glucocorticoids on expression of surfactant protein (SP)-B, crucial for the physiological function of pulmonary surfactant. We measured expression levels of SP-B, various SP-B transcription factors including erythroblastic leukemia viral oncogene homolog 4 (ErbB4) and thyroid transcription factor-1 (TTF-1), as well as the glucocorticoid receptor (GR) after administering different doses of glucocorticoids, caffeine, cAMP, or the phosphodiesterase-4 inhibitor rolipram in the human airway epithelial cell line NCI-H441. Administration of dexamethasone (1 µM) or caffeine (5 mM) stimulated SP-B mRNA expression with a maximal of 38.8±11.1-fold and 5.2±1.4-fold increase, respectively. Synergistic induction was achieved after co-administration of dexamethasone (1 mM) in combination with caffeine (10 mM) (206±59.7-fold increase, p<0.0001) or cAMP (1 mM) (213±111-fold increase, p = 0.0108). SP-B mRNA was synergistically induced also by administration of caffeine with hydrocortisone (87.9±39.0), prednisolone (154±66.8), and betamethasone (123±6.4). Rolipram also induced SP-B mRNA (64.9±21.0-fold increase). We detected a higher expression of ErbB4 and GR mRNA (7.0- and 1.7-fold increase, respectively), whereas TTF-1, Jun B, c-Jun, SP1, SP3, and HNF-3α mRNA expression was predominantly unchanged. In accordance with mRNA data, mature SP-B was induced significantly by dexamethasone with caffeine (13.8±9.0-fold increase, p = 0.0134). We found a synergistic upregulation of SP-B mRNA expression induced by co-administration of various glucocorticoids and caffeine, achieved by accumulation of intracellular cAMP. This effect was mediated by a caffeine-dependent phosphodiesterase inhibition and by upregulation of both ErbB4 and the GR. These results suggested that caffeine is able to induce the expression of SP-transcription factors and affects the signaling pathways of glucocorticoids, amplifying their effects. Co-administration of caffeine and corticosteroids may therefore be of benefit in surfactant homeostasis.
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Takahashi Y, Izumi Y, Kohno M, Kawamura M, Ikeda E, Nomori H. Airway administration of dexamethasone, 3'-5'-cyclic adenosine monophosphate, and isobutylmethylxanthine facilitates compensatory lung growth in adult mice. Am J Physiol Lung Cell Mol Physiol 2010; 300:L453-61. [PMID: 21224213 DOI: 10.1152/ajplung.00100.2010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The combination of dexamethasone, 8-bromo-3'-5'-cyclic adenosine monophosphate, and isobutylmethylxanthine, referred to as DCI, has been reported to optimally induce cell differentiation in fetal lung explants and type II epithelial cells. DCI administration is also known to modulate the expression levels of many genes known to be involved in the facilitation of lung growth. Recently, we found that RNA silencing of thyroid transcription factor 1 (TTF-1) delayed compensatory lung growth. DCI is also known to induce TTF-1 expression in pulmonary epithelial cells. From these findings, we hypothesized that DCI administration may facilitate compensatory lung growth. In the present study, using a postpneumonectomy lung growth model in 9-wk-old male mice, we found that compensatory lung growth was significantly facilitated by airway administration of DCI immediately following left pneumonectomy, as indicated by the increase in the residual right lung dry weight index. TTF-1 expression was significantly elevated by DCI administration, and transient knockdown of TTF-1 attenuated the facilitation of compensatory lung growth by DCI. These results suggested that DCI facilitated compensatory lung growth, at least in part, through the induction of TTF-1. Morphological analyses suggested that DCI administration increased the number of alveoli, made each of them smaller, and produced a net increase in the calculated surface area of the alveoli per volume of lung. The effect of a single administration was maintained during the observation period, which was 28 days. DCI with further modifications may provide the material to potentially augment residual lung function after resection.
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Affiliation(s)
- Yusuke Takahashi
- Division of General Thoracic Surgery, Dept. of Surgery, School of Medicine, Keio Univ., Tokyo, Japan
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Kolla V, Gonzales LW, Bailey NA, Wang P, Angampalli S, Godinez MH, Madesh M, Ballard PL. Carcinoembryonic cell adhesion molecule 6 in human lung: regulated expression of a multifunctional type II cell protein. Am J Physiol Lung Cell Mol Physiol 2009; 296:L1019-30. [PMID: 19329538 DOI: 10.1152/ajplung.90596.2008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Carcinoembryonic cell adhesion molecule 6 (CEACAM6) is a glycosylated, glycosylphosphatidylinositol (GPI)-anchored protein expressed in epithelial cells of various human tissues. It binds gram-negative bacteria and is overexpressed in cancers, where it is antiapoptotic and promotes metastases. To characterize CEACAM6 expression in developing lung, we cultured human fetal lung epithelial cells and examined responses to differentiation-promoting hormones, adenovirus expressing thyroid transcription factor-1 (TTF-1), and silencing of TTF-1 with small inhibitory RNA. Glucocorticoid and cAMP had additive stimulatory effects on CEACAM6 content, and combined treatment maximally increased transcription rate, mRNA, and protein approximately 10-fold. Knockdown of TTF-1 reduced hormone induction of CEACAM6 by 80%, and expression of recombinant TTF-1 increased CEACAM6 in a dose-dependent fashion. CEACAM6 content of lung tissue increased during the third trimester and postnatally. By immunostaining, CEACAM6 was present in fetal type II cells, but not mesenchymal cells, and localized to both the plasma membrane and within surfactant-containing lamellar bodies. CEACAM6 was secreted from cultured type II cells and was present in both surfactant and supernatant fractions of infant tracheal aspirates. In functional studies, CEACAM6 reduced inhibition of surfactant surface properties by proteins in vitro and blocked apoptosis of electroporated cultured cells. We conclude that CEACAM6 in fetal lung epithelial cells is developmentally and hormonally regulated and a target protein for TTF-1. Because CEACAM6 acts as an antiapoptotic factor and stabilizes surfactant function, in addition to a putative role in innate defense against bacteria, we propose that it is a multifunctional alveolar protein.
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Affiliation(s)
- Venkatadri Kolla
- Department of Pediatrics , Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Torday JS, Rehan VK. Up-regulation of fetal rat lung parathyroid hormone-related protein gene regulatory network down-regulates the Sonic Hedgehog/Wnt/betacatenin gene regulatory network. Pediatr Res 2006; 60:382-8. [PMID: 16940239 DOI: 10.1203/01.pdr.0000238326.42590.03] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Lung development depends on endodermal Sonic Hedgehog (Shh) signaling to mesodermal Wingless/int/beta catenin (Wnt/betacatenin), followed by parathyroid hormone-related protein (PTHrP) signaling from endoderm to mesoderm. Fluid distension of fetal rat lung explants up-regulates PTHrP signaling and down-regulates Shh/Wnt/betacatenin signaling, marked by decreases in Patched, Gli, Frizzled, and Dishevelled, inducing fibroblast triglyceride uptake, type II cell saturated phosphatidylcholine, and surfactant protein-B expression. Bumetanide, which inhibits fluid distension, blocked down-regulation of the Shh/Wnt/betacatenin pathway and up-regulation of the PTHrP pathway, whereas PTHrP (1-34, 5 x 10(-7) M) treatment overcame bumetanide inhibition, and the PTHrP receptor antagonist PTHrP (7-34) amide (5 x 10(-6) M) mimicked bumetanide, indicating that PTHrP signaling mediates fluid distension-induced alveolar differentiation. Fetal rat lung explant automaturation was characterized by decreased Wnt/betacatenin signaling and increased PTHrP/PTHrP receptor signaling, up-regulating fibroblast-specific adipocyte differentiation related protein (ADRP) and peroxisome proliferator-activated receptor gamma. Wnt/betacatenin agonists (LiCl or SB415268) maintained Shh/Wnt/betacatenin signaling, blocking spontaneous up-regulation of the PTHrP pathway, whereas PTHrP or cAMP down-regulated Shh/Wnt/betacatenin signaling and stimulated PTHrP signaling for fibroblast and type II cell differentiation. This is the first evidence that alveolar fluid distension is an organizing principle for PTHrP signaling down-regulation of the Shh/Wnt/betacatenin pathway.
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Affiliation(s)
- John S Torday
- Department of Pediatrics, Los Angeles Biomedical Research Institute at Harbor-UCLA, Torrance, California 90502, USA.
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Wang Y, Maciejewski BS, Lee N, Silbert O, McKnight NL, Frangos JA, Sanchez-Esteban J. Strain-induced fetal type II epithelial cell differentiation is mediated via cAMP-PKA-dependent signaling pathway. Am J Physiol Lung Cell Mol Physiol 2006; 291:L820-7. [PMID: 16751225 DOI: 10.1152/ajplung.00068.2006] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The signaling pathways by which mechanical forces modulate fetal lung development remain largely unknown. In the present study, we tested the hypothesis that strain-induced fetal type II cell differentiation is mediated via the cAMP signaling pathway. Freshly isolated E19 fetal type II epithelial cells were cultured on collagen-coated silastic membranes and exposed to mechanical strain for varying intervals, to simulate mechanical forces during lung development. Unstretched samples were used as controls. Mechanical strain activated heterotrimeric G-protein alpha(s) subunit, cAMP, and the transcription factor cAMP response element binding protein (CREB). Incubation of E19 cells with the PKA inhibitor H-89 significantly decreased strain-induced CREB phosphorylation. Moreover, adenylate cyclase 5 and CREB genes were also mechanically induced. In contrast, components of the PKA-independent (Epac) pathway, including Rap-1 or B-Raf, were not phosphorylated by strain. The addition of forskolin or dibutyryl cAMP to unstretched E19 monolayers markedly upregulated expression of the type II cell differentiation marker surfactant protein C, whereas the Epac agonist 8-pCPT-2'-O-Me-cAMP had no effect. Furthermore, incubation of E19 cells with the PKA inhibitor Rp-2'-O-monobutyryladenosine 3',5'-cyclic monophosphorothioate or transient transfection with plasmid DNA containing a PKA inhibitor expression vector significantly decreased strain-induced surfactant protein C mRNA expression. In conclusion, these studies indicate that the cAMP-PKA-dependent signaling pathway is activated by force in fetal type II cells and participates in strain-induced fetal type II cell differentiation.
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Affiliation(s)
- Yulian Wang
- Department of Pediatrics, Women & Infants Hospital of Rhode Island, Brown Medical School, 101 Dudley St., Providence, RI 02905, USA
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Postle AD, Gonzales LW, Bernhard W, Clark GT, Godinez MH, Godinez RI, Ballard PL. Lipidomics of cellular and secreted phospholipids from differentiated human fetal type II alveolar epithelial cells. J Lipid Res 2006; 47:1322-31. [PMID: 16513897 DOI: 10.1194/jlr.m600054-jlr200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Maturation of fetal alveolar type II epithelial cells in utero is characterized by specific changes to lung surfactant phospholipids. Here, we quantified the effects of hormonal differentiation in vitro on the molecular specificity of cellular and secreted phospholipids from human fetal type II epithelial cells using electrospray ionization mass spectrometry. Differentiation, assessed by morphology and changes in gene expression, was accompanied by restricted and specific modifications to cell phospholipids, principally enrichments of shorter chain species of phosphatidylcholine (PC) and phosphatidylinositol, that were not observed in fetal lung fibroblasts. Treatment of differentiated epithelial cells with secretagogues stimulated the secretion of functional surfactant-containing surfactant proteins B and C (SP-B and SP-C). Secreted material was further enriched in this same set of phospholipid species but was characterized by increased contents of short-chain monounsaturated and disaturated species other than dipalmitoyl PC (PC16:0/16:0), principally palmitoylmyristoyl PC (PC16:0/14:0) and palmitoylpalmitoleoyl PC (PC16:0/16:1). Mixtures of these PC molecular species, phosphatidylglycerol, and SP-B and SP-C were functionally active and rapidly generated low surface tension on compression in a pulsating bubble surfactometer. These results suggest that hormonally differentiated human fetal type II cells do not select the molecular composition of surfactant phospholipid on the basis of saturation but, more likely, on the basis of acyl chain length.
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Affiliation(s)
- Anthony D Postle
- Division of Infection, Inflammation, and Repair, School of Medicine, University of Southampton, Southampton, UK.
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Nguyen NM, Kelley DG, Schlueter JA, Meyer MJ, Senior RM, Miner JH. Epithelial laminin alpha5 is necessary for distal epithelial cell maturation, VEGF production, and alveolization in the developing murine lung. Dev Biol 2005; 282:111-25. [PMID: 15936333 DOI: 10.1016/j.ydbio.2005.02.031] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Revised: 02/18/2005] [Accepted: 02/23/2005] [Indexed: 01/13/2023]
Abstract
Laminin alpha5 is prominent in the basement membrane of alveolar walls, airways, and pleura in developing and adult lung. Targeted deletion of laminin alpha5 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 alpha5 in lung development, we have generated an inducible lung epithelial cell-specific Lama5 null (SP-CLama5(fl/-)) mouse through use of the Cre/loxP system, the human surfactant protein C promoter, and the reverse tetracycline transactivator. SP-CLama5(fl/-) embryos exposed to doxycycline from E6.5 died a few hours after birth. Compared to control littermates, SP-CLama5(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 alpha5, independent of its structural function, is necessary for murine lung development, and suggest a role for laminin alpha5 in signaling pathways that promote alveolar epithelial cell differentiation and VEGF expression.
