Expression of intermediate filament proteins in fetal and adult human lung tissues

The molecular biophysics of extracellular vimentin and its role in pathogen-host interactions

Vimentin, an intermediate filament protein typically located in the cytoplasm of mesenchymal cells, can also be secreted as an extracellular protein. The organization of extracellular vimentin strongly determines its functions in physiological and pathological conditions, making it a promising target for future therapeutic interventions. The extracellular form of vimentin has been found to play a role in the interaction between host cells and pathogens. In this review, we first discuss the molecular biophysics of extracellular vimentin, including its structure, secretion, and adhesion properties. We then provide a general overview of the role of extracellular vimentin in mediating pathogen-host interactions, with a focus on its interactions with viruses and bacteria. We also discuss the implications of these findings for the development of new therapeutic strategies for combating infectious diseases.

Vimentin affects colorectal cancer proliferation, invasion, and migration via regulated by activator protein 1

Uncontrolled recurrence and metastasis are important reasons for the high mortality rate of malignant tumors. Vimentin is positively correlated with the degree of malignancy of cancer cells. Vimentin is also highly expressed in colorectal cancer (CRC) cells and plays a critical role in the metastasis and prognosis of CRC. However, the molecular mechanism of vimentin in the progression of CRC is incompletely understood. Therefore, the most active regions (nucleotides: 785-1085 nt) of the vimentin promoter in CRC were identified using luciferase experiments. By transcription factor sequence search and mutation analysis, the activator protein 1 (AP-1) binding site in the region of 785-1085 nt was confirmed. The vimentin promoter activity was enhanced by overexpression of AP-1. The electrophoretic mobility shift assay and chromatin immunoprecipitation assay showed that the binding site was recognized by AP-1. By cell proliferation assay, colony-forming assay, scratch-wound assay, cell migration assay, and cell invasion assay, we demonstrated that the AP-1 overexpression increased CRC cell proliferation, migration, and invasion. However, when vimentin was knocked down by vimentin small hairpin RNA in the CRC cell of AP-1 overexpression, this trend disappeared. Animal experiments and immunohistochemistry showed that AP-1 promoted tumor growth by regulating the vimentin gene. In summary, AP-1 affected metastasis, invasion of CRC cells in vitro, and tumor growth in vivo by activating the vimentin promoter. This study might provide new insights into the molecular mechanisms of the development of CRC and provide potential therapeutic targets for CRC.

Vimentin as a Multifaceted Player and Potential Therapeutic Target in Viral Infections

Vimentin is an intermediate filament protein that plays key roles in integration of cytoskeletal functions, and therefore in basic cellular processes such as cell division and migration. Consequently, vimentin has complex implications in pathophysiology. Vimentin is required for a proper immune response, but it can also act as an autoantigen in autoimmune diseases or as a damage signal. Although vimentin is a predominantly cytoplasmic protein, it can also appear at extracellular locations, either in a secreted form or at the surface of numerous cell types, often in relation to cell activation, inflammation, injury or senescence. Cell surface targeting of vimentin appears to associate with the occurrence of certain posttranslational modifications, such as phosphorylation and/or oxidative damage. At the cell surface, vimentin can act as a receptor for bacterial and viral pathogens. Indeed, vimentin has been shown to play important roles in virus attachment and entry of severe acute respiratory syndrome-related coronavirus (SARS-CoV), dengue and encephalitis viruses, among others. Moreover, the presence of vimentin in specific virus-targeted cells and its induction by proinflammatory cytokines and tissue damage contribute to its implication in viral infection. Here, we recapitulate some of the pathophysiological implications of vimentin, including the involvement of cell surface vimentin in interaction with pathogens, with a special focus on its role as a cellular receptor or co-receptor for viruses. In addition, we provide a perspective on approaches to target vimentin, including antibodies or chemical agents that could modulate these interactions to potentially interfere with viral pathogenesis, which could be useful when multi-target antiviral strategies are needed.

CPEB4 promotes cell migration and invasion via upregulating Vimentin expression in breast cancer

Cytoplasmic polyadenylation element binding protein 4 (CPEB4) is a member of CPEB family which is overexpressed in variety of cancers. However, the biological role and regulatory mechanism of CPEB4 in cancers remain unknown. Here, we first investigate the role of CPEB4 in breast cancer progression and metastasis. The expression of CPEB4 is elevated in breast cancer tissues compared with adjacent normal tissues. Furthermore, high expression levels of CPEB4 is associated with tumor metastasis in breast cancer patients. Ectopic expression of CPEB4 dramatically promotes EMT, migration and invasion of breast cancer cells, while silencing CPEB4 expression significantly reduces these events. Mechanically, overexpression of CPEB4 upregulates Vimentin expression and silencing Vimentin expression blocks CPEB4-induced migration and invasion of breast cancer cells. These results implicate the potential role of CPEB4 and Vimentin in breast cancer metastasis, which is further confirmed by the finding that there is a physical interaction between the two proteins. Altogether, our results provide a novel insight into CPEB4 in regulating breast cancer progression and metastasis.

Fibroblastic foci, covered with alveolar epithelia exhibiting epithelial-mesenchymal transition, destroy alveolar septa by disrupting blood flow in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive interstitial lung disease of unknown cause. IPF has a distinct histopathological pattern of usual interstitial pneumonia in which fibroblastic foci (FF) represent the leading edge of fibrotic destruction of the lung. Currently there are three major hypotheses for how FF are generated: (1) from resident fibroblasts, (2) from bone marrow-derived progenitors of fibroblasts, and (3) from alveolar epithelial cells that have undergone epithelial-mesenchymal transition (EMT). We found that FF dissociated capillary vessels from the alveolar epithelia, the basement membranes of which are fused in normal physiological conditions, and pushed the capillaries and elastic fibers down ~100 μm below the alveolar epithelia. Furthermore, the alveolar epithelial cells covering the FF exhibited a partial EMT phenotype. In addition, normal human alveolar epithelial cells in vitro underwent dynamic EMT in response to transforming growth factor-β signaling within 72 h. Because it seems that resident fibroblasts or bone marrow-derived cells cannot easily infiltrate and form FF between the alveolar epithelia and capillaries in tight contact with each other, FF are more likely to be derived from the epithelial-to-mesenchymal transitioned alveolar epithelia located over them. Moreover, histology and immunohistochemistry suggested that the FF formed in the lung parenchyma disrupt blood flow to the alveolar septa, thus destroying them. Consequently, collapse of the alveolar septa is likely to be the first step toward honeycombing in the lung during late stage IPF. On the basis of these findings, inhibition of transforming growth factor-β signaling, which can suppress EMT of the alveolar epithelial cells in vitro, is a potential strategy for treating IPF.

Vessel co-option is common in human lung metastases and mediates resistance to anti-angiogenic therapy in preclinical lung metastasis models

Anti‐angiogenic therapies have shown limited efficacy in the clinical management of metastatic disease, including lung metastases. Moreover, the mechanisms via which tumours resist anti‐angiogenic therapies are poorly understood. Importantly, rather than utilizing angiogenesis, some metastases may instead incorporate pre‐existing vessels from surrounding tissue (vessel co‐option). As anti‐angiogenic therapies were designed to target only new blood vessel growth, vessel co‐option has been proposed as a mechanism that could drive resistance to anti‐angiogenic therapy. However, vessel co‐option has not been extensively studied in lung metastases, and its potential to mediate resistance to anti‐angiogenic therapy in lung metastases is not established. Here, we examined the mechanism of tumour vascularization in 164 human lung metastasis specimens (composed of breast, colorectal and renal cancer lung metastasis cases). We identified four distinct histopathological growth patterns (HGPs) of lung metastasis (alveolar, interstitial, perivascular cuffing, and pushing), each of which vascularized via a different mechanism. In the alveolar HGP, cancer cells invaded the alveolar air spaces, facilitating the co‐option of alveolar capillaries. In the interstitial HGP, cancer cells invaded the alveolar walls to co‐opt alveolar capillaries. In the perivascular cuffing HGP, cancer cells grew by co‐opting larger vessels of the lung. Only in the pushing HGP did the tumours vascularize by angiogenesis. Importantly, vessel co‐option occurred with high frequency, being present in >80% of the cases examined. Moreover, we provide evidence that vessel co‐option mediates resistance to the anti‐angiogenic drug sunitinib in preclinical lung metastasis models. Assuming that our interpretation of the data is correct, we conclude that vessel co‐option in lung metastases occurs through at least three distinct mechanisms, that vessel co‐option occurs frequently in lung metastases, and that vessel co‐option could mediate resistance to anti‐angiogenic therapy in lung metastases. Novel therapies designed to target both angiogenesis and vessel co‐option are therefore warranted. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Elevated expression of UBE2T exhibits oncogenic properties in human prostate cancer

