Contribution of MT1-MMP and of human laminin-5 gamma2 chain degradation to mammary epithelial cell migration.

Membrane-type matrix metalloproteinase 1 (MT1-MMP) is a membrane-anchored matrix metalloproteinase (MMP) that is frequently associated with processes involving tissue remodelling and cell migration. We have examined MT1-MMP expression and subcellular distribution as a function of MCF10A mammary epithelial cell migration using an in vitro outgrowth migration assay. Stronger expression of MT1-MMP was observed at the mRNA and at the protein level in cells at the periphery of the outgrowth. As shown by videomicroscopy, these cells were involved in an orientated cell migration, in contrast to stationary cells distant from the periphery. Furthermore, MT1-MMP was mainly distributed in lamellipodia of migratory cells, as well as at their basal surface in contact with the substrate. Laminin-5 (Ln-5), a recently described substrate for MT1-MMP, was deposited preferentially in the matrix by migratory cells. Fragments of the gamma2 subunit of Ln-5 were also identified in migratory cultures of MCF10A cells, attesting to its proteolytic degradation. These fragments corresponded in size to those we observed after incubation of purified human Ln-5 with the recombinant catalytic domain of human MT1-MMP. We also show that anti-Ln5 blocking antibodies, MMP inhibitors (BB94 and TIMP-2) and MT1-MMP antisense oligonucleotides significantly decreased MCF10A cell migration. Taken together, these observations demonstrate that MT1-MMP is spatially and temporally regulated during MCF10A cell migration, and suggest that MT1-MMP-mediated pericellular proteolysis of Ln-5 gamma2 chain could contribute to this process.

uPA/plasmin system-mediated MMP-9 activation is implicated in bronchial epithelial cell migration.

To examine the effects of the uPA/plasmin system on cell migration in relation to the activation of MMP-9, we used ex vivo and in vitro wound-repair models of human bronchial epithelial cells and videomicroscopy techniques that make possible cell tracking and quantification of cell migration speeds. We observed that uPA was only detected in migrating cells at the wound edges and located at crucial sites for cell/extracellular matrix interactions. The implication of uPA in human bronchial epithelial cell migration was studied by incubating cultures with a monoclonal antibody raised against uPA and these experiments led to a 70% reduction in cell velocity. To examine the effects of the plasmin system on cell migration, we incubated cultures with increasing concentrations of plasmin or activated MMP-9. We observed a significant dose-dependent increase in cell migration velocity with plasmin (P < 0.001) and MMP-9 (P < 0.001). Moreover, addition of exogenous plasmin led to a twofold increase of activated MMP-9 in migrating cells. We also demonstrated that the addition of anti-uPA IgG led to an inhibition of 43% of activated MMP-9. In conclusion, these results show that uPA is involved in human bronchial epithelial cells migration. This action is mediated by the generation of plasmin, which in turn activates MMP-9, thus making possible cell migration.

Expression of the extracellular matrix metalloproteinase inducer (EMMPRIN) and the matrix metalloproteinase-2 in bronchopulmonary and breast lesions.

Tumor cells interact with stromal cells via soluble or cell-bound factors stimulating the production of matrix metalloproteinases (MMPs), a group of enzymes largely involved in the extracellular matrix (ECM) remodeling in tumor invasion. Among these factors, extracellular matrix metalloproteinase inducer (EMMPRIN) has been shown to stimulate in vitro the fibroblast production of various MMPs such as interstitial collagenase (MMP-1), stromelysin-1 (MMP-3), and gelatinase A (MMP-2). In this study, the EMMPRIN protein was detected by immunohistochemistry prominently in malignant proliferations of the breast and the lung. It was present at the surface of both tumor epithelial and peritumor stromal cells. Because previous studies have reported that stromal cells do not express EMMPRIN mRNAs, it is very likely that EMMPRIN is bound to stromal cells via a specific receptor. Moreover, our observations also demonstrated that the same peritumor stromal cells strongly express MMP-2. Our results show that EMMPRIN is an important factor in tumor progression by causing tumor-associated stromal cells to increase their MMP-2 production, thus facilitating tumor invasion and neoangiogenesis. (J Histochem Cytochem 47: 1575-1580, 1999)

Vimentin contributes to human mammary epithelial cell migration.

