Distribution of intermediate-filament proteins in the human enamel organ: unusually complex pattern of coexpression of cytokeratin polypeptides and vimentin

Vimentin Localization in the Zebrafish Oral Cavity: A Potential Role in Taste Buds Regeneration

The morphology of the oral cavity of fish is related to their feeding habits. In this context, taste buds are studied for their ability to catch chemical stimuli and their cell renewal capacity. Vimentin RV202 is a protein employed as a marker for mesenchymal cells that can differentiate along different lineages and to self-renew, while Calretinin N-18 is employed as a marker of sensory cells, and ubiquitin is a protein crucial for guiding the fate of stem cells throughout development. In this study, a surface morphology investigation and an immunohistochemical analysis have been conducted. The results of the present study reveal, for the first time, the presence of Vimentin RV202 in a taste bud cell population of zebrafish. Some taste bud cells are just Vimentin RV202-immunoreactive, while in other cells Vimentin RV202 and Calretinin N-18 colocalize. Some taste buds are just reactive to Calretinin N-18. Vimentin RV202-immunoreactive cells have been observed in the connective layer and in the basal portion of the taste buds. The immunoreactivity of ubiquitin was restricted to sensory cells. Further studies are needed to elucidate the role of Vimentin RV202 in the maturation of taste bud cells, its potential involvement in the regeneration of these chemosensory organs, and its eventual synergic work with ubiquitin.

Alterations in Circulating Bile Acids in Metabolic Dysfunction-Associated Steatotic Liver Disease: A Systematic Review and Meta-Analysis

Background: Previous studies have suggested that bile acids (BAs) may participate in the development and/or progression of metabolic dysfunction-associated steatotic liver disease (MASLD). The present study aimed to define whether specific BA molecular species are selectively associated with MASLD development, disease severity, or geographic region. Methods: We comprehensively identified all eligible studies reporting circulating BAs in both MASLD patients and healthy controls through 30 July 2023. The pooled results were expressed as the standard mean difference (SMD) and 95% confidence interval (CI). Subgroup, sensitivity, and meta-regression analyses were performed to address heterogeneity. Results: Nineteen studies with 154,807 individuals were included. Meta-analysis results showed that total BA levels in MASLD patients were higher than those in healthy controls (SMD = 1.03, 95% CI: 0.63-1.42). When total BAs were divided into unconjugated and conjugated BAs or primary and secondary BAs, the pooled results were consistent with the overall estimates except for secondary BAs. Furthermore, we examined each individual BA and found that 9 of the 15 BAs were increased in MASLD patients, especially ursodeoxycholic acids (UDCA), taurococholic acid (TCA), chenodeoxycholic acids (CDCA), taurochenodeoxycholic acids (TCDCA), and glycocholic acids (GCA). Subgroup analysis revealed that different geographic regions or disease severities led to diverse BA profiles. Notably, TCA, taurodeoxycholic acid (TDCA), taurolithocholic acids (TLCA), and glycolithocholic acids (GLCA) showed a potential ability to differentiate metabolic dysfunction-associated steatohepatitis (MASH) (all p < 0.05). Conclusions: An altered profile of circulating BAs was shown in MASLD patients, providing potential targets for the diagnosis and treatment of MASLD.

Adenomatoid odontogenic tumor: evidence for a mixed odontogenic tumor

OBJECTIVE

Adenomatoid odontogenic tumor (AOT) was classified by the World Health Organization as a mixed odontogenic tumor in 1992 and reclassified without a clear rationale as an epithelium-only tumor in 2005. The purpose of this study was to investigate if there was any evidence to suggest AOT might be a mixed odontogenic tumor.

STUDY DESIGN

Immunohistochemical studies with nestin, dentin sialophosphoprotein (DSPP), cytokeratin, and vimentin were performed using 21 cases of AOT, and the staining results were analyzed according to the various morphologic patterns seen in AOT. Sirius red stain was used to detect the presence of collagen types I and III in AOT products.

RESULTS

Our results showed that 20 of 21 (95.23%), 0 of 21 (0%), 21 of 21 (100%), and 20 of 21 (95.23%) cases expressed nestin, DSPP, cytokeratin, and vimentin, respectively. Some cells in rosette/duct-like structures (RDSs) expressed nestin, vimentin, or both, without cytokeratin. Coexpression of vimentin and cytokeratin or of nestin, cytokeratin, and vimentin was noted in some cells. Sirius red staining was positive in eosinophilic products in RDSs, double-layered spheres, and dentinoids.

CONCLUSION

Although most AOT cells appear epithelial, there is a small population of cells expressing mesenchymal proteins and secreting collagen types I and III. This evidence suggests that AOT is a mixed odontogenic tumor.

Ameloblastic carcinoma in horses: case report and literature review

Ameloblastic carcinoma is a malignant odontogenic neoplasm that has been reported only rarely in veterinary species. A 16-y-old Arabian crossbred mare was presented for evaluation of a hard mass on the body of the mandible, with evidence of osteolysis on radiographs. Incisional biopsies revealed an invasive neoplasm comprised of spindloid epithelial cells with a high mitotic count and partial dual cytokeratin-vimentin immunoreactivity. The horse was euthanized because of rapid tumor progression 3 mo after presentation. Postmortem evaluation revealed partial obliteration of the mandible by a large, firm-to-hard, tan, locally destructive and invasive mass with no gross or histologic evidence of metastasis. Postmortem histology revealed a poorly differentiated epithelial neoplasm with variably prominent features suggestive of odontogenic histogenesis: a plexiform ribbon architecture, infrequent basilar palisading with antibasilar nuclei, rare basilar cytoplasmic clearing, subepithelial matrix hyalinization, and partial dual cytokeratin-vimentin immunoreactivity. Features of malignancy included regions of necrosis, pronounced cellular atypia, a high mitotic count, extensive tissue invasion and local tissue destruction, and extension of neoplastic cells beyond the margins of the mandibular bone. Collectively, these features are most consistent with mandibular ameloblastic carcinoma. Including our case described here, ameloblastic carcinoma has been reported in only 5 horses. The microscopic features reported most consistently are dual cytokeratin-vimentin immunoreactivity, a high mitotic count, and basilar palisading. Ameloblastic carcinoma should be considered as a differential diagnosis for rapidly growing, locally invasive masses arising from the dentate jaw of horses.

Bile acids profile, histopathological indices and genetic variants for non-alcoholic fatty liver disease progression

OBJECTIVE

Metabolomic studies suggest plasma levels of bile acids (BAs) are elevated amongst subjects with non-alcoholic fatty liver disease (NAFLD) compared to healthy controls. However, it remains unclear whether or not specific BAs are associated with the clinically relevant transition from nonalcoholic fatty liver (i.e. simple steatosis) to non-alcoholic steatohepatitis (NASH), or enhanced progression of hepatic fibrosis, or genetic determinants of NAFLD/NASH.