Increased expression of ubiquitin-conjugating enzyme E2T (UBE2T) is reported in human prostate cancer. However, whether UBE2T plays any functional role in prostate cancer development remains unknown. We here report the first functional characterization of UBE2T in prostate carcinogenesis. Prostate cancer tissue array analysis confirmed upregulation of UBE2T in prostate cancer, especially these with distant metastasis. Moreover, higher level of UBE2T expression is associated with poorer prognosis of prostate cancer patients. Ectopic expression of UBE2T significantly promotes prostate cancer cell proliferation, motility and invasion, while UBE2T depletion by shRNA significantly inhibits these abilities of prostate cancer cells. Xenograft mouse model studies showed that overexpression of UBE2T promotes whereas UBE2T depletion inhibits tumor formation and metastasis significantly. Collectively, we identify critical roles of UBE2T in prostate cancer development and progression. These findings may serve as a framework for future investigations designed to more comprehensive determination of UBE2T as a potential therapeutic target.

Keratin 34betaE12/keratin7 expression is a prognostic factor of cancer-specific and overall survival in patients with early stage non-small cell lung cancer

BACKGROUND

Carcinomas and their metastases often retain the keratin patterns of their epithelial origin, and are therefore useful as lineage-specific markers in diagnostic pathology. Recently, it has become clear that intermediate filaments composed by keratins play a role in modulation of cell proliferation, migration, and possibly cancer invasion, factors impacting prognosis in early stage non-small cell lung cancer (NSCLC).

MATERIAL AND METHODS

Tumor tissue from a retrospective Danish cohort of 177 patients with completely resected NSCLC, stage I-IIIA tumors, were analyzed for keratin 7 (K7) and keratin 34βE12 expression by immunohistochemistry and validated in a comparable independent Norwegian cohort of 276 stage I-IIIA NSCLC patients.

RESULTS

Based on keratin 34βE12/K7 expression, three subgroups with significantly different median cancer-specific survival rates were identified (34βE12+/K7+, 168 months vs. 34βE12+/K7+, 73 months vs. 34βE12-/K7+, 30 months; p = 0.0004). In multivariate analysis, stage II-IIIA (HR 2.9), 34βE12+/K7+ (HR 1.90) and 34βE12-/K7+ (HR 3.7), were prognostic factors of poor cancer-specific survival (CSS) (p < 0.001). Validation in the Norwegian cohort confirmed that stage II-IIIA (HR 2.3), 34βE12+/K7+ (HR 1.6), and 34βE12-/K7+ (HR 2.0) were prognostic factors of poor CSS (p < 0.05). Multivariate Cox proportional-hazard analysis demonstrated that 34βE12+/K7 + and 34βE12+/K7 + status was significantly associated with poor overall survival (p < 0.05).

CONCLUSION

Keratin 34βE12/K7 expression is a prognostic parameter in resected early stage NSCLC that allows identification of high-risk NSCLC patients with poor cancer-specific and overall survival.

Coexpression of type 2 immune targets in sputum-derived epithelial and dendritic cells from asthmatic subjects

BACKGROUND

Noninvasive sputum sampling has enabled the identification of biomarkers in asthmatic patients. Studies of discrete cell populations in sputum can enhance measurements compared with whole sputum in which changes in rare cells and cell-cell interactions can be masked.

OBJECTIVE

We sought to enrich for sputum-derived human bronchial epithelial cells (sHBECs) and sputum-derived myeloid type 1 dendritic cells (sDCs) to describe transcriptional coexpression of targets associated with a type 2 immune response.

METHODS

A case-control study was conducted with patients with mild asthma (asthmatic cases) and healthy control subjects. Induced sputum was obtained for simultaneous enrichment of sHBECs and sDCs by using flow cytometry. Quantitative PCR was used to measure mRNA for sHBEC thymic stromal lymphopoietin (TSLP), IL33, POSTN, and IL25 and downstream targets in sDCs (OX40 ligand [OX40L], CCL17, PPP1R14A, CD1E, CD1b, CD80, and CD86).

RESULTS

Final analyses for the study sample were based on 11 control subjects and 13 asthmatic cases. Expression of TSLP, IL33, and POSTN mRNA was increased in sHBECs in asthmatic cases (P = .001, P = .05, and P = .04, respectively). Expression of sDC OX40L and CCL17 mRNA was increased in asthmatic cases (P = .003 and P = .0001, respectively). sHBEC TSLP mRNA expression was strongly associated with sDC OX40L mRNA expression (R = 0.65, P = .001) and less strongly with sDC CCL17 mRNA expression. sHBEC IL33 mRNA expression was associated with sDC OX40L mRNA expression (R = 0.42, P = .04) but not sDC CCL17 mRNA expression.

CONCLUSIONS

Noninvasive sampling and enrichment of select cell populations from sputum can further our understanding of cell-cell interactions in asthmatic patients with the potential to enhance endotyping of asthmatic patients.

Identification of a proximal progenitor population from murine fetal lungs with clonogenic and multilineage differentiation potential

Lung development-associated diseases are major causes of morbidity and lethality in preterm infants and children. Access to the lung progenitor/stem cell populations controlling pulmonary development during embryogenesis and early postnatal years is essential to understand the molecular basis of such diseases. Using a Nkx2-1^mCherry reporter mouse, we have identified and captured Nkx2-1-expressing lung progenitor cells from the proximal lung epithelium during fetal development. These cells formed clonal spheres in semisolid culture that could be maintained in vitro and demonstrated self-renewal and expansion capabilities over multiple passages. In-vitro-derived Nkx2-1-expressing clonal spheres differentiated into a polarized epithelium comprised of multiple cell lineages, including basal and secretory cells, that could repopulate decellularized lung scaffolds. Nkx2-1 expression thus defines a fetal lung epithelial progenitor cell population that can be used as a model system to study pulmonary development and associated pediatric diseases.

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Nkx2-1 expression can be used to isolate proximal lung progenitors

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The fetal proximal lung progenitors are distinct from currently known progenitors

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The fetal proximal lung progenitors are clonogenic and self-renewing

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The fetal proximal lung progenitors are multipotent for airway lineages

Differentiation of porcine mesenchymal stem cells into epithelial cells as a potential therapeutic application to facilitate epithelial regeneration

Epithelial denudation is one of the characteristics of chronic asthma. To restore its functions, the airway epithelium has to rapidly repair the injuries and regenerate its structure and integrity. Mesenchymal stem cells (MSCs) have the ability to differentiate into many cell lineages. However, the differentiation of MSCs into epithelial cells has not been fully studied. Here, we examined the differentiation of MSCs into epithelial cells using three different media compositions with various growth supplementations. The MSCs were isolated from porcine bone marrow by density gradient centrifugation. The isolated MSCs were CD11(-) CD34(-) CD45(-) CD44(+) CD90(+) and CD105(+) by immunostaining and flow cytometry. MSCs were stimulated with EpiGRO (Millipore), BEpiCM (ScienCell) and AECGM (PromoCell) media for 5 and 10 days, and epithelial differentiation was assessed by qPCR (keratin 14, 18 and EpCAM), fluorometry (cytokeratin 7-8, cytokeratin 14-15-16-19 and EpCAM), western blot analysis (pancytokeratin, EpCAM) and flow cytometry (cytokeratin 7-8, cytokeratin 14-15-16-19 and EpCAM). The functional marker MUC1 was also assessed after 10 days of air-liquid interface (ALI) culture in optimized media. Cells cultured in BEpiCM containing fibroblast growth factor and prostaglandin E2 showed the highest expression of the epithelial markers: CK7-8 (85.90%); CK-14-15-16-19 (10.14%); and EpCAM (64.61%). The cells also expressed functional marker MUC1 after ALI culture. The differentiated MSCs when cultured in BEpiCM medium ex vivo in a bioreactor on a decellularized trachea for 10 days retained the epithelial-like phenotype. In conclusion, porcine bone marrow-derived MSCs demonstrate commitment to the epithelial lineage and might be a potential therapy for facilitating the repair of denuded airway epithelium.

