The growth and structure of human oral keratinocytes in culture

Effects of Organic and Inorganic Selenium on Mercury Accumulation in Cultures of Normal Human Epithelial Cells

Cultures of normal human epithelial cells were exposed to methylmercury alone or in combination with organic or inorganic selenium. The resulting subcellular distribution of mercury accumulation was demonstrated cytochemically by the silver enhancement method. With this method, accumulation of mercury-selenide complexes is visualised at both the light microscope and electron microscope levels. Substantially more mercury complexes were found in cultures exposed to mercury and selenite than in cultures exposed to mercury and selenomethionine. All visualised mercury-complexes were localised in lysosome-like structures.

Autophagy and Hsp70 activation alleviate oral epithelial cell death induced by food-derived hypertonicity

Stable intracellular and intercellular osmolarity is vital for all physiological processes. Although it is the first organ that receives food, the osmolarity around the mouth epithelium has never been systematically investigated. We found that oral epithelial cells are a population of ignored cells routinely exposed to hypertonic environments mainly composed of saline, glucose, etc. in vivo after chewing food. By using cultured oral epithelial cells as an in vitro model, we found that the hypotonic environments caused by both high NaCl and high glucose induced cell death in a dose- and time-dependent manner. Transcriptomics revealed similar expression profiles after high NaCl and high glucose stimulation. Most of the common differentially expressed genes were enriched in "mitophagy" and "autophagy" according to KEGG pathway enrichment analysis. Hypertonic stimulation for 1 to 6 h resulted in autophagosome formation. The activation of autophagy protected cells from high osmolarity-induced cell death. The activation of Hsp70 by the pharmacological activator handelin significantly improved the cell survival rate after hypertonic stimulation. The protective role of Hsp70 activation was partially dependent on autophagy activation, indicating a crosstalk between Hsp70 and autophagy in hypertonic stress response. The extract of the handelin-containing herb Chrysanthemum indicum significantly protected oral epithelial cells from hypertonic-induced death, providing an inexpensive way to protect against hypertonic-induced oral epithelial damage. In conclusion, the present study emphasized the importance of changes in osmolarity in oral health for the first time. The identification of novel compounds or herbal plant extracts that can activate autophagy or HSPs may contribute to oral health and the food industry.

Cytoprotective effects of olesoxime on isolated human pancreatic islets in order to attenuate apoptotic pathway

BACKGROUND AND PURPOSE

Islet transplantation is considered as a promising approach in the treatment of diabetes type 1. In this regard, optimal culture of the pancreatic islets is promising in the success of transplantation. In the present study, the effect of olesoxime, as an antiapoptotic substance, was evaluated on human islet culture.

EXPERIMENTAL APPROACH

The pancreatic islets were isolated by mechanical and enzymatic techniques. After overnight recovery, the islets were treated by different concentrations of olesoxime for 24 and 72 h. Then, they were examined in terms of viability, apoptosis, genes and proteins expression including BAX, BCL2, active caspase-3, and insulin. Moreover, the islets function was evaluated through the glucose-induced insulin and C-peptide secretion assay.

KEY RESULTS

Our findings showed that the islets increased in apoptosis and the decreased in viability after 72 h; also, insulin and C-peptide secretion reduced. However, in the presence of olesoxime, BAX/BCL2 ratio and the activation of caspase-3 were decreased. Therefore, olesoxime could improve the viability of the islets with the decrease of apoptosis.

CONCLUSION

The application of olesoxime can reduce the stressful condition for the islets in vitro and subsequently improve their viability and functionality.

In vitro study on proliferation kinetics of oral mucosal keratinocytes

OBJECTIVE

The limited availability of autogenous oral mucosa in oral and maxillofacial surgery for intraoral grafting after trauma or tumor resection can be balanced by the use of tissue-engineered oral mucosa. However, the use of tissue engineering in autologous grafts is still subject to further research. The aim of this study was to evaluate conditions that lead to a rapid proliferation of vital and highly proliferative oral keratinocytes, which can be used in tissue engineering and consequently help improve surgical management of intraoral mucosal defects.

MATERIAL AND METHODS

Human oral keratinocytes were obtained from oral mucosal specimens and cultivated. According to their affinity to β1-integrin, epidermal stem cell populations were isolated by using collagen type IV and laminin-coated dishes. Cell proliferation and cell viability were measured by using the CASY cell counter, WST-1 assays, and real-time cell analysis (xCELLigence).

RESULTS

Measurements on cell proliferation (CASY cell counter) and cell viability (WST-1 assay) showed the characteristic proliferation stages of in vitro-cultivated cells. No statistically significant differences could be monitored (P > .05). Real-time cell analysis, as a more direct and precise technique, revealed a steeper growth curve of adherent cells and therefore generally higher proliferation kinetics compared with cells derived from the supernate.

CONCLUSION

Data from real-time cell analysis showed an increased proliferation of adherent cells compared with those derived from the supernate. These results demonstrate the increase of the proliferation capacity by cultivation of keratinocytes derived by adhesion to extracellular matrix proteins.

Tissue-engineered oral mucosa: a review of the scientific literature

Tissue-engineered oral mucosal equivalents have been developed for clinical applications and also for in vitro studies of biocompatibility, mucosal irritation, disease, and other basic oral biology phenomena. This paper reviews different tissue-engineering strategies used for the production of human oral mucosal equivalents, their relative advantages and drawbacks, and their applications. Techniques used for skin tissue engineering that may possibly be used for in vitro reconstruction of human oral mucosa are also discussed.

Clinical application of tissue-engineered transplants. Part I: mucosa

OBJECTIVES

The study series aims at testing the feasibility of the clinical application of tissue-engineered oral mucosa. The preliminary results were gathered over a period varying from 6 months to 12 years depending on the surgical method.

METHODS

Tissue-engineered oral mucosa was used to cover defects in various surgical procedures like vestibuloplasty (n=42), freeing of the tongue (n=10), prelaminating the radial flap (n=5) and reconstruction of the urethra (n=16). In all interventions small samples of oral mucosa were harvested, cut into small pieces, resuspended in culture medium and seeded into a culture flask. Cultured keratinocytes were transferred onto membranes which then were used to cover mucosal defects in the oral cavity.

RESULTS

To gain a graft of 15 cm(2) size a mucosa biopsy of 4-8 mm(2) and 40 ml autologous patients serum is needed. Tissue-engineered oral mucosa was applied successfully in all four surgical methods. Six months after transplantation a regular epithelial layering with a histological delimitation of the stratum, epithelial crest and a strong basal membrane appeared. According to the reception site the tissue engineered oral mucosa differentiated in several ways.

CONCLUSION

Tissue-engineered oral mucosa fulfils the requirements for clinical routine. With view to healing time and outcome it does not appear to be superior to regular harvested oral mucosa transplants. Because of a smaller harvesting defect and primary wound closure at the actual operation site the patients' convenience is increased. Thus this method reduces morbidity and advances the quality of life.

Differences in the fatty acid composition of KB-cells and gingival keratinocytes is culture medium additive dependent

The influence of culture medium additives foetal bovine serum (FBS), serum effective substitutes (SES) and human autologous serum on the fatty acid profile of KB-cells and human gingival keratinocytes was examined. The KB-cells were cultivated in RPMI medium added with FBS or SES and the gingival keratinocytes in D-MEM added with FBS or human autologous serum. Two days before the cells were prepared for gas chromatography (GC), the media were changed to serum- and antibiotic-free media. Whole fatty acids of the cells were analysed using GC and the fatty acid profiles were compared. KB-cells as well as gingival keratinocytes changed their fatty acid composition, according to the medium additive used. Significant differences were observed. In the case of KB-cells cultivated with SES the fatty acid changes suggest an increase of the membrane fluidity. Corresponding and significant differences were observed with gingival keratinocytes cultivated in medium added with human autologous serum: the membrane fluidity of the gingival keratinocytes was increased. It is supposed that an increased membrane fluidity caused by a different fatty acid spectrum of the host cell may relate to mechanisms of bacterial adhesion. Consequently, in vitro studies on invasion and adhesion of bacteria or virus are dependent on the medium used. Further analyses are necessary of the functional effects caused by differences in the content of specific FAs, especially with regard to the application of cultivated cells in the field of tissue engineering.

Influence of donor age and culture conditions on tissue engineering of mucosa autografts

In oral surgery the transplantation of tissue engineered mucosa is used more frequently. The conventional single cell suspension culture method (SCSM) involves murine feeder cells and foetal calf serum. The explant technique (ET) has been used as alternative culture procedure. Aim was to study the efficacy of the ET and the SCSM without feeder cells to grow primary cultures and to test the effects of donor age, of extracellular matrix proteins (ECMP), and of autogenous serum on cell growth in explant cultures. These factors were assessed in cultures of 58 patients overall. In 48 cultures of 12 patients primary cell growth was compared between the ET and the SCSM. Eighteen of 24 cultures were established with the ET whereas only 3 of 24 were established with the SCSM. To test the influence of donor age on cell multiplication, the proliferation rate (DNA synthesis measured by bromodeoxyuridine uptake) and the overall growth (DNA content) was determined in cultures of five young and five old donors. In cultures from old donors (mean age 56 years) proliferation was lower but more sustained relative to the cultures from the young donors (mean age 25 years). In old donors overall in vitro cell growth was only 2/3 of that in young donors. In cultures of 20 donors the influence on cell adhesion and growth of the ECMP fibronectin and laminin was assessed by planimetry. While ECMP augmented explant adhesion, these substances did not enhance keratinocyte growth significantly. Comparing the influence of autogenous and foetal calf serum on cell growth no differences were observed in all cultures of the six donors. In conclusion, the ET without additional ECMP coating and with autogenous instead of foetal calf serum are now used to culture gingival keratinocytes for tissue engineering mucosa grafts. Consequently xenogenous components are avoided, being a considerable advantage.

How to optimize seeding and culturing of human osteoblast-like cells on various biomaterials

The optimization of seeding and culturing of human osteoblast-like cells on three collagen-based biomaterials (bovine, equine and calf collagen membrane) was studied by cell proliferation and cell colonization (scanning electron microscopy) analysis. Osteoblasts of five patients were seeded onto the three biomaterials and two different parameters were varied: the time intervals between initial seeding and adding culture medium (2 h 6 h. 12 h, 24 h) and the seeding concentration (1 x 10(5), 1 x 10(6), 2 x 10(6)cells/ml) of cells onto biomaterials. The results of the study demonstrated that the time interval between seeding osteoblasts and adding culture medium as well as the seeding concentration effects the cell proliferation and the cell colonization. The best proliferation rate was achieved by adding the culture medium 2 h after initial seeding and with a seeding density of 1 x 10(5) cells/ml. Moreover, all three biomaterials resulted in different proliferation rates. The best proliferation rate resulted with the bovine collagen membrane. In conclusion, the examined parameters are very important for the development of the tissue engineering techniques and in a larger perspective also for reconstructive surgery.

Formaldehyde cytotoxicity in three human cell types assessed in three different assays

International standards for preclinical screening of the cytotoxicity of dental materials so far recommend the use of established cell lines. The aim of this study was to assess the relative susceptibility of human dental pulp fibroblasts (HPF), human buccal epithelial cells (HBE) and HeLa cervix cancer cells exposed to identical cytotoxic challenges. Formaldehyde, which may be released from dental materials such as dental composites, glassionomer cements, and endodontic sealers, was used as test chemical. Cytotoxicity data including dose-response relations and TC(50) values were assessed in three different assays: BrdU incorporation, neutral red uptake and MTT assays. HBE and HPF demonstrated statistically significant lower TC(50) values in both the neutral red and the BrdU assay in comparison to HeLa cells. In the MTT assay no statistically significant differences were observed between the cell types. In the two target-tissue cell types (HPF and HBE) the Neutral Red assay revealed lower TC(50) values in comparison to the BrdU assay. In HeLa cells no statistically significant differences were observed between the assays. In conclusion, the present study confirms that cytotoxicity data obtained by cell culture studies are influenced by both cell culture model and choice of assay. Under identical experimental conditions, human target tissue cells appeared to be more sensitive to formaldehyde toxicity than human HeLa cancer cells.

IL-1ra and IL-1 production in human oral mucosal epithelial cells in culture: differential modulation by TGF-beta1 and IL-4

Regulatory cytokines mediate the participation of oral mucosal epithelial cells (OMEC) in local immune responses. The aim of this study was to characterize the isoforms of IL-1 receptor antagonist (IL-1ra) in cultured human primary OMECs and to compare its production with that of IL-1 alpha (IL-1alpha) and IL-1 beta (IL-1beta). Western blot analysis showed that IL-1ra was 22 kDa in size hence slightly smaller than monocyte IL-1ra (25 kDa). A minor form of 20 kDa was also found in unstimulated cell culture lysates. In culture supernatants, IL-1 bioactivity increased after IL-1ra neutralization, indicating that the baseline production of IL-1ra is biologically relevant. Immunohistochemistry showed a relation between IL-1ra and involucrin expressions, suggesting that intracytoplasmic IL-1ra may be involved in cell terminal differentiation. In unstimulated culture lysates, there was far more IL-1ra than IL-1alpha and IL-1beta. TGF-beta1 markedly increased the IL-1ra/IL-1beta ratio from 93.6 : 1 to 300 : 1. IL-4, which is generally described as an anti-inflammatory cytokine, increased IL-1 but not IL-1ra production. TNF-alpha increased intracellular production of the three IL-1 members. IL-1ra levels were lower in supernatants than in lysates of cultured cells. Our results show that human OMECs constitutively produce significant amounts of a biologically active form of IL-1ra. TGF-beta1 mu(p)-regulation points to a positive amplification loop and IL-4 to a down-regulation loop, both including Th2 cells and OMECs. They may be important in oral tolerance and IgA production, respectively.

The titanium surface texture effects adherence and growth of human gingival keratinocytes and human maxillar osteoblast-like cells in vitro

The adhesion, orientation and proliferation of human gingival epithelial cells and human maxillar osteoblast-like cells in primary and secondary culture were studied on glossy polished, sandblasted and plasma-sprayed titanium surfaces by scanning electron microscopy and in thin sections. The primary cultured explants of human gingival epithelial cells attached, spread and proliferated on all titanium surfaces with the greatest extension on the polished and the smallest extension on plasma-sprayed surfaces. In secondary suspension cultures of gingival keratinocytes, attachment spreading and growth was only observed on polished and plasma-sprayed surfaces, but not on sandblasted surfaces. Moreover, the attachment of these cells depended on the seeding concentration as well as on the coating with fetal calf serum. Cells on polished surfaces developed an extremely flat cell shape, but on sandblasted and plasma-sprayed surfaces a more cuboidal shape. In contrast human maxillar osteoblasts seeded as secondary suspension cultures attached very well to all three differently textured titanium surfaces and showed identical growth patterns independent of the titanium surface structure. These findings suggest that cell morphology, orientation, proliferation and adhesion of human gingival epithelial cells in primary or secondary culture are dependent on the texture of the titanium surface whereas no such differences were observed for maxillar osteoblast-like cells. In conclusion, the soft tissue integration and response is more influenced by the surface texture than the process of osseointegration.

Ex vivo development of a composite human oral mucosal equivalent

PURPOSE

The aim of this study was the ex vivo development of a composite oral mucosal equivalent composed of a continuous stratified layer of human oral keratinocytes grown on a cadaveric human dermal matrix in a defined medium without a feeder layer.

MATERIALS AND METHODS

Enzymatically dissociated human oral keratinocytes from keratinized oral mucosa were cultured, submerged in a serum-free, low-calcium (0.15 mmol/L) supplemented medium, and expanded through several passages. Once a sufficient population of keratinocytes was reached, they were seeded on 1-cm2 pieces of AlloDerm (LifeCell Co, Woodlands, TX), an acellular nonimmunogenic cadaveric human dermis, at cell densities of 2.5 X 10(4), 5.0 X 10(4), 1.25 X 10(5), or 2.5 X 10(5). The oral keratinocyte-AlloDerm composites were cultured while submerged in a high-calcium (1.8 mmol/L) medium for 4 days. After 4 days, the composites were raised to an air-liquid interface. Samples of the composites were taken for histologic examination at 4, 11, and 18 days postseeding of the keratinocytes on the AlloDerm.

RESULTS

At day 4, only the seeded cell density of 2.5 X 10(5) cells/cm2 formed a continuous monolayer on the AlloDerm. At day 11, a continuous stratified epithelium was seen, and at day 18 a well-differentiated, confluent parakeratotic epithelial layer was developed at cell densities of 5.0 X 10(4), 1.25 X 10(5), and 2.5 X 10(5)cells/cm2.

CONCLUSION

With the method used, it was possible to successfully develop an ex vivo composite oral mucosal equivalent that consisted of a stratified epidermis on a dermal matrix.

Tissue engineering of skin

The skin plays a crucial role in protecting the integrity of the body's internal milieu. The loss of this largest organ is incompatible with sustained life. In reconstructive surgery or burn management, substitution of the skin is often necessary. In addition to traditional approaches such as split- or full-thickness skin grafts, tissue flaps and free-tissue transfers, skin bioengineering in vitro or in vivo has been developing over the past decades. It applies the principles and methods of both engineering and life sciences toward the development of substitutes to restore and maintain skin structure and function. Currently, these methods are valuable alternatives or complements to other techniques in reconstructive surgery. This review article deals with the evolution and current approaches to the development of in vitro and in vivo epidermis and dermis.

An Ultrastructural Evaluation of the SKIN2™ ZK1200 System as an in Vitro Model of the Human Oral Mucosa

At present, there are no validated experimental models for the preclinical oral mucosa irritancy screening of dental materials and oral hygiene products. Standardised in vitro models for the assessment of skin irritancy have been marketed, and have made possible the application of such models in preclinical skin irritancy testing. Some of these are currently undergoing international interlaboratory validation. The aim of the present study was to evaluate the histology of the commercially available SKIN2™ ZK1200 system as a potential in vitro model of the human oral mucosa. Histological evaluation by light microscopy and transmission electron microscopy over 6 days revealed a fibroblast-rich matrix covered by an 8–12 cell layer of stratifying epithelium, which shared a number of basic characteristics with non-keratinised human oral mucosa (for example, desmosomes, dispersed tonofilaments, glycogen deposits, membrane-coating granules, and keratohyalin granules, both the spherical and ribosome-associated types). Exposure to a methacrylate-based dental fissure sealant for 24 hours caused structural changes in the epithelium which were not reflected by a cytochemical cytotoxicity assay (MTT).

Optimized growth medium for primary culture of human oral keratinocytes

The effect of different media additives in defining optimal growth conditions for primary cultures of human oral keratinocytes was studied. A cocultivation technique with irradiated Swiss-3T3-fibroblasts in 96-well plates enables the comparison of additives for primary keratinocyte cultures derived from one patient. 3H-labeled thymidine uptake showed no growth or growth inhibition with adenine, choleratoxin or transferrin compared to basal medium (Dulbecco's modified Eagle's medium (DMEM) and 10% fetal calf serum). Among single additives, 5 micrograms/ml hydrocortisone, 5 micrograms/ml insulin, 10 ng/ml EGF, 2 micrograms/ml bovine pituitary extract, and 10(-9) M triiodothyronine showed the greatest capacity to promote keratinocyte growth. With all possible combinations of additives, maximum stimulation was found with a combination of EGF (10 ng/ml), insulin (5 micrograms/ml), and hydrocortisone (5 micrograms/ml); none of the other combinations were more effective. Our data indicate that in short-term cultures (up to 5 days) various media additives described in the literature are not necessarily required in this system of primary culture of human oral keratinocytes.

Culture of rabbit middle ear epithelial cells. A method for primary culture and subculture with identification, characterization and growth specification

During the last decade middle ear epithelium has been cultured from various species. Until now, subcultivation has been achieved only with the use of a feeder-cell layer or conditioned medium. These factors are possible confounders in the in vitro model. On the other hand, subcultivation is necessary for exact quantitative studies. We present a reproducible culture method allowing subcultivation without feeder-cells or conditioned medium. The main features in our method are a low-serum, hormone-supplemented medium, an incubation temperature of 34 degrees C, fixation of explants, gentle trypsinization and replating with high cell density. Cells were identified by immunohistochemistry through a battery of monclonal antibodies. The percentage of epithelial cells in the subculture was 99.2%. To our knowledge, this is the first report describing subcultivation of middle ear epithelial cells exclusively in a completely controlled environment. These are optimal circumstances for future investigation and quantification of various factors influencing proliferation and differentiation of middle ear epithelium.

Use of cultured mucosal grafts to cover defects caused by vestibuloplasty: an in vivo study

PURPOSE

In oral and maxillofacial surgery palatal mucosal grafts are routinely used to cover mucosal defects caused by vestibuloplasty. However, the quantity of palatal mucosa is a limiting factor in more extensive operations. This study investigated whether autologous cultured sheets of mucosa can serve as a dressing for these wounds.

MATERIALS AND METHODS

Punch biopsies (diameter, 4 mm) were taken from the hard palate of eight patients (five men, three women; mean age 43 years). Epithelial cells were enzymatically dissociated from these tissue specimens and grown in vitro in the presence of a fibroblast feeder layer. Within 3 weeks, a transplantable epithelial sheet of about 20 cm2 was obtained. The sheet was detached from the culture flask by enzyme treatment and fixed to a carrier of Vaseline (Cheeseborough Ponds Inc, Greenwich, CT) gauze. Using a split-mouth technique, the sheet was placed on half of a mucosal defect created by vestibuloplasty, while the other half of the defect was covered by a conventional split-thickness palatal graft. Both the cultured and conventional graft were held in place by the patient's relined denture fixed with perimandibular sutures. One week postsurgery, the denture and Vaseline gauze were removed. Three months after vestibuloplasty, biopsy specimens of each grafted site were taken and processed for light and transmission electron microscopy (LM, TEM).

RESULTS

Three months postsurgery, the grafted mucosa of both sites bore close resemblance to palatal mucosa. Both the cultured and split-thickness grafts were vascularized, did not evoke a homograft reaction, and showed a smooth graft/lip mucosal junction and minimal wound contraction. LM and TEM revealed that both types of grafts formed a fully differentiated keratinizing mucosa with a well-developed basement membrane and rete ridges, comparable with the histology and ultrastructure of palatal mucosa in situ.

CONCLUSION

It was concluded from this study that cultured mucosa can serve as a proper dressing for mucosal defects after vestibuloplasty.

Specific lymphocytotoxic destruction of autologous epithelial cell targets in recurrent aphthous stomatitis

Concepts of the immunopathogenesis of recurrent aphthous stomatitis (RAS) based on lesion histology suggest an early role for CD4+ T cells. Other in vitro studies show enhanced destruction of epithelial targets by peripheral blood mononuclear cells (PBMC) from RAS subjects. The present project aimed to extend these studies under conditions simulating the in vivo situation. Epithelial cells were cultured and induced to express class I and class II major histocompatibility complex (MHC) antigens with gamma interferon (gamma-IFN). Co-cultures with autologous PBMC showed evidence of specific destruction of epithelial targets in RAS patients when compared with a control group. Co-culture with CD4+ enriched cells also showed specific epithelial cell lysis. Effector cells pre-incubated with interleukin-2 (IL-2) did not produce increased destruction of epithelial cells. This study has supported previous work and identified an early role of CD4+ cells.

Autografting of feeder-cell free cultured gingival epithelium. Method and clinical application

In oral and maxillofacial surgery an adequate mucosa/gingiva transplant is often not available in the amount required. Use of cultured gingival keratinocytes is a possibility in overcoming this problem. Keratinocytes were cultured in primary culture from gingival biopsies without xenogenous feeder-cells. The cells grew out of explants and formed, within 4 to 6 weeks, a sheet of keratinocytes up to size of 75 cm2. We have a success rate of 65% in cultures of people older than 40 years. This and the culture without feeder-cells encouraged us to use the cultured gingival cells as an autologous transplant in pre-prosthetic surgery for anterior vestibuloplasty.

In vitro evaluation of dental materials

Biocompatibility has been described as the ability of a material to perform with an appropriate host response in a specific application. Appropriate host response means no (or a tolerable) adverse reaction of a living system to the presence of such a material. An adverse reaction may be due to the toxicity of a dental material. Therefore toxicity may be regarded as one reason for nonbiocompatibility of a dental material. The toxicity of a dental material can be evaluated by in vitro tests, animal experiments and clinical trials. There exists a variety of different in vitro test methods. The most widely used biological systems for toxicity screening of dental materials are cell cultures. Cell cultures for toxicity screening of dental materials are valuable tools for understanding their biological behavior, if the limitations of the methods are taken into consideration, especially concerning the interpretation of the results. Further research should concentrate on better simulations of the in vivo situation in cell cultures. In this review the applications of various cell culture methods to evaluate the cytotoxicity of a wide range of dental materials, e.g. metals, alloys, polymers and cements, are described.

Morphologic and growth effects of tobacco-associated chemical carcinogens and smokeless tobacco extracts on human oral epithelial cells in culture

Epidemiologic studies show an increase in the use of smokeless tobacco but few in vitro studies have directly assessed the potential for smokeless tobacco-induced oral carcinogenesis. Oral keratinocytes were grown to 90% confluence from explants of human labial and gingival mucosa at 34 degrees C, 5% CO2 in defined media. Epithelial monolayers were subsequently subcultured and then treated for 1 hour with aqueous extracts of moist or leaf smokeless tobacco, or with 0.25 to 1.0 ng/ml of three common smokeless tobacco carcinogens: 4-(N-methyl-N-nitrosamino)-1-(3-pyridinyl)-1-butanone; N-nitrosonornicotine; and benzo(a)pyrene. Even though the controls and most treatment groups terminally differentiated, cells exposed to 4-(N-methyl-N-nitrosamino)-1-(3-pyridinyl)-1-butanone, N-nitrosonornicotine, and moist and dry extract continued to divide, maintained a differentiated phenotype for 8 1/2 to 10 weeks in culture, and displayed focal growth and morphologic changes suggestive of early stages in cell transformation.

Toxicity of Sodium Dodecyl Sulphate and Other Detergents in Cultures of Human Oral Mucosa Epithelium

The aim of the present study was to investigate the relative cytotoxic effects of the detergents sodium dodecyl sulphate, Triton X-100, sodium oleate, stearyl etoxylate, sodium cholate and sodium taurocholate. Sodium dodecyl sulphate and stearyl etoxylate are used as dentifrice ingredients. Cultures of human oral epithelial cells were exposed to dilutions of the detergents for five minutes. Acute cytomorphological changes and membrane damage (leakage of lactate dehydrogenase, acid phosphatase and UV-absorbing material [280nm]) were monitored. Cytomorphological changes and cell proliferation were subsequently observed during the following week of recovery. Sodium dodecyl sulphate and Triton X-100 caused the most pronounced cytotoxic reactions, and it is concluded that more attention should be focused on the use of non-toxic detergents in oral hygiene products.

The perinuclear factor, a rheumatoid arthritis-specific autoantigen, is not present in keratohyalin granules of cultured buccal mucosa cells

Rheumatoid arthritis patients have antibodies in their serum directed against the perinuclear factor, a protein component present in keratohyalin granules in the cytoplasm of human buccal mucosa cells. The anti-perinuclear factor (APF) can only be detected by an indirect immunofluorescence test performed on fresh buccal mucosa cells from 'selected donors'. To obtain a more reliable antigen source and to gain more insight into the origin and nature of the perinuclear factor we attempted to culture perinuclear factor-containing buccal mucosa cells. Here we describe the successful culturing of such cells, which, however, did not contain keratohyalin granules nor the perinuclear factor. By adding the phorbol ester 12-o-tetradecanoylphorbol-13-acetate (TPA) we were able to induce keratohyalin granules in both cultured primary buccal mucosa cells and a squamous carcinoma cell line of the cheek (SqCC/Y1). These induced keratohyalin granules do contain the protein profilaggrin, which in vivo, in fresh buccal mucosa cells, co-localizes with the perinuclear factor. However, we were not able to demonstrate the presence of the perinuclear factor, not even after induction of terminal differentiation of the cultured cells nor after Epstein-Barr virus infection. Our results suggest that the perinuclear factor, in contrast to profilaggrin, is not an integral component of buccal mucosa cells.

The possible role of oral epithelial cells in tissue-type plasminogen activator-related fibrinolysis in human saliva

We studied the fibrinolytic activities of the following subfractions of unstimulated human whole saliva on plasminogen-rich fibrin plates: (1) submandibular saliva, (2) parotid saliva, and (3) smears of buccal epithelial cells from ten healthy males. A cell-bound plasminogen activator could be demonstrated in the sediments of all three subfractions of whole saliva. The incorporation of antibodies (goat IgG) against human two-chain tissue-type plasminogen activator (t-PA) could quench the assessed fibrinolytic activities, whereas additional experiments suggested the absence of urokinase-like and F XII-dependent activators of fibrinolysis. The determinations in growth medium from buccal-epithelial cell culture of t-PA antigen by means of enzyme-linked immunosorbent assay showed the presence of t-PA. These clinical and experimental findings suggest that buccal-epithelial cells produce t-PA, while the activity of t-PA in parotid and submandibular saliva is very low.

The use of cultured epithelial and endothelial cells for drug transport and metabolism studies

In an effort to develop novel strategies for delivery of drug candidates arising from rational drug design and recombinant DNA technology, pharmaceutical scientists have begun to employ the techniques of cell culture to study drug transport and metabolism at specific biological barriers. This review describes some of the general factors that should be considered in developing a cell culture model for transport studies and metabolism studies. In addition, we review in detail the recent progress that has been made in establishing, validating, and using cell cultures of epithelial barriers (e.g., cells that constitute the intestinal, rectal, buccal, sublingual, nasal, and ophthalmic mucosa as well as the epidermis of the skin) and the endothelial barriers (e.g., brain microvessel endothelial cells).

Characterization of two types of human oral fibroblast with a potential application to cellular toxicity studies: tooth pulp fibroblasts and buