Expression of simple epithelial type cytokeratins in stratified epithelia as detected by immunolocalization and hybridization in situ

Differential distribution of intermediate filament proteins in the bovine and ovine tongues

Intermediate filaments constitute the most heterogeneous class among the major classes of cytoskeletal proteins of mammalian cells. The 40 or more intermediate filament proteins have been classified into five types which show very specific rules of expression in specialized cell types. This study aimed to investigate the immunohistochemical distribution of cytokeratins (CKs) 8, 18, and 19 as well as the intermediate filaments vimentin, laminin, and desmin in bovine and ovine tongues. Immunohistochemical staining was performed for CKs 8, 18, 19, vimentin, laminin, and desmin. Our results revealed similar immunostaining intensity and distribution among various CKs, contrasting with distinct patterns for vimentin, laminin, and desmin. Immunoreactions were primarily localized in serous acini and ductal epithelium for cytokeratins, while vimentin and laminin were evident in connective tissue, endothelium, serous acini, and desmin in striated and smooth muscles. This study highlighted the absence of CKs 8, 18, 19, vimentin, and desmin in the lingual epithelium of bovine and ovine tongues. These findings enabled the classification of epithelial cells based on their specific cytokeratin patterns. Furthermore, vimentin was identified in mesodermal tissues and organs, desmin in muscle tissue, and laminin played crucial roles in basement membrane formation, nerve tissue regeneration, innervation of epithelial taste buds, and tissue separation and connection. Our findings provide essential insights into intermediate filament dynamics at the cellular and tissue levels. They serve as a foundation for future studies using systematic molecular biological techniques in this field.

Trichilemmal cysts with proteinaceous material: A potential diagnostic pitfall

BACKGROUND

Cysts of the skin are observed frequently and their diagnoses are generally straightforward. However, atypical cystic lesions for which differentiation is indistinct have been noted.

METHODS

We examined five cases of trichilemmal cyst with proteinaceous material (TCPM), which required differentiation from sweat duct/gland tumors. We investigated the histopathological findings of TCPMs and evaluated the immunohistochemical expression of cytokeratin (CK) 10, CK13, CK17, CK19, CD8, and CD117. Immunohistochemical analysis was performed on the five TCPMs, 10 trichilemmal cysts (TCs), five clear cell hidradenomas, five poroid hidradenomas, and cutaneous normal adnexa.

RESULTS

Apoptotic cells were present in the cyst wall with a small amount of keratin or calcification in the cavity of TCPMs. The TCPMs and TCs were negative for CK19 and CD117, whereas clear cell hidradenoma and poroid hidradenoma were positive for CK19 and CD117. The restricted positivity for CK10 was detected in the suprabasal layers of the cyst walls of TCPMs and TCs. The immunostaining patterns of TCPMs and TCs were similar to those of normal follicular isthmus.

CONCLUSIONS

The histopathological findings with characteristics of TCs and a panel of immunohistochemical antibodies including CD117, CK19, and CK10 contributed to a correct diagnosis of TCPM. This article is protected by copyright. All rights reserved.

In Vitro Organotypic Systems to Model Tumor Microenvironment in Human Papillomavirus (HPV)-Related Cancers

Despite the well-known role of chronic human papillomavirus (HPV) infections in causing tumors (i.e., all cervical cancers and other human malignancies from the mucosal squamous epithelia, including anogenital and oropharyngeal cavity), its persistence is not sufficient for cancer development. Other co-factors contribute to the carcinogenesis process. Recently, the critical role of the underlying stroma during the HPV life cycle and HPV-induced disease have been investigated. The tumor stroma is a key component of the tumor microenvironment (TME), which is a specialized entity. The TME is dynamic, interactive, and constantly changing—able to trigger, support, and drive tumor initiation, progression, and metastasis. In previous years, in vitro organotypic raft cultures and in vivo genetically engineered mouse models have provided researchers with important information on the interactions between HPVs and the epithelium. Further development for an in-depth understanding of the interaction between HPV-infected tissue and the surrounding microenvironment is strongly required. In this review, we critically describe the HPV-related cancers modeled in vitro from the simplified ‘raft culture’ to complex three-dimensional (3D) organotypic models, focusing on HPV-associated cervical cancer disease platforms. In addition, we review the latest knowledge in the field of in vitro culture systems of HPV-associated malignancies of other mucosal squamous epithelia (anogenital and oropharynx), as well as rare cutaneous non-melanoma associated cancer.

Expression of keratins 8, 18, and 19 in epithelia of atrophic oral lichen planus

Keratins form intermediate filaments of the cytoskeleton in keratinocytes and have roles in cell structure, signaling, intracellular transport, and cell death. Oral lichen planus (OLP) is an oral inflammatory disease with derangements in basal keratinocytes and disruption of the basal membrane. Here, we focused on epithelial expression of keratins 8, 18, and 19 because these proteins are known to modulate cell death. Biopsies were taken from buccal oral mucosa of persons with normal oral mucosa (n = 10) or atrophic OLP (n = 10). Cultured normal oral keratinocytes (n = 4) showed expression of mRNA and protein for keratins 8, 18, and 19. Immunohistochemistry showed consistent staining for keratins 8 and 18 in basal keratinocytes of normal oral mucosa. In OLP, staining for keratin (K)8 was mostly negative and staining for K18 was weak. Keratin 19 was expressed irregularly in most biopsies of normal oral mucosa and not at all in OLP. Several mononuclear leukocytes in the cellular infiltrate showed membrane staining for K8 and K18. Positive staining for K16 confirmed partial collapse of the basal cell layer in OLP. The basal cell niche in OLP therefore appeared to be partly populated with keratinocytes demonstrating a higher degree of differentiation (K8^-  K18^-  K19^-  K16⁺ ); consequently, such areas may be more susceptible to the action of cell death factors released from the cell infiltrate as a result of lacking the protective, normal keratin present in the basal epithelial cell layer of normal oral mucosa.

Resistin Activates p65 Pathway and Reduces Glycogen Content through Keratin 8

Resistin is associated with metabolic syndrome and inflammatory conditions. Many studies have suggested that resistin inhibits the accumulation of glycogen; however, the exact mechanisms of resistin-induced decrease in glycogen content remain unclear. Keratin 8 is a typical epithelial intermediate filament protein, but numerous studies suggest a vital role of K8 in glucose metabolism. However, it is still not known whether K8 participates in the mediation of resistin-induced reduction of cellular glycogen accumulation. In this study, we found that resistin upregulated expression of the p65 subunit of NF-κB, which led to the promotion of K8 transcriptional expression; in turn, the expression of K8 inhibited glycogen accumulation in HepG2 cells.

Activin A-mediated epithelial de-differentiation contributes to injury repair in an in vitro gastrointestinal reflux model

Reflux esophagitis is a result of esophageal exposure to acid and bile during episodes of gastroesophageal reflux. Aside from chemical injury to the esophageal epithelium, it has been shown that acid and bile induce cytokine-mediated injury by stimulating the release of pro-inflammatory cytokines. During the repair and healing process following reflux injury, the squamous esophageal cells are replaced with a columnar epithelium causing Barrett's metaplasia, which predisposes patients to esophageal adenocarcinoma. We identified a novel player in gastroesophageal reflux injury, the TGFβ family member Activin A (ActA), which is a known regulator of inflammation and tissue repair. In this study, we show that in response to bile salt and acidified media (pH 4) exposure, emulating the milieu to which the distal esophagus is exposed during gastroesophageal reflux, long-term treated, tolerant esophageal keratinocytes exhibit increased ActA secretion and a pro-inflammatory cytokine signature. Furthermore, we noted increased motility and expression of the stem cell markers SOX9, LGR5 and DCLK1 supporting the notion that repair mechanisms were activated in the bile salt/acid-tolerant keratinocytes. Additionally, these experiments demonstrated that de-differentiation as characterized by the induction of YAP1, FOXO3 and KRT17 was altered by ActA/TGFβ signaling. Collectively, our results suggest a pivotal role for ActA in the inflammatory GERD environment by modulating esophageal tissue repair and de-differentiation.