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Affiliation(s)
- Nguyet M Nguyen
- Pulmonary and Critical Care Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Gonzales LW, Guttentag SH, Wade KC, Postle AD, Ballard PL. Differentiation of human pulmonary type II cells in vitro by glucocorticoid plus cAMP. Am J Physiol Lung Cell Mol Physiol 2002; 283:L940-51. [PMID: 12376347 DOI: 10.1152/ajplung.00127.2002] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mature alveolar type II cells that produce pulmonary surfactant are essential for adaptation to extrauterine life and prevention of infant respiratory distress syndrome. We have developed a new in vitro model to further investigate regulation of type II cell differentiation. Epithelial cells isolated from human fetal lung were cultured in serum-free medium on plastic. Cells treated with dexamethasone + cAMP analog and isobutylmethylxanthine for 4 days exhibited increased phosphatidylcholine synthesis and content of disaturated phosphatidylcholine species, manyfold increases in all surfactant proteins with processing to mature forms, and abundant lamellar bodies. DNA microarray analysis identified approximately 3,100 expressed genes, including subsets of genes induced 2- to >100-fold (approximately 2.5%) or repressed 2- to 18-fold (approximately 1.2%) by hormone treatment. Of the highly regulated genes, most were coregulated in an additive or synergistic manner by dexamethasone and cAMP agents. Approximately 90% of the regulated genes identified by this initial microarray analysis have not been previously recognized as hormone responsive. One newly identified hormone-induced gene is Nkx2.1 (thyroid transcription factor-1), which has a critical role in surfactant protein gene expression. Our findings indicate that glucocorticoid + cAMP is sufficient and necessary for precocious induction of functional type II cells in this in vitro system and that these hormones act primarily in combination to regulate expression of a subset of specific genes.
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Affiliation(s)
- Linda W Gonzales
- Division of Neonatology, Department of Pediatrics, The Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-4318, USA
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13
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Strayer M, Savani RC, Gonzales LW, Zaman A, Cui Z, Veszelovszky E, Wood E, Ho YS, Ballard PL. Human surfactant protein B promoter in transgenic mice: temporal, spatial, and stimulus-responsive regulation. Am J Physiol Lung Cell Mol Physiol 2002; 282:L394-404. [PMID: 11839532 DOI: 10.1152/ajplung.00188.2001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Surfactant protein B (SP-B) is a developmentally and hormonally regulated lung protein that is required for normal surfactant function. We generated transgenic mice carrying the human SP-B promoter (-1,039/+431 bp) linked to chloramphenicol acetyltransferase (CAT). CAT activity was high in lung and immunoreactive protein localized to alveolar type II and bronchiolar epithelial cells. In addition, thyroid, trachea, and intestine demonstrated CAT activity, and each of these tissues also expressed low levels of SP-B mRNA. Developmental expression of CAT activity and SP-B mRNA in fetal lung were similar and both increased during explant culture. SP-B mRNA but not CAT activity decreased during culture of adult lung, and both were reduced by transforming growth factor (TGF)-beta(1). Treatment of adult mice with intratracheal bleomycin caused similar time-dependent decreases in lung SP-B mRNA and CAT activity. These findings indicate that the human SP-B promoter fragment directs tissue- and lung cell-specific transgene expression and contains cis-acting elements involved in regulated expression during development, fetal lung explant culture, and responsiveness to TGF-beta and bleomycin-induced lung injury.
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Affiliation(s)
- Marlene Strayer
- Division of Neonatology, Department of Pediatrics, The Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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14
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Bates SR, Gonzales LW, Tao JQ, Rueckert P, Ballard PL, Fisher AB. Recovery of rat type II cell surfactant components during primary cell culture. Am J Physiol Lung Cell Mol Physiol 2002; 282:L267-76. [PMID: 11792631 DOI: 10.1152/ajplung.00227.2001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A culture system designed to maintain the differentiated characteristics of rat type II cells based on protocols used for human fetal lung pneumocytes was investigated. Type II cells were isolated either from adult rats with elastase (adult type II cells) or from young rats (4-11 days postnatal) with collagenase and trypsin (young type II cells) and were incubated with dexamethasone (Dex, 10 nM) and cAMP (0.1 mM). By day 4 of culture with hormone treatment, the mRNA levels in adult type II cells were less than 3% of day 0 values, whereas surfactant protein (SP)-A protein content was 26%. However, young type II cells maintained lamellar bodies and microvilli and secreted phospholipid in response to ATP. SP-A, -B, and -C mRNA levels were elevated to 159, 350, and 39%, respectively, of day 0 values with a synergistic response to Dex and cAMP, whereas SP-A protein content rose to 119%. Surfactant mRNA and protein did not recover in cells cultured without hormones. This cell culture system restored surfactant components in rat type II cells.
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Affiliation(s)
- Sandra R Bates
- The Institute for Environmental Medicine, University of Pennsylvania, 19104, USA.
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15
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Gonzales LW, Angampalli S, Guttentag SH, Beers MF, Feinstein SI, Matlapudi A, Ballard PL. Maintenance of differentiated function of the surfactant system in human fetal lung type II epithelial cells cultured on plastic. PEDIATRIC PATHOLOGY & MOLECULAR MEDICINE 2001; 20:387-412. [PMID: 11552739 DOI: 10.1080/15513810109168622] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
We report a simplified culture system for human fetal lung type II cells that maintains surfactant expression. Type II cells isolated from explant cultures of hormone-treated lungs (18-22 wk gestation) by collagenase + trypsin digestion were cultured on plastic for 4 days in serum-free medium containing dexamethasone (Dex, 10 nM) + 8-bromo-cAMP (0.1 mM + isobutylmethylxanthine (0.1 mM) or were untreated (control). Surfactant protein (SP) mRNAs decreased markedly in control cells between days 1 and 4 of culture, but mRNA levels were high in treated cells on day) 4 (SP-A, SP-B, SP-C, SP-D; 600%, 100%, 85%, 130% of day 0 content, respectively). Dex or cAMP alone increased SP-B, SP-C, and SP-D mRNAs and together had additive effects. The greatest increase in SP-A mRNA occurred with cAMP alone. Treated cells processed pro-SP-B and pro-SP-C proteins to mature forms and had a higher rate of phosphatidylcholine (PC) synthesis (2-fold) and higher saturation of PC (approximately 34% versus 27%) than controls. Only treated cells maintained secretagogue-responsive phospholipid synthesis. By electron microscopy, the treated cells retained lamellar bodies and extensive microvilli. We conclude that Dex and cAMP additively stimulate expression of surfactant components in isolated fetal type II cells, providing a simplified culture system for investigation of surfactant-related, and perhaps other, type II cell functions.