Vimentin in cancer and its potential as a molecular target for cancer therapy

Vimentin, a major constituent of the intermediate filament family of proteins, is ubiquitously expressed in normal mesenchymal cells and is known to maintain cellular integrity and provide resistance against stress. Vimentin is overexpressed in various epithelial cancers, including prostate cancer, gastrointestinal tumors, tumors of the central nervous system, breast cancer, malignant melanoma, and lung cancer. Vimentin's overexpression in cancer correlates well with accelerated tumor growth, invasion, and poor prognosis; however, the role of vimentin in cancer progression remains obscure. In recent years, vimentin has been recognized as a marker for epithelial-mesenchymal transition (EMT). Although EMT is associated with several tumorigenic events, vimentin's role in the underlying events mediating these processes remains unknown. By virtue of its overexpression in cancer and its association with tumor growth and metastasis, vimentin serves as an attractive potential target for cancer therapy; however, more research would be crucial to evaluate its specific role in cancer. Our recent discovery of a vimentin-binding mini-peptide has generated further impetus for vimentin-targeted tumor-specific therapy. Furthermore, research directed toward elucidating the role of vimentin in various signaling pathways would reveal new approaches for the development of therapeutic agents. This review summarizes the expression and functions of vimentin in various types of cancer and suggests some directions toward future cancer therapy utilizing vimentin as a potential molecular target.

Vimentin is a novel AKT1 target mediating motility and invasion

The PI3K/AKT signaling pathway is aberrant in a wide variety of cancers. Downstream effectors of AKT are involved in survival, growth and metabolic-related pathways. In contrast, contradictory data relating to AKT effects on cell motility and invasion, crucial prometastatic processes, have been reported pointing to a potential cell type and isoform type-specific AKT-driven function. By implication, study of AKT signaling should optimally be conducted in an appropriate intracellular environment. Prognosis in soft-tissue sarcoma (STS), the aggressive malignancies of mesenchymal origin, is poor, reflecting our modest ability to control metastasis, an effort hampered by lack of insight into molecular mechanisms driving STS progression and dissemination. We examined the impact of the cancer progression-relevant AKT pathway on the mesenchymal tumor cell internal milieu. We demonstrate that AKT1 activation induces STS cell motility and invasiveness at least partially through a novel interaction with the intermediate filament vimentin (Vim). The binding of AKT (tail region) to Vim (head region) results in Vim Ser39 phosphorylation enhancing the ability of Vim to induce motility and invasion while protecting Vim from caspase-induced proteolysis. Moreover, vimentin phosphorylation was shown to enhance tumor and metastasis growth in vivo. Insights into this mesenchymal-related molecular mechanism may facilitate the development of critically lacking therapeutic options for these devastating malignancies.

Characterisation of the proximal airway squamous metaplasia induced by chronic tobacco smoke exposure in spontaneously hypertensive rats

Background

Continuous exposure to tobacco smoke (TS) is a key cause of chronic obstructive pulmonary disease (COPD), a complex multifactorial disease that is difficult to model in rodents. The spontaneously hypertensive (SH) rat exhibits several COPD-associated co-morbidities such as hypertension and increased coagulation. We have investigated whether SH rats are a more appropriate animal paradigm of COPD.

Methods

SH rats were exposed to TS for 6 hours/day, 3 days/week for 14 weeks, and the lung tissues examined by immunohistochemistry.

Results

TS induced a CK13-positive squamous metaplasia in proximal airways, which also stained for Ki67 and p63. We hypothesise that this lesion arises by basal cell proliferation, which differentiates to a squamous cell phenotype. Differences in staining profiles for the functional markers CC10 and surfactant D, but not phospho-p38, indicated loss of ability to function appropriately as secretory cells. Within the parenchyma, there were also differences in the staining profiles for CC10 and surfactant D, indicating a possible attempt to compensate for losses in proximal airways. In human COPD sections, areas of CK13-positive squamous metaplasia showed sporadic p63 staining, suggesting that unlike the rat, this is not a basal cell-driven lesion.

Conclusion

This study demonstrates that although proximal airway metaplasia in rat and human are both CK13+ and therefore squamous, they potentially arise by different mechanisms.

Global transcriptional characterization of a mouse pulmonary epithelial cell line for use in genetic toxicology

Prior to its application for in vitro toxicological assays, thorough characterization of a cell line is essential. The present study uses global transcriptional profiling to characterize a lung epithelial cell line (FE1) derived from MutaMouse [White, P.A., Douglas, G.R., Gingerich, J., Parfett, C., Shwed, P., Seligy, V., Soper, L., Berndt, L., Bayley, J., Wagner, S., Pound, K., Blakey, D., 2003. Development and characterization of a stable epithelial cell line from Muta Mouse lung. Environmental and Molecular Mutagenesis 42, 166-184]. Results presented here demonstrate the origin of the FE1 lung cell line as epithelial, presenting both type I and type II alveolar phenotype. An assessment of toxicologically-relevant genes, including those involved in the response to stress and stimuli, DNA repair, cellular metabolism, and programmed cell death, revealed changes in expression of 22-27% of genes in one or more culture type (proliferating and static FE1 cultures, primary epithelial cultures) compared with whole lung isolates. Gene expression analysis at 4 and 24h following benzo(a)pyrene exposure revealed the induction of cyp1a1, cyp1a2, and cyp1b1 in FE1 cells and lung isolates. The use of DNA microarrays for gene expression profiling allows an improved understanding of global, coordinated cellular events arising in cells under different physiological conditions. Taken together, these data indicate that the FE1 cell line is derived from a cell type relevant to toxic responses in vivo, and shows some similarity in response to chemical insult as the original tissue.

Morphogenetic lung defects of JSAP1-deficient embryos proceeds via the disruptions of the normal expressions of cytoskeletal and chaperone proteins

Recent studies have shown that JNK/stress-activated protein kinase-associated protein 1 (JSAP1)-deficient mice die from respiratory failure shortly after birth. To understand the underlying mechanism, we investigated the histological appearances and cell type changes in developing jsap1(-/-) lungs between E12.5 and E18.5. At the light microscopic level, no overt abnormality was detected in jsap1(-/-) until E16.5. However, alveoli and airway formations that normally occur after E16.5 were poorly advanced in jsap1(-/-). Despite these morphological defects, surfactant secreting cells labeled by anti-SP-B or anti-SP-C were present in normal ranges in jsap1(-/-) lungs. Smooth muscle alpha-actin expressing cells were also developed in jsap1(-/-) lungs, although actin expression was decreased. The expressions of transcriptional factors, such as, nuclear factor Ib (Nfib), N-myc, and octamer transcriptional factor 1 (Oct-1), which play a critical role in lung morphogenesis, were found to be down-regulated, whereas signal transducer and activator of transcription 3 (Stat3), sonic hedgehog (Shh), and smoothened (Smo) were up-regulated, in jsap1(-/-) lungs at E17.5-E18.5 compared with those in jsap1(+/+) lungs. Proteomics analysis of E17.5 lung identified 39 proteins with altered expressions, which included actin, tropomyosin, myosin light chain, vimentin, heat shock protein (Hsp27), and Hsp84. These results suggest that JSAP1 is required for the normal expressions of cytoskeletal and chaperone proteins in the developing lung, and that impaired expressions of these proteins might cause morphogenetic defects observed in jsap1(-/-) lungs.

Poly(ADP-ribose) polymerase-1 regulates vimentin expression in lung cancer cells

Vimentin is one of the mammalian intermediate filament proteins. It is expressed in cells of mesenchymal origin and is characteristic of proliferating cells at the fetal stage. During malignancy, vimentin expression is activated in certain lung epithelial cells. Examination of a group of lung cancer cells showed a marked difference in their vimentin expression. The difference in vimentin expression among lung cancer cells is due to differential regulation at the transcriptional level. Analysis of the vimentin promoter revealed a 102-bp promoter sequence that is important for promoter activity in a lung cancer cell line in which vimentin is strongly expressed. This promoter region interacts with poly(ADP-ribose) polymerase-1 (PARP-1), which is also a transcription regulator. Exogenous expression of PARP-1 increased vimentin promoter activity. A shortened PARP-1 without the COOH-terminal catalytic domain showed the same promoter activation effect. Treatment of cells with H(2)O(2) reduced PARP-1 and vimentin expression at the protein level. H(2)O(2) also dose dependently suppressed vimentin promoter activity in cells overexpressing PARP-1. These results demonstrate that vimentin expression in lung cancer cells is regulated at the transcriptional level and that PARP-1 binds and activates the vimentin promoter independent of its catalytic domain and may play a role in H(2)O(2)-induced inhibition of vimentin expression.