Fabrication and investigation of nanofibrous matrices as esophageal tissue scaffolds using human non-keratinized, stratified, squamous epithelial cells

Clinical conditions of the esophagus are conventionally treated by autologous grafts and are generally associated with complications such as leakage, infection and stenosis necessitating an alternative synthetic graft with superior outcomes.

CCR 20th Anniversary Commentary: The Development of Breast Cancer Molecular Subtyping

In the August 15, 2004, issue of Clinical Cancer Research, Nielsen and colleagues demonstrated how a cancer subtype identified by gene expression profiling could be validated using a widely accessible technology (immunohistochemistry). This opened the door to large-scale studies of archival cohorts and clinical trials, which allowed detailed clinical understanding of a new genomic discovery. Clin Cancer Res; 21(8); 1779-81. ©2015 AACR. See related article by Nielsen et al., Clin Cancer Res 2004;10(16) Aug 15, 2004;5367-74.

Alternative functional in vitro models of human intestinal epithelia

Physiologically relevant sources of absorptive intestinal epithelial cells are crucial for human drug transport studies. Human adenocarcinoma-derived intestinal cell lines, such as Caco-2, offer conveniences of easy culture maintenance and scalability, but do not fully recapitulate in vivo intestinal phenotypes. Additional sources of renewable physiologically relevant human intestinal cells would provide a much needed tool for drug discovery and intestinal physiology. We compared two alternative sources of human intestinal cells, commercially available primary human intestinal epithelial cells (hInEpCs) and induced pluripotent stem cell (iPSC)-derived intestinal cells to Caco-2, for use in in vitro transwell monolayer intestinal transport assays. To achieve this for iPSC-derived cells, intestinal organogenesis was adapted to transwell differentiation. Intestinal cells were assessed by marker expression through immunocytochemical and mRNA expression analyses, monolayer integrity through Transepithelial Electrical Resistance (TEER) measurements and molecule permeability, and functionality by taking advantage the well-characterized intestinal transport mechanisms. In most cases, marker expression for primary hInEpCs and iPSC-derived cells appeared to be as good as or better than Caco-2. Furthermore, transwell monolayers exhibited high TEER with low permeability. Primary hInEpCs showed molecule efflux indicative of P-glycoprotein (Pgp) transport. Primary hInEpCs and iPSC-derived cells also showed neonatal Fc receptor-dependent binding of immunoglobulin G variants. Primary hInEpCs and iPSC-derived intestinal cells exhibit expected marker expression and demonstrate basic functional monolayer formation, similar to or better than Caco-2. These cells could offer an alternative source of human intestinal cells for understanding normal intestinal epithelial physiology and drug transport.

Comparative immunohistochemical study of ameloblastoma and ameloblastic carcinoma

OBJECTIVE

Ameloblastic carcinoma combines the histologic features of ameloblastoma with cytologic atypia, regardless of whether it has metastasized. Because of its rarity, there are few immunoprofile studies of ameloblastic carcinoma and few comparative studies of ameloblastic carcinoma and ameloblastoma. In this study, we compared the expression levels of cytokeratins (CKs), matrix metalloproteinases (MMPs), and Ki-67 between ameloblastoma and ameloblastic carcinoma, and assessed the usefulness of these markers for differentiating the tumors.

STUDY DESIGN

We assessed CK7, CK14, CK18, CK19, MMP-2, MMP-9, and Ki-67 expression by immunohistochemistry in 10 cases of ameloblastoma and 7 cases of ameloblastic carcinoma and then compared expression patterns between the 2 groups.

RESULTS

Immunostaining for CK14 and CK19 was diffuse and strongly positive in both tumor types, but staining for CK7 was focally positive in only 1 case of ameloblastoma and absent in all cases of ameloblastic carcinoma. However, there was a significant difference in CK18 expression between the 2 tumors (P = .000). Whereas 80% of ameloblastomas showed negative reactivity for CK18, most cases of ameloblastic carcinomas showed a moderate to strong intensity of immunostaining for CK18. Regarding the expression of MMPs, there were significant differences in parenchymal MMP-2 and stromal MMP-9 expression between the 2 tumors. Compared to ameloblastoma, ameloblastic carcinoma showed significantly strong expression of MMP-2 in parenchymal cells (P = .001) and MMP-9 in stromal cells (P = .013). However, there were no differences in MMP-2 expression of stromal cells and MMP-9 expression of parenchymal cells between ameloblastoma and ameloblastic carcinoma. The mean Ki-67 labeling index (LI) of ameloblastic carcinomas was 17.21%, which was significantly higher than that of ameloblastomas (3.57%; P = .002).

CONCLUSIONS

The significant expression of CK18, parenchymal MMP-2, stromal MMP-9, and Ki-67 could provide useful markers for differentiating ameloblastic carcinoma from ameloblastoma.

Immunohistochemical Characterization of Canine Neuroepithelial Tumors

The expression of cell differentiation and proliferation markers of canine neuroepithelial tumors was examined immunohistochemically to identify the histogenesis of these tumors. Astrocytomas ( n = 4) consisted of cells positive for glial fibrillary acidic protein (GFAP) and nestin and a few cells positive for doublecortin (DCX). Immunoreactive cells for receptor tyrosine kinases (epidermal growth factor receptor and c-erbB2) and their downstream molecules (phospho-extracellular signal-regulated kinase 1/2 and phospho-Akt) were often detected in astrocytomas, especially in medium- and high-grade tumors. Gliomatosis cerebri ( n = 3) consisted of cells positive for ionized calcium–binding adaptor molecule 1 and GFAP, including a minor population of cells positive for nestin, DCX, and beta III tubulin, suggesting their glial differentiation. In choroid plexus tumors ( n = 4), most tumor cells were positive for cytokeratins AE1/AE3 and 18, and few were positive for GFAP. The majority of cells of oligodendrogliomas ( n = 5) were DCX positive, but the tumors also contained minor populations of cells positive for GFAP, nestin, or beta III tubulin. Primitive neuroectodermal tumors (PNETs; n = 2) consisted of heterogeneous cell populations, and the tumor cells were positive for nestin, beta III tubulin, and DCX, suggesting glial and neuronal differentiation. The major population of neuroblastoma cells ( n = 3) were positive for beta III tubulin and DCX, suggesting single neuronal differentiation. As for antiapoptotic cell death molecules, most tumor cells in the choroid plexus tumors, PNETs, and neuroblastomas were intensely positive for Bcl-2 and Bcl-xL, whereas those in gliomatosis cerebri were almost negative. In astrocytomas, Bcl-xL-positive cells predominated over Bcl-2-positive cells, but the opposite was observed in oligodendrogliomas. The immunohistochemical results were analyzed by hierarchical clustering, and the constructed dendrogram clearly indicated a novel position of oligodendrogliomas: the primitive glial and neuronal differentiation.