METHODS

Among sequential subjects (n=102) undergoing diagnostic liver biopsy, we examined the associations of a broad panel of BAs with distinct histopathological features of NAFLD, the presence of NASH, and their associations with genetic variants linked to NAFLD and NASH.

RESULTS

Plasma BA alterations were observed through the entire spectrum of NAFLD, with several glycine conjugated forms of the BAs demonstrating significant associations with higher grades of inflammation and fibrosis. Plasma 7-Keto-DCA levels showed the strongest associations with advanced stages of hepatic fibrosis [odds ratio(95% confidence interval)], 4.2(1.2-16.4), NASH 24.5(4.1-473), and ballooning 18.7(4.8-91.9). Plasma 7-Keto-LCA levels were associated with NASH 9.4(1.5-185) and ballooning 5.9(1.4-28.8). Genetic variants at several NAFLD/NASH loci were nominally associated with increased levels of 7-Keto- and glycine-conjugated forms of BAs, and the NAFLD risk allele at the TRIB1 locus showed strong tendency toward increased plasma levels of GCA (p=0.02) and GUDCA (p=0.009).

CONCLUSIONS

Circulating bile acid levels are associated with histopathological and genetic determinants of the transition from simple hepatic steatosis into NASH. Further studies exploring the potential involvement of bile acid metabolism in the development and/or progression of distinct histopathological features of NASH are warranted.

Primordial odontogenic tumor: a case report and literature review

Background

A primordial odontogenic tumor (POT) is a rare, benign, mixed epithelial and mesenchymal odontogenic tumor that has been included as a new entity in the latest World Health Organization (WHO) classification (2017). POT consists of dental papilla-like myxoid connective tissue covered with a delicate membrane of ameloblastic epithelium. Only 15 cases have been documented worldwide, and here, we report the sixteenth case and the first one of South Korea.

Case presentation

An asymptomatic lesion was discovered as an incidental radiographic finding in a 10-year-old boy. The patient had no complaints about the lesion. Cone-beam computerized tomograms revealed a round cavity with a defined cortical border measuring approximately 5 × 5 × 5 mm in size. The lesion was a POT. The patient was treated with enucleation. The tumor showed no recurrence for one year.

Conclusion

This is the first report of POT in South Korea using the novel diagnosis of POT after it was recognized and defined in the latest WHO classification. This novel diagnosis will be useful for pathologists and clinicians in diagnosing and differentiating this new and rare disease from other odontogenic tumors.

Primordial Odontogenic Tumor: A case report with histopathological analyses

Primordial odontogenic tumor (POT) is a benign mixed epithelial and mesenchymal odontogenic tumor included into the current World Health Organization (WHO) classification of Head and Neck tumours in 2017. As far as the authors have confirmed, only eight cases of this tumor have been reported so far. This paper reports a case of POT that occurred in the right mandible of a 5-year-old patient. Panoramic radiograph showed a well-defined homogeneous radiolucency displacing the unerupted second deciduous molar to the deep part of the mandible. Histopathologically, the tumor was composed of cell-rich mesenchymal tissue with myxoid areas, surrounded by columnar epithelium and non-keratinized cuboidal epithelium in the outer layers. The histopathological diagnosis was POT. The expression patterns of cytokeratins (CK) 14, 18, 19, vimentin and CD34 suggested that the grade of differentiation of the POT was approximately equivalent to that of normal primary tooth germ tissues in cap stage to late bell stage.

Integrative Temporo-Spatial, Mineralogic, Spectroscopic, and Proteomic Analysis of Postnatal Enamel Development in Teeth with Limited Growth

Tooth amelogenesis is a complex process beginning with enamel organ cell differentiation and enamel matrix secretion, transitioning through changes in ameloblast polarity, cytoskeletal, and matrix organization, that affects crucial biomineralization events such as mineral nucleation, enamel crystal growth, and enamel prism organization. Here we have harvested the enamel organ including the pliable enamel matrix of postnatal first mandibular mouse molars during the first 8 days of tooth enamel development to conduct a step-wise cross-sectional analysis of the changes in the mineral and protein phase. Mineral phase diffraction pattern analysis using single-crystal, powder sample X-ray diffraction analysis indicated conversion of calcium phosphate precursors to partially fluoride substituted hydroxyapatite from postnatal day 4 (4 dpn) onwards. Attenuated total reflectance spectra (ATR) revealed a substantial elevation in phosphate and carbonate incorporation as well as structural reconfiguration between postnatal days 6 and 8. Nanoscale liquid chromatography coupled with tandem mass spectrometry (nanoLC-MS/MS) demonstrated highest protein counts for ECM/cell surface proteins, stress/heat shock proteins, and alkaline phosphatase on postnatal day 2, high counts for ameloblast cytoskeletal proteins such as tubulin β5, tropomyosin, β-actin, and vimentin on postnatal day 4, and elevated levels of cofilin-1, calmodulin, and peptidyl-prolyl cis-trans isomerase on day 6. Western blot analysis of hydrophobic enamel proteins illustrated continuously increasing amelogenin levels from 1 dpn until 8 dpn, while enamelin peaked on days 1 and 2 dpn, and ameloblastin on days 1-5 dpn. In summary, these data document the substantial changes in the enamel matrix protein and mineral phase that take place during postnatal mouse molar amelogenesis from a systems biological perspective, including (i) relatively high levels of matrix protein expression during the early secretory stage on postnatal day 2, (ii) conversion of calcium phosphates to apatite, peak protein folding and stress protein counts, and increased cytoskeletal protein levels such as actin and tubulin on day 4, as well as (iii) secondary structure changes, isomerase activity, highest amelogenin levels, and peak phosphate/carbonate incorporation between postnatal days 6 and 8. Together, this study provides a baseline for a comprehensive understanding of the mineralogic and proteomic events that contribute to the complexity of mammalian tooth enamel development.

Twist and Snail expression in tumor and stromal cells of epithelial odontogenic tumors

BACKGROUND

The aims of this study were to evaluate expression of Twist and Snail in tumor and stromal cells of epithelial odontogenic tumors and to analyze relationships between Twist and Snail expression and between tumor and stromal expression.

METHODS

Immunohistochemistry was performed using Twist and Snail antibodies in 60 ameloblastomas (AMs; 20 solid/multicystic, 20 unicystic, and 20 recurrent), six ameloblastic carcinomas (ACs), 10 adenomatoid odontogenic tumors (AOTs), and six calcifying epithelial odontogenic tumors (CEOTs).

RESULTS

A higher rate of tumor cells strongly positive for Twist was observed in AC compared to the other tumors (P = 0.019). The rate of tumor cells strongly positive for Snail tended to be higher in AC than in AM (P = 0.060). AM and AC showed a higher rate of Twist-positive stromal cells than AOT and CEOT (P < 0.001). Tumor cells of recurrent AM showed stronger expression of Twist (P < 0.001) and Snail (P = 0.001) compared to AM without recurrence. A moderate positive correlation was observed between tumor expression of Twist and Snail (r = 0.376, P = 0.001) and between tumor and stromal expression of Snail (r = 0.334, P = 0.002).

CONCLUSIONS

Twist and Snail may affect the epithelial-mesenchymal transition in AC and be involved in recurrence of AM. Stromal Twist expression may be associated with aggressive clinical behavior of epithelial odontogenic tumors. A Twist-Snail pathway may participate in the development and progression of odontogenic tumors, and tumor-stroma interaction in odontogenic tumors may be mediated by Snail.

Peripheral Clear Cell Variant of Calcifying Epithelial Odontogenic Tumor: Case Report and Review of the Literature

Calcifying epithelial odontogenic tumor (CEOT) is classified as an uncommon, benign, odontogenic neoplasm that is exclusively epithelial in origin. Of all reported cases, peripheral tumors account for 5-6 %, among which clear cell variants are still rare. A rare case of peripheral clear cell variant of CEOT occurring in the mandibular gingiva of a 47-year-old female is presented.

Epithelial cell migration requires the interaction between the vimentin and keratin intermediate filaments

Epithelial migration plays a central role in development, wound repair and tumor metastasis, but the role of intermediate filament in this important event is unknown. We showed recently that vimentin coexists in the same cell with keratin-KRT14 at the leading edge of the migrating epidermal cells, and knockdown of vimentin impaired colony growth. Here we demonstrate that vimentin co-localizes and co-immunoprecipitates with keratin-KRT14, and mutations in the -YRKLLEGEE- sequence of vimentin significantly reduced migration of the keratinocytes. Our data demonstrates that keratinocyte migration requires the interaction between vimentin and keratins at the -YRKLLEGEE- sequence at the helical 2B domain of vimentin. These findings have broad implications for understanding the roles of vimentin intermediate filaments in normal and neoplastic epithelial cells.

Expression of Wilms' tumor 1 (WT1) in ameloblastomas

The Wilms' tumor 1 gene (WT1) was originally isolated and described as the gene responsible for Wilms' tumor. Although there is growing evidence linking the overexpression of WT1 to tumorigenesis, no reports on ameloblastoma are available at present. The aim of this study was to examine the expression of WT1 in various histological subtypes of ameloblastoma tissue specimens and in human ameloblastoma cell lines. Immunohistochemical analyses were performed on a total of 168 cases of ameloblastoma, one case of ameloblastic carcinoma, and five cases of tooth germs (control). Three immortalized human dental epithelial cell lines (HAM1, HAM2, and HAM3) derived from the same ameloblastoma patient were used for reverse transcription-polymerase chain reaction (RT-PCR) and western blot assays. The tooth germs did not express WT1 (0%), and more than half of the ameloblastoma cases showed WT1 overexpression (54.7%). Immunoreactivity of solid-type ameloblastoma (76.1%) was more evident than that of unicystic-type ameloblastoma (40.9%). The expression level of WT1 mRNA in HAM2 was higher than that in HAM1 (moderate) and HAM3 (weak), showing the heterogeneity of tumor cells. The WT1 protein was strongly detected in HAM2 and minimally detected in HAM1 and HAM3. Our results suggest that WT1 expression influences the pathogenesis of ameloblastoma by varying its expression level in different histological types. (J Oral Sci 58, 407-413, 2016).

Expression of cytokeratins in enamel organ, junctional epithelium and epithelial cell rests of Malassez

BACKGROUND AND OBJECTIVE

After tooth formation is complete, it is suggested that continuity exists between the epithelial cell rests of Malassez (ERM), reduced enamel epithelium (REE) and subsequently the junctional epithelium. However, the junctional epithelium was reported to differ from REE and ERM. The developmental relationships between and among them remain controversial. Therefore, in the present study we examined the expression of cytokeratins in the three types of epithelia to investigate the epithelial phenotypes.

MATERIAL AND METHODS

The maxillae of Wistar rats, 1, 2, 3 and 7 wk of age, were used, and the expression of CK14, CK17, CK19, CK10/CK13 and AE1/AE3 was detected using immunoperoxidase techniques.

RESULTS

There was negative staining for CK10/CK13 in all the epithelia. ERM stained strongly for AE1/AE3, CK14, CK17 and CK19. During the transformation of inner enamel epithelial (IEE) cells into reduced ameloblasts and subsequently into junctional epithelium, strong staining for CK14 was evident in IEE, REE and junctional epithelium, whereas the expression of AE1/AE3 and of CK19 were initially negative in IEE and then strong in REE and junctional epithelium, respectively. In particular, the expression of CK17 was strongly positive in ERM and REE, but was negative in IEE and junctional epithelium.

CONCLUSION

ERM are of odontogenic origin and junctional epithelium has an epithelial phenotype different from REE and ERM. This is the first report to demonstrate that CK17 can be used as a marker to distinguish junctional epithelium from ERM.

Vimentin is necessary for colony growth of human diploid keratinocytes

The role of vimentin (Vim) in diploid epithelial cells is not well known. To understand its biological function, we cultured human epidermal keratinocytes under conditions that support migration, proliferation, stratification and terminal differentiation. We identified a keratinocyte subpopulation that shows a p63(+)/α5β1(bright) phenotype and displays Vim intermediate filaments (IFs) besides their keratin IF network. These cells were mainly located at the proliferative/migratory rim of the growing colonies; but also, they were scarce and scattered or formed small groups of basal cells in confluent stratified epithelia. Stimulation of cells with EGF and wounding experiments in confluent arrested epithelia increased the number of Vim(+) keratinocytes in an extent higher to the expected for a cell population doubling. BrdU labeling demonstrated that most of the proliferative cells located at the migratory border of the colony have Vim, in contrast with proliferative cells located at the basal layer at the center of big colonies which lacked of Vim IFs, suggesting that Vim expression was not solely linked to proliferation. Therefore, we silenced Vim mRNA in the cultured keratinocytes and observed an inhibition of colony growth. Such results, together with long-term cultivation assays which showed that Vim might be associated to pattern formation in cultured epithelia, suggest that Vim expression is essential for a highly motile phenotype, which is necessary for keratinocyte colony growth and possibly for development and wound healing. Vim(+)/p63(+)/α5β1(bright) epithelial cells may play a significant physiological role in embryonic morphogenetic movements; wound healing and other pathologies such as carcinomas and hyperproliferative diseases.

Expression of cytokeratin 8, vimentin, syndecan-1 and Ki-67 during human tooth development

Spatio-temporal immunolocalizations of cytokeratin 8 (CK8), vimentin, syndecan-1 and Ki-67 were analyzed in ten human incisors and canine tooth germs between the 7th and 20th developmental weeks. CK8 expression was mild to moderate in the epithelial tooth parts, while it shifted from absent or mild in its mesenchymal parts, but few cells, sparsely distributed throughout the tooth germ, strongly expressed CK8. As development progressed, CK8 expression increased to strong in preameloblasts, while expression of vimentin increased to moderate in the epithelial and mesenchymal tooth parts, particularly in the dental papilla and sac. Co-expression of CK8 and vimentin was observed in some parts of the tooth germ, and was increasing in the differentiating preameloblasts and preodontoblasts. Syndecan-1 showed characteristic shift of expression from epithelial to mesenchymal tooth parts, being particularly strong in dental papilla, sac and cervical loops, while co-expression of Ki-67/syndecan-1 was strong in the dental papilla. Our study demonstrated spatio-temporal expression and restricted co-expression of the investigated markers, indicating participation of CK8 and vimentin in cell proliferation and migration, and differentiation of preodontoblasts and preameloblasts. Our data also suggest involvement of syndecan-1 in morphogenesis of the developing tooth crown and cervical loops, and together with CK8 and vimentin in differentiation of preameloblasts and preodontoblasts.

Spindle cell ameloblastic carcinoma in a labrador retriever dog

A 13-year-old castrated male Labrador retriever dog presented with a mass caudal to the first molar of his left mandible. Although the tumor was excised, a recurrent tumor was detected one month later and resected. Both tumors displayed invasive growth and were composed of neoplastic proliferation arranged in irregular lobules, nests and cords continuous with mucosal epithelium. The most prominent feature of the tumors was the presence of many proliferating spindle cells admixed with palisading basal-like cells, acanthocytes and stellate cells. In immunohistochemical examinations, the spindle cells were found to be positive for vimentin; cytokeratin AE1/AE3, 5/6, 14 and 19; and p63. The other neoplastic cells were positive for all of these markers shown above except vimentin. Based on these findings, the tumors were diagnosed as spindle cell ameloblastic carcinoma.

Potential contribution of neural crest cells to dental enamel formation

Neural crest cells (NCCs) are a multipotent embryonic cell population that contributes to the formation of various craniofacial structures including teeth. It has been generally believed that dental enamel is an ectodermal derivative, whereas the dentin-pulp complex and the surrounding supporting tissues originate from NCC-derived mesenchyme. These traditional concepts stem mainly from several early studies of fishes and amphibians. Recently, Wnt1-Cre/R26R mice, a mouse model for NCC lineage analysis, revealed the contribution of NCCs to mammalian tooth development. However, the discrepancy of expression patterns between different NCC-specific transgenic mouse lines makes it compulsory to revisit the cell lineage in mammalian tooth development. Here, we reevaluated the NCC lineage during mouse tooth development by using P0-Cre/R26R mice, another NCC-specific transgenic mouse line. Inconsistent with the traditional concepts, we observed the potential contribution of NCCs to developing enamel organ and enamel formation. We also demonstrated that the P0-Cre transgene was specifically expressed in migrating NCC in the hindbrain region, where NCC contributes to tooth, validating their applicability for NCC lineage analysis. Our unanticipated finding may change the general understanding of tooth development and provide new insights into dental stem cell biology.

Immunohistochemical localization of cytokeratins in the junctional region of ectoderm and endoderm

Although tridermic species have two junctional regions of ectoderm and endoderm between their epidermis and digestive tract, we actually know little about these particular boundaries. Cytokeratins are the major intermediate filaments of epithelial cells and show a high degree of tissue specificity. Therefore, to characterize the epithelial cells in the junctional region of ectoderm and endoderm, we immunohistochemically examined the localization of cytokeratins 5, 7/17, 14, 18, Sox17, and alpha-fetoprotein (AFP) in the oropharyngeal and anorectal regions during the mouse gastrulation process. At embryonic day (E) 9.5, cytokeratins 5, 7/17, 14, and 18 were detected in all epithelial cells of the oropharyngeal region. At E12.5, cytokeratin 5-positive cells were not observed in the middle area of the oral cavity; however, the immunoreactivity was strong in the anterior and posterior areas. The immunoreaction of cytokeratins 18 was seen only in the middle and posterior areas of the oral mucosa. Cytokeratins 7/17 and 14 were localized in all areas of the oropharyngeal region. Sox17 and AFP, which are endodermal markers, were detected in the middle and posterior areas of the oral mucosa, but not in the anterior area. Moreover, this same localization pattern of cytokeratins also existed in the anorectal region of the E12.5 embryo, suggesting that the localization of cytokeratins and endodermal markers might give an implication for the boundary between ectoderm and endoderm. These results also suggest that these cytokeratins are useful molecules for monitoring the epithelial cell differentiation in the junctional region of the germ layers.

Maxillary Ameloblastic Fibroma in a Dog

A 4-year-old spayed female Golden Retriever was presented for evaluation of a rostral maxillary gingival mass. An en bloc resection was performed after histologic diagnosis of ameloblastic fibroma from an incisional biopsy specimen. Histologically, the tumor was composed of (1) poorly differentiated vimentin-positive mesenchymal cells that surrounded islands and (2) thin anastomosing trabeculae of odontogenic epithelium that variably coexpressed pancytokeratin and vimentin. To the authors' knowledge, this is the first report of ameloblastic fibroma in a dog. The clinical, radiographic, and histologic findings in this case are compared to those in other domestic animals and humans.

Expression, localisation and synthesis of versican by the enamel organ of developing mouse molar tooth germ: an in vivo and in vitro study

OBJECTIVE

Versican is a large, aggregating chondroitin sulphate proteoglycan. In dental tissue, versican expression occurs primarily in mesenchymal tissue but rarely in epithelial tissue. We investigated the expression, localisation and synthesis of versican in the enamel organ of the developing tooth germ.

DESIGN

To elucidate versican localisation in vivo, in situ hybridisation and immunohistochemistry were conducted in foetal ICR mice at E11.5-E18.5. Epithelium and mesenchyme from the lower first molars at E16.0 were enzymatically separated and versican mRNA expression was investigated by semi-quantitative RT-PCR. Organ culture of the separated samples combined with metabolic labelling with [(35)S], followed by gel filtration, was performed to analyse secreted proteoglycans.

RESULTS

Versican mRNA was first expressed in the thickened dental epithelium at E12.0 and continued to be expressed in the enamel organ until the bell stage. Versican immunostaining was detected in the stellate reticulum areas from the bud stage to the apposition stage. The enamel organ at E16.0 expressed versican mRNA at a level comparable to that in dental mesenchyme. Furthermore, when compared to dental mesenchyme, about 1/2-3/4 of the [(35)S]-labelled versican-like large proteoglycan was synthesised and released into tissue explants by the enamel organ.

CONCLUSIONS

The dental epithelium of developing tooth germ is able to synthesise significant amounts of versican.

Adenomatoid odontogenic tumor concomitant with cystic complex odontoma: case report

This case report describes a 10-year-old female patient with an adenomatoid odontogenic tumor developing together with a cystic complex odontoma. This occurrence is considered very unusual. Immunohistochemical detection of cytokeratins AE1/AE3, CK5, CK8, CK10, CK14, CK19 and Ki-67 was performed.

Development of immortalized rat conjunctival epithelial cell lines: an in vitro model to examine transepithelial antigen delivery

The objective of these studies was to develop conjunctival epithelial cell lines for investigation of antigen translocation across a mucosal barrier. Conjunctival epithelial cells from Fischer 344 rats were immortalized with pSV3(neo) resulting in two cell lines--CJ4.1A and CJ4.3C. Each formed confluent cell layers with epithelial morphology when grown on permeable membrane filters. They expressed the SV40 T antigen, the conjunctiva-specific cytokeratin 4, the goblet cell-specific cytokeratin 7 and were negative for the corneal epithelial cell-specific cytokeratin 12. The cell lines have been in culture for over 60 passages, and the population doubling times were 22+/-7h for CJ4.1A and 23+/-9h for CJ4.3C. When grown on Transwell membranes, each cell line achieved a transepithelial electrical resistance of 600-800 Omega cm2 by 3-4 days and maintained a high resistance for several days. Both cell lines expressed zona occludens-1 at confluence. At 24h following addition of 250 microg of FITC-labeled ovalbumin to the apical chambers, 15+/-6 microg could be detected in the basal chamber of CJ4.1A and 6+/-1 microg in the basal medium of CJ4.3C. In contrast, 82+/-6 microg was detected in the lower chambers of cell-free Transwells. Similarly, Transwells containing confluent CJ4.1A or CJ4.3C cells impeded passage of 0.1 microm diameter polystyrene microspheres (5+/-1% and 4+/-1%, respectively, of the apical input), compared to 26+/-6% of the input microspheres recovered from the basal chambers of cell-free Transwells. Pretreatment with 4mM EGTA for 10 min caused an increase in OVA-FITC translocation across CJ4.3C cells. Incubation in the presence of 4mM EGTA significantly increased OVA-FITC translocation across both cell lines, relative to untreated cell layers. Morphological and functional characterization indicates that these cells provide a useful experimental tool to assess strategies for enhancing transepithelial antigen uptake.

Human pulp-derived cells immortalized with Simian Virus 40 T-antigen

Primary cells in culture have a limited capacity to divide and soon reach a non-proliferative state. This cellular senescence limits the investigation of cells derived from human pulp concerning cellular pathways, gene regulation, mechanisms of dentin formation, or responses to material exposure. To overcome this problem, primary human pulp-derived cells were established and transfected with a plasmid containing coding sequences of Simian Virus 40 (SV40) large T-antigen. This resulted in the establishment of several cell clones showing an extension of life span. Expression of T-antigen transcripts and protein was verified by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. Primary human pulp cells were cultured until senescence (i.e. up to passage 7) and transfected cells could be cultured to passage 18 after transfection, when a cellular crisis with massive cell death occurred. One clone escaped from crisis and has been maintained in culture for 55 wk. Experiments were performed to characterize transfected cells in comparison to primary cells. Cell morphology and proliferation were analyzed, and expression of cell-specific gene transcripts and proteins (including collagen types I and III, alkaline phosphatase, bone sialoprotein, osteocalcin, and dentin sialophosphoprotein and dentin matrix protein I) was detected by RT-PCR and immunohistochemistry. Transfection of human pulp-derived cells resulted in an immortalized cell line retaining many of the phenotypic characteristics observed in primary cells.

Targeted disruption of two small leucine-rich proteoglycans, biglycan and decorin, excerpts divergent effects on enamel and dentin formation

Small leucine-rich proteoglycans have been suggested to affect mineralization of dental hard tissues. To determine the functions of two of these small proteoglycans during the early stages of tooth formation, we characterized the dental phenotypes of biglycan (BGN KO) and decorin deficient (DCN KO) mice and compared them to that of wild type mice. Each targeted gene disruption resulted in specific effects on dentin and enamel formation. Dentin was hypomineralized in both knock out mice, although the effect was more prominent in the absence of decorin. Enamel formation was dramatically increased in newborn biglycan knockout mice but delayed in absence of decorin. Increased enamel formation in the former case resulted from an upregulation of amelogenin synthesis whereas delayed enamel formation in the later case was most probably an indirect consequence of the high porosity of the underlying dentin. Enamelin expression was unchanged in BGN KO, and reduced in DCN KO. Dentin sialoprotein (DSP), a member of the family of phosphorylated extracellular matrix proteins that play a role in dentinogenesis, was overexpressed in BGN-KO odontoblasts and in the sub-odontoblastic layer. In contrast, a decreased expression of DSP was detected in DCN KO. Dentin matrix protein-1 (DMP-1), bone sialoprotein (BSP) and osteopontin (OPN) were upregulated in BGN KO and downregulated in the DCN KO. Despite the strong effects induced by these deficiencies in newborn mice, no significant difference was detected between the three genotypes in adult mice, suggesting that the effects reported here in newborn mice are transient and subjected to self-repair.

Proteomic profiling of facial development in chick embryos

Craniofacial disorders are associated with one-third of human birth defects but the underlying molecular and cellular causes remain poorly understood. Proteomics seems well-placed to benefit this medically important area but the scarcity of embryonic tissues poses a major challenge. In this study, we applied a microsample proteomics strategy to investigate the first branchial arch, an embryonic structure crucial for facial development, and found that proteome analysis is both practicable and informative despite the scarcity of tissue. Exploiting the embryonic chick as a tractable source of accurately staged tissue, we developed a sequential extraction procedure to interface with one-dimensional polyacrylamide gel electrophoresis (1-D PAGE) and 2-D PAGE. In 2-D gels, about 8% of the visible proteome changed between embryonic days 3 and 5, and the identities determined for 21 proteins accorded with the rapid growth during this period. These results led to the first molecular identification of chicken alpha-fetoprotein, and an unusual localisation of vimentin to endoderm. With over 470 protein spots accessible, this comparative proteomics approach has good prospects for providing new markers, functional hypotheses and genes to target in functional tests. A broader value of extending these approaches to facial development in other species and to other areas in embryology can be anticipated.

Database on monoclonal antibodies to Cytokeratins

Cytokeratins (CK) are being extensively used as diagnostic markers for various malignancies and other diseases, including human oral precancer and cancer, due to their tissue specific expression. CK are epithelia specific intermediate filament (IF) proteins, which are expressed in a differentiation dependent and tissue specific manner. There are about 30 polypeptides of CK expressed by different human epithelia. Each type of epithelium expresses about 4-6 polypeptides. CK polypeptides share many common epitopes, due to which the antibodies developed against CK tend to cross react. Therefore, a large number of monoclonal and polyclonal antibodies have been developed to distinguish among these proteins. Many of these antibodies are not only monospecific but are also epitope specific. These antibodies are being used in pathology laboratories for routine diagnosis using immunohistochemistry. A number of fixatives are used for fixation of tissue sections prior to the use of these antibodies. Sometimes, this leads in epitope masking. Hence, it becomes necessary to use a battery of monoclonal antibodies (MAb) for accurate diagnosis. Apart from the use of these antibodies in diagnostics, they are also being used in basic research for the study of CK function and their interactions with associated proteins and membrane proteins. In the present communication an effort has been made to make a comprehensive list of MAb to CK giving information like cross-reactivity, epitope specificity, various fixatives used, etc. along with the source of the antibodies, which will provide useful information to the users.

Amelogenin interacts with cytokeratin-5 in ameloblasts during enamel growth

The enamel protein amelogenin binds to GlcNAc (Ravindranath, R. M. H., Moradian-Oldak, R., and Fincham, A.G. (1999) J. Biol. Chem. 274, 2464-2471) and to the GlcNAc-mimicking peptide (GMp) (Ravindranath, R. M. H., Tam, W., Nguyen, P., and Fincham, A. G. (2000) J. Biol. Chem. 275, 39654-39661). The GMp motif in the N-terminal region of the cytokeratin 14 of ameloblasts binds to trityrosyl motif peptide (ATMP) of amelogenin (Ravindranath, R. M. H., Tam, W., Bringas, P., Santos, V., and Fincham, A. G. (2001) J. Biol. Chem. 276, 36586 - 36597). K14 (Type I) pairs with K5 (Type II) in basal epithelial cells; GlcNAc-acylated K5 is identified in ameloblasts. Dosimetric analysis showed the binding affinity of amelogenin to K5 and to GlcNAc-acylated-positive control, ovalbumin. The specific binding of [3H]ATMP with K5 or ovalbumin was confirmed by Scatchard analysis. [3H]ATMP failed to bind to K5 after removal of GlcNAc. Blocking K5 with ATMP abrogates the K5-amelogenin interaction. K5 failed to bind to ATMP when the third proline was substituted with threonine, as in some cases of human X-linked amelogenesis imperfecta or when tyrosyl residues were substituted with phenylalanine. Confocal laser scan microscopic observations on ameloblasts during postnatal (PN) growth of the teeth showed that the K5-amelogenin complex migrated from the cytoplasm to the periphery (on PN day 1) and accumulated at the apical region on day 3. Secretion of amelogenin commences from day 1. K5, similar to K14, may play a role of chaperone during secretion of amelogenin. Upon secretion of amelogenin, K5 pairs with K14. Pairing of K5 and K14 commences on day 3 and ends on day 9. The pairing of K5 and K14 marks the end of secretion of amelogenin.

Immunohistochemical investigation on the pattern of vimentin expression in regenerated and intact monkey and human periodontal ligament

The expression of vimentin is well documented in the intact animal and human periodontal ligament (PDL), but there is limited information on the pattern of vimentin expression in the regenerated PDL. The aim of the present study was to investigate the pattern of vimentin expression in the regenerated and intact monkey and human PDL. A total of 12 chronic recession-type defects were created in three monkeys (Macaca fascicularis) and treated either with guided tissue regeneration (GTR), or with an enamel matrix protein derivative (EMD). After 5 months, the animals were sacrificed and specimens containing the defects and surrounding tissues were dissected free, decalcified in EDTA and embedded in paraffin. Sections were labelled immunohistochemically by using monoclonal antibody against vimentin (VIM 3B4). Twelve patients, each of whom displayed one deep intrabony defect scheduled for extraction were treated with GTR, EMD or combination of EMD+natural bone mineral (NBM). Following a healing period of 6 months, the teeth were extracted "en block" and immunohistochemically analysed according to the same protocol as described in monkeys. The results revealed that in both monkeys and humans the newly formed PDL was labelled similarly for vimentin to the intact (non-treated) PDL. In all specimens, the newly formed PDL was in continuation with the intact parts of PDL, thus suggesting that the mesenchymal cells capable of regenerating the attachment apparatus may have their origin in the intact PDL. In conclusion, the present findings indicate that (a) the reformed PDL displayed a similar expression of vimentin to the intact (original) PDL, and (b) the cells capable of regenerating new PDL and new cementum appear to be of mesenchymal origin and their source may be in the intact PDL.

A case of multiple AOT-like jawbone lesions in a young patient--a new odontogenic entity?

We assessed the immunohistochemical profile of an unusual case of multiple similarly looking tumors in the jawbone of a young patient. Histologically, the tumors exhibited features of adenomatoid odontogenic tumor (AOT) and adenomatoid dentinoma but showed no resemblance to any other defined odontogenic tumor entities. They expressed high amounts of cytokeratin (CK) 8 and 14 together with some Vimentin. A small rim of peripheral cells showed CK 5, 17, and 19 reactivity. Also, these lesions expressed some bcl-2 as well as p53 and Ki67. Histologically and immunohistochemically, the unusual multiple lesions differed in details from a simultaneously examined group of 24 classical AOT cases, suggesting that they may represent a hitherto less well-defined odontogenic tumor entity.

Cytokeratins in epithelia of odontogenic neoplasms

Neoplasms and tumours related to the odontogenic apparatus may be composed only of epithelial tissue or epithelial tissue associated with odontogenic ectomesenchyme. The immunohistochemical detection of different cytokeratins (CKs) polypeptides and vimentin has made it easier to explain the histogenesis of many epithelial diseases. The present study aimed to describe the immunohistochemical expression of cytokeratins 7, 8, 10, 13, 14, 18, 19 and vimentin in the epithelial components of the dental germ and of five types of odontogenic tumours. The results were compared and histogenesis discussed. All cells of the dental germ were positive for CK14, except for the preameloblasts and secreting ameloblasts, in which CK14 was gradually replaced by CK19. CK7 was especially expressed in the cells of the Hertwig root sheath and the stellate reticulum. The dental lamina was the only structure to express CK13. The reduced epithelium of the enamel organ contained CK14 and occasionally CK13. Cells similar to the stellate reticulum, present in the ameloblastoma and in the ameloblastic fibroma, were positive for CK13, which indicates a nature other than that of the stellate reticulum of the normal dental germ. The expression of CK14 and the ultrastructural aspects of the adenomatoid odontogenic tumour probably indicated its origin in the reduced dental epithelium. Calcifying odontogenic epithelial tumour is thought to be composed of primordial cells due to the expression of vimentin. Odontomas exhibited an immunohistochemical profile similar to that of the dental germ. In conclusion, the typical IF of odontogenic epithelium was CK14, while CK8, 10 and 18 were absent. Cytokeratins 13 and 19 labelled squamous differentiation or epithelial cells near the surface epithelium, and CK7 had variable expression.

Cytokeratins expression of constituting cells in ameloblastoma

The purposes of this study were to investigate the distribution of cytokeratins in the different tissue types of ameloblastoma and to discuss the histogenesis of this tumor. CK19 and CK8, which are markers for odontogenic epithelium, reacted positively to the constituting cells in all types of ameloblastoma. This suggests that all types of ameloblastoma derive from odontogenic epithelium. However, the desmoplastic type diminished the odontogenic characteristics because the basal cells are negative to CK19. Immunoreactions of five kinds of cytokeratin revealed similar results in plexiform, follicular, acanthomatous, and granular cell types. The plexiform type is probably the original type of ameloblastoma; the other types have the characteristics of squamous epithelium, and the follicular, acanthomatous, and granular cell types can develop due to the differentiation of cells of the plexiform type into squamous epithelium.

Clear cell odontogenic carcinoma: a clinicopathologic and immunocytochemical study of 5 cases

CONTEXT

Odontogenic tumor composed predominantly of clear cells is a rare neoplasm of the jaws that was initially designated as clear cell odontogenic tumor. Subsequent reports in the literature, however, all have indicated that this tumor exhibits an aggressive behavior characterized by infiltrative local growth, recurrence, or metastases.

OBJECTIVE

To ascertain the clinicomorphologic features and biologic behavior of this tumor group, we present 5 additional cases using the term clear cell odontogenic carcinoma.

DESIGN

Histologic and immunohistochemical examinations were performed on clear cell odontogenic carcinomas from 5 patients. Clinical and follow-up data were recorded, and the literature was reviewed.

RESULTS

The patients were 1 man and 4 women with an average age of 42.4 years at diagnosis. Three tumors occurred in the mandible and the other 2 in the maxilla. Four of the 5 cases occurred in the anterior or premolar areas of the jaws, appearing as poorly marginated radiolucencies. All cases consisted of islands and sheets of large clear cells and small basaloid cells with scanty eosinophilic cytoplasm, which were separated by thin, mature, fibrous septae. The tumors were unencapsulated and showed aggressive infiltration of the surrounding muscle and perineural tissues. Most of the clear cells contained cytoplasmic glycogen. Immunocytochemically, the tumor cells were positive for pan-keratin, cytokeratin 19, and epithelial membrane antigen, but were negative for vimentin, S100 protein, desmin, smooth muscle actin, human melanoma antigen (HMB-45), and alpha(1)-antichymotrypsin. Follow-up data showed 4 of 5 patients to have multiple local recurrences, and 1 of these 4 had submandibular lymph node metastasis and a fatal outcome due to uncontrollable tumor growth.

CONCLUSION

These results suggest that odontogenic clear cell neoplasms are at least low-grade malignancies and should be classified as carcinomas.

Amelogenin-cytokeratin 14 interaction in ameloblasts during enamel formation

The enamel protein amelogenin binds to the GlcNAc-mimicking peptide (GMp) (Ravindranath, R. M. H., Tam, W., Nguyen, P., and Fincham, A. G. (2000) J. Biol. Chem. 275, 39654-39661). The GMp motif is found in the N-terminal region of CK14, a differentiation marker for ameloblasts. The binding affinity of CK14 and amelogenin was confirmed by dosimetric binding of CK14 to recombinant amelogenin (rM179), and to the tyrosine-rich amelogenin polypeptide. The specific binding site for CK14 was identified in the amelogenin trityrosyl motif peptide (ATMP) of tyrosine-rich amelogenin polypeptide and specific interaction between CK14 and [(3)H]ATMP was confirmed by Scatchard analysis. Blocking rM179 with GlcNAc, GMp, or CK14 with ATMP abrogates the CK14-amelogenin interaction. CK14 failed to bind to ATMP when the third proline was substituted with threonine, as in some cases of human X-linked amelogenesis imperfecta or when tyrosyl residues were substituted with phenylalanine. Morphometry of developing teeth distinguished three phases of enamel formation; growth initiation phase (days 0-1), prolific growth phase (days 1-7), and growth cessation phase (post-day 7). Confocal microscopy revealed co-assembly of CK14/amelogenin in the perinuclear region of ameloblasts on day 0, migration of the co-assembled CK14/amelogenin to the apical region of the ameloblasts from day 1, reaching a peak on days 3-5, and a collapse of the co-assembly. Autoradiography with [(3)H]ATMP and [(3)H]GMp corroborated the dissociation of the co-assembly at the ameloblast Tomes' process. It is proposed that CK14 play a chaperon role for nascent amelogenin polypeptide during amelogenesis.

Identification of tuftelin- and amelogenin-interacting proteins using the yeast two-hybrid system

Biomineralization of enamel is a complex process that involves the eventual replacement of an extracellular protein matrix by hydroxyapatite crystallites. To date four different enamel matrix proteins have been identified; the amelogenins, tuftelin, enamelin and ameloblastin. Assembly of the enamel extracellular matrix from these component proteins is believed to be critical in producing a matrix competent to undergo mineral replacement. Enamel formation is a complex process and additional proteins are likely to have a role in the assembly of the extracellular matrix. In order to identify additional proteins involved in the assembly process, the yeast two-hybrid system developed by Fields and Song (1989) has been implemented. This system allows for the identification of unknown proteins that interact with proteins of interest. Typically a known protein is used as "bait" to screen a cDNA expression library of interest. In our studies, tuftelin or amelogenin have been used to screen a mouse tooth library produced from one day old pups. A library screening of six million clones with amelogenin as bait resulted in eleven positive clones all of which show high homology to the human leukocyte antigen-B (HLA-B) associated transcript (BAT) family of genes. A library screening of one million clones using tuftelin as the bait identified twenty-one tuftelin-interacting proteins. Ten of these proteins are either keratin K5 or keratin K6, four are constitutively expressed and the remaining seven are novel. Further characterization of the proteins shown to interact with amelogenin or tuftelin may shed additional light on this complex process of enamel matrix assembly.

The enamel protein amelogenin binds to the N-acetyl-D-glucosamine-mimicking peptide motif of cytokeratins

Amelogenins bind to GlcNAc of the dentine-enamel matrix proteins (Ravindranath, R. M. H., Moradian-Oldak, J., Fincham, A. G. (1999) J. Biol. Chem. 274, 2464-2471). The hypothesis that amelogenins may interact with the peptides that mimic GlcNAc is tested. GlcNAc-mimicking peptide (SFGSGFGGGY) but not its variants with single amino acid substitution at serine, tyrosine, or phenylalanine residues inhibited hemagglutination of amelogenins and the terminal tyrosine-rich amelogenin polypeptide (TRAP). The binding affinity of SFGSGFGGGY to amelogenins was confirmed by dosimetric binding of amelogenins or TRAP with [(3)H]peptide, specific binding in varying concentrations of the peptide, Scatchard plot analysis, and competitive inhibition with the unlabeled peptide. The ability of the peptide or GlcNAc to stoichiometrically inhibit TRAP binding of [(14)C]GlcNAc or [(3)H]peptide indicated that both the peptide and GlcNAc compete for a single binding site. Using different fragments of amelogenins, we have identified the peptide-binding motif in amelogenin to be the same as the GlcNAc-binding "amelogenin trityrosyl motif peptide." The GlcNAc-mimicking peptide failed to bind to the amelogenin trityrosyl motif peptide when the tyrosyl residues were substituted with phenylalanine or when the third proline was replaced with threonine, as in some cases of human X-linked amelogenesis imperfecta. This study documents that molecular mimicry may play a role in stability and organization of amelogenin during amelogenesis.

Cytokeratin expression in human fetal tongue and buccal mucosa

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

An immunohistochemical study of keratin expression in ameloblastoma from a Kenyan population

OBJECTIVES

Ameloblastomas appear to exhibit biological heterogeneity and, except in the case of malignancy, histological appearances that do not always allow their behaviour to be predicted. The aim of this study was to assess keratin expression in African ameloblastomas and to correlate this with their clinical and histological features.

MATERIALS AND METHODS

Expression of simple keratins 7, 8, 18 and 19; cornification keratins 1 and 10; basal and differentiation keratins 5 and 14 and hyperproliferation-related keratins 6 and 16 in 14-39 cases of ameloblastoma was assessed by immunohistochemical methods.

RESULTS

There was patchy expression of keratin 7 in the suprabasal and stellate reticulum-like cells in some cases. All cases showed similar weak expression for keratins 8 and 18 in suprabasal and stellate reticulum-like cells but none showed keratin 1 or 10 expression. There was intense expression of keratins 5, 14 and 19 by all tumour cells suggesting that they may retain basal cell characteristics with a potential for proliferation. No consistent relationship was seen between histological types and keratin expression pattern. However, keratins 6 and 16, expressed by suprabasal and stellate reticulum-like cells, showed a marked variation within and between cases, with the highest levels of expression in squamous strands.

CONCLUSIONS

We propose that squamous strands may represent the sites of most active growth within individual tumours and expression of keratins 6, 16 and 19 may be predictors of rapid growth. There is a need for further investigation of this in longitudinal clinical studies.

Aberrant gene expression in epithelial cells of mixed odontogenic tumors

Comparative investigations of odontogenic cells in normally forming teeth and tumors may provide insights into the mechanisms of the differentiation process. The present study is devoted to late phenotypic markers of ameloblast and odontoblast cells, i.e., proteins involved in biomineralization. The in situ expression of amelogenins, keratins, collagens type III and IV, vimentin, fibronectin, osteonectin, and osteocalcin was performed on normal and tumor odontogenic human cells. The pattern of protein expression showed some similarities between ameloblasts and odontoblasts present in normally developing human teeth and cells present in neoplastic tissues of ameloblastic fibroma, ameloblastic fibro-odontomas, and complex odontomas. Amelogenins (for ameloblasts) and osteocalcin (for odontoblasts) were detected in cells with well-organized enamel and dentin, respectively. In contrast, "mixed" cells located in epithelial zones of mixed odontogenic tumors co-expressed amelogenins and osteocalcin, as shown by immunostaining. The presence of osteocalcin transcripts was also demonstrated by in situ hybridization in these cells. Keratins and vimentin were detected in the same epithelial zones. Tumor epithelial cells were associated with various amounts of polymorphic matrix (amelogenin- and osteocalcin-immunoreactive), depending on the types of mixed tumors. No osteocalcin labeling was found in epithelial tumors. This study confirms that the differentiation of normal and tumor odontogenic cells is accompanied by the expression of some common molecules. Furthermore, the gene products present in normal mesenchymal cells were also shown in odontogenic tumor epithelium. These data may be related to a tumor-specific overexpression of the corresponding genes transcribed at an undetectable level during normal development and/or to an epithelial-mesenchymal transition proposed to occur during normal root formation. A plausible explanation for the results is that the odontogenic tumor epithelial cells are recapitulating genetic programs expressed during normal odontogenesis, but the tumor cells demonstrate abnormal expression patterns for these genes.

Characterization of epithelial primary cultures from human conjunctiva

Primary cultures of human epithelial cells from normal conjunctiva were developed and characterized to determine whether they retained epithelial characteristics. Conjunctival explants were obtained from the upper fornix of healthy donors and cultured in supplemented DMEM/F-12 medium for 5 days. The epithelial outgrowth was maintained for an additional 10 days. Primary cultures were then processed for light microscopy, transmission and scanning electron microscopy (TEM, SEM), and immunocytochemistry. They exhibited typical features of conjunctival epithelium on light microscopy (polygonal morphology, intimate cohesion, production of mucins), TEM (abundant desmosomes, keratin bundles, granules, microvilli), SEM (polygonal shape, microvilli, intimate cohesion), and immunocytochemistry (positivity for the receptor of epidermal growth factor, desmosomal proteins, and cytokeratins). In conclusion, primary cultures developed from normal human conjunctiva maintained the epithelial characteristics in vitro. Because the conjunctiva is a major component of the anterior ocular surface, we propose this in vitro system as suitable for physiopathologic and toxicologic studies.

Expression of cytokeratin 14 in ameloblast-lineage cells of the developing tooth of rat, both in vivo and in vitro

In the search for a cell marker useful for studying tooth development, immunohistochemical studies using antibodies against cytokeratin 14 (K14), c-Met/hepatocyte growth factor receptor and amelogenin were carried out in the developing tooth of the newborn rat and in primary cultured cells of the ameloblast lineage, including inner enamel epithelium cells, preameloblasts and ameloblasts, prepared from the mandibular incisors of postnatal 7-day-old rats. The appearance of K14 was cell- and differentiation-stage specific, i.e. there was a weak expression signal within inner enamel epithelial cells that were in the proliferating stage, and there were strong signals within preameloblasts and ameloblasts that were in the post-proliferating and amelogenesis stages, respectively. In the culture system, c-Met appeared in all cells, whereas K14 and amelogenin appeared mainly in clustered cells that were considered to be in the post-proliferating stage. K14 was detected earlier than amelogenin, and it was also confirmed by immunofluorostaining that c-Met, K14 and amelogenin were coexpressed in ameloblasts. These findings indicate that K14 is a good new marker for ameloblast-lineage cells during rat tooth development both in vivo and in vitro.