A three-dimensional model of differentiation of immortalized human bronchial epithelial cells

A therapeutic approach being investigated for a variety of pathologies is tissue regeneration using a patient's own cells. Such studies have been hampered due to the difficulty in growing epithelial cells for prolonged periods in culture. Replicative senescence due to short telomeres and p16 induced by culture stress work together to inhibit cell growth. Forced expression of telomerase (hTERT) can prevent replicative senescence, and expression of the cell cycle protein cdk4 can sequester p16, thereby immortalizing epithelial cells in culture. In the present study, we used this method to immortalize human bronchial epithelial cells (HBECs) to determine whether immortalized HBECs retain the ability to differentiate normally. HBECs were plated atop contracted collagen gels containing lung fibroblasts. This three-dimensional (3D) tissue model was cultured initially submerged, then raised to the air/liquid interface for up to 28 days. Normal differentiation was assessed by the presence of ciliated cells, goblet (mucin-producing) cells, and basal epithelial cells. Scanning electron microscopic observations revealed both ciliated and non-ciliated cells in these 3D tissues. Histological examination revealed the presence of mucin-producing cells, and immunohistochemistry using antibodies against p63 and keratin 14 showed the presence of basal cells. These results demonstrate that immortalized HBECs retain the capacity to differentiate into each of three cell types: basal, mucin-producing, and columnar ciliated epithelial cells. Such cells will be useful cellular reagents for research in aging, cancer progression, as well as normal bronchial epithelial differentiation and will help progress the use of engineered cells to enhance tissue regeneration.

Expression of peptidylarginine deiminase type 4 (PAD4) in various tumors

Peptidylarginine deiminase type 4 (PAD4/PADI4) posttranslationally converts peptidylarginine to citrulline, in a process known as citrullination. Evidence suggests that PAD4 plays an essential role in pathogenesis of rheumatoid arthritis (RA). RA synovium has many features in common with tumor tissues, including abnormal cell proliferation, extensive fibrin deposition, high coagulation activity, and extreme angiogenesis. The purpose of the present study was to investigate expression of PAD4 in various tumor tissues. Immunohistochemistry indicated that PAD4 had significant expression in many tumor tissues, especially various adenocarcinoma. Western blotting with anti PAD4 antibody and immunostaining with anti citrulline antibody confirmed the expression of the enzyme in these tumors. Furthermore, our immunohistochemistry also detected co-location of PAD4 with cytokeratin (CK), a well-known tumor marker for oncological study in many tumors. Western blot analysis also detected citrulline signals in CK extracted from the tumors. In addition, CK 8, 18, and 19 following in vitro citrullination resisted to the digestion of caspase. The results further confirm the expression of PAD4 in the tumors and support that PAD4 may contribute to the disrupted apoptosis of tumors by caspase-mediated cleavage of CK. Double immunofluorescent labeling detected co-location of PAD4 with CD34, a cell marker of heamatopoietic progenitor cells (HPC) in bone marrow and other normal tissues, as well as in some fibroblast-like cells at stroma region of tumors, but not in the tumor cells. The findings imply that PAD4 is initially expressed in CD34(+) cells of bone marrow and then distributed in derives of the multi-potent progenitor cells in diverse tissues. The development of tumor cells expressing PAD4 is possibly associated with abnormal proliferation of CD34(+) stem cells.

Protein profiling the effects of in vitro hyperoxic exposure on fetal rabbit lung

The aim of this study was to test the hypothesis that acute in vitro exposure of prematurely delivered fetal rabbit lungs to hyperoxic conditions will induce the expression of an adaptive cassette of proteins that mediates antioxidant and inflammatory processes. To test this hypothesis, ex situ fetal rabbit lung explants were prepared from New Zealand white rabbits delivered by cesarean section on day 29 of gestation and incubated under air (21% O2; 5% CO2) or hyperoxic (95% O2; 5% CO2) atmospheres. Total tissue protein was extracted following incubation and subjected to 2-DE. Using this technique, 1500-2000 protein spots were resolved per gel. Treatment-dependent, differentially expressed proteins were identified by image analysis (Melanie II) and MALDI-TOF MS and MALDI-MS/MS. The analysis identified 12 protein spots that were differentially expressed by 1.5-fold or more (p<0.05) by exposure to hyperoxic conditions. Six of these differentially expressed proteins were identified as vimentin, annexin I, inorganic pyrophosphatase, prohibitin, an N-terminal fragment of ATP synthase and heat shock protein 27. The data obtained are consistent with the roles of these proteins in mediating cellular response to oxidative stress and in regulating cell proliferation.

Desmin modulates lung elastic recoil and airway responsiveness

Desmin is a structural protein that is expressed in smooth muscle cells of both airways and alveolar ducts. Therefore, desmin could be well situated to participate in passive and contractile force transmission in the lung. We hypothesized that desmin modulates lung compliance, lung recoil pressure, and airway contractile response. To test this hypothesis, respiratory system complex impedance (Zin,rs) at different positive end-expiratory pressure (PEEP) levels and quasi-static pressure-volume data were obtained in desmin-null and wild-type mice at baseline and during methacholine administration. Airways and lung tissue properties were partitioned by fitting Zin,rs to a constant-phase model. Relative to controls, desmin-null mice showed 1) lower values for lung stiffness and recoil pressure at baseline and induced airway constriction, 2) greater negative PEEP dependence of H and airway resistance under baseline conditions and cholinergic stimulation, and 3) airway hyporesponsiveness. These results demonstrate that desmin is a load-bearing protein that stiffens the airways and consequently the lung and modulates airway contractile response.

Laminin-5 γ2Chain in Cryptogenic Organizing Pneumonia and Idiopathic Pulmonary Fibrosis

Insufficient reepithelialization of injured alveolar walls may be important in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Laminin-5 is expressed in epithelial cells of healing wounds, promoting cell attachment and migration. In this study we have studied the extent of reepithelialization of newly formed intraluminal connective tissue, the immunohistochemical expression and ultrastructural localization of the laminin-5 gamma2 chain protein, and the synthesis of the laminin-5 gamma2 chain mRNA in regenerating epithelial cells in cryptogenic organizing pneumonia (COP) and IPF. The results show that the mean extent of reepithelialization of intraluminal connective tissue lesions was 76% (SD, +/- 27%) in COP, and 54% (SD, +/- 23%) in IPF (p < 0.025). The laminin-5 gamma2 chain was synthesized and widely expressed in regenerating epithelial cells in both diseases. Immunohistochemistry for surfactant-associated protein A suggests a pneumocyte origin for the regenerating epithelial cells in IPF. It is concluded that both in COP and IPF, regenerating epithelial cells are capable of synthesizing the laminin-5 gamma2 chain needed for adhesive connections to the underlying basement membrane. However, in IPF, the reepithelialization seems to be disturbed or delayed.

Expression of cytokeratin 18 during pre- and post-natal porcine lung development

The expression pattern of the intermediate filament protein cytokeratin 18 (CK 18) is described during pre- and post-natal development of the porcine lung using a monoclonal antibody against human CK 18. Lungs from 16 foetuses in pseudoglandular, canalicular, saccular and alveolar stages of lung development and lungs from 12 pigs ranging in age from birth to 49 days after birth were studied by immunohistochemistry. In the early pseudoglandular stage of development (day 70 of gestation) all the columnar epithelial cells lining the tubular endbuds strongly expressed CK 18 predominantly in the apical cell compartment. A modest staining was found in the more cuboidal cells of the canalicular stage (day 80 of gestation) where the labelling occurred as a distinct positive rim at the apical cell membrane in most of the cells lining the canaliculi. In 96- and 100-day-old foetuses, parts of the gas exchanging area were formed as terminal sacs by extreme attenuation of the epithelium. In this stage, CK 18 was clearly detectable in the flat type I as well as in the cuboidal type II alveolar epithelial cells. A marked change of the CK 18 expression pattern occurred during formation of the alveoli by septal outgrowth and maturation of the epithelium in 105- and 111-day-old foetuses. Differentiated type I cells no longer expressed CK 18, whereas type II cells were still labelled. Moreover, a specific change in the subcellular distribution pattern from the luminal periphery in immature porcine type II cells to a cytoplasmic localization in differentiated type II cells could be observed. Our investigation additionally demonstrated that the epithelium of bronchi, bronchioli and terminal bronchioli expressed CK 18 in all pre- and post-natal developmental stages. From the 96 days of gestation onwards the epithelial cells of developing bronchial glands were also labelled. Our results clearly show that during porcine lung development profound changes in the cellular expression pattern of CK 18 occur and that CK 18 can be regarded as a selective marker for differentiated porcine alveolar type II cells from the 105th day of gestation onwards. We also assume that the intermediate filament CK 18 could be of significance in the maturation process of the type II alveolar cells.

