Reconstituted human oral and esophageal mucosa in culture

Full-thickness tissue engineered oral mucosa for genitourinary reconstruction: A comparison of different collagen-based biodegradable membranes

Tissue engineering is a method of growing importance regarding clinical application in the genitourinary region. One of the key factors in successfully development of an artificially tissue engineered mucosa equivalent (TEOM) is the optimal choice of the scaffold. Collagen scaffolds are regarded as gold standard in dermal tissue reconstruction. Four distinct collagen scaffolds were evaluated for the ability to support the development of an organotypical tissue architecture. TEOMs were established by seeding cocultures of primary oral epithelial cells and fibroblasts on four distinct collagen membranes. Cell viability was assessed by MTT-assay. The 3D architecture and functionality of the tissue engineered oral mucosa equivalents were evaluated by confocal laser-scanning microscopy and immunostaining. Cell viability was reduced on the TissuFoil E® membrane. A multi-stratified epithelial layer was established on all four materials, however the TEOMs on the Bio-Gide® scaffold showed the best fibroblast differentiation, secretion of tenascin and fibroblast migration into the membrane. The TEOMs generated on Bio-Gide® scaffold exhibited the optimal cellular organization into a cellular 3D network. Thus, the Bio-Gide® scaffold is a suitable matrix for engineering of mucosa substitutes in vitro.

Recombinant human interleukin 17A enhances the anti-Candida effect of human oral mucosal epithelial cells by inhibiting Candida albicans growth and inducing antimicrobial peptides secretion

BACKGROUND

Candida albicans (C albicans) is the most common fungal pathogen causing opportunistic infections. IL17 (IL17A) is a vital mediator of antifungal immunity. The aim of the study was to investigate the effect of recombinant human interleukin 17A (rhIL17A) on human oral mucosal epithelial cells (hOMECs) defending against C albicans infection.

METHODS

Human oral mucosal epithelial cells were divided into four groups: C albicans+ (MOI = 0.1), rhIL17A+ (100 μg/L), rhIL17A + C albicans+ (MOI = 0.1, rhIL17A:100 μg/L) and blank control. Then, C albicans growth was observed after 24 hours. Human beta-2 defensin (hBD-2), S100A8 and LL-37 in supernatants and their mRNAs in cells were measured by enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction, respectively.

RESULTS

In C albicans+ group, C albicans hyphae formation and the death of infected hOMECs were observed. However, in the rhIL17A + C albicans+ group, IL17 inhibited both hypha formation, and C albicans from infecting hOMECs and its further growth. There was no statistical significance in adhesion rates of C albicans to hOMECs. Compared with the control group, the level of hBD-2 mRNA has increased, while hBD-2 and hBD-2 mRNA levels in the rhIL17A + C albicans+ group were the highest. Both hBD-2 and hBD-2 mRNA levels were higher in the rhIL17A+ group than in the C albicans+ group. S100A8 and LL-37 mRNAs have similar trend, and both upregulated after treatment with rhIL17A; however, protein levels were undetectable.

CONCLUSION

Recombinant human interleukin 17A may inhibit C albicans from infecting hOMECs by affecting the growth and reproduction of C albicans as well as the formation of hyphae. Besides, rhIL17A might induce hBD-2, S100A8 and LL-37 secretion from hOMECs to strengthen their anti-infective ability.

Impact of Implant Surface Micropatterns on Epithelial Cell Behavior

PURPOSE

This study investigated the effect of topography on cell behavior by screening polydimethylsiloxane (PDMS) molds with different nanoscale micropatterns to determine the ideal surface characteristics for attachment of human epithelial cells.

MATERIALS AND METHODS

A soft PDMS mold with regular dot arrays was fabricated based on an aluminum oxide template with ordered nanotube arrays and used as a substrate for cell culture. Cell proliferation, spread, and morphology, as well as features of the extracellular matrix and the actin cytoskeleton were assessed.

DISCUSSION

Cells grown on 100-nm regular dot arrays had the highest proliferation rate and spread, with the longest pseudopodia; they showed robust actin distribution relative to the control group.