Vimentin expression in human mammary epithelial MCF10A cells was examined as a function of their migratory status using an in vitro wound-healing model. Analysis of the trajectories of the cells and their migratory speeds by time lapse-video microscopy revealed that vimentin mRNA and protein expression were exclusively induced in cells at the wound's edge which were actively migrating towards the center of the lesion. Actin labeling showed the reorganization of actin filaments in cells at the wound's edge which confirmed the migratory phenotype of this cell subpopulation. Moreover, the vimentin protein disappeared when the cells became stationary after wound closure. Using cells transfected with the vimentin promoter controlling the green fluorescent protein gene, we also demonstrated the specific activation of the vimentin promoter in the migratory cells at the wound's edge. Transfection of the antisense vimentin cDNA into MCF10A cells clearly reduced both their ability to express vimentin and their migratory speed. Taken together, these observations demonstrate that vimentin is transiently associated with, and could be functionally involved in, the migratory status of human epithelial cells.

Fibronectin and alpha5beta1 integrin mediate binding of Pseudomonas aeruginosa to repairing airway epithelium.

Initial infection of the airway by Pseudomonas aeruginosa may occur through a variety of bacterial strategies including binding to epithelial receptors present at the surface of the respiratory epithelium. In order to characterize the adherence sites for P. aeruginosa in damaged and repairing bronchial tissue, an ex vivo model of airway epithelial injury and repair was developed using primary cell cultures of nasal cells from 14 subjects with polyposis. P. aeruginosa strongly adhered to flattened dedifferentiated (FD) bronchial and nasal cytokeratin 13-positive epithelial cells in the process of migration for repair. In in vitro experiments, competitive binding inhibition assays demonstrated that alpha5beta1 integrins and cellular fibronectin, in particular the RGD sequence, are receptors involved in P. aeruginosa adherence to FD nasal epithelial cells. Fluorescent cell sorting analysis and immunofluorescence techniques revealed that the alpha5beta1 integrins are overexpressed and apically exposed in FD nasal epithelial cells. One 50 kDa outer membrane protein was identified in piliated and nonpiliated strains of P. aeruginosa that was involved in binding to cellular fibronectin and alpha5beta1 epithelial integrins. These results demonstrate that Pseudomonas aeruginosa adherence is related to the dedifferentiation of airway epithelium during the repair process which unmasks and upregulates the alpha5beta1 integrin expression and induces active synthesis of cellular fibronectin. These epithelial receptors are then used by a Pseudomonas aeruginosa 50 kDa outer membrane protein as sites of bacterial adherence.

Airway epithelial cell migration dynamics. MMP-9 role in cell-extracellular matrix remodeling.

Cell spreading and migration associated with the expression of the 92-kD gelatinase (matrix metalloproteinase 9 or MMP-9) are important mechanisms involved in the repair of the respiratory epithelium. We investigated the location of MMP-9 and its potential role in migrating human bronchial epithelial cells (HBEC). In vivo and in vitro, MMP-9 accumulated in migrating HBEC located at the leading edge of a wound and MMP-9 expression paralleled cell migration speed. MMP-9 accumulated through an actin-dependent pathway in the advancing lamellipodia of migrating cells and was subsequently found active in the extracellular matrix (ECM). Lamellipodia became anchored through primordial contacts established with type IV collagen. MMP-9 became amassed behind collagen IV where there were fewer cell-ECM contacts. Both collagen IV and MMP-9 were involved in cell migration because when cell-collagen IV interaction was blocked, cells spread slightly but did not migrate; and when MMP-9 activation was prevented, cells remained fixed on primordial contacts and did not advance at all. These observations suggest that MMP-9 controls the migration of repairing HBEC by remodeling the provisional ECM implicated in primordial contacts.

Cytoplasmic redistribution of E-cadherin-catenin adhesion complex is associated with down-regulated tyrosine phosphorylation of E-cadherin in human bronchopulmonary carcinomas.

The E-cadherin-catenin complex, by mediating intercellular adhesion, regulates the architectural integrity of epithelia. Down-regulation of its expression is thought to contribute to invasion of carcinoma cells. To investigate the involvement of the E-cadherin-catenin adhesion system in the progression of human bronchopulmonary carcinomas, we compared the immunohistochemical distribution of E-cadherin, alpha-catenin, and beta-catenin in four human bronchial cancer cell lines with different invasive abilities and in 44 primary bronchopulmonary tumors. Although invasive bronchial cell lines did not express E-cadherin and alpha-catenin, complete down-regulation of cadherin-catenin complex expression was a rare event in vivo in bronchopulmonary carcinomas. Nevertheless, a spotty and cytoplasmic pattern of E-cadherin and catenins was observed in 32 primary tumors, only in invasive tumor clusters. Immunoprecipitation experiments showed that this redistribution was not related to a disruption of cadherin-catenin interaction but to down-regulated tyrosine phosphorylation of E-cadherin. We conclude that loss of E-cadherin and/or catenins is not a prominent early event in the invasive progression of human bronchopulmonary carcinomas in vivo. The decreased tyrosine phosphorylation of E-cadherin may reflect a loss of functionality of the complex and implicates a major role in tumor invasion.