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Affiliation(s)
- L W Gonzales
- Department of Pediatrics, Children's Hospital of Philadelphia, Pennsylvania, USA.
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16
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Dobbs LG, Gutierrez JA. Mechanical forces modulate alveolar epithelial phenotypic expression. Comp Biochem Physiol A Mol Integr Physiol 2001; 129:261-6. [PMID: 11369550 DOI: 10.1016/s1095-6433(01)00322-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Physical forces play an important role in modulating lung development, growth, compliance, differentiation and metabolism. Both tonic distension and phasic changes in volume occur during development and after birth. Morphometric studies have shown that alveolar epithelial cells are distended during lung expansion from functional residual capacity. In both in vivo and in vitro model systems, mechanical distension stimulates surfactant secretion. Drawing on the results of developmental anomalies and experiments in vivo, we and others have generated the underlying hypothesis that mechanical distension promotes expression of the type I cell phenotype and inhibits expression that of the type II; contraction has the opposite effects. The results of recent experiments, using both cultured type II cells from adult rodents and fetal lung explant tissue to test this hypothesis, provide support. The molecular and biochemical mechanisms by which physical forces affect lung functions are currently under investigation.
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Affiliation(s)
- L G Dobbs
- Cardiovascular Research Institute, University of California San Francisco: LH Campus, 3333 California Street; Suite 150, San Francisco, CA 94118, USA.
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17
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Wagle S, Bui A, Ballard PL, Shuman H, Gonzales J, Gonzales LW. Hormonal regulation and cellular localization of fatty acid synthase in human fetal lung. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:L381-90. [PMID: 10444533 DOI: 10.1152/ajplung.1999.277.2.l381] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fatty acid synthase (FAS; EC 2.3.1.85) supplies de novo fatty acids for pulmonary surfactant synthesis, and FAS gene expression is both developmentally and hormonally regulated in the fetal lung. To further examine hormonal regulation of FAS mRNA and to determine the cellular localization of FAS gene expression, we cultured human fetal lungs (18-22 wk gestation) as explants for 1-4 days in the absence (control) or presence of glucocorticoid [dexamethasone (Dex), 10 nM] and/or cAMP agents (8-bromo-cAMP, 0.1 mM and IBMX, 0.1 mM). FAS protein content and activity increased similarly in the presence of Dex (109 and 83%, respectively) or cAMP (87 and 111%, respectively), and responses were additive in the presence of both hormones (230 and 203%, respectively). With a rabbit anti-rat FAS antibody, FAS immunoreactivity was not detected in preculture lung specimens but appeared in epithelial cells lining the tubules with time in culture. Dex and/or cAMP markedly increased staining of epithelial cells, identified as type II cells, whereas staining of mesenchymal fibroblasts was very low under all conditions. With in situ hybridization, FAS mRNA was found to be enriched in epithelial cells lining the alveolar spaces, and the reaction product increased in these cells when the explants were cultured with the hormones. The increased FAS mRNA content in the presence of Dex and/or cAMP is primarily due to increased stabilization of mRNA, although Dex alone increased the transcription rate by approximately 30%. We conclude that hormonal treatment of cultured human fetal lungs increases FAS gene expression primarily by increasing stability of the message. The induction of FAS during explant culture and by hormones occurs selectively in type II epithelial cells, consistent with the regulatory role of this enzyme in de novo synthesis of fatty acid substrate for surfactant synthesis in perinatal lungs.
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Affiliation(s)
- S Wagle
- Department of Pediatrics, University of Pennsylvania, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
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18
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Shaul PW, Pace MC, Chen Z, Brannon TS. Developmental changes in prostacyclin synthesis are conserved in cultured pulmonary endothelium and vascular smooth muscle. Am J Respir Cell Mol Biol 1999; 20:113-21. [PMID: 9870924 DOI: 10.1165/ajrcmb.20.1.3135] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Prostacyclin (PGI2) is a key mediator of pulmonary vascular and parenchymal function during late fetal and early postnatal life, and its synthesis in intrapulmonary arteries increases markedly during that period. The rate-limiting enzyme in PGI2 synthesis in the developing lung is cyclooxygenase (COX). To understand better the mechanisms underlying the developmental increase in PGI2 synthesis, we evaluated PGI2 production in early-passage, cultured pulmonary artery endothelial cells (PAEC) and pulmonary vascular smooth-muscle cells (VSM) from fetal and newborn lambs. In arterial segments, PGI2 synthesis was sevenfold greater in intact arteries from newborn than from fetal lambs, and it was 12-fold greater in endothelium-denuded newborn than in fetal arteries, indicating that the developmental increase occurs in both the endothelium and medial layer. Similarly, basal PGI2 production was three-fold greater in newborn than in fetal PAEC, and 2.5-fold greater in newborn than in fetal pulmonary VSM cells. Calcium ionophore (A23187)-stimulated and arachidonic acid-stimulated PGI2 synthesis were also greater in newborn than in fetal PAEC and VSM, revealing a developmental upregulation in COX enzymatic activity in both cell types. Immunoblot analysis showed that this is due to greater COX-1 protein expression in newborn than in fetal vascular cells; COX-2 protein expression was not detected. In addition, COX-1 messenger RNA (mRNA) abundance was greater in newborn than in fetal PAEC, and this was not due to a difference in COX-1 mRNA stability. Thus, the developmental upregulation of PGI2 synthesis is conserved in early-passage PAEC and pulmonary VSM, and is related to a maturational increase in COX-1 gene expression. Further studies with the cultured cell model will enable determination of the factors that directly regulate COX-1 expression in the developing pulmonary vasculature.
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MESH Headings
- Animals
- Animals, Newborn
- Arachidonic Acid/pharmacology
- Calcimycin/pharmacology
- Cells, Cultured
- Cyclooxygenase 1
- Endothelium, Vascular/embryology
- Endothelium, Vascular/enzymology
- Endothelium, Vascular/growth & development
- Epoprostenol/biosynthesis
- Gene Expression
- Immunoblotting
- Isoenzymes/genetics
- Muscle Development
- Muscle, Smooth, Vascular/embryology
- Muscle, Smooth, Vascular/enzymology
- Muscle, Smooth, Vascular/growth & development
- Prostaglandin-Endoperoxide Synthases/genetics
- Prostaglandin-Endoperoxide Synthases/metabolism
- Pulmonary Artery/embryology
- Pulmonary Artery/enzymology
- Pulmonary Artery/growth & development
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sheep
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Affiliation(s)
- P W Shaul
- Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA.