Proteomic analysis of cytokeratin isoforms uncovers association with survival in lung adenocarcinoma

Cytokeratins (CK) are intermediate filaments whose expression is often altered in epithelial cancer. Systematic identification of lung adenocarcinoma proteins using two-dimensional polyacrylamide gel electrophoresis and mass spectrometry has uncovered numerous CK isoforms. In this study, 93 lung adenocarcinomas (64 stage I and 29 stage III) and 10 uninvolved lung samples were quantitatively examined for protein expression. Fourteen of 21 isoforms of CK 7, 8, 18, and 19 occurred at significantly higher levels (P < .05) in tumors compared to uninvolved adjacent tissue. Specific isoforms of the four types of CK identified correlated with either clinical outcome or individual clinical-pathological parameters. All five of the CK7 isoforms associated with patient survival represented cleavage products. Two of five CK7 isoforms (nos. 2165 and 2091), one of eight CK8 isoforms (no. 439), and one of three CK19 isoforms (no. 1955) were associated with survival and significantly correlated to their mRNA levels, suggesting that transcription underlies overexpression of these CK isoforms. Our data indicate substantial heterogeneity among CK in lung adenocarcinomas resulting from posttranslational modifications, some of which correlated with patient survival and other clinical parameters. Therefore, specific isoforms of individual CK may have utility as diagnostic or predictive markers in lung adenocarcinomas.

Lung epithelial stem cells

This review concentrates on recent evidence about lung stem cell origins and plasticity. The range of potential cells which can repopulate the injured lung, classically the basal and mucous secretory cells of the trachea, the Clara cells of the bronchiole, and the type II pneumocyte of the alveolus, has been extended to include the mucus-gland duct cells of the trachea and bronchus. Some evidence suggests that there are variant Clara cells that lack cytochrome P-450 and so are spared toxic activation of xenobiotics, and may aid bronchiolar repopulation after injury, such as with naphthalene. There may even be involvement of the neuroepithelial bodies or cells in this, though the evidence is not yet conclusive. The search for a resident pulmonary multipotent cell for repopulating any lung epithelium has not yet been successful. The picture remains similar to earlier conclusions, in that the local stem or precursor cell is the most likely to contribute to local needs in times of tissue damage. There remains a major challenge for lung cancer treatment, where high-dose chemo- or radio-therapy may be hoped to promote the seeding and repair of lung parenchyma by circulating bone marrow stem cells, as seen in liver models. Patient survival rates do not yet suggest that this occurs to any great extent, but this remains to be shown formally. The effects of prior fibrosis and tumour necrosis are probably confounding factors in this lack of rescue.

Evidence for stem-cell niches in the tracheal epithelium

It is generally important to elucidate airway epithelial cell lineages and to identify multipotent progenitors as targets for gene therapy. Stem (S) cells are typically present in specialized compartments spatially proximal to their differentiated progeny, but an equivalent paradigm has not been demonstrated in the airway. We discovered a distinct population of cells displaying high levels of keratin expression in murine tracheal submucosal gland ducts, and tested the hypothesis that bromodeoxyuridine (BrdU) label-retaining cells (LRCs), thought to represent the S-cells, were present in this compartment. Mice received weekly epithelial damage by intratracheal detergent or SO(2) inhalation for 4 wk and received intraperitoneal injections of BrdU every 48 h during the injury and repair period. At 3 and 6 d after injury, BrdU-positive epithelial cells were noted along the entire tracheal length in both basal and lumenal cell positions. At later time points (20 and 95 d) LRCs were localized to gland ducts in the upper trachea and to systematically arrayed foci in the lower trachea, typically near the cartilage-intercartilage junction. LRCs were not pulmonary neuroendocrine cells. Heterotopic tracheal grafts after surface epithelial removal demonstrated reconstitution of a surface-like epithelium from gland remnants. These results suggest that airway epithelial S cells are localized to specific niches.

Cytokeratin expression in human fetal tongue and buccal mucosa

Expression of cytokeratins (CK), a subset of intermediate filament (IF) proteins in epithelia, is developmentally regulated. CK expression may also change after malignant transformation. Our earlier studies on CK expression in human oral tumours and pre-cancerous lesions have shown specific changes in CK expression. We analysed CK expression in human tongue and buccal mucosa (BM) in fetuses in the embryonic age group of 16 to 27 weeks using biochemical and immunohistochemical techniques to find out whether there is any similarity in CK expression in human oral squamous cell carcinomas (SCC) and fetal oral tissues. CK 1, 8 and 18 were detected in a majority of samples using both techniques. Our earlier studies had shown aberrant expression of CK 1 and 18 in many of the oral SCC and leukoplakias. Studies by immunohistochemistry showed that these different CK antigens were expressed in different cell layers. CK 1(2) were present in the stratified epithelial layers whereas CK 8 and 18 were restricted to glandular epithelium. Till 27 weeks of gestation, both tongue and BM expressed CK 1, 8 and 18 along with CK 6 and 16. Thus, fetal tissues showed some similarities in CK pattern with their respective SCC.

Epithelial stem cell-mediated development of the human respiratory mucosa in SCID mice

We have developed an in vivo assay for progenitor cells of the human tracheobronchial epithelium relying on the transplantation of human prenatal respiratory tissues into severe combined immunodeficiency mice. Engrafted embryonic or fetal open tracheobronchial rudiments are rapidly closed at each end by a neoformed membrane that we named the operculum. After 2–4 weeks, differentiated human respiratory epithelium covers both the native airway matrix and the new operculum. Human epithelial cells dissociated from either emerging embryonic lung primordia or mature xenografts were seeded in host human airway grafts, of which native epithelium had been eliminated by several cycles of freezing and thawing. All grafts seeded with donor epithelial cells and implanted back into SCID mice recovered a surface mucociliary epithelium expressing expected markers and secreting mucus. Spontaneous epithelium regrowth was never observed in control unseeded, denuded grafts. In some experiments, donor epithelial cells and host denuded airway were sex-mismatched and the donor origin of newly formed epithelial structures was confirmed by sex chromosome detection. After two rounds of seeding and reimplantation, a normal epithelium was observed to line the 3rd generation operculum. These observations substantiate a functional assay for human candidate airway epithelium stem cells.

Immunohistochemical and ultrastructural studies of basal cells, Clara cells and bronchiolar cuboidal cells in normal human airways

Immunohistochemical studies were made of the distribution of various cytokeratins (CK), Clara cell secretory protein (CC10), surfactant protein A (SP-A) and type VII collagen in normal human airways. Electron microscopic studies were made to identify hemidesmosomes and anchoring fibrils on the basal surfaces of the epithelial cells. CK19 was detected in all epithelial cells, and CK17 in all basal cells. CK14 was coexpressed in a few basal cells, and this coexpression was decreased in the distal airways. Two types of basal cells were recognized. One type, found mainly in large airways, was characterized by abundant intermediate filaments and well-developed hemidesmosomes and anchoring fibrils. The second type contained few intermediate filaments and poorly developed hemidesmosomes and anchoring fibrils. Reactivity for type VII collagen was found along the basement membrane throughout the airways, but not in the alveoli. Clara cells were reactive for CC10 and CK17, but not for CK14 and SP-A. The bronchiolar cuboidal cells in the respiratory bronchioles were positive only for CK19. Surfactant protein A was present only in type II alveolar epithelial cells. Thus, two types of basal cells are present in airways, and the bronchiolar cuboidal cells appear distinct from these basal cells, Clara cells and type II alveolar epithelial cells.