Association of fibroblastoid features with the invasive phenotype in human bronchial cancer cell lines.

The acquisition of a metastatic phenotype by epithelial cells implicates a series of changes altering their differentiation, their overall behavior and morphology. In the present study, we have examined the relationships between the cellular morphology, E-cadherin expression, matrix metalloproteinases expression and in vitro invasive properties in two human bronchial immortalized cell lines. The (16HBE14o-) cell line which did not show any invasive abilities in the Boyden chamber assay displayed a typical epithelial morphology in monolayer, expressed high levels of E-cadherin and synthesized neither MMP-2 and MT1-MMP nor vimentin. In contrast, the BZR cell line which was highly invasive displayed a more elongated phenotype in monolayer, did not produce E-cadherin but expressed vimentin, MMP-2 and MT1-MMP. Our data therefore suggest that the metastatic progression of broncho-pulmonary cancer cells results in a cellular dedifferentiation and the gain of some mesenchymal attributes (loss of E-cadherin and expression of vimentin) associated with enhanced degradative properties (expression of metalloproteinases).

Expression of matrix metalloproteinases and their inhibitors in human bronchopulmonary carcinomas: quantificative and morphological analyses.

The expression of various matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in 88 primary bronchopulmonary cancers and in 13 neighbouring pulmonary parenchyma samples was quantified by Northern-blot analysis, and morphologically examined by in situ hybridization and immunohistochemistry in order to evaluate the involvement of MMPs in the pathophysiology of these carcinomas and to look for potential markers of aggressivity of lung tumours. Northern-blot analysis showed that the predominantly expressed MMPs in bronchopulmonary cancers were gelatinase A (66%), its activator MT1-MMP (membrane-type-1 matrix metalloproteinase) (56%) and stromelysin-3 (61%). MMP expression frequencies and mRNA levels increased progressively with malignant phenotype, lack of differentiation and TNM stage of the tumours, whereas TIMP expression decreased very early during tumour progression. Moreover, the principal MMPs were significantly co-expressed in primary tumours, suggesting their co-regulation. Morphological studies revealed the expression of MMPs and TIMPs essentially in stromal cells in close contact with tumour clusters. These results indicate that tumour progression in bronchopulmonary carcinomas implies a progressive disruption of the MMP/TIMP balance leading to an excess of several MMPs that act in concert in vivo. Furthermore, the fact that stromal cells are the principal source of MMPs emphasizes the close cooperation between host cells and cancer cells in tumour invasion.

Distribution of a1(IV) and a3(IV) chains of type IV collagen in lung tumours.

Tumour invasion is associated with strong remodelling of the extracellular matrix, including the basement membrane (BM). The major structural component of BMs is type IV collagen, which is composed of an association of three a chains. In this study, the distribution of the a1 and a3 chains in both normal and neoplastic lung tissues has been examined by immunohistochemistry, using specific monoclonal antibodies. In normal tissues, the a1(IV) chain was found in all BMs, whereas the a3(IV) chain was only found in alveolar BMs. In 36 lung tumours, the a1(IV) chain was detected in all cases, with irregular positivity around tumour clusters and in the stroma. It was noteworthy that this stromal distribution was particularly associated with the presence of cancer cells, whatever their invasive properties. In contrast, in 22 tumours out of 36, the a3(IV) chain was only found at the interface between invasive tumour clusters and stroma, with a linear and disrupted pattern. These data show a distinctive distribution of type IV collagen chains in lung tumours, with expression of a1(IV) chain and likely neosynthesis of the a3(IV) chain around some invasive tumour clusters. The results suggest the involvement of these BM components in the process of tumour invasion.

Tumor collagenase stimulatory factor (TCSF) expression and localization in human lung and breast cancers.