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19
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Acarregui MJ, Penisten ST, Goss KL, Ramirez K, Snyder JM. Vascular endothelial growth factor gene expression in human fetal lung in vitro. Am J Respir Cell Mol Biol 1999; 20:14-23. [PMID: 9870913 DOI: 10.1165/ajrcmb.20.1.3251] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Neonatal respiratory function depends on the development of a well-formed pulmonary capillary bed. Vascular endothelial growth factor (VEGF) is a potent inducer of endothelial cell growth and angiogenesis. High levels of VEGF protein and messenger RNA (mRNA) have been detected in the developing lung, suggesting that VEGF plays a role in the development of the pulmonary capillary bed. To begin to understand the role of VEGF in human lung development, we explored the regulation of VEGF gene expression and the localization of VEGF protein and mRNA in a model of the developing human lung. VEGF protein and mRNA were detected in midtrimester human fetal lung tissue, and their levels increased with time in explant culture. VEGF protein and mRNA were increased by the maintenance of human fetal lung explants in 2% O2 environments compared with 20% O2 environments. VEGF mRNA levels were found to be increased by cyclic adenosine monophosphate (cAMP) in explants that were incubated in 20% O2, but not in those incubated in 2% O2. Immunostaining for VEGF protein demonstrated localization primarily in airway epithelial cells in midtrimester human fetal lung tissue. Immunostaining for VEGF increased with incubation of human fetal lung explants in 2% and 20% O2. Interestingly, VEGF protein was localized primarily in the basement membrane subjacent to airway epithelial cells after 4 d of incubation in 20% O2. Incubation of tissues in the presence of dibutyryl cAMP resulted in an increase in immunostaining for VEGF, primarily in the basement membranes of prealveolar ducts in 20% O2-treated tissues. In situ hybridization studies indicated that VEGF mRNA was present in both mesenchymal cells and airway epithelial cells. These data suggest that VEGF gene expression is regulated by both oxygen and cAMP in the developing human lung. The detection of VEGF mRNA and protein in distal airway epithelial cells and the detection of VEGF protein in the basement membrane subjacent to the airway epithelial cells suggest that translocation of VEGF protein occurs after its synthesis in the epithelium. Localization of VEGF to the basement membrane of airway epithelial cells may be important for directing capillary development in the human lung.
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Affiliation(s)
- M J Acarregui
- Department of Pediatrics, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.
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20
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Scavo LM, Ertsey R, Gao BQ. Human surfactant proteins A1 and A2 are differentially regulated during development and by soluble factors. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:L653-69. [PMID: 9755097 DOI: 10.1152/ajplung.1998.275.4.l653] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An RT-PCR method for the relative quantitation of the mRNAs for human surfactant protein (SP) A1 and SP-A2 was developed, verified, and then utilized to determine the relative levels of these mRNAs in fetal and adult lung samples in vivo, as well as in cultured human fetal lung explants and H441 cells. For the cultured tissue and cells, we assessed the effects of a variety of soluble factors known to modulate total SP-A. Comprehensive analysis revealed many significant findings, including the following: both mRNAs were expressed as early as 15 wk of gestation; throughout midgestation, SP-A1 was present at higher levels than SP-A2, with an average ratio of 30:1. In the adult lung, SP-A1 mRNA was present at lower levels than SP-A2, with a ratio of 0.4:1, whereas in H441 cells, the ratio was 0.85:1. In fetal lung cultured for 4 days, both mRNAs increased, with a greater increase in SP-A2 (97-fold) than in SP-A1 (15-fold), resulting in a final ratio of 4:1. Differential regulation was demonstrated for 8-(4-chlorophenylthio)-cAMP, interferon (IFN)-gamma, tumor necrosis factor-alpha, and transforming growth factor (TGF)-beta in the human fetal lung explant system, with SP-A2 being more affected, and for IFN-gamma and TGF-beta in the H441 cells, where SP-A1 showed greater regulation. Of the soluble factors tested, IFN-gamma and TGF-beta had the most potent and consistent effects in both systems.
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Affiliation(s)
- L M Scavo
- Cardiovascular Research Institute and Department of Pediatrics, University of California, San Francisco, California 94143-9972, USA
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21
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Acarregui MJ, Brown JJ, Penisten ST. Cyclic AMP-dependent protein kinase (PKA) gene expression is developmentally regulated in fetal lung. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1402:303-12. [PMID: 9606989 DOI: 10.1016/s0167-4889(98)00004-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We characterized the ontogeny of cAMP-dependent protein kinase (PKA) enzymatic activity and PKA subunit mRNA expression in developing lung. The lungs of fetal Sprague-Dawley rat pups were removed after 16, 18, or 20 days of gestation and at term. PKA activity was greatest in the 18- and 20-day gestation lungs. Tissue cAMP levels were lowest in the 16-day lungs and increased with lung maturity. We were able to detect only low levels of mRNA for the C beta subunit of PKA by northern blot analysis of total lung RNA and we were able to detect mRNA for the RI beta and RII beta subunits only by RT-PCR. Therefore, we limited our analysis of PKA subunit mRNA levels to those for C alpha, RI alpha and RII alpha. The mRNA levels for C alpha, were highest in the 16-day lung, decreased at 18 and 20 days, were lower in the newborn and lowest in the adult lung. RI alpha mRNA levels were also highest at 16 days and lowest in the adult lung. However, RII alpha mRNA levels were similar in the 18-day, 20-day and newborn lungs. Dexamethasone treatment of fetal lung explants resulted in a small decrease in RI alpha mRNA levels but was not associated with a change in PKA activity. We conclude that PKA activity and PKA subunit mRNA expression are developmentally regulated in fetal lung. Such regulation results in optimal PKA activity at the time of type II alveolar cell differentiation, presumably in preparation for air breathing. The absence of an effect of glucocorticoid on PKA activity suggests that glucocorticoids are not responsible for the increase in PKA activity which accompanies this critical time in lung maturation.
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Affiliation(s)
- M J Acarregui
- Department of Pediatrics, University of Iowa College of Medicine, Iowa City 52242, USA.