Ciliated differentiation of rabbit tracheal epithelial cells in vitro

Primary cultures of rabbit tracheal epithelial (RbTE) cells have been performed in two different ways. Quantitative analysis of both proliferative capacities and ciliated differentiation process were carried out using epithelial cell cultures from tracheal explants and from dissociated tracheal epithelial cells in air-liquid interface conditions. We show that both alpha- and beta-tubulins from RbTE cells are polyglutamylated and that this posttranslational modification is restricted to cilia axonemes and centrioles of non-ciliated cells. A monoclonal antibody raised against polyglutamylated tubulins was used to quantify the proportion of ciliated cells. Even though epithelial cells from outgrowths obtained by the explant technique highly proliferated during the first days of culture, no ciliated differentiation occurred. On the other hand, using air-liquid interface conditions after proliferation of dissociated cells, we could observe and quantify a ciliated cell differentiation in vitro by both Western blot and flow cytometric analysis. The specific detection and quantification of ciliated cells open the way for the biochemical and molecular characterization of centriolar components during ciliated differentiation.

The limited difference between keratin patterns of squamous cell carcinomas and adenocarcinomas is explicable by both cell lineage and state of differentiation of tumour cells

AIM

To study the differentiation of epithelial tissues within their histological context, and to identify hypothetically, on the basis of keratin pattern, the putative tissue origin of a (metastatic) carcinoma.

METHODS

Using well characterised monoclonal antibodies against individual keratins 7, 8, 18, and 19, which are predominantly found in columnar epithelia, and keratins 4, 10, 13, and 14, predominantly expressed in (non)-keratinising squamous epithelia, the keratin patterns for a series of 45 squamous cell carcinomas and 44 adenocarcinomas originating from various epithelial tissues were characterised.

RESULTS

The predominant keratins in all adenocarcinomas proved to be 8, 18, and 19. In addition, these keratins were also abundantly present in squamous cell carcinomas of the lung, cervix, and rectum and, to a lesser extent, of the larynx, oesophagus, and tongue, but not in those of the vulva and skin. Keratins 4, 10, 13, and 14 were present in almost all squamous cell carcinomas, but also focally in some of the adenocarcinomas studied.

CONCLUSIONS

There is a limited differential expression of distinctive keratin filaments between squamous cell carcinomas and adenocarcinomas. Apparently, squamous cell carcinomas that originate from columnar epithelium by squamous metaplasia gain the keratins of squamous cells but retain the keratins of columnar epithelial cells. However, the simultaneous expression of two of three squamous keratins (4, 10, and 13) identifies a squamous cell carcinoma, and thus might be useful in solving differential diagnostic problems.

Cytokeratin and vimentin expression in normal epithelium and squamous cell carcinomas of the larynx

The immunohistochemical expression patterns of cytokeratin polypeptides and vimentin were investigated in normal epithelia and squamous cell carcinomas of the larynx with special emphasis on tumor grading. During malignant transformation of epithelial cells, the cytokeratin expression patterns changed, depending on the differentiation grade of the carcinomas. In low-grade carcinomas, the expression patterns were close to those of the normal epithelium. With increasing tumor grade, there was decreased expression of stratification cytokeratins and increased expression of basal cell, simple cell and hyperproliferation-related cytokeratins. Increasing tumor grade was also associated with the expression of vimentin, a cytoskeletal protein of mesenchymal cells. No relationship was found between vimentin expression and the presence of lymph-node metastases.

Immunolocation of mitochondria-rich cells in epidermis of the common toad, Bufo bufo L

The mitochondria-rich cells (MRCs) in adult toad epidermis have an important osmoregulatory function, being specialized for chloride transport. Immunostaining with monoclonal antibodies against human keratins was used to compare the keratin expressed by MRCs with that of principal cells (PCs). By the indirect immunoperoxidase technique, keratin epitopes in vertical cryosections (4-6 microns) of toad skin were labelled and examined by light microscopy. MRCs were stained selectively by the antibodies 6B10 (anti-keratin 4) and RCK102 (anti-keratins 5 and 8). In contrast, MRCs were not detected by the oligospecific MoAb K 8.12 that recognized the intermediate PCs, but not the basal ones. The polyspecific antibody LP34 stained both the MRCs and the basal PCs, whereas the antibody RCK107 (anti-keratin 14) stained MRCs intensely and part of the basal PCs more weakly. These immunoreactions indicate that the MRCs and the intermediate PCs express amphibian equivalents to the human keratins 4/5 and 13/15, respectively. Notably, MRCs were detected in all epidermal layers except stratum corneum. Presumably, the MRCs originate in the basal layer and retain their expression of an amphibian equivalent to the human keratin pair 4/5 + 14 throughout epidermis.

Lectins and antibodies to blood group antigens as markers for the basal cells of the human respiratory epithelium

We used a pattern of 30 lectins and antibodies against antigens of the ABO-blood group system to find specific and sensitive markers for the basal cells of the human respiratory surface epithelium. Three lectins always stained the basal cells: Aaptos papillata agglutinin I (APA I), peanut agglutinin (PNA), and wheat germ agglutinin (WGA): Other lectins and the antibodies gave positive results only in tissue of secretors (blood group antigens in secretions) and these were dependent on the ABO-blood group. Griffonia simplicifolia agglutinin (GSA I B4) bound to basal cells of humans with blood group B and AB, Helix pomatia agglutinin (HPA), Soy bean agglutinin (SBA), and Dolichos biflorus agglutinin (DBA) bound to blood group A and AB, Lens tetragonolobus agglutinin (LTA) and Ulex europaeus agglutinin I (UEA) bound to secretors in every case, and strongly to blood group O. The antibodies bound to basal cells only in the tissue of secretors, dependent on the ABO-blood group. The results show that lectins and antibodies may be used as markers for the detection of basal cells in the human respiratory epithelium. Furthermore they suggest that the glycosylation of some glycocomponents of the basal cells is under the control of the genes of the secretor- and ABO-blood group system.

Adenovirus-mediated gene transfer to ciliated airway epithelia requires prolonged incubation time

The efficiency of adenovirus-mediated gene transfer to airway epithelia will be an important factor in determining whether recombinant adenoviruses can be developed as vectors for transferring cystic fibrosis transmembrane conductance regulator (CFTR) cDNA to patients with cystic fibrosis. Current understanding of the biology of CF lung disease suggests that vectors should express transgene in mature, ciliated airway epithelia. We evaluated the efficiency of adenovirus-mediated gene transfer to primary cultures of normal and CF human airway epithelia. Our studies showed that the airway cells developed from an undifferentiated epithelium with markers characteristic of basal cells and a surface covered by short microvilli 3 days after seeding to a mature epithelium whose apical surface was covered with cilia by 10 to 14 days. The ability of adenovirus vectors to express a reporter gene and to correct defective cyclic AMP-stimulated Cl- transport in CF epithelia was correlated inversely with the state of differentiation. However, the inefficiency of adenovirus-mediated gene transfer could be partially corrected when the contact time between vector and epithelium was prolonged. After prolonged contact, we observed complete correction of the CF Cl- transport defect in differentiated CF airway epithelia in culture and of the Cl- transport defect in the nasal epithelia of mice homozygous for the deltaF508 mutation. The fact that gene transfer to airway epithelia required prolonged incubation with vector contrasts with the rapid infection observed in cell models such as 293 and HeLa cells, which are commonly used to study adenovirus infection. Gene transfer observed after prolonged incubation may result from mechanisms different from those that mediate infection of 293 cells. These observations suggest that interventions that either increase the contact time or alter the epithelium or the vector may be required to facilitate gene transfer to ciliated respiratory epithelia.

Alkaline phosphatase reactivity in rabbit airway epithelium: a potentially useful marker for airway basal cells

The purpose of this study was to investigate alkaline phosphatase (ALPase) reactivity in rabbit airway epithelial cells. Acetone-fixed, methyl benzoate and xylene-cleared (AMeX-treated) paraffin sections of trachea, bronchus, and lung tissue were stained by an azo dye coupling method for ALPase and examined by light microscopy. Electron histochemical staining was also performed in order to study the sensitivity and specificity of reactivity in each cell type. ALPase reactivity at the light microscopic level was observed exclusively in tracheo-bronchial basal cells, and not in bronchiolar basal cells. By electron microscopy, ALPase reactivity was noted in 97.9% of basal cells in the trachea, 97.0% of basal cells in the bronchus, and 94.5% of basal cells and 15.4% of Clara cells in the bronchiole. This was also true for dispersed tracheal epithelial cells. Reactivity was rarely observed in ciliated cells, non-goblet-type secretory cells, and undetermined cells. The reactivity was heat-labile, levamisole-sensitive, and of a non-specific type. These findings indicate that basal cells of rabbit trachea and bonchus have fairly high specificity for ALPase of a non-specific isozyme (92.2% and 95.6%, respectively). Therefore, ALPase is considered to be a useful marker for these cells.