Tumor cell-derived collagenase stimulatory factor (TCSF) stimulates in vitro the biosynthesis of various matrix metalloproteinases involved in tumor invasion, such as interstitial collagenase, gelatinase A, and stromelysin 1. The expression of TCSF mRNAs was studied in vivo, using in situ hybridization and Northern blotting analysis, in seven normal tissues and in 22 squamous cell carcinomas of the lung, and in seven benign proliferations and in 22 ductal carcinomas of the mammary gland. By in situ hybridization, TCSF mRNAs were detected in 40 of 44 carcinomas, in pre-invasive and invasive cancer cells of both lung and breast cancers. TCSF mRNAs and gelatinase A mRNAs were both visualized in the same areas in serial sections in breast cancers, and were expressed by different cells, tumor cells, and fibroblasts. The histological results were confirmed by Northern blot analysis, which showed a higher expression of TCSF mRNAs in cancers than in benign and normal tissues. These observations support the hypothesis that TCSF is an important factor in lung and breast tumor progression.

Induction of membrane-type matrix metalloproteinase 1 (MT1-MMP) expression in human fibroblasts by breast adenocarcinoma cells.

Membrane-type matrix metalloproteinase 1 (MT1-MMP) has been recently described as an activator of proMMP-2 (MMP-2) which is involved in tumor invasion. We have shown by in situ hybridization that MT1-MMP is produced by stromal cells in close contact to preinvasive and invasive tumor cells of breast carcinomas. Of particular interest was the observation that some fibroblasts express this enzyme in focal areas in preinvasive lesions, suggesting that particular tumor cells may stimulate fibroblasts to produce MT1-MMP. We have therefore compared the ability of two different breast cancer cell lines, one non-invasive (MCF7) and one invasive (MDA-MB-231) to stimulate MT1-MMP production in human fibroblasts with consequent proMMP-2-activation. The MDA-MB-231 conditioned medium induced MT1-MMP mRNAs in human fibroblasts and a parallel activation of proMMP-2 whereas MCF7 conditioned medium did not have any effect. These results suggest the existence of soluble factor(s) secreted by invasive or some preinvasive breast tumor cells which stimulate fibroblasts to produce and activate MMPs, and emphasize the cooperation between cancer and stromal cells in tumor invasion.

The elastase-induced expression of secretory leukocyte protease inhibitor is decreased in remodelled airway epithelium.

During airway inflammation, proteinases such as human leukocyte elastase are actively secreted. Secretory leukocyte protease inhibitor is a major serine proteinase inhibitor, secreted by bronchial, bronchiolar and lung epithelial cells. We recently identified secretory leukocyte protease inhibitor in human nasal epithelium, exclusively in remodelled areas of the surface epithelium. We now investigated the influence of remodelling and inflammation of the nasal tissue on the in vitro capacity of these cells to respond to human leukocyte elastase. Primary cultures of surface epithelial cells were established from various nasal polyp samples. At confluency, cell cultures were exposed to different human leukocyte elastase concentrations. The secretory leukocyte protease inhibitor immunocytolocalisation, expression and secretion were then investigated. Immunocytochemistry, showed a human leukocyte elastase dose-dependent increase of secretory leukocyte protease inhibitor containing cells and a basal extracellular localization of secretory leukocyte protease inhibitor after incubation with 100 microg/ml human leukocyte elastase. The relative amount of secretory leukocyte protease inhibitor mRNA transcripts increased with respect to the human leukocyte elastase concentration. Nevertheless, the potential stimulation of secretory leukocyte protease inhibitor secretion by human leukocyte elastase was lower in the more remodelled and inflamed tissue. Our results suggest that the contribution of the surface epithelial cells of poorly remodelled tissues to the protection against the deleterious effect of neutrophil proteinases is severely decreased in highly remodelled and inflamed tissues.

Membrane-type matrix metalloproteinase-1 expression at the site of human placentation.

Human trophoblast implantation is a highly regulated process of invasion that requires action of proteolytic enzymes to degrade extracellular matrix components of the endometrium. Among these enzymes, matrix metalloproteinases (MMPs) seem to be particularly important in this degradative process. We previously showed that gelatinase A is extensively expressed in vivo in the human placenta. A new MMP, MT-MMP-1 (membrane-type matrix metalloproteinase-1), which is thought to activate progelatinase A, has recently been described. In this study, we examined the expression of MT-MMP-1, by immunohistochemistry and in situ hybridization, in human placental bed biopsies taken during the first trimester of gestation. Human first trimester intermediate trophoblasts synthesized MT-MMP-1 mRNAs and the protein. The MT-MMP-1 pattern of distribution in placental beds was similar to that of gelatinase A, suggesting a pivotal role for MT-MMP-1 in placentation, perhaps by activating progelatinase A.