Structure and functions of keratin proteins in simple, stratified, keratinized and cornified epithelia

Historically, the term 'keratin' stood for all of the proteins extracted from skin modifications, such as horns, claws and hooves. Subsequently, it was realized that this keratin is actually a mixture of keratins, keratin filament-associated proteins and other proteins, such as enzymes. Keratins were then defined as certain filament-forming proteins with specific physicochemical properties and extracted from the cornified layer of the epidermis, whereas those filament-forming proteins that were extracted from the living layers of the epidermis were grouped as 'prekeratins' or 'cytokeratins'. Currently, the term 'keratin' covers all intermediate filament-forming proteins with specific physicochemical properties and produced in any vertebrate epithelia. Similarly, the nomenclature of epithelia as cornified, keratinized or non-keratinized is based historically on the notion that only the epidermis of skin modifications such as horns, claws and hooves is cornified, that the non-modified epidermis is a keratinized stratified epithelium, and that all other stratified and non-stratified epithelia are non-keratinized epithelia. At this point in time, the concepts of keratins and of keratinized or cornified epithelia need clarification and revision concerning the structure and function of keratin and keratin filaments in various epithelia of different species, as well as of keratin genes and their modifications, in view of recent research, such as the sequencing of keratin proteins and their genes, cell culture, transfection of epithelial cells, immunohistochemistry and immunoblotting. Recently, new functions of keratins and keratin filaments in cell signaling and intracellular vesicle transport have been discovered. It is currently understood that all stratified epithelia are keratinized and that some of these keratinized stratified epithelia cornify by forming a Stratum corneum. The processes of keratinization and cornification in skin modifications are different especially with respect to the keratins that are produced. Future research in keratins will provide a better understanding of the processes of keratinization and cornification of stratified epithelia, including those of skin modifications, of the adaptability of epithelia in general, of skin diseases, and of the changes in structure and function of epithelia in the course of evolution. This review focuses on keratins and keratin filaments in mammalian tissue but keratins in the tissues of some other vertebrates are also considered.

Cytokeratins 8 and 18 in adult human corneal endothelium

The aim of this study was to determine if cytokeratins (CKs) 8 and 18--typical epithelial cell markers--are constitutively expressed in adult human corneal endothelium. Cryosections, paraffin-embedded sections and corneal endothelial imprints obtained from eleven adult human corneal discs not suitable for transplantation were used. Different fixative solutions were applied before indirect immunofluorescent or enzymatic staining was performed with antibodies against CK8 (Chemicon), CK18 (Dako and Sigma) and CK8/18 (Novocastra). Semi-quantitative RT-PCR and Western blotting (mRNA or proteins were isolated from Millicell membranes) were used to determine cytokeratin mRNA and protein levels. Approximately 50% of the corneal endothelial cells were positive for CK8 (Chemicon), CK18 (Sigma) and the CK pair 8/18 (Novocastra) in the endothelium when acetone was used for fixation. Four and 52% CK18-positive cells were observed using immunofluorescent and enzymatic immunohistochemistry, respectively, when the CK18 antibody from Dako was used. No signal was detected when 4% formalin or 10% paraformaldehyde was used as a fixative, irrespective of the antibody used. CK8 and CK18 proteins and mRNAs were detected in the endothelium of all tested corneas by Western blotting or semi-quantitative RT-PCR, respectively. We detected both CK8 and CK18 in the endothelium of all specimens at both the protein and mRNA levels. These results clearly demonstrate that cells of the corneal endothelium express CKs 8 and 18 and share some features with simple epithelia.

Netrin-1 can affect morphogenesis and differentiation of the mouse mammary gland

Netrin-1 has been shown to regulate the function of the EGF-like protein Cripto-1 (Cr-1) and affect mammary gland development. Since Cr-1 is a target gene of Nanog and Oct4, we investigated the relationship between Netrin-1 and Cr-1, Nanog and Oct4 during different stages of development in the mouse mammary gland. Results from histological analysis show that exogenous Netrin-1 was able to induce formation of alveolar-like structures within the mammary gland terminal end buds of virgin transgenic Cripto-1 mice and enhance mammary gland alveologenesis in early pregnant FVB/N mice. Results from immunostaining and Western blot analysis show that Netrin-1, Nanog and Oct4 are expressed in the mouse embryonic mammary anlage epithelium while Cripto-1 is predominantly expressed outside this structure in the surrounding mesenchyme. We find that in lactating mammary glands of postnatal FVB/N mice, Netrin-1 expression is highest while Cripto-1 and Nanog levels are lowest indicating that Netrin-1 may perform a role in the mammary gland during lactation. HC-11 mouse mammary epithelial cells stimulated with lactogenic hormones and exogenous soluble Netrin-1 showed increased beta-casein expression as compared to control thus supporting the potential role for Netrin-1 during functional differentiation of mouse mammary epithelial cells. Finally, mouse ES cells treated with exogenous soluble Netrin-1 showed reduced levels of Nanog and Cripto-1 and higher levels of beta-III tubulin during differentiation. These results suggest that Netrin-1 may facilitate functional differentiation of mammary epithelial cells and possibly affect the expression of Nanog and/or Cripto-1 in multipotent cells that may reside in the mammary gland.

A CK19(CreERT) knockin mouse line allows for conditional DNA recombination in epithelial cells in multiple endodermal organs

Cre/LoxP-mediated DNA recombination allows for gene function and cell lineage analyses during embryonic development and tissue regeneration. Here, we describe the derivation of a K19(CreERT) mouse line in which the tamoxifen-activable CreER(T) was knocked into the endogenous cytokeratin 19 locus. In the absence of tamoxifen, leaky Cre activity could be detected only in less than 1% of stomach and intestinal epithelial cells, but not in pancreatic or hepatic epithelial tissues. Tamoxifen administration in postnatal animals induced widespread DNA recombination in epithelial cells of pancreatic ducts, hepatic ducts, stomach, and intestine in a dose-dependent manner. Significantly, we found that Cre activity could be induced in the putative gut stem/progenitor cells that sustained long-term gut epithelial expression of a Cre reporter. This mouse line should therefore provide a valuable reagent for manipulating gene activity and for cell lineage marking in multiorgans during normal tissue homeostasis and regeneration.

The human keratins: biology and pathology

The keratins are the typical intermediate filament proteins of epithelia, showing an outstanding degree of molecular diversity. Heteropolymeric filaments are formed by pairing of type I and type II molecules. In humans 54 functional keratin genes exist. They are expressed in highly specific patterns related to the epithelial type and stage of cellular differentiation. About half of all keratins—including numerous keratins characterized only recently—are restricted to the various compartments of hair follicles. As part of the epithelial cytoskeleton, keratins are important for the mechanical stability and integrity of epithelial cells and tissues. Moreover, some keratins also have regulatory functions and are involved in intracellular signaling pathways, e.g. protection from stress, wound healing, and apoptosis. Applying the new consensus nomenclature, this article summarizes, for all human keratins, their cell type and tissue distribution and their functional significance in relation to transgenic mouse models and human hereditary keratin diseases. Furthermore, since keratins also exhibit characteristic expression patterns in human tumors, several of them (notably K5, K7, K8/K18, K19, and K20) have great importance in immunohistochemical tumor diagnosis of carcinomas, in particular of unclear metastases and in precise classification and subtyping. Future research might open further fields of clinical application for this remarkable protein family.

Differential expression of E-cadherin and cytokeratin 19 and net proliferative rate of gingival keratinocytes in oral epithelium in periodontal health and disease

BACKGROUND

The effects of periodontal disease on the oral gingival epithelium (OGE) have not been documented fully because they may not be as dramatic as those seen on the junctional epithelium. The aim of this study was to estimate the changes occurring in the OGE with respect to its proliferation and E-cadherin and cytokeratin 19 (K19) expression during pocket formation.

METHODS

Gingival samples were collected from 17 periodontally healthy subjects and 18 subjects with chronic periodontitis. K19 and E-cadherin levels were analyzed immunohistochemically. The net proliferative rate was calculated as the difference between the proliferative rate and the apoptotic rate as determined by immunohistochemical analysis of Ki-67 and p53, respectively.