Intermediate filament typing of the human embryonic and fetal notochord

In order to characterize human notochordal tissue we investigated notochords from 32 human embryos and fetuses ranging between the 5th and 13th gestational week, using immunohistochemistry to detect intermediate filament proteins cytokeratin, vimentin and desmin, the cytokeratin subtypes 7, 8, 18, 19 and 20, epithelial membrane antigen (EMA), and adhesion molecules pan-cadherin and E-cadherin. Strong immunoreactions could be demonstrated for pan-cytokeratin, but not for desmin or EMA. Staining for pan-cadherin and weak staining for E-cadherin was found on cell membranes of notochordal cells. Also it was demonstrated that notochordal cells of all developmental stages contain the cytokeratins 8, 18 and 19, but not 7 or 20. Some cells in the embryonic notochord also contained some vimentin. Vimentin reactivity increased between the 8th and 13th gestational week parallel to morphological changes leading from an epithelial phenotype to the chorda reticulum which represents a mesenchymal tissue within the intervertebral disc anlagen. This coexpression reflects the epithelial-mesenchymal transformation of the notochord, which also loses E-cadherin expression during later stages. Our findings cannot elucidate a histogenetic germ layer origin of the human notochord but demonstrate its epithelial character. Thus, morphogenetic inductive processes between the human notochord and its surrounding vertebral column anlagen can be classified as epithelial-mesenchymal interactions.

Cytokeratin profile of the junctional epithelium in partially erupted teeth

This study uses cytokeratins (CK) as markers to investigate the phenotype of the junctional epithelium (JE) in partially erupted human teeth. The gingival samples, which were clinically healthy, were carefully dissected from the teeth. Cryostat sections were cut for histological staining, immunofluorescence microscopy and gel electrophoresis. Cytokeratins were extracted after microdissection. The basal and suprabasal epithelial cell markers, cytokeratins 4, 5, 13, 14 and 19 were detected with specific monoclonal antibodies. They showed that the junctional epithelium in erupting teeth has a complex topography. The cytokeratin immunohistochemical profile distinguished between the primary junctional epithelium (CK 5, 14 and 19 in basal and suprabasal cells and CK 13 faintly stained throughout the suprabasal layers) and the adjacent epithelium that had the same cytokeratin profile as the sulcular epithelium (CK 5, 14 and 19 in basal cells and CK 4 and 13 intensively stained in the suprabasal cells). Extraction, two-dimensional electrophoresis and western blotting showed that this transitional JE during eruption also contained CK 6, 16 and perhaps CK 4. Thus, the JE in erupting teeth shows patterns of CK distribution that are very similar to that of developing oral epithelia.

Simple cytokeratins in the serum of patients with lung cancer: relationship to cell death

An important role in differentiation and proliferation has been demonstrated for the 20 cytokeratin (CK) polypeptides. The serum of 24 patients with biopsy-proven non-small cell lung cancer (NSCLC) and a similar number of controls was examined for evidence of CK8 and CK18. Using enzyme-linked immunosorbent assay (ELISA), all the control sera were negative, but 9 of the 24 patients were positive (mean 2.62 ng/ml; range 1.4-5.8; P = 0.0036). Western blotting confirmed the results of the ELISA in all cases, and indicated full size CK polypeptides. Advanced stage disease patients were more likely to be seropositive (P = 0.00024). Biopsy specimens showed CK8 expression in all 24 cases by immunochemistry and CK18 in 22 cases. This is the first study to demonstrate that a subgroup of NSCLC patients have intact CK8 and CK18 peptides in their serum, and their detection may correlate with advanced disease.

Extracellular matrix-dependent differentiation of rabbit tracheal epithelial cells in primary culture

The differentiation of tracheal epithelial cells in primary culture was investigated according to the nature of the extracellular matrix used. Cultures obtained by the explant technique were realized on a type I collagen substratum either as a thin, dried coating or as a thick, hydrated gel supplemented with culture medium and serum. These two types of substratum induced distinct cell morphology and cytokeratin expression in the explant derived cells. Where cells are less proliferating (from Day 7 to 10 of culture), differentiation was evaluated by morphologic ultrastructural observations, immunocytochemical detection of cytokeratins, and determination of cytokeratin pattern by biochemical analysis. The epithelium obtained on gel was multilayered, with small, round basal cells under large, flattened upper cells. The determination of the keratin pattern expressed by cells grown on gel revealed an expression of keratin 13, already considered as a specific marker of squamous metaplasia, that diminished with retinoic acid treatment. Present results demonstrated by confocal microscopy that K13-positive cells were large upper cells with a dense keratin network, whereas lower cells were positively stained with a specific monoclonal antibody to basal cells (KB37). Moreover, keratin neosynthesis analysis pointed out a higher expression of K6, a marker of hyperproliferation, on gel than on coating. All these data suggest a differentiation of rabbit tracheal epithelial cells grown on gel toward squamous metaplasia. By contrast, the epithelium observed on coating is nearly a monolayer of very large and spread out cells. No K13-positive cells were observed, but an increase in the synthesis of simple epithelium marker (K18) was detected. These two substrata, similar in composition and different in structure, induce separate differentiation and appear as good tools to explore the mechanisms of differentiation of epithelial tracheal cells.

Changes in cytokeratin, vimentin and desmoplakin distribution during the repair of irradiation-induced lung injury in adult rats

The expression of cytokeratins, desmoplakin and vimentin has been studied immunohistochemically in the rat lung injured by x-irradiation using 14 well characterized monoclonal antibodies. A time-dependent relationship between the cytokeratin expression pattern and the morphological alterations observed was apparent. A cytokeratin 8 and 18 expression in normally cytokeratectable even at 3-6 h after irradiation. Between 14 days and 2 months, a remarkable heterogeneity in the epithelial cell cytokeratin pattern and an increasing immunoreaction for desmoplakin was found. In terminal bronchial epithelial cells, a heterogeneous CK8, 18 and 19 staining and a neoexpression of cytokeratins 4 and 7 was detected. Finally, peribronchiolar and vascular smooth muscle cells were cytokeratin-positive. At 6 months after irradiation, cytokeratin 13 and vimentin were focally present in bronchial epithelial cells and atypical type I and II pneumocytes as well as scattered epithelioid cell complexes were noted. During the course of injury, a loss of type III alveolar epithelial cells was found, which was characterized in the rat by a specific globular cytokeratin pattern and restricted immunoreactivity with cytokeratin-specific antibodies. These results show that the expression pattern of cytokeratins is a sensitive marker in monitoring epithelial alterations during lung injury.

Immuno- and lectin histochemistry of epithelial subtypes and their changes in a radiation-induced lung fibrosis model of the mini pig

Cell types of lung epithelia of mini pigs have been studied using a panel of monoclonal and polyclonal antibodies against cytokeratins (CKs) and vimentin and three lectins before and after radiation-induced fibrosis. In normal tissues, CK18 specific antibodies reacted above all with type II alveolar epithelial cells, while CK7 and pan CK-specific antibodies stained the whole alveolar epithelium. In bronchial epithelial cells, CKs 7, 8, 18 and focally CKs 4 and 13 as well as vimentin were found. Cell specificity of the CK pattern was confirmed by double label immunofluorescence using type II cell-specific Maclura pomifera (MPA) lectin, type I cell specific Lycopersicon esculentum (LEA) lectin and capillary endothelium-binding Dolichos biflorus (DBA) lectin. In experimental pulmonary fibrosis, enhanced coexpression of CK and vimentin was observed in bronchial epithelium. Subtypes of alveolar epithelial cells were no longer easily distinguishable. CK18 was found to be expressed in the entire alveolar epithelium. The gradual loss of the normal alveolar epithelial marker, as seen by the binding of MPA to type I-like cells, of LEA to type II-like cells and the partial loss of MPA-binding to type II cells, was paralleled by the appearance of CK4, typical for squamous epithelia, and the occurrence of DBA-binding in epithelial cells. Implications of these results for general concepts of intermediate filament protein expression and lectin binding in the fibrotic process are discussed.