MT-MMP expression and localisation in human lung and breast cancers.

Thirteen primary pulmonary squamous cell carcinomas, 4 specimens of normal lung from around tumours, 4 benign proliferations of the mammary gland and 16 breast carcinomas were analysed by in situ hybridisation. Northern blot and immunohistochemistry for the expression of a recently described metalloproteinase (MMP), the MT-MMP (membrane-type matrix metalloproteinase). This MT-MMP can activate gelatinase A, involved in the degradation of basement membranes. In situ hybridisation revealed MT-MMP transcripts distributed in both tumour and stromal cells in squamous cell lung cancers, whereas these mRNAs were principally detected in stromal cells in close contact to tumour clusters in breast carcinomas and in lung adenocarcinomas. Northern blot analysis showed a parallel expression of MT-MMP and gelatinase A transcripts in both lung and breast cancers. Immunohistochemistry displayed a more extensive distribution of MT-MMP in pulmonary and mammary carcinomas with numerous labelled preinvasive and infiltrating cancer cells and stromal cells near the tumour cells. The large degree of expression of MT-MMP in these cancers indicates a potential role of this enzyme in tumour progression. The finding of MT-MMP transcripts in stromal cells in the vicinity of lung and breast tumour cells emphasises the cooperation between these cells and cancer cells for the expression of MT-MMP and in tumour invasion in vivo.

Expression and localization of epidermal growth factor, transforming growth factor-alpha, and localization of their common receptor in fetal human lung development.

Transforming growth factor-alpha (TGF-alpha), epidermal growth factor (EGF), and their common EGF receptor have been shown to be involved in cell proliferation and lung maturation. The aim of the study was to determine the site of production of TGF-alpha and EGF mRNA and the cellular distribution of TGF-alpha/EGF proteins and EGF receptor, in fetal human lung. By using in situ hybridization with 35S-labeled cDNA probes in frozen sections from eight lungs from fetuses ranging from 12 to 33 wk of gestation, TGF-alpha and EGF mRNA transcripts appeared to be confined to the mesenchymal cells and mainly found in the dense connective tissue along the pleura, bronchi, and large vessels, but undetected in bronchial epithelial cells. The streptavidin-biotin immunoperoxidase method, applied to paraffin-embedded specimens from 39 fetuses ranging from 10 to 41 wk, showed that TGF-alpha, EGF, and EGF receptor exhibited a similar cellular distribution during the whole period of gestation. They were detected in the undifferentiated cells of the airway surface epithelium, mesothelial cells, smooth muscle, and a few mesenchymal cells, as early as 10 wk. After 12 wk, the immunoreactivity was strong in the ciliated, secretory, and basal cells, and in growing glands along the large airways, but proved lower in the distal airways. After 24 wk, the immunoreactivity remained in the airway epithelium, but was mainly localized in the apical domain of ciliated cells, in alveolar cells, and in the serous cells of the glands. The presence of TGF-alpha, EGF, and EGF receptor during the whole period of fetal lung development suggests that these factors are not only mitogenic, but can also be involved in epithelial maturation, through paracrine secretion, as most TGF-alpha and EGF mRNA transcripts are expressed in mesenchymal cells.

Wound repair-induced expression of a stromelysins is associated with the acquisition of a mesenchymal phenotype in human respiratory epithelial cells.

Wound repair involves many processes including cell migration, provisional matrix deposition, and remodeling. All of these processes are likely to be affected by matrix-modifying enzymes. Members of the matrix metalloproteinases family are physiologic mediators of the extracellular matrix degradation. Within this matrix metalloproteinases family, stromelysins can degrade many components of the extracellular matrix. We therefore tested the hypothesis that stromelysins could be produced by human surface respiratory epithelial (HSRE) cells repairing a wound. Experimental wounds were created in vitro in HSRE cell cultures and in situ in human bronchial mucosa maintained in organ culture. Stromelysin production was measured by casein-gel zymography in cellular protein extracts derived from repairing migratory and nonrepairing stationary cells of wounded HSRE cell cultures. Stromelysin-producing cells present in cell and tissue cultures were localized and characterized using immunofluorescence techniques. Zymographic and immunofluorescence techniques showed that stromelysins were produced exclusively by the migratory HSRE cells. Zymogram analysis showed that stromelysins were overexpressed and overactivated during the wound repair process, with the maximal production observed at wound closure. Using an anti-cytokeratin 14 antibody, we identified stromelysin-3-producing cells as basal epithelial cells. Moreover, most stromelysin-3-producing cells expressed the mesenchymal marker vimentin. Similar to stromelysins localization, vimentin-positive HSRE cells were exclusively located in the wounded area, and they were also positive to cytokeratin 14. In conclusion, stromelysins are suggested to be involved in HSRE cell migration and extracellular matrix remodeling during wound repair. Furthermore, stromelysin production by repairing HSRE cells is linked to the acquisition of a mesenchymal phenotype. HSRE cell migration may then be associated with the shift from an epithelial to a mesenchymal phenotype.