RESULTS

There was a significant increase in the net proliferative rate of the OGE during pocket formation (periodontitis group, 220.90+/-46.85; healthy group, 107.60+/-25.86; P<0.001). There was a significant reduction in E-cadherin expression (periodontitis group, 0.837+/-0.428; healthy group, 1.846+/-0.555) and a significant increase in K19 expression during pocket formation (periodontitis group, 1.45+/-0.686; healthy group, 0.533+/-0.410).

CONCLUSION

OGE appears to undergo significant changes in proliferation and differentiation during pocket formation that do not seem to be restricted to proteolytic destruction by the invading microorganisms.

Human rectal mucosal gene expression after consumption of digestible and non-digestible carbohydrates

The effect of regular consumption of the low-digestible and prebiotic isomalt versus the digestible sucrose on gene expression in rectal mucosa was examined in a randomized double-blind crossover trial. Nineteen healthy volunteers received 30 g isomalt per day or 30 g sucrose as part of a controlled diet over two 4-week test periods with a 4-week washout period in between. At the end of each test phase rectal biopsies were obtained. After RNA extraction mucosal gene expression was assayed using GeneChip microarrays. In addition, expression of cathelicidin hCap18/LL37, cellular detoxification enzymes GSTpi, UGT1A1 and CYP3A4, cyclooxygenase 2 and barrier factors MUC2 and ZO-1 were determined by real-time RT-PCR. Microbiological analyses of fecal samples revealed a shift of the gut flora towards an increase of bifidobacteria following consumption of the diet containing isomalt. Isomalt consumption did not affect rectal mucosal gene expression in microarray analyses as compared to sucrose. In addition, the expression of cathelicidin LL37, GSTpi, UGT1A1, CYP3A4, COX-2, MUC2 and ZO-1 was not changed in rectal biopsies. We conclude that gene expression of the human rectal mucosa can reliably be measured in biopsy material taken at endoscopy. Dietary intervention with the low digestible isomalt compared with the digestible sucrose did not affect gene expression in the lining rectal mucosa.

Ultrastructural study of autologous cultivated conjunctival epithelium

BACKGROUND AND OBJECTIVE

This report is one of the first in the literature on the attempted cultivation and clinical application of human conjunctival epithelium. The authors investigated the possibility of restoring severely damaged ocular surface with autologous cultivated conjunctival epithelium.

PATIENTS AND METHODS

The conjunctival cells needed for the experiment were harvested from six patients with oculopalpebral diseases. Confluent epithelial sheets were developed from each biopsy specimen. The new epithelium was then implanted on the patients' or donors' eye surface.

RESULTS

The histologic examination showed a pluristratified squamous non-keratinized epithelium lying on a basement membrane and with a lamina propria of well-vascularized connective tissue. Normal ultrastructural characteristics were evident on electron microscopy.

CONCLUSION

The cultivation of autologous conjunctival cells may be a good option for rapid and safe repair of large single or bilateral conjunctival defects, as an alternative to heterotopic or allogenic grafts.

Assessment of apoptosis by immunohistochemical markers compared to cellular morphology in ex vivo-stressed colonic mucosa

Apoptosis competence is central to the prevention of cancer. Frequency of apoptotic cells, after a sample of colonic tissue is stressed, can be used to gauge apoptosis competence and, thus, possible susceptibility to colon cancer. The gold standard for assessment of apoptosis is morphological evaluation, but this requires an experienced microscopist. Easier-to-use immunohistochemical markers of apoptosis, applicable in archived paraffin-embedded tissue, have been commercially developed. Potentially useful apoptosis markers include cleaved cytokeratin-18 (c-CK18), cleaved caspase-3 (c-cas-3), cleaved lamin A (c-lam-A), phosphorylated histone H2AX (gammaH2AX), cleaved poly(ADP ribose) polymerase (c-PARP), and translocation of apoptosis-inducing factor (AIF). When tissue samples from freshly resected colon segments were challenged ex vivo with the bile acid deoxycholate, approximately 50% of goblet cells became apoptotic by morphologic criteria. This high level of morphologic apoptosis allowed quantitative comparison with the usefulness and specificity of immunohistochemical markers of apoptosis. The antibody to c-CK18 was almost as useful and about as specific as morphology for identifying apoptotic colonic epithelial cells. Antibodies to c-cas-3, c-lam-A, and gammaH2AX, though specific for apoptotic cells, were less useful. The antibody to c-PARP, though specific for apoptotic cells, had low usefulness, and the antibody to AIF was relatively nonspecific, under our conditions.

Apoptosis resistance in Barrett's esophagus: ex vivo bioassay of live stressed tissues

BACKGROUND AND AIMS

Barrett's esophagus (BE) is a premalignant lesion of the distal esophagus in which squamous epithelial cells are replaced by metaplastic intestinal-like columnar epithelium that contains goblet cells. The factors that contribute to the progression from normal squamous mucosa to BE, Barrett's dysplasia, and adenocarcinoma are not well understood at the molecular level. Since reflux of bile acids is associated with BE development, we speculate that cells with an apoptosis-resistant phenotype are selected after long-term repeated exposure to pulses of bile acids. This will result in the survival of cells with unrepaired DNA damage, and a consequent increase in genomic instability leading to cancer progression. The major goal of this study is to compare sensitivity to apoptosis induced by the bile acid, deoxycholate (DOC), a known inducer of apoptosis, in normal esophageal squamous epithelium, normal colon epithelium, and BE.

METHODS

Thirteen patients with a confirmed diagnosis of BE and four patients who had undergone clinically indicated colectomy were included in the present study. Freshly obtained biopsies were incubated with control medium or medium supplemented with 1 mM DOC for 3 h and then evaluated for apoptotic changes using transmission electron microscopy and immunohistochemical staining for two apoptotic markers, cleaved caspase 3 and cleaved cytokeratin 18.

RESULTS

Our results indicate that BE is resistant to apoptosis induced by DOC compared to esophageal squamous epithelium and normal colon epithelium. In addition, electron micrographs revealed mitochondrial swelling in squamous epithelial cells treated ex vivo with DOC, which was absent in epithelial cells of BE. Formation of swollen mitochondria is an early marker of apoptotic cell death. Altogether, the data indicate that reduced apoptosis capability in BE tissue may contribute to progression to esophageal adenocarcinoma.

Keratins and skin disorders

The association of keratin mutations with genetic skin fragility disorders is now one of the best-established examples of cytoskeleton disorders. It has served as a paradigm for many other diseases and has been highly informative for the study of intermediate filaments and their associated components, in helping to understand the functions of this large family of structural proteins. The keratin diseases have shown unequivocally that, at least in the case of the epidermal keratins, a major function of intermediate filaments is to provide physical resilience for epithelial cells. This review article reflects on the variety of phenotypes arising from mutations in keratins and the reasons for this variation.

Discriminating expression of differentiation markers evolves in transplants of benign and malignant human skin keratinocytes through stromal interactions

Accumulating evidence indicates a decisive role for the adjacent stroma in tumour growth and dissemination. However, it is not clear how far altered differentiation such as expression of aberrant keratins and vimentin, common in invasive human carcinomas, may reflect intrinsic cell properties or a response to the tumour environment. We have addressed this by transplanting benign and malignant human HaCaT-ras keratinocytes, seeded on collagen matrix, onto nude mice. Initially, epithelia derived from benign and malignant cells, being separated from host stroma by collagen, were poorly organized and exhibited the same differentiation markers, as identified by immunofluorescence and in situ hybridization. Epidermal basal and suprabasal keratins were expressed persistently even upon contact with newly formed stroma and malignant cell invasion. In contrast, non-epidermal keratins (K4/K13, K8/18, K19), which were similarly synthesized by benign and malignant cells in culture and in early transplants, were differentially regulated with increasing stromal vicinity. While both proteins and mRNAs were downregulated in benign epithelia, the malignant, invasive tumour cells continuously expressed these non-epidermal keratins throughout (K19), suprabasally (K4/13) or at invasive sites (K8/18). Furthermore, the mesenchymal protein vimentin was expressed de novo in invasive areas confronting tumour stroma. Thus, atypical tissue markers, similarly synthesized in isolated cells in vitro, are downregulated in benign but maintained and upregulated in malignant epithelia. This is presumably caused by the neighbouring stroma being permanently activated by malignant epithelia.