CONCLUSION

Three-dimensional PDMS microstructures with 100 nm regular dot arrays were the most effective surface for epithelial cell attachment. These findings can aid in the manufacture of superior materials for use in implants to better integrate into recipient tissue.

Isolation and characterization of mouse and human esophageal epithelial cells in 3D organotypic culture

This protocol describes the isolation and characterization of mouse and human esophageal epithelial cells and the application of 3D organotypic culture (OTC), a form of tissue engineering. This model system permits the interrogation of mechanisms underlying epithelial-stromal interactions. We provide guidelines for isolating and cultivating several sources of epithelial cells and fibroblasts, as well as genetic manipulation of these cell types, as a prelude to their integration into OTC. The protocol includes a number of important applications, including histology, immunohistochemistry/immunofluorescence, genetic modification of epithelial cells and fibroblasts with retroviral and lentiviral vectors for overexpression of genes or RNA interference strategies, confocal imaging, laser capture microdissection, RNA microarrays of individual cellular compartments and protein-based assays. The OTC (3D) culture protocol takes 15 d to perform.

Fabrication and in vitro and in vivo cell infiltration study of a bilayered cryogenic electrospun poly(D,L-lactide) scaffold

Cryogenic electrospinning has previously been demonstrated for controlling the pore sizes of electrospun scaffolds, which has been impossible with traditional electrospinning processes. This article describes the application of the cryogenic technique to fabricate a bilayered electrospun poly(D,L-lactide) scaffold (BLES) in a single uninterrupted process. The resulting BLES consisted of a traditional electrospun (ES) fibrous layer with a dense pore area of 17 +/- 3 microm(2) adjacent to a cryogenic electrospun layer (CES) with a pore area of 3300 +/- 500 microm(2). The significance of this bilayered scaffold was to mimic the anatomical structure of tissues with dense basement membrane followed by loose and highly porous connective tissue such as skin and blood vessels. Cell infiltration in the BLES was compared in vitro and in vivo. Both studies suggested the CES supported high cell infiltration, whereas the ES could serve as a physical barrier to prevent cell infiltration across the CES-ES boundary because of its size exclusion. The bilayered structure produced by this technique suggests a great potential for engineering tissues with similar architectures.

The lytic activation of KSHV during keratinocyte differentiation is dependent upon a suprabasal position, the loss of integrin engagement, and calcium, but not the interaction of cadherins

We previously found that KSHV (HHV-8) lytic activation occurs during differentiation of oral keratinocytes in organotypic raft cultures. To further investigate the spatial and temporal aspects of KSHV lytic activation and the roles of integrins, cadherins, and calcium, we used rKSHV.219-infected primary oral keratinocytes in submerged, suspension, and direct suprabasal plating, models of differentiation. We found that early keratinocyte differentiation did not activate lytic KSHV in cells attached to a substratum, with activation only occurring in suprabasal cells. Temporally, KSHV lytic expression occurred between the expression of early and late differentiation markers. Keratinocytes differentiated in suspension culture, which mimics substratum loss that occurs with stratification, activated lytic KSHV. This lytic activation was inhibited by integrin engagement, showing that integrins are a control point for KSHV reactivation. A role for cadherins was not found. Elevated extracellular calcium was necessary, but not sufficient, for lytic activation.

Esophagus tissue engineering: hybrid approach with esophageal epithelium and unidirectional smooth muscle tissue component generation in vitro

PURPOSE

The aim of this study was to engineer the two main components of the esophagus in vitro: (a) esophageal epithelium and (b) smooth muscle tissue. Furthermore, (a) survivability of esophageal epithelial cells (EEC) on basement membrane matrix (BMM)-coated scaffolds and (b) oriented smooth muscle tissue formation on unidirectional BMM-coated collagen scaffolds was investigated.

METHODS

Both EEC and smooth muscle cells (SMC) were sourced from Sprague-Dawley rats. The EEC were maintained in vitro and seeded onto BMM-coated 2-D collagen scaffolds. Similarly, smooth muscle cells were obtained using an explants technique and seeded on unidirectional 3-D BMM-coated collagen scaffolds. Cell-polymer constructs for EEC and SMC were maintained in vitro for 8 weeks.