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22
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Torday JS, Sun H, Qin J. Prostaglandin E2 integrates the effects of fluid distension and glucocorticoid on lung maturation. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:L106-11. [PMID: 9458807 DOI: 10.1152/ajplung.1998.274.1.l106] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Both glucocorticoids and alveolar fluid distension affect the rate of fetal lung maturation, possibly representing a common cellular pathway. In an explant culture, there is a spontaneous increase in triglyceride incorporation into saturated phosphatidylcholine over time. This mechanism is stimulated by prostaglandin (PG) E2, blocked by both bumetanide and indomethacin, and overridden by exogenous PGE2. Type II cells synthesized and produced PGE2 between days 16 and 21 postconception, increasing fourfold between days 19 and 21. Fetal rat lung fibroblasts released triglyceride in response to PGE2, increasing 10- to 14-fold between days 19 and 21 postconception; phloretin (1 x 10(-5) M) completely blocked this effect of PGE2 on triglyceride release. Dexamethasone stimulated both type II cell PGE2 synthesis (threefold) and fibroblast triglyceride release in response to PGE2 (60%) by day 20 cells. Stretching type II cells also increased PGE2 synthesis (approximately 100% at 1, 2, and 3 h vs. static cultures). Recombination of [3H]triglyceride-labeled fibroblasts with type II cells in an organotypic culture resulted in progressive incorporation of label into saturated phosphatidylcholine by type II cells. This process was also blocked by the addition of indomethacin and overridden by exogenous PGE2. These data suggest that the combined effects of alveolar fluid dilatation and glucocorticoids may coordinate the timely transfer of triglyceride from fibroblasts to type II cells for augmented surfactant production through their effects on PGE2 production and action as term approaches.
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Affiliation(s)
- J S Torday
- Department of Pediatrics, University of Maryland Medical School, Baltimore 21201, USA
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23
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Scavo LM, Ertsey R, Chapin CJ, Allen L, Kitterman JA. Apoptosis in the development of rat and human fetal lungs. Am J Respir Cell Mol Biol 1998; 18:21-31. [PMID: 9448042 DOI: 10.1165/ajrcmb.18.1.2744] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The establishment of an effective pulmonary alveolar-capillary interface occurs during mid to late gestation. This requires an expansion of endothelial, epithelial, and air space compartments with relative thinning of the interstitial compartment. Traditionally, these changes have been attributed to differences in the rate of cell growth in the respective compartments. We hypothesized that apoptosis also participates in this lung remodeling. Using light and electron microscopy, the nucleosomal ladder pattern of DNA digestion, and the detection of apoptotic cells in situ by the TUNEL method (Gavrieli, et al. J. Cell Biol. 1992;119:493-501), we demonstrated the occurrence of apoptosis in fetal lungs in vivo and in explant culture. In the rat fetal lung (RFL) in vivo we detected apoptosis from 16 through 22 d gestation. There was variation in the amount of DNA digestion between fetal lungs, but no correlation with gestational age. The findings in human fetal lungs (HFL) from 15 through 24 wk gestation were similar to those of the RFL; the apoptotic indices for both were about 2 apoptotic cells per thousand, suggesting that a significant percentage of cells are eliminated by this mechanism. In the HFL explant culture system, a rapid and massive wave of apoptosis occurred. In all samples of RFL and HFL examined, apoptosis was restricted to interstitial cells. This work has demonstrated for the first time that apoptosis is a feature of normal fetal lung development and that the process is accelerated in lung explant culture.
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Affiliation(s)
- L M Scavo
- Cardiovascular Research Institute and Department of Pediatrics, University of California, San Francisco 94143-0748, USA
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24
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Brannon TS, MacRitchie AN, Jaramillo MA, Sherman TS, Yuhanna IS, Margraf LR, Shaul PW. Ontogeny of cyclooxygenase-1 and cyclooxygenase-2 gene expression in ovine lung. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:L66-71. [PMID: 9458802 DOI: 10.1152/ajplung.1998.274.1.l66] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Prostacyclin is a key mediator of pulmonary vascular and parenchymal function during late fetal and early postnatal life, and its synthesis in whole lung increases during that period. The rate-limiting enzyme in prostacyclin synthesis in the developing lung is cyclooxygenase (COX). We investigated the ontogeny and cellular localization of COX-1 (constitutive) and COX-2 (inducible) gene expression in lungs from late-gestation fetal lambs, 1-wk-old newborn lambs (NB1), and 1- to 4-mo-old newborn lambs (NB2). COX-1 mRNA abundance rose progressively from fetal to NB1 to NB2, increasing 12-fold overall. In parallel, immunoblot analysis revealed a progressive increase in COX-1 protein, rising fourfold from fetal lambs to NB2. COX-2 mRNA levels increased fivefold from fetal to NB1 but were similar in NB1 and NB2. However, COX-2 protein was not detectable by immunoblot analysis in any age group. Immunohistochemistry for COX-1 showed intense immunostaining in endothelial cells at all ages. COX-1 was also expressed in airway epithelium at all ages, with a greater number of epithelial cells staining positively in NB2 compared with fetal and NB1 groups. In addition, COX-1 was expressed in airway smooth muscle from NB1. COX-2 immunostaining was absent in all age groups. These findings indicate that there is differential expression of COX-1 and COX-2 in the developing lung and that the enzymes are expressed in a cell-specific manner. The developmental upregulation in COX-1 may optimize the capacity for prostaglandin-mediated vasodilation, bronchodilation, and surfactant synthesis in the newborn lung.
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Affiliation(s)
- T S Brannon
- Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas 75235-9063, USA
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25
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Messina E, Muhlhauser J, Giuliano M, Pandolfi A, Morgese G, Procopio A. Surfactant protein A-producing cells in human fetal lung are good targets for recombinant adenovirus-mediated gene transfer. Pediatr Res 1996; 40:142-7. [PMID: 8798260 DOI: 10.1203/00006450-199607000-00024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Local delivery of Escherichia coli beta-galactosidase gene (beta-gal) to surfactant protein-A (SP-A)-producing cells by a replication-defective recombinant adenovirus (AdCMV.beta-gal) was tested in human 8-12-wk-old fetal lung explants cultured in Waymouth's medium. In contrast to uninfected explants, direct addition of 0.8-1.6 x 10(6) plaque-forming units of AdCMV.beta-gal resulted in beta-galactosidase (beta-Gal)-specific staining of the pulmonary epithelium. SP-A localization by indirect immunofluorescence showed positive specific staining of the beta-Gal+ lung epithelial cells, demonstrating that recombinant-defective adenoviruses efficiently transfer reporter genes to fetal lung SP-A+ cells. The reporter gene expression in SPA+ cells persisted for more than 1 mo. No apparent alteration of morphology, phenotype, and growth was observed. The in vitro human lung model described may be useful for testing DNA constructs for vector-mediated gene therapy, as an approach to the treatment of congenital defects and neonatal disorders, such as respiratory distress syndrome and bronchopulmonary dysplasia.