Establishment and characterization of clonal cell lines from the vagina of p53-deficient young mice

Clonal cell lines have been established from vagina of prepubertal female p53(-/-) mice. Because the mouse vagina has a dual origin (the cranial three-fifths derived from the Müllerian duct and the caudal two-fifths derived from the urogenital sinus), both parts were separately subjected to cloning. Sixteen epithelial and two fibroblastic cell lines were established from the cranial three-fifths (Müllerian vagina group), and four epithelial and three fibroblastic cell lines were established from the caudal two-fifths (sinus vagina group). They were maintained in Dulbecco's modified Eagle medium and Ham's nutrient mixture F-12 containing 10% fetal calf serum and 17 beta-estradiol at 10(-8) M. Two cell lines (one epithelial and one fibroblastic) were examined using soft agar assay, but no colonies were formed. The doubling time of the cell lines was approximately 24 h, and all of them divided more than 200 times without crisis, suggesting that they were immortalized. All epithelial cell lines expressed cytokeratin 8. However, the epithelial cell lines expressed cytokeratin 14 and cytokeratin 10 when exposed to medium containing different concentrations of Ca(2+). Fibroblastic cell lines expressed vimentin. All epithelial and fibroblastic cell lines expressed estrogen receptor-alpha protein. This is the first successful establishment of clonal cell lines from the normal mouse vagina, and these lines may provide good models in vitro of the vagina for the study of the mechanism of estrogen action.

Detection of cytokeratins in normal and malignant laryngeal epithelia by means of reverse transcriptase-polymerase chain reaction

Cytokeratins (CKs) are a subgroup of intermediate filament proteins that take part in forming the cytoskeleton. The epithelial cells in different organs express distinct CKs, and this expression may be modified during malignant transformation. Here we describe the use of reverse transcriptase-polymerase chain reaction followed by Southern blotting to determine the profile of expression of CKs in both normal and malignant laryngeal samples. Thirty-six samples were subjected to histologic examination and classified as 17 squamous cell carcinomas, 3 dysplastic lesions, and 16 normal samples. CK8 and CK19 were expressed in almost all samples, both cancerous and normal, and were therefore used to verify the integrity of RNA. Expression of CK2, CK9, and CK20 was not detected in any of the samples, normal or cancerous. CK15 and CK18 showed low sensitivity for detection of cancer (36.4% and 45.5%, respectively). CK10 showed relatively high sensitivity (91%), but only moderate specificity (69.2%). Only CK17 showed both high sensitivity and specificity (91% and 92.3%, respectively; positive predictive value, 91%). We propose that CK17 may be considered a promising candidate to use as a molecular marker for malignant transformation in laryngeal squamous cell carcinoma.

Porphyromonas gingivalis fimbriae bind to cytokeratin of epithelial cells

The adherence of Porphyromonas gingivalis to host cells is likely a prerequisite step in the pathogenesis of P. gingivalis-induced periodontal disease. P. gingivalis binds to and invades epithelial cells, and fimbriae are shown to be involved in this process. Little is known regarding epithelial receptor(s) involved in binding of P. gingivalis fimbriae. Using an overlay assay with purified P. gingivalis fimbriae as a probe, two major epithelial cell proteins with masses of 50 and 40 kDa were identified by immunoblotting with fimbria-specific antibodies. Iodinated purified fimbriae also bound to the same two epithelial cell proteins. An affinity chromatography technique was utilized to isolate and purify the epithelial components to which P. gingivalis fimbriae bind. Purified fimbriae were coupled to CNBr-activated Sepharose-4B, and the solubilized epithelial cell extract proteins bound to the immobilized fimbriae were isolated from the column. A major 50-kDa component and a minor 40-kDa component were purified and could be digested with trypsin, suggesting that they were proteins. These affinity-eluted 50- and 40-kDa proteins were then subjected to amino-terminal sequencing, and no sequence could be determined, suggesting that these proteins have blocked amino-terminal residues. CNBr digestion of the 50-kDa component resulted in an internal sequence homologous to that of Keratin I molecules. Further evidence that P. gingivalis fimbriae bind to cytokeratin molecule(s) comes from studies showing that multicytokeratin rabbit polyclonal antibodies cross-react with the affinity-purified 50-kDa epithelial cell surface component. Also, binding of purified P. gingivalis fimbriae to epithelial components can be inhibited in an overlay assay by multicytokeratin rabbit polyclonal antibodies. Furthermore, we showed that biotinylated purified fimbriae bind to purified human epidermal keratin in an overlay assay. These studies suggest that the surface-accessible epithelial cytokeratins may act as receptor(s) for P. gingivalis fimbriae. We hypothesize that adherence of P. gingivalis fimbriae to cytokeratin may be important for colonization of oral mucous membranes and possibly also for activation of epithelial cells.

Cytokeratins as markers of follicular differentiation: an immunohistochemical study of trichoblastoma and basal cell carcinoma

Trichoblastoma(s) (TB) are benign neoplasms of follicular differentiation frequently found in nevus sebaceus. Many morphologic features are shared with nodular basal cell carcinoma(s) (BCC), sometimes rendering the differential diagnosis difficult. Because both neoplasms can simulate components of mature hair follicles histologically, we attempted to corroborate this by immunohistochemical examination of cytokeratins and hair keratins differentially expressed in the hair follicle. Trichoblastoma(s) and BCC showed homogenous expression of CK14 and CK17. The innermost cells of the tumor nodules in all TB and in 72% of BCC were positive for CK6hf. Using a specific CK15 antibody, 38% of TB showed a focal labeling and all BCC remained negative; 70% of TB and 22% of BCC expressed CK19. CK8 was expressed by numerous Merkel cells present in all TB but in none of the BCC examined. All type I and II hair keratins tested, (especially hHa1, hHa5, and hHa8) remained negative in all tumors examined. Trichoblastoma(s) and BCC show consistent expression of CK6hf, CK14, and CK17; variable expression of CK15 and CK19; and absence of hair keratins. This indicates a differentiation toward the outer root sheath epithelium or the companion layer and not toward the inner root sheath, matrix, or cortex.

Expression of p53-related protein p63 in the gastrointestinal tract and in esophageal metaplastic and neoplastic disorders

p63 is a p53-related DNA-binding protein that helps regulate differentiation and proliferation in epithelial progenitor cells. Its expression has never been evaluated in the human gastrointestinal tract. The aim of this study was to evaluate the expression of p63 in the esophagus and related metaplastic and neoplastic disorders to gain insight into the pathogenesis of these processes. Of particular interest was the expression of p63 in Barrett esophagus (BE) and in BE-associated multilayered epithelium. Multilayered epithelium has been postulated to represent an early precursor to the development of BE primarily because it shares morphologic and immunophenotypic features of both squamous and columnar epithelium, and has been shown prospectively to be highly associated with BE. Routinely processed mucosal biopsy or resection specimens that contained normal esophageal squamous epithelium (n = 20), squamous dysplasia (n = 4), squamous cell carcinoma (n = 7), BE (n = 10), BE-associated multilayered epithelium (n = 13), esophageal mucosal gland ducts (n = 10), BE-associated dysplasia (n = 12), and BE-associated adenocarcinoma (n = 7) were immunostained for p63 to determine the extent and location of staining. p63 staining was compared with the staining patterns observed for p53, Ki 67 (proliferation marker), and cytokeratins (CKs) 13 (squamous marker), 14 (basal squamous marker), 8/18 (columnar marker), and 19 (basal/columnar marker). Expression of p63 messenger RNA (mRNA) isoforms was also analyzed by reverse-transcription polymerase chain reaction of freshly isolated tissues. In the normal esophagus, p63 was expressed in the basal and suprabasal layers of the squamous epithelium and in basal cells that line the mucosal gland ducts but was negative in all other epithelia of the gastrointestinal tract, including the stomach, small intestine, and colon. Similarly, p63 was not expressed in BE, but it, was present in the basal layer of multilayered epithelium in 9 of 13 cases (69%). p63-positive cells in multilayered epithelium and in the mucosal gland duct epithelium were positive for CK8/18 (100%) and CK13 (67% and 30%, respectively) and negative for CK14 (0%), in contrast to p63-positive cells in squamous epithelium, which were positive for CK14 and CK13 (100%) but negative for CK8/18. In neoplastic tissues, p63 was diffusely expressed in all cases of esophageal squamous cell dysplasia and carcinoma but was negative in all cases of esophageal and colorectal adenocarcinoma. The DeltaN isoform of p63 mRNA predominated in all benign and neoplastic squamous tissues examined. p63 may represent a marker of 2 distinct epithelial progenitor cells (basal squamous epithelium and gland duct epithelium) in the esophagus. P63 is upregulated in squamous neoplastic conditions and in this manner may play a role in squamous carcinogenesis. These data also indicate that multilayered epithelium is phenotypically similar to, and may share a lineage relationship with, mucosal gland duct epithelium.

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.

Epithelial structural proteins of the skin and oral cavity: function in health and disease

Epithelial tissues function to protect the organism from physical, chemical, and microbial damage and are essential for survival. To perform this role, epithelial keratinocytes undergo a well-defined differentiation program that results in the expression of structural proteins which maintain the integrity of epithelial tissues and function as a protective barrier. This review focuses on structural proteins of the epidermis and oral mucosa. Keratin proteins comprise the predominant cytoskeletal component of these epithelia. Keratin filaments are attached to the plasma membrane via desmosomes, and together these structural components form a three-dimensional array within the cytoplasm of epithelial cells and tissues. Desmosomes contain two types of transmembrane proteins, the desmogleins and desmocollins, that are members of the cadherin family. The desmosomal cadherins are linked to the keratin cytoskeleton via several cytoplasmic plaque proteins, including desmoplakin and plakoglobin (gamma-catenin). Epidermal and oral keratinocytes express additional differentiation markers, including filaggrin and trichohyalin, that associate with the keratin cytoskeleton during terminal differentiation, and proteins such as loricrin, small proline-rich proteins, and involucrin, that are cross-linked into the cornified envelope by transglutaminase enzymes. The importance of these cellular structures is highlighted by the large numbers of genetic and acquired (autoimmune) human disorders that involve mutations in, or autoantibodies to, keratins and desmosomal and cornified envelope proteins. While much progress has been made in the identification of the structural proteins and enzymes involved in epithelial differentiation, regulation of this process is less clear. Both calcium and retinoids influence epithelial differentiation by altering the transcription of target genes and by regulating activity of enzymes critical in epithelial differentiation, such as transglutaminases, proteinases, and protein kinases. These studies have furthered our understanding of how epithelial tissue and cell integrity is maintained and provide a basis for the future treatment of skin and oral disorders by gene therapy and other novel therapeutics.

Cytokeratins 8 and 19 in the mouse placental development

To investigate the expression and biological roles of cytokeratin 19 (K19) in development and in adult tissues, we inactivated the mouse K19 gene (Krt1-19) by inserting a bacterial beta-galactosidase gene (lacZ) by homologous recombination in embryonic stem cells, and established germ line mutant mice. Both heterozygous and homozygous mutant mice were viable, fertile, and appeared normal. By 7.5-8.0 days post coitum (dpc), heterozygous mutant embryos expressed lacZ in the notochordal plate and hindgut diverticulum, reflecting the fact that the notochord and the gut endoderm are derived from the axial mesoderm-originated cells. In the adult mutant, lacZ was expressed mainly in epithelial tissues. To investigate the possible functional cooperation and synergy between K19 and K8, we then constructed compound homozygous mutants, whose embryos died approximately 10 dpc. The lethality resulted from defects in the placenta where both K19 and K8 are normally expressed. As early as 9. 5 dpc, the compound mutant placenta had an excessive number of giant trophoblasts, but lacked proper labyrinthine trophoblast or spongiotrophoblast development, which apparently caused flooding of the maternal blood into the embryonic placenta. These results indicate that K19 and K8 cooperate in ensuring the normal development of placental tissues.

Group B streptococci and other gram-positive cocci bind to cytokeratin 8

Group B streptococci (GBS) adhere to surface receptors present on epithelial cells; these receptors include fibronectin and laminin. To identify other possible receptors, plasma membranes from A549 cells, a respiratory tract epithelial cell line, were prepared. These plasma membranes were tested in a protein blot analysis using radiolabeled GBS as a probe. GBS adhered to two species, with molecular masses of 50 kDa (p50) and 57 kDa (p57). We concluded that p50 and p57 correspond to two forms of cytokeratin 8 (CK8) on the basis of the following results: (i) protein blot results demonstrated that p50 and p57 exactly comigrated with two forms of CK8 after separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE); (ii) p50 and p57 exactly comigrated with CK8 after separation by two-dimensional PAGE; (iii) CK8 in solution bound to GBS, as demonstrated by immunoblot analysis of proteins from A549 lysates that bound to GBS in a liquid-phase assay; and (iv) radiolabeled GBS bound to A549 lysate-derived CK8 that had been captured in anti-CK8-coated microtiter wells. CK8 bound to COH1-13, an acapsular mutant of COH1, demonstrating that adherence is not mediated by capsular polysaccharide. Trypsin-treated GBS did not bind to CK8, indicating that adherence is mediated via a protein on the surface of GBS. Soluble CK8 bound to six of six GBS strains tested. Soluble CK8 also bound to Staphylococcus aureus, Lactococcus lactis, Enterococcus faecalis, and Streptococcus pyogenes. We hypothesize that adherence of GBS to cytokeratin may be important for maintenance of colonization at sites of keratinized epithelium, such as the vagina, or for adherence of these bacteria to damaged epithelial cells at other sites.

Blood-group-related carbohydrates are expressed in organotypic cultures of human skin and oral mucosa

Cellular maturation and migration are usually associated with changes in cell-surface carbohydrates, but the relationship between these changes and cell behaviour is at present largely unknown. To investigate whether an organotypic culture system can be used as an in vitro model to study the function of cell-surface carbohydrates, we established organotypic cultures of skin and buccal mucosa. In these cultures, keratinocytes are grown at the air-liquid interface on a supporting matrix consisting of homologous fibroblasts embedded in a collagen type I gel. We examined the expression of blood-group-related carbohydrate structures, including Lewis x, sialylated Lewis x, Lewis y, Lewis a, and Lewis b, on the surface of epithelial cells in the cultures. We compared the results with the expression of more well-established markers, including cytokeratins, integrins, bullous pemphigoid antigen and laminin, in the same cultures. The organotypic skin and oral mucosa cultures showed a histological differentiation pattern analogous to that of normal skin and buccal mucosa, and a tissue-specific expression of carbohydrate structures and cytokeratins. However, both types of organotypic cultures also expressed markers which are normally seen during wound healing, including Lewis y, cytokeratin 16, and cytokeratin 19. We conclude that the organotypic cultures of oral mucosa and skin are suitable models for future studies of the function of cell-surface carbohydrates, although the expression of wound healing markers has to be taken into consideration.

Forms of epithelial differentiation of draining sinus in acne inversa (hidradenitis suppurativa)

The draining sinus is a late complication of several forms of severe acne, leading to extensive, periodically inflamed lesions that are undermined by a system of fistulas, supposed to be of follicular origin. We investigated the expression of various cytokeratins (CKs) and desmosomal proteins in the draining sinus of acne inversa (hidradenitis suppurativa) using monoclonal antibodies in immunohistochemistry on paraffin-embedded sections. We were able to define three different phenotypes of stratified squamous epithelia covering the sinus tracts. Type I epithelium was cornifying and characterized by the presence of CK 10, desmogleins 1-3 and desmocollins 1-3 in an epidermis-like pattern. Type II epithelium was non-cornifying, negative for CK 10 and positive for CK 13. It was negative for desmocollin 1 but strongly immunopositive for desmoglein 1 suprabasally and for desmoglein 2 in the basal cells. Type III epithelium was non-cornifying and strongly inflamed. It was marked by the presence of CK 7, CK 19 and desmoglein 2 and the absence of CK 10, desmoglein 1 and desmocollin 1. In both type II and III epithelium, desmoglein 3, desmocollin 2 and desmocollin 3 showed an inverted staining pattern as compared with normal epidermis and type I epithelium. Desmoglein 2 and CK 5/14 always remained restricted to the basal cell layer. Antibodies against CK 6 and CK 13/15/16 were immunopositive in all three phenotypes and CK 17 was predominantly immunolocalized to suprabasal layers of type II and III epithelium. The three phenotypes are characterized as pathological stratified squamous epithelia reflecting the dynamic process of inflammation, proliferation and stratification taking place in acne inversa.

180-kD bullous pemphigoid antigen/type XVII collagen: tissue-specific expression and molecular interactions with keratin 18

The 180-kD bullous pemphigoid antigen (BPAG2) is a hemidesmosomal transmembrane protein, also known as type XVII collagen. In this study, potential interactions of BPAG2 with other proteins expressed in epidermal keratinocytes were explored by yeast two-hybrid system using the amino-terminal intracellular domain of BPAG2 as a bait. Several independent interacting clones encoding keratin 18 (K18) were identified when the keratinocyte cDNA library, cloned into the yeast two-hybrid activation domain vector, was screened. The peptide sequence responsible for the interaction of BPAG2 was restricted to amino acids 15-25, and substitution of a valine residue in the middle of this sequence by a proline (V23P) by site-directed mutagenesis abolished the interaction. Further examination of the K18 sequences by restricted cDNA constructs in yeast two-hybrid system identified a carboxyl-terminal segment corresponding to helix 2B domain as critical for BPAG2 binding. The interaction of BPAG2/K18 was confirmed by an in vitro protein-protein interaction assay, which also confirmed that normal human keratinocytes express K18 in culture. The tissue specific expression of BPAG2 was first examined using a multi-tissue RNA blot. Human multiple tissue cDNA panels representing a variety of adult and fetal tissues as well as tumor cells were used as PCR-templates to study the expression patterns of both BPAG2 and K18. The results demonstrated significant level of expression of BPAG2, besides in epidermal keratinocytes, also in a variety of tissues with predominant epithelial component, such as mammary, salivary and thyroid glands, colon, prostate, testis, placenta, and adult and fetal thymus, as well as in colon, pancreatic and prostatic adenocarcinoma cell lines, and an ovarian carcinoma. As expected, K18 transcript is present in liver, pancreas, colon, placenta, and in fetal kidney. Collectively, the results suggest that BPAG2 has a relatively broad tissue distribution including specialized and simple epithelia, and that within the tissues such as colon and placenta, BPAG2 may have direct interactions with K18, a keratin characteristically expressed in a simple epithelia.

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 expression patterns in the rat respiratory tract as markers of epithelial differentiation in inhalation toxicology. I. Determination of normal cytokeratin expression patterns in nose, larynx, trachea, and lung

Cytokeratin (CK) polypeptides constitute the intermediate filament cytoskeleton of epithelial cells. The patterns of CK expression can be regarded as specific markers for the epithelial differentiation status. Our objective was to map the cell type-specific CK expression patterns at all representative sites of the respiratory tract of untreated rats to use as a base for the detection of inhalation exposure-related differentiation changes. Using routine paraffin-embedded sections and a panel of well-characterized monoclonal antibodies for immunohistochemistry, we obtained CK staining patterns as follows. Nasal cavity: respiratory epithelium CK18, CK19 (basal, ciliated, nonciliated cells), CK14, and/or CK15 (basal and nonciliated cells); olfactory epithelium CK18 (basal, mid, apical zones and Bowman's glands), CK14, and CK15 (basal zone); squamous epithelium of ventral meatus CK14, CK15 (basal and suprabasal cells), CK1, 10/11, and CK13 (suprabasal cells); glands and columnar epithelia of vomeronasal organ and nasolacrimal duct CK7 and CK13 in addition to respiratory epithelial CK pattern. Trachea: similar to nasal respiratory epithelium with pronounced CK15 and additional CK7. Larynx: CK14, CK15 (basal, ciliated, nonciliated cells), CK8, CK18, CK19 (not in basal cells), CK4, and CK13 (cuboidal and squamoid cells of ventral half). Lung: bronchial epithelium CK14 and CK15 (basal cells only); bronchial and alveolar epithelium CK7, CK8, CK18, and CK19; bronchiolar epithelium similar but less CK8 and no CK7; pleural mesothelium CK7, CK8, and CK19. This inventory of complex CK expression patterns provides the basis for investigating test substance-related effects in inhalation toxicology, e.g., cigarette smoke-induced changes.

Immunocytochemical identification of different cell types in bovine nasolabial glands with particular emphasis on cytoskeletal protein expression

Nasolabial glands are serous glands forming a thick subcutaneous layer in the bovine muzzle. In order to identify the different epithelial cell types, both immunofluorescent and immunoperoxidase techniques were employed on frozen and fixed sections using monoclonal antibodies to cytoskeletal proteins and S-100. Actin was also detected with phalloidin. The results show that four cell types can be identified on the ground of the different composition of the cytoskeletal filaments: acinar, basket, luminal duct and basal duct cells. Acinar, luminal duct cells and basal duct cells express different patterns of cytokeratins, as shown by the 12 anti-cytokeratin monoclonal antibodies used, and both basket cells and the basal cells of intercalated ducts are also reactive to phalloidin and anti-alpha-smooth muscle actin monoclonal antibody. The presence of actin supports the conclusion that basal duct cells are also contractile elements, i.e. myoepithelial cells. Vimentin, glial fibrillary acidic protein (GFAP), and S-100, molecules considered to be markers of myoepithelial cells by many AA., were not found. The intermediate filaments of the duct epithelium appear more complex and heterogeneous in comparison with those present in the acinar cells.

5-Lipoxygenase expression in Langerhans cells of normal human epidermis

We studied expression of the 5-lipoxygenase (5-LO) pathway in normal human skin. In situ hybridization revealed a 5-LO mRNA-containing epidermal cell (EC) population that was predominantly located in the midportion of the spinous layer, in outer hair root sheaths, and in the epithelial compartment of sebaceous glands. Examination of skin specimens by immunohistochemistry and of primary ECs by flow cytometry mapped the 5-LO protein exclusively to Langerhans cells (LCs). The LC 5-LO protein was largely found in the nuclear matrix, in nuclear envelopes, and perinuclear regions as indicated by in situ confocal laser scan microscopy. Reverse transcription-PCR and immunoblot analyses of purified primary EC populations further indicated that LCs are major 5-LO expressing cells. Enriched primary LCs were also found to contain 5-LO activating protein (FLAP), leukotriene (LT) C4 synthase, and LTA4 hydrolase. By contrast, 5-LO, FLAP, and LTC4 synthase were undetectable or largely reduced, but LTA4 hydrolase transcripts and protein were identified in ECs depleted of LCs. These data show that naive LCs are major, and possibly the sole, 5-LO pathway expressing cells in the normal human epidermis.

In situ hybridization study of cytokeratin 4, 13, 16 and 19 mRNAs in human developing junctional epithelium

Cytokeratins (CKs) are now considered to be reliable markers for following the development and differentiation of epithelial tissue. We have investigated the pathway of differentiation in human developing junctional epithelium using monoclonal antibodies and two-dimensional gel electrophoresis of microdissected tissue to identify CK 19, CK 16, CK 14, CK 13, CK 6, CK 5, CK 4 in the junctional epithelium (JE) over partially erupted human teeth. The CK profile was similar to that of developing oral epithelia, suggesting that the junctional epithelium in teeth during eruption is of odontogenic origin. The present study used in situ hybridization to determine the distribution of the mRNAs of CKs 19, 16, 13 and 4 in human developing junctional epithelium and to examine the correlation between mRNAs and their encoded proteins. CK 19 mRNA was abundant in the basal cell layers of the primary junctional epithelium (PJE) but less concentrated in the suprabasal layers. CK16, 13 and 4 mRNAs were abundant in the basal cell layers of the PJE. The parabasal cell layers reacted intensely to the cRNA probe complementary to CK16 mRNA, as were the reactions in the suprabasal cell layers of the PJE for the CK 13 and 4 probes. Our results demonstrate that the PJE express the genes encoding for CKs 16 and 4 that have been revealed previously only by electrophoresis. They therefore confirm that the PJE is a well-differentiated stratified epithelium with a complex unique phenotype that produces CKs specific for basal cells (CK 19), CKs associated with hyperproliferation (CK 16), and finally those associated with stratification (CKs 4 and 13). Only synthesis of CK 19 protein and mRNA are strictly parallel. CKs 4 and 13 mRNAs are present in basal and suprasal cells, while their encoded proteins were not, except for CK 13 in suprabasal cell layers of PJE, where the amount of its mRNAs was coincident with the expression of the protein.

Effects of acetaldehyde on cell regeneration and differentiation of the upper gastrointestinal tract mucosa

BACKGROUND

The tumor-promoting effect of ethanol on cancer of the upper respiratory-digestive tract is not well understood. Although ethanol itself is not carcinogenic, the first product of ethanol metabolism-acetaldehyde is. Acetaldehyde can be produced from ethanol by oral bacteria, and high concentrations have been observed in human saliva after ethanol consumption. The purpose of this study was to investigate whether acetaldehyde administered orally to rats induces altered differentiation and proliferation in the animals' upper gastrointestinal tracts.

METHODS

Twenty Wistar rats were given either water containing acetaldehyde at a concentration of 120 mM or tap water to drink for 8 months. Tissue specimens were then taken from the tongue, epiglottis, and forestomach of each animal and immunohistochemically stained for markers of cellular proliferation (Ki67 nuclear antigen) or differentiation (cytokeratins 1, 4, 10, 11, 14, and 19). The mean epithelial thickness of each sample was measured via light microscopy, using an eyepiece containing grid lines. Differences between the control and acetaldehyde-treated groups were analyzed by use of the unpaired Student's t test. All reported P values are two-sided.

RESULTS

Although no tumors were observed, staining for cytokeratins 4 and 14 revealed an enlarged basal layer of squamous epithelia in the rats receiving acetaldehyde. In these animals, cell proliferation was significantly greater than that observed in the control animals for samples from the tongue (P<.0001), epiglottis (P<.001), and forestomach (P<.0001). In addition, the epithelia from acetaldehyde-treated rats were significantly thicker than in epithelia from control animals (P<.05 for all three sites).

CONCLUSIONS

Acetaldehyde, administered orally to rats, can cause hyperplastic and hyperproliferative changes in epithelia of the upper gastrointestinal tract. This finding suggests that microbially produced acetaldehyde in saliva may explain the tumor-promoting effect of ethanol on these epithelia.

The relationship of adamantinomatous craniopharyngioma to ghost cell ameloblastoma of the jaws: a histopathologic and immunohistochemical study

The objective of this investigation was to study the relationship of the ghost cell ameloblastoma (GCA), which is a form of type II calcifying odontogenic cyst (COC), to the adamantinomatous craniopharyngioma (ACP). H&E sections of 26 examples of ACP were compared to three cases of GCA and to the reported microscopic features of that tumor. Clinical records of the ACPs were studied to determine their biologic behavior compared to that of the ameloblastomas. Immunohistochemical studies of nine examples of ACP were performed for KL1 (high mol.wt cytokeratins), 5D3 (low mol.wt cytokeratins) and involucrin (characteristic of terminally differentiated keratinocytes) using the peroxidase-antiperoxidase method. The results were compared with those reported for COC and ameloblastoma. ACP and GCA exhibited similar microscopic features, including pre-ameloblasts, tissue resembling stellate reticulum, ghost cells and calcifications; both tumors grew slowly and were invasive. ACP and COC, and by interpolation GCA, exhibited similar features with all three antibodies. The ghost cells did not exhibit any immunoreactivity but the adjacent cells stained positively for involucrin. The immunological features of ACP were similar to those reported in ameloblastomas for squamous differentiation. However, because of their rarity, no ameloblastomas exhibiting keratinization, including ghost cells, have yet been studied with these antibodies. We conclude that ACP and GCA are homologous lesions.

Histomorphological and biochemical differentiation capacity in organotypic co-cultures of primary gingival cells

To establish a three-dimensional in vitro test system mimicking the physiological situation of the oral cavity, organotypic co-cultures consisting of primary gingival cells on a collagen matrix with fibroblasts were generated. The histomorphological development after 7 and 14 d revealed close similarity with the non-keratinized gingiva epithelium. Furthermore, as epithelial specific markers synthesis and localization of keratins as well as the deposition of basement membrane components were assessed on frozen sections by immunofluorescence and keratin expression by in situ hybridization. Primary keratinocytes in conventional culture strained positive for keratin K14 and the mucosal differentiation-specific keratins K4 and K13, while primary fibroblasts, isolated from the same tissue source, and also some keratinocytes, were positive for vimentin. In organotypic co-cultures the keratinocytes formed a multilayered epithelium within 14 d containing basal cells and flattened cells in the uppermost layers. Comparable to native non-keratinized gingiva keratin 14 gene expression was clearly detectable in the basal cell compartment but showed extending immunolocalization. In addition, particularly at the early stage (7 d), basally located keratinocytes were also vimentin positive. According to morphological differentiation K4 and K13 were detectable in suprabasal position a the RNA and protein level. The major basement membrane constituents collagen type IV and laminin increased with time revealing first an interrupted and later a fully extended staining underneath the basal cells. Maintenance of basal cell function was further demonstrated by cell proliferation (BrdU incorporation) which was initially high (7 d) but declined towards the later stages (14-21 d). The results demonstrate i) that this co-culture system leads to a stratified surface epithelium with morphological and biochemical characteristics of the non-keratinized gingiva epithelium and ii) that a state of physiological tissue balance was reached, thus rendering a suitable model for tissue compatibility studies.