Heterogeneity in the immunolocalization of cytokeratin-specific monoclonal antibodies in the rat lung: evaluation of three different alveolar epithelial cell types

The distribution of individual cytokeratin polypeptides in the adult rat lung parenchyma was investigated by immunohistochemistry with 44 monoclonal and 2 polyclonal antibodies. Simple epithelial cytokeratins 7, 8, 18 and 19 were found to be expressed differently in alveolar and bronchial epithelial cells. Three distinct types of alveolar cells were detected according to their pattern of immunoreactivity: type II cells strongly expressing cytokeratins 8 and 18 and weakly expressing cytokeratins 7 and 19 in the cell periphery; type I cells predominantly positive for cytokeratins 7 and 19 and weakly for cytokeratin 8; and a newly defined third cell type III (alveolar brush cell) with cytokeratin 18 abundantly expressed but organized in an unusual intracellular ("globular") structure. The latter cell type failed to bind the type II specific Maclura pomifera lectin, and contained no surfactant proteins. Bronchial epithelial cells exhibited a more or less uniform staining pattern for cytokeratins 8, 18 and 19 and focally for cytokeratins 4 and 7.

Phenotypic marker expression during fetal and neonatal differentiation of rat tracheal epithelial cells

The expression of phenotypic markers was examined during fetal and neonatal differentiation of rat tracheal epithelial (RTE) cells. The rat counterpart of human keratin 18 was predominantly found in columnar cells in the adult trachea. It was detected in the primordial tracheal epithelium first seen on gestational day (GD) 12 (term = 21.5 days). Staining intensity gradually increased, and by GD 17 it was principally localized to the apical portion of the epithelium. The rat counterpart of human keratin 19 was barely detectable in the trachea on GD 13 but became abundant in almost all RTE cells on and after GD 19. Morphologically and immunocytochemically identifiable secretory and ciliated cells appeared on GD 18. Ciliated cell number slowly rose while secretory cells increased dramatically on GD 19 through postnatal day 1. The secretory granule antigens detected by monoclonal antibodies RTE 9 and 11 were rare in the adult trachea but were highly expressed in virtually all of the perinatal secretory cells. In contrast, the epitope detected by monoclonal antibody RTE 12, which was present in all adult tracheal surface secretory cells, did not appear until postnatal day 1 and slowly increased. These results demonstrate marked shifts in the biochemical composition of secretory cells during development and postnatal maturation. For the above-mentioned molecules, a similar expression pattern was observed during epithelial regeneration in tracheal grafts (Am. J. Respir. Cell Mol. Biol. 1992; 7:30-41). Pseudo-stratification of the epithelium and basal cells was first observed on GD 20. Keratin 14, which is confined to basal cells in the normal adult trachea, was not present in the nascent basal cells but appeared after postnatal day 1. In contrast to the present results, during epithelial regeneration in tracheal grafts keratin 14 appeared before markers of highly differentiated secretory or ciliated cells. Thus, the biochemical sequence of cellular differentiation during regeneration did not precisely recapitulate development.

Development of human fetal lung in organ culture compared with in utero ontogeny

In utero, at around 23 wk gestation, the progenitor epithelium of distal airway differentiates into type I and type II pneumatocytes. Human fetal lung organ cultures, as early as 12 wk gestation, have the competence to self-differentiate. Distal airway epithelial immunoreactivity to cytokeratins CK 7, 8, and 18 decreases with differentiation both in utero and in organ culture, whereas reactivity to epithelial membrane antigen remains constant in both. As distal airways dilate, the mean percentage airspace of fetal lungs in organ culture increases to 58%, equivalent to lung of gestation 26.0 +/- 7.3 wk. In organ culture, capillary blood vessels, visualized by vimentin immunoreactivity, remodel and more closely approximate the epithelium but without direct invasion. In utero, at 23 wk gestation, elastin appears as condensation around airways and forms a basis for secondary crests which, by 29 wk gestation, evolve into alveolar septae. In organ culture, no elastin is deposited, no secondary or alveolar crests form, and the lung retains a simple saccular structure. Differentiation of the terminal airway epithelium and mesodermal maturational events to facilitate gas exchange, such as capillary invasion or secondary-alveolar crest formation, are almost synchronous in human lung in utero but clearly dissociate in organ culture.

Organization of cytokeratin intermediate filaments in basal cells of growing rat trachea

The basal cell in airway epithelium plays a major role in attachment of ciliated and nonciliated columnar cells to the basal lamina. As the airway grows in diameter and the columnar epithelium in height, the number of basal cells and the amount of tonofilaments (cytokeratin filaments) and anchoring junctions increase. In this way they maintain a constant attachment strength between the increased volume of the epithelium and the basal lamina. The purpose of this study was to determine which cytokeratins (CKs) are expressed in growing basal cells of the rat and demonstrate where they are localized in the cytoskeleton. Sprague Dawley rats 10, 30 and 90 days of age were used in this study. For light microscopy, tracheal samples were fixed in 95% alcohol or 4% formalin for 2 hr and then embedded in paraffin. For electron microscopy, the tracheal samples were placed in 20 mM EDTA in HBSS media minus Ca++ and Mg++ at pH 7.4 for 60 min to permeabilize the cells and expose the intracellular structures. Antibodies to cytokeratins 7, 8, 10, 13 and 18 did not react to basal cells at any age studied. Antibodies to CKs 5 + 8, 14, 16 + 13, and 19 gave a positive reaction with basal cells at each age studied. Immunogold particles representing antibodies to CK 14 were heavily distributed over intermediate filaments making up the cytoskeleton. Both CK 16 + 13 and 19 were also over intermediate filaments but at a much lower density.(ABSTRACT TRUNCATED AT 250 WORDS)

Squamous cell metaplasia in the human lung: molecular characteristics of epithelial stratification

Squamous cell metaplasia (SCM) is a frequent epithelial alteration of the human tracheobronchial mucosa. This review pays particular attention to the fact that SCM can mimic esophageal, and in some instances even skin-type differentiation, showing striking similarities not only in morphology but also in terms of gene expression. Therefore, characterization of this dynamic process lends insight into the process of stratification, squamous cell formation, and "keratinization" in a pathologically relevant in vivo situation in man. First, the concept of metaplasia is presented with certain historical viewpoints on histogenesis. Then, the morphological characteristics of normal bronchial epithelium are compared with the altered phenotype of cells in SCM. These changes are described as a disturbance of the finely tuned balance of differentiation and proliferation through the action of a variety of extrinsic and intrinsic factors. Molecular aspects of altered cell/cell and cell/extracellular matrix interactions in stratified compared with single-layered epithelia are discussed with reference to SCM in the lung. Intracellular organizational and compositional changes are then summarized with special emphasis on the differential distribution of the cytokeratin (CK) polypeptides. Finally, the still unresolved problems of the histogenetic relationships between normal bronchial mucosa, SCM, and pulmonary neoplasms are addressed. As these questions remain open, examples for detection of well defined "markers" are provided that may be employed as objective criteria for determining clinically important cellular differentiation features.

Expression of "cell-type-specific" markers during rat tracheal epithelial regeneration

Previous studies showed that Griffonia simplicifolia I-isolectin B4 (GS I-B4) and monoclonal antibodies (mAbs) against keratin 14 labeled basal cells in the adult rat trachea while other mAbs specifically stained secretory and/or ciliated cells. We used these "cell-type-specific" markers to study cellular differentiation during tracheal epithelial regeneration. Denuded tracheal grafts were inoculated with rat tracheal epithelial cells and were implanted in syngeneic hosts. Marker expression was correlated with the appearance of morphologically defined cell types. At 4 days, the epithelium was squamoid, one to three cell layers thick, and was apparently composed of a single morphologic cell type. Because this cell did not exhibit distinguishing features of any mature tracheal cell, we provisionally termed it the "poorly differentiated cell" (PD cell). PD cells expressed keratin 14 and GS I-B4 binding sites; they contained glycogen and had lipid droplets but did not react with secretory or ciliated cell-specific mAbs. At 7 days, areas of the epithelium were pseudostratified and secretory cell-specific markers were present at the apex of differentiating columnar cells; ultrastructurally, these cells resembled secretory cells in adult tracheas. Simultaneously, a few preciliated and ciliated cells appeared that expressed a ciliated cell-specific epitope. No cells were observed coexpressing secretory and ciliated cell markers. Basal cells also became recognizable on day 7. These expressed keratin 14 and GS I-B4 binding sites throughout the study. Newly appearing secretory and ciliated cells also expressed these two markers initially but lost them gradually as the mucociliary epithelium matured. In the tracheal graft model of epithelial regeneration, the PD cells were pivotal intermediates from which all differentiated cells developed. Basal cells continued to express the same markers as PD cells, which were gradually lost in secretory and ciliated cells as they acquired new sets of specific epitopes.