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Affiliation(s)
- E Messina
- Experimental Center on Gene Therapy and Diagnosis, Gabriele D'Annunzio University, Chieti, Italy
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26
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Affiliation(s)
- R Hume
- Department of Child Health, University of Dundee Medical School, Ninewells Hospital
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27
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Hume R, Bell J, Cossar D, Giles M, Hallas A, Kelly R. Differential release of prostaglandins by organ cultures of human fetal trachea and lung. In Vitro Cell Dev Biol Anim 1996; 32:24-9. [PMID: 8835315 DOI: 10.1007/bf02722990] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Human fetal lung at 16-19 weeks gestation has a partially differentiated epithelium, and in organ culture, distal airsacs dilate and the epithelium autodifferentiates to type I and II pneumatocytes, processes regulated by endogenous prostaglandin PGE2. Human fetal trachea, at the same gestation, has a terminally differentiated mucociliary epithelium but after 4-6 d in organ culture, develops squamous metaplasia. Tracheal cultures restricted to 3 d have normal phase-contrast and light microscopy appearances and immunohistochemical reactivities (epithelium: cytokeratin 7,8,18; glutathione S-transferase pi-isozyme; epithelial membrane antigen and mesenchyme; desmin; vimentin). In human fetal trachea organ cultures, the predominant prostaglandins released are 6-keto-PGF1 alpha, PGF2 alpha, and PGE2, a pattern similar to that previously described for human adult trachea and lung. In fetal lung cultures, 13,14-dihydro-15-keto-PGF2 alpha is the major prostaglandin released with lesser amounts of 13,14-dihydro-15-keto-PFG2 alpha,PGF2 alpha,PGE2, and 6-keto-PGF1 alpha. Human fetal lung in vitro has the competence to self-differentiate, as early as 12 weeks gestation and presence of high levels in fetal lung of the inactive metabolite 13,14-dihydro-15-keto-PGE2 relative to PGE2 suggests that active prostaglandin catabolism may be one of the mechanisms to retard this stage of maturation in vivo by limiting PGE2 availability. Surprisingly, the profile of prostaglandins released from fetal lung organ culture does not change to that of a mature lung with terminal differentiation of the epithelium, and this may indicate differences in the expression of key prostaglandin-metabolizing enzymes in developing human fetal lung in culture and with in utero ontogeny.
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Affiliation(s)
- R Hume
- Department of Obstetrics and Gynaecology, University of Dundee, Scotland, United Kingdom
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Chinoy MR, Antonio-Santiago MT, Scarpelli EM. Maturation of undifferentiated lung epithelial cells into type II cells in vitro: a temporal process that parallels cell differentiation in vivo. Anat Rec (Hoboken) 1994; 240:545-54. [PMID: 7879906 DOI: 10.1002/ar.1092400412] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND Formation of alveolar-like structures (ALS) by mature fetal rabbit type II pneumocytes (day 29 gestation) and long-term differentiation on Engelbreth-Holms-Swarm mouse tumor extract or EHS gel (Matrigel) were reported by our group (Blau et al., 1988. J. Cell Physiol., 136:203-214). We now describe structural organization and differentiation of immature lung epithelial cells, isolated at day 22 gestation, into mature type II cells in vitro. METHODS Peripheral pulmonary tissue was pooled and undifferentiated epithelial cells isolated for primary culture on Matrigel. Cells were examined 12-16 h after plating and on days 1, 3, 5, and 7 of culture and assessed by phase contrast and by transmission electron microscopy after fixation in situ. RESULTS Cells formed ALS 12-16 h after plating. Spherule diameter increased about four to eight times from day 1-7 in culture. There was rapid transformation of tall columnar cells to cuboidal, normal polarization of cells with respect to cell-free lumen of ALS, progressive reduction of glycogen zones, apparent gradual increase of cell organelles such as Golgi apparatus, rough endoplasmic reticulum and mitochondria, and apparent extrusion of lipidic figures into the lumen. These morphologic transformations in vitro temporally paralleled cell differentiation in vivo. The relative increase of 14C-acetate precursor into phosphatidylcholine in contrast to cardiolipin was consistent with these transformations. CONCLUSIONS Under the conditions of our culture system, maturation of undifferentiated pulmonary epithelial cells is reproduced in vitro along the same time course and according to the same developmental sequence of fetal lungs in vivo.
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Affiliation(s)
- M R Chinoy
- Department of Cellular and Molecular Physiology, Hershey Medical Center, Hershey, Pennsylvania
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Gonzales LW, Ballard PL, Gonzales J. Glucocorticoid and cAMP increase fatty acid synthetase mRNA in human fetal lung explants. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1215:49-58. [PMID: 7948007 DOI: 10.1016/0005-2760(94)90090-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
During late fetal development, synthesis of surfactant phospholipid requires a large supply of fatty acid precursor. Fatty acid synthetase is a regulatory enzyme for de novo fatty acid synthesis in lung as well as other lipogenic tissues. In this study, we report hormonal induction of FAS mRNA in human fetal lung explants (16-23 week gestation) cultured up to 7 days in Waymouth's medium (no serum) supplemented with dexamethasone (Dex, 10 nM) or agents that increase cAMP (8-Br-cAMP, 0.1 mM; isobutylmethylxanthine, 0.1 mM; forskolin, 0.01 mM; PGE1, 0.01 mM). Exposure of explants to Dex or cAMP agents increased FAS mRNA content by 6 h and maximal stimulation occurred at 72 h for Dex (approx. 3-fold increase) and 24 h for cAMP (approx. 2-fold increase). In the presence of both Dex and cAMP there was a synergistic increase in FAS mRNA content at all times (approx. 11-fold increase at 72 h). Induction of FAS mRNA was specific for steroids with glucocorticoid activity, reversible on removal of hormone, and was half-maximal at 2-3 nM Dex consistent with receptor mediation. Actinomycin D blocked induction by Dex but not by cAMP suggesting a transcriptional effect by glucocorticoid but not by cAMP. T3, which increases phosphatidylcholine synthesis, did not induce FAS mRNA. The findings indicate that both glucocorticoid and cAMP increase FAS gene expression consistent with an important role for FAS in regulating the supply of fatty acid for surfactant phospholipid synthesis.
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Affiliation(s)
- L W Gonzales
- Department of Pediatrics, University of Pennsylvania, Children's Hospital of Philadelphia 19104
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Peters-Golden M, Feyssa A. Augmented expression of cytosolic phospholipase A2 during phenotypic transformation of cultured type II pneumocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 266:C382-90. [PMID: 8141252 DOI: 10.1152/ajpcell.1994.266.2.c382] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Over time in culture, rat type II alveolar epithelial cells (AEC) demonstrate increased levels of unesterified arachidonic acid (AA) and increased prostanoid synthesis, while assuming certain morphological and biochemical characteristics of the type I cell phenotype. The objective of this study was to elucidate the enzymatic mechanism(s) responsible for increased AA accumulation in this model. Cells were examined both early in culture (2 days), when they retained type II cell features, and later in culture (7 days), when they are known to express a number of type I cell characteristics. An increase in AA levels at day 7 persisted despite inhibition of AA reacylation, suggesting that differences in deacylation were responsible for differences in free fatty acid levels. These differences in deacylation were not explained by differing susceptibilities to hydrolysis of radiolabeled endogenous lipids from day 2 and day 7 cells. The phospholipase A2 (PLA2) activities at both days in culture were qualitatively similar and typical of the recently described high-molecular-mass cytosolic PLA2 (cPLA2), but activity in day 7 cytosol was threefold greater than that present in day 2 cytosol. A neutralizing anti-cPLA2 antibody reduced the PLA2 activity in day 7 cytosol to the level found in day 2 cytosol. Immunoblot analysis failed to detect expression of low-molecular-mass PLA2 proteins but confirmed that expression of the 97-kDa cPLA2 was greater in day 7 cytosol than in day 2 cytosol. These results indicate that increased levels of unesterified AA in AEC with phenotype altered during culture are due to augmented steady-state expression of cPLA2 and suggest for the first time that expression of cPLA2 is differentiation dependent.
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Affiliation(s)
- M Peters-Golden
- Department of Internal Medicine, University of Michigan, Ann Arbor
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31
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Sharma A, Gonzales LW, Ballard PL. Hormonal regulation of cholinephosphate cytidylyltransferase in human fetal lung. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1170:237-44. [PMID: 8218341 DOI: 10.1016/0005-2760(93)90005-t] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Cytidylyltransferase (CTP: cholinephosphate cytidylyltransferase, EC 2.7.7.15, CYT) is a regulatory enzyme for synthesis of pulmonary surfactant phosphatidylcholine (PC). The effects of glucocorticoid, T3, and cAMP on CYT activity were studied in explants of human fetal lung (18-22 weeks gestation) cultured for 1-6 days in serum-free medium. Dexamethasone (Dex, 10 nM) treatment for 5 days increased homogenate CYT activity (+115%, P < 0.02) when assayed in the presence of added lipid co-factor (L-alpha-phosphatidylglycerol, PG, 1.1 mM) and tended to increase activity in its absence (+77%, P = 0.12). Cytosolic activity was also significantly elevated in the presence of added co-factor (+124%, P < 0.01), but there was no effect of Dex on microsomal specific activity. Dex increased the recovery of CYT activity in the cytosolic fraction (75% vs. 43% (control) of the homogenate activity), but not in the microsomal, nuclear or mitochondrial fractions. Assayed in the presence of added co-factor, stimulation of CYT by Dex was apparent after 48 h exposure and maximal by 5-6 days exposure to < or = 30 nM concentration. T3 or agents that increase endogenous cAMP stimulated cytosolic activity by 40% and 36-74%, respectively, after 4-6 days exposure, but none produced an additive increase in the presence of Dex. We conclude that stimulation of CYT activity contributes to hormonal induction of surfactant lipids by each of these hormones. Glucocorticoids may increase the amount of CYT enzyme as well as activate the enzyme via increased synthesis of lipid co-factor.
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Affiliation(s)
- A Sharma
- Department of Pediatrics, University of California, San Francisco 94143
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32
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Strayer D, Yang S, Jerng H. Surfactant protein A-binding proteins. Characterization and structures. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(17)46683-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Xu J, Possmayer F. Exposure of rabbit fetal lung to glucocorticoids in vitro does not enhance transcription of the gene encoding pulmonary surfactant-associated protein-B (SP-B). BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1169:146-55. [PMID: 8343538 DOI: 10.1016/0005-2760(93)90199-j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We have investigated the ontogeny and hormonal regulation of both synthesis rates and cellular accumulation of the mRNA for surfactant-associated protein B (SP-B) in rabbit fetal lung. The developmental pattern for SP-B mRNA synthesis increased as a function of gestational age and paralleled that for SP-B mRNA levels except on days 22-26 of gestation where relatively higher levels of gene transcription were observed. Time-course studies with explants from 26- and 30-day fetal lung maintained in culture revealed a gradual increase in mRNA levels and a much smaller increase in gene transcription relative to adult values. Within 48 h of exposure of 26-day explants to dexamethasone at 10(-8) M there was a rapid increase in SP-B mRNA levels to 7-fold adult levels. A similar overall although somewhat slower and attenuated pattern was observed with 30-day explants. Dexamethasone at 10(-8) M had no effect on SP-B gene transcription with explants of either gestational age. We conclude that the major effect of dexamethasone treatment in vitro on SP-B mRNA levels appears to be post-transcriptional and there are small but distinct differences in the effects of glucocorticoids on SP-B mRNA levels with explant cultures from early and late stages of fetal lung maturation.
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Affiliation(s)
- J Xu
- MRC Group in Fetal and Neonatal Health and Development, University of Western Ontario, University Hospital, London, Canada
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Hume R, Bell J, Gourlay M, Giles M, Hallas A, Cossar D, Kelly R. Prostaglandin production and metabolism in self-differentiating human fetal lung organ culture. Exp Lung Res 1993; 19:361-76. [PMID: 8319605 DOI: 10.3109/01902149309064352] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
PGE2 and PGF2 alpha are released into the media of human fetal lung organ cultures in decreasing amounts with time. This decline in PGs is not due to culture failure or loss of synthetic capacity, which can be stimulated by fetal bovine serum, nor is it due to increased catabolism of PGE2 to 13,14-dihydro-15-keto-PGE2 (PGEM) or of PGF2 alpha to 13,14-dihydro-15-keto-PGF2 alpha (PGFM). Immunohistochemically reactive PGs are not retained within lung cells. Antisera against methyl-moximated derivatives of PGEM or PGFM and preceded by derivatization on tissue sections of PGs by methyl-moximation not only demonstrate the localization of PGEM and PGFM in epithelial cells and blood vessels, but also show an overall decline in immunoreactivity with time. In addition electron microscopy of uncultured fetal lung removed directly after termination reveals various degrees of mitochondrial damage and in some cases plasma membrane blebs which resolve during the period in culture and as fetal lung self-differentiates. It is proposed that oxidative and mechanical stresses, occurring during termination of pregnancy or tissue preparation, result in cell damage and increased lung prostaglandin production, which, although decreasing during culture as cells recover, is sufficient to trigger terminal self-differentiation.
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Affiliation(s)
- R Hume
- Department of Child Health, University of Dundee, Scotland
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