RESULTS

Protocols to obtain higher yield of EEC were established. EEC formed a layer of differentiated epithelium after 14 days. EEC survivability on polymers was observed up to 8 weeks. Unidirectional smooth muscle tissue strands were successfully engineered.

CONCLUSION

Esophageal epithelium generation, survivability of EEC on BMM-coated scaffolds, and engineering of unidirectional smooth muscle strands were successful in vitro. The hybrid approach of assembling individual tissue components in vitro using BMM-coated scaffolds and later amalgamating them to form composite tissue holds promises in the tissue engineering of complex organ systems.

Esophagus tissue engineering: in vitro generation of esophageal epithelial cell sheets and viability on scaffold

PURPOSE

Management of long gap esophageal atresia poses challenges. The surgical techniques for esophageal replacement are associated with complications and high morbidity. The aim of this study was to develop protocols to obtain single layer sheets of esophageal epithelial cells (EECs) and to investigate their survival on collagen scaffolds.

METHODS

Esophageal epithelial cells were sourced from adult Sprague-Dawley rats. Briefly, the esophagus was treated with dispase to separate the epithelial layer and further trypsined to obtained EEC. The esophageal epithelial cells were cultured in vitro and seeded on to new generation of 3-dimensional collagen scaffolds.

RESULTS

Esophageal epithelial cells organized after 48 hours in culture and formed clusters after 72 to 96 hours. Organization of the EEC was completed after 7 days in culture and characteristic sheets of EEC with the histologic morphology of mature esophageal epithelium were obtained after 14 days of culture. Immunohistochemistry demonstrated pure EEC culture using cytokeratin (CK-14) markers. The esophageal epithelial cells transferred on to collagen polymers demonstrated excellent viability after 8 weeks of in vitro culture.

CONCLUSION

Successful protocols for EEC isolation and proliferation have been established. The engineering of sheets of EEC and the viability of EEC on collagen scaffolds for 8 weeks in vitro, which are prerequisites for esophagus tissue engineering, was demonstrated.

Clinical puzzle: Barrett's oesophagus

The incidence of oesophageal adenocarcinoma has increased dramatically in the Western world over the past two decades. Owing to its dismal 5-year prognosis in advanced stages, early diagnosis is required in order to improve survival rates. Barrett's oesophagus (Barrett's) has been recognised as a pre-cancerous condition generally associated with chronic and severe gastro-oesophageal reflux disease (GORD). Barrett's is defined as the substitution of the normal stratified squamous epithelium of the oesophagus with a columnar cell lining with intestinal-type differentiation; a phenomenon commonly referred to as intestinal metaplasia. Clinical challenges include finding cost-effective ways to identify patients with Barrett's, stratifying them according to their cancer risk and improving the diagnostic potential of endoscopic sampling. Research has generally focused on identifying tissue biomarkers to predict cancer risk in these patients. The oesophagus is easily accessible, making it possible to work with human samples, but most studies have been retrospective and underpowered. Endoscopic surveillance programmes are problematic due to sampling bias and the subjective grading of dysplasia. The lack of an animal model has hampered studies to elucidate markers of the transition from Barrett's to cancer and to test potential therapeutics. However, a number of in vitro model systems are ripe for further development into more physiologically complete systems.

Reconstitution of stratified murine and human oesophageal epithelia in an in vivo transplant culture system

OBJECTIVE

The molecular and cellular events responsible for regulating development of the oesophageal epithelium are not well understood. At least in part, this is due to the lack of a suitable model system with which to study the process. Here, we report development of a manipulable in vivo transplant model for mouse or human oesophageal epithelium.

MATERIAL AND METHODS

Epithelial cells were isolated from mouse or human oesophagus and inoculated into de-epithelialized and devitalized rat tracheas. The rat trachea, containing cells, was placed subcutaneously under the dorsal skin of immunodeficient mice.

RESULTS

We show that a multilayered stratified squamous epithelium can be generated in 4-6 weeks from as few as 5 x 10(4) isolated oesophageal epithelial cells. The reconstituted epithelium recapitulates many of the structural and histological features of the normal oesophageal epithelium, including a basal layer of cuboidal-like cells, suprabasal layers of differentiating squamous cells and, in the case of murine cells, a superficial layer of cornified material.

CONCLUSION

Our model can be used to generate a multilayered normal murine or human epithelium from a single cell suspension of oesophageal epithelial cells. The ability to genetically manipulate the cells prior to growth in the model is a powerful tool with which to study the molecular mechanisms involved in the development of normal oesophagus or in pathogenic processes such as Barrett's metaplasia or tumorigenesis.

Esophageal epithelial cell interaction with synthetic and natural scaffolds for tissue engineering

As an initial step towards a tissue-engineered esophagus, rat esophageal epithelial cells (REEC) were isolated and characterized for epithelial identity, adhesion protein preference, and in vitro interaction with natural and synthetic scaffolds. The scaffolds consisted of AlloDerm (LifeCell Corporation, Branchburg, NJ), poly(L-lactic acid) (PLLA), poly(lactic-co-glycolic) acid (75:25) (PLGA75), poly(lactic-co-glycolic) acid (50:50) (PLGA50), and polycaprolactone/poly(L-lactic acid) (50:50) (PCL/PLLA). Various factors-including calcium concentration, scaffold composition, and pore size--were evaluated for their influence on epithelial growth and differentiation. By day 18, keratinocytes seeded on AlloDerm cultured under high Ca(++) (1.5mm) conditions showed a proliferating basal cell layer, epithelial stratification (5--6 layers) and a thick keratin layer. The synthetic scaffolds (PLGA, PLLA, PCL/PLLA) also showed complete surface coverage, regions of proliferating basal cells, and evidence of stratification (2--3 layers) and keratinization. The highly porous nature of the synthetic scaffolds, however, limited the formation of a continuous epithelial layer and resulted in a lack of overall spatially-defined differentiation. In conclusion, rat esophageal epithelial cells were successfully isolated and characterized, with cells seeded on AlloDerm showing superior epithelial organization and stratification compared to synthetic scaffolds. Modification of the synthetic scaffold's surface properties and pore size may be necessary to mimic epithelial behavior on natural scaffolds.

The phenotype of in vitro reconstituted normal human oral epithelium is essentially determined by culture medium

OBJECTIVE

To evaluate the role of various culture media and serum supplement on growth of oral cells in monolayer, and on morphogenesis of in vitro reconstituted normal human oral epithelium.

METHODS

Primary keratinocytes and fibroblasts were isolated from normal human buccal mucosa. The monolayers were assessed by growth curve analysis and morphology. The organotypic cultures were evaluated by morphometry, immunohistochemistry, and TUNEL.

RESULTS

FAD medium (a 3:1 mixture of Dulbecco's modified Eagle's medium and Ham's F12 medium) was able to support fibroblast growth in defined conditions, and to diminish the negative effect of physiological Ca concentration on keratinocytes in monolayers. Medium type had a profound influence on morphogenesis of in vitro reconstituted human oral epithelium. FAD medium was superior to other types of medium tested in supporting both epithelial growth and differentiation. Defined conditions supported epithelial morphogenesis equally well as serum-containing medium.

CONCLUSIONS

This study points to an essential role of medium composition for optimized growth and differentiation of primary organotypic cultures.

Phenotypic and microarray gene expression analysis of tri-dimensional raft-modeled human head and neck squamous cell carcinoma

OBJECTIVES

To describe the phenotypic and gene expression differences in monolayer and tri-dimensional cultures systems.

METHODS

Normal oral epithelial cells (NOEC), primary head and neck squamous cell carcinoma (HNSCC), and HNSCC cell lines were used to create and study modeled tri-dimensional tissue. Using cDNA microarray analysis, monolayer and raft-modeled tri-dimensional HNSCC cell lines were compared.

RESULTS

NOEC, HNSCC, and both together can be modeled with tri-dimensional differentiation and cytokeratin characteristics analogous to in vivo tissue. Modeling of primary HNSCC resulted in a morphology of invasive HNSCC with areas of direct collagen invasion and MMP2 expression. Gene array analysis suggests that the individual cell lines themselves are the primary gene expression predictor and not the presence of tri-dimensional tissue architecture.

CONCLUSIONS

This tissue culture modeling system approximates the differentiation and tri-dimensional structure of in vivo tissues, and that raft modeled tri-dimensional HNSCC does not have a significantly different gene expression profile than the corresponding monolayer culture.

Safrole–DNA adducts in tissues from esophageal cancer patients: clues to areca-related esophageal carcinogenesis

Epidemiological studies have demonstrated that areca quid chewing can be an independent risk factor for developing esophageal cancer. However, no studies are available to elucidate the mechanisms of how areca induces carcinogenesis in the esophagus. Since the areca nut in Taiwan contains a high concentration of safrole, a well-known carcinogenic agent, we analyzed safrole-DNA adducts by the 32P-postlabelling method in tissue specimens from esophageal cancer patients. In total, we evaluated 47 patients with esophageal cancer (16 areca chewers and 31 non-chewers) who underwent esophagectomy at the National Taiwan University Hospital between 1996 and 2002. Of the individuals with a history of habitual areca chewing (14 cigarette smokers and two non-smokers), one of the tumor tissue samples and five of the normal esophageal mucosa samples were positive for safrole-DNA adducts. All patients positive for safrole-DNA adducts were also cigarette smokers. Such adducts could not be found in patients who did not chew areca, irrespective of their habits of alcohol consumption or cigarette smoking (p<0.001, comparing the areca chewers with non-chewers). The genotoxicity of safrole was also tested in vitro in three esophageal cell lines and four cultures of primary esophageal keratinocytes. In two of the esophageal keratinocyte cultures, adduct formation was increased by treatment with safrole after induction of cytochrome P450 by 3-methyl-cholanthrene. This paper provides the first observation of how areca induces esophageal carcinogenesis, i.e., through the genotoxicity of safrole, a component of the areca juice.

Oral Cancer Cells Differ From Normal Oral Epithelial Cells in Tissuelike Organization and in Response to Lycopene Treatment: An Organotypic Cell Culture Study

We established distinctive monolayer and organotypic cell culture techniques to assess possible differences in cross-talk and spatial and structural organization of oral cancer cells compared with normal oral cells and also to evaluate possible differential responses of the cells to carotenoids. In monolayers, we investigated the effect of lycopene on the proliferation of an established oral cancer cell line, KB-1, and compared it with a primary cell line obtained from normal oral mucosa. Lycopene exerted a significant inhibitory effect on KB-1 cell proliferation inducing a dose-dependent downregulation of proliferating cell nuclear antigen (PCNA) associated with upregulation of connexin-43 (Cx-43) expression, whereas in the normal oral mucosal cells lycopene did not affect either PCNA expression, which was very low, or the expression of Cx-43, which was basically very high. Lycopene significantly inhibited the formation of colonies induced by the carcinogen 3-methylcholanthrene (MCA) on normal oral cells and almost completely abrogated the hyperplastic effect induced by MCA. KB-1 cells and normal oral epithelial cells in the organotypic cell culture method differed in their stratification and intercellular adhesion patterns as well as in the expression profile of cytokeratins, vimentin, and Cx-43. Lycopene induced Cx-43 expression in KB-1 cells grown by the organotypic raft method, similar to KB-1 cells grown as monolayers. We conclude that lycopene is a promising chemopreventive, pro-differentiating, and anticarcinogenic agent. No adverse effects of lycopene were detected in normal cells cultured in either monolayer or organotypic systems.

Stimulation of human colonic epithelial cells by leukemia inhibitory factor is dependent on collagen-embedded fibroblasts in organotypic culture

The colonic epithelium undergoes a continuous cycle of proliferation, differentiation, and apoptosis. To characterize factors important for colonic homeostasis and its dysregulation, human fetal colonic epithelial cells were isolated and seeded on a collagen type I matrix with embedded colonic fibroblasts. The epithelial cells rapidly spread from clusters and proliferated, and within 3 days, a columnar layer of polarized epithelium surrounded the surface of the constricted collagen matrix. The polarized enterocytes developed brush borders, tight junctions and desmosomes, and goblet and enteroendocrine cells were present. A balance of growth and differentiation was maintained for several weeks in the presence of collagen-embedded fibroblasts and a complex mixture of growth factors. Leukemia inhibitory factor (LIF) was critical for proliferation of enterocytes and inhibited expression of the differentiation marker carbonic anhydrase II. In the presence of LIF, the relative number of goblet cells remained stable, whereas enteroendocrine relative cell number declined. LIF-stimulated epithelial cells remained dependent on the presence of fibroblasts in the matrix. In combination with stem cell factor and endothelin 3, LIF induced formation of disorganized structures of stratified and semi-stratified cells, suggesting that the homeostatic balance in the normal human colon requires cooperation with differentiation-inducing factors.

Analysis of proliferation, apoptosis and keratin expression in cultured normal and immortalized human buccal keratinocytes

The current study was undertaken to analyse growth and differentiation-related functions of normal keratinocytes (NOK) and an SV40T-immortalized keratinocyte line (SVpgC2a) from buccal mucosa, viewing the latter cell line as a model of a dysplastic epithelium. Morphological and immunohistochemical assessments of organotypic epithelia generated from 10 or 17 d of culture showed three- to five-fold higher apoptotic and proliferative activity in SVpgC2a relative to NOK. Conditions with or without serum (up to 10%) did not significantly influence these parameters in NOK whereas serum supported proliferation of SVpgC2a. Both cell types showed basal expression of collagen IV and laminin 1, indicating basal lamina, as well as vimentin, indicating an activated, proliferative state. Reduced expression of keratin, including the non-keratinizing marker K13, was seen in SVpgC2a. Assessment of proliferative monolayer cultures by microarray showed that NOK transcribed tissue-specific keratins, but also the epidermal keratin K2a, several simple epithelial keratins and low levels of hair keratins. SVpgC2a transcribed keratins seen in epithelial dysplasia, and K2a and hair keratins, albeit at low level. Overall, the results implied aberrant apoptosis, proliferation and keratin expression in the immortalized state of SVpgC2a. Comparison of NOK and SVpgC2a under identical culture conditions may serve to model the progression from a normal to a pre-neoplastic state of buccal epithelium.

Activation of the esophagin promoter during esophageal epithelial cell differentiation

Esophagin is a member of the small proline-rich protein family of cell envelope precursor proteins, which are expressed during squamous cell differentiation. Esophagin is expressed at high levels in normal esophageal epithelium, but its expression is absent from esophageal squamous cell carcinomas and adenocarcinomas. Moreover, loss of esophagin expression is present in areas of dysplasia or normal mucosa adjacent to carcinomas, suggesting that absence of esophagin may constitute a harbinger of early esophageal malignant transformation. A greater understanding of transcriptional control of esophagin may provide valuable insights into esophageal malignancy. Therefore, this study was undertaken in order to isolate and carry out initial characterization of a functional promoter for esophagin. A genomic clone containing esophagin was isolated and sequenced, including 2.7 kb of the esophagin promoter region. Esophagin expression was studied in response to various treatments of primary cultured human esophageal epithelial cells and squamous cell carcinoma cell lines. Calcium was the strongest inducer of the endogenous esophagin promoter, with induction occurring at 12-72 hours. In primary cultured esophageal epithelial cells, a region spanning 116 bp upstream of the transcriptional start site to 45 bp downstream was sufficient to direct low, basal, in vitro esophagin expression. However, responsiveness of primary esophageal cells to calcium required inclusion of promoter elements 1688 bp upstream of the transcriptional start site. Site-directed mutagenesis studies suggested a putative role for C/EBP-beta, OCT-1, and OCT-3 transcription factor binding sites in the minimal promoter region. In conjunction with published human in vivo studies, these data support the hypothesis that esophagin is a biomarker of esophageal squamous cell differentiation and provide an in vitro model to evaluate regulatory factors involved in this differentiation process.

Temporal expression of the Candida albicans genes CHK1 and CSSK1, adherence, and morphogenesis in a model of reconstituted human esophageal epithelial candidiasis

We previously demonstrated that genes encoding a putative two-component histidine kinase (CHK1) or a response regulator (CSSK1) are each required for virulence in a murine model of hematogenously disseminated candidiasis and that strains with each gene deleted are also defective in morphogenesis under certain growth conditions. In the present study, the role of these two genes in the adherence to and colonization of reconstituted human esophageal tissue (RHE) is described. We compared strains of Candida albicans with deletions of chk1 (strain CHK21) and cssk1 (strain CSSK21) to wild-type cells (CAF2), as well as strains with CHK1 and CSSK1 reconstituted (strains CHK23 and CSSK23, respectively). Adherence and colonization of RHE were evaluated in periodic acid-Schiff-stained sections, as well as by SEM. We observed that both deletion-containing strains colonized the RHE to a lesser extent than did CAF2 and that the percent germination by both strains was reduced in comparison to that of control strains at 1 h postinfection. Expression of CHK1 or CSSK1 was quantitated by reverse transcription (RT)-PCR from RHE tissues infected with wild-type C. albicans yeast cells. Expression of both CHK1 and CSSK1 increased over the 48-h period following infection of the tissue, although expression of CHK1 was greater than that of CSSK1. By RT-PCR, we have also shown that expression of CHK1 and CSSK1 in the strains with cssk1 and chk1 deleted, respectively, was similar to that of CAF2, indicating that CHK1 and CSSK1 do not regulate each other but probably encode signal proteins of different pathways. Our observations indicate that CHK1 and CSSK1 are each partially required for colonization and conversion to filamentous growth on RHE tissue.

Expression of keratins in normal, immortalized and malignant oral epithelia in organotypic culture

Keratins have been extensively studied in tissues and cultured keratinocytes but limited information is available on epithelia reconstructed in vitro. The aim of this study was to examine keratin expression in organotypic epithelia with normal (NOK), immortalized (SVpgC2a) and malignant (SqCC/Y1) human buccal cells. Organotypic epithelia were derived from 10 days of culture at the air-liquid interface of collagen gels containing human oral fibroblasts using a standardized serum-free medium. Sections were stained immunohistochemically with selected mono-specific antibodies to a range of keratins. Organotypic epithelia showed sharp differences in keratin expression and distribution. K4/K13, K1/K10, K6/K16 were variably expressed in NOK and SqCC/Y1 but were not detected in SVpgC2a. K5 was expressed in all organotypic epithelia but K14 was absent in SVpgC2a. K7 and K8 showed variable expression while K18 was expressed uniformly in all epithelia. K19 was expressed consistently in NOK and K20 was distributed heterogeneously in SVpgC2a. Overall, organotypic cultures of normal keratinocytes express many of the same keratins as buccal mucosa. Further, the loss of keratins in SVpgC2a and their retention in SqCC/Y1 have several features in common with the respective keratin profile of oral epithelial dysplasia and well-differentiated oral squamous cell carcinoma. Although qualitative and quantitative differences exist compared to keratin expression in vivo, these cell lines in organotypic culture may serve in studies of the multi-step progression of oral cancer.

Efficiency of adenovirus-mediated gene transfer to oropharyngeal epithelial cells correlates with cellular differentiation and human coxsackie and adenovirus receptor expression

Adenovirus-mediated gene transfer is a novel treatment strategy for head and neck squamous cell carcinoma (HNSCC) that may improve the unacceptable morbidity and mortality associated with conventional treatment. Efficient adenoviral (AdV) infection largely depends on cellular expression of the human coxsackie and adenovirus receptor (hCAR); however, the relatively recent identification of this receptor precludes a comprehensive description of its tissue distribution. We have created tissue culture model systems that approximate the differentiation and three-dimensional structure of stratified squamous epithelium characteristic of head and neck mucosa. Using these systems, we have found that expression of hCAR in native and modeled normal oropharyngeal epithelium decreased as cells differentiated with the most superficial and differentiated cells expressing no detectable hCAR. In contrast, modeled stratified HNSCC cells, which did not differentiate morphologically and did not express cytokeratin markers of differentiation, had equivalent expression of hCAR in superficial and basal layers. The expression of hCAR in our models correlated not only with the undifferentiated state, but also with efficiency of AdV infection. Despite expression of hCAR in underlying basal and suprabasal cells, topical application of AdV to normal modeled epithelium resulted in inefficient transduction of the most superficial cell layer without any infection of underlying cells. These data suggest that in normal epithelium the overlying squamous cells act as a barrier preventing infection of underlying cells that would otherwise be easily infected. In modeled stratified HNSCC, transduction was much more efficient and occurred up to four cell layers deep, suggesting that unlike normal superficial epithelial cells, the superficial cells of stratified HNSCC do not act as an effective barrier to adenoviral infection. The distribution of hCAR in native tissue and the enhanced susceptibility of undifferentiated oropharyngeal epithelial cells, including undifferentiated cancer cells, to AdV infection has important implications for the development of AdV-based targeting strategies for the treatment of head and neck cancer or premalignancies.

Development and characterization of a tissue-engineered human oral mucosa equivalent produced in a serum-free culture system

A problem maxillofacial surgeons face is a lack of sufficient autogenous oral mucosa for reconstruction of the oral cavity. Split-thickness or oral mucosa grafts require more than one surgical procedure and can result in donor site morbidity. Skin has disadvantages of adnexal structures and a different keratinization pattern than oral mucosa. In this study, we successfully assembled, ex vivo, a human oral mucosa equivalent, consisting of epidermal and dermal components, in a defined, essential-fatty-acid-deficient, serum-free culture medium without a feeder layer, that could be used for intra-oral grafting in humans. Autogenous oral keratinocytes were seeded onto a cadaveric dermis, AlloDerm. The oral mucosa equivalent was cultured at an air-liquid interface for 2 wks. The resulting equivalent had a well-stratified parakeratinized epithelial layer similar to native oral keratinized mucosa. Expression of differentiation markers, filaggrin and cytokeratin 10/13, suggested a premature keratinized state. The presence of proliferation markers, proliferating cell nuclear antigen (PCNA) and Ki-67, suggested a state of hyperproliferation. Fatty acid composition of the equivalent was similar to that of in vitro cultured oral keratinocytes but differed from the that of in vivo native tissue, showing a lower content of 18:2 and 20:4, and a higher content of 16:1 and 18:1 fatty acids, respectively. The keratinocytes of the equivalent appeared to be in a more active and proliferative state than native keratinized mucosa. The dynamic nature of the cell population on the oral mucosa equivalent may be beneficial for intra-oral grafting procedures and for transfection of the keratinocytes.

Response of human oral epithelial cells to oxidative damage and the effect of vitamin E

Smoking and periodontal inflammation are various conditions with the potential to induce oxidative stress and thus DNA damage in the oral cavity. In cellular defense systems, vitamin E is considered the most powerful lipid-soluble antioxidant. To investigate whether oxygen-free radicals alter normal progression of the cell cycle and whether vitamin E prevents this damage, we exposed cultured normal human oral epithelial cells to hydrogen peroxide (H2O2) in the presence or absence of vitamin E. Two primary cell lines were analyzed for the presence of hydroxyl radical, cell cycle distribution and morphology. Each cell line received five treatments: control, ethanol only, vitamin E only, H2O2 only or vitamin E followed by H2O2. Degradation of hydroxyl radicals was detected by electron paramagnetic resonance analysis, cell cycle by flow cytometry and morphology by organotypic technique. Hydroxyl radicals were generated in H2O2-treated cells at an initial concentration, which decreased over a period of time. Cell cycle analysis showed that H2O2-treated cells differed from normal cells in that the percentage of cells in the G1 phase decreased markedly (34.3 vs. 61.2% in control) and the S phase increased (35.5 vs. 15.6% in control). Organotypic cultures treated with H2O2 demonstrated nuclear hyperchromatism, loss of maturation and prominent nucleoli, features consistent with premalignant epithelial transformation. In conclusion, our data suggest that H2O2 produced hydroxyl radicals and altered the cell cycle. Also, vitamin E may have the potential to reduce oxidative damage caused by hydroxyl radicals.