Pseudomonas aeruginosa strains possess specific adhesins for laminin.

Pseudomonas aeruginosa is a major human pathogen known to infect tissues that have been previously damaged in some way. In wounded human respiratory tissues, P. aeruginosa cells were found attached to exposed basement membranes following epithelial denudation, suggesting that the affinity for extracellular matrix proteins may account for the bacterium's opportunistic character. By using microtiter wells coated with different P. aeruginosa strains, we demonstrated that laminin binds to both colonizing bacterial strains, isolated from asymptomatic carriers, and strains isolated from infected patients. Binding of soluble laminin to piliated P. aeruginosa PAK and to the nonpiliated isogenic mutant PAK/p--was shown to be saturable. Binding of laminin to the piliated PAK strain was not different from binding to th nonpiliated PAK/p--strain but was significantly higher than binding to the avirulent, nonpiliated PAK-N1 rpoN mutant. By transmission electron microscopy, we localized the laminin-binding sites on a loose material in the outermost layer of the bacteria. Western immunoblotting results suggested that 57- and 59-kDa nonpilus adhesins from the microbial outer membranes account for the binding of P. aeruginosa to laminin. We speculate that bacterial affinity for laminin may be of biological significance in the pathogenesis of P. aeruginosa infection of injured tissues.

Gelatinase B is involved in the in vitro wound repair of human respiratory epithelium.

Following epithelial injury, extracellular matrix undergoes imposing remodelings. We examined the contribution of matrix metalloproteinases, gelatinases A and B, in an in vitro wound repair model of human respiratory epithelium. Confluent human surface respiratory epithelial (HSRE) cells cultured from dissociated surface cells of human nasal polyps were chemically injured. Over the next 3 to 5 days, cells migrated onto the injured area to repair the circular wound. Repair kinetics of these wounds was monitored until wound closure occurred. Gelatinolytic activities were analysed in culture supernates and in cell protein extracts derived from repairing migratory and non repairing stationary cells. Small amounts of gelatinase A were expressed by HSRE cells, and variations of this gelatinase remained very weak for the time of the wound repair. In contrast, gelatinase B was upregulated during the wound repair process, with a maximum peak observed at wound closure. A marked gelatinase B activation occurred only in cells involved in the repair process. Gelatinase B was localized in some migratory basal cells, recognized by an anti-cytokeratin 14 antibody and located around the wound. We could not detect any gelatinase A in repairing or in stationary HSRE cells. Addition of the 6-6B monoclonal antibody, known to inhibit gelatinase B activation, to the culture medium during the repair process resulted in a dose-dependent decrease of the wound repair speed. These results suggest that gelatinase B, produced by epithelial cells, actively contributes to the wound repair process of the respiratory epithelium.

Identification of antileucoprotease in remodelled human adult nasal surface epithelium.

Antileucoprotease (ALP) is generally considered as a specific marker for glandular serous cells, and plays a major role in the defence of the respiratory tract against proteolytic damage. Nevertheless, several studies have identified ALP in bronchial and bronchiolar surface epithelial cells, and also an increased number of ALP-containing cells in bronchiolar tissue during the development of pulmonary diseases. In order to define more clearly whether the surface epithelium might be involved in the defence of the respiratory mucosa, we have investigated the expression of ALP by cells of the nasal surface epithelium. Indirect immunocytochemistry and in situ hybridization for ALP were performed on human nasal polyp sections. The height of the surface epithelium, its morphology, and the degree of local inflammation were assessed in parallel. Surface epithelium morphology was highly heterogeneous. ALP-containing cells were identified, but only in remodelled areas of the surface epithelium (foldings, basal cell and/or mucous cell hyperplasia), with no association to the degree of inflammation. These results demonstrate that the surface epithelial cells of the human adult nasal mucosa can express ALP in remodelled surface epithelium, and may be actively involved in the biochemical defence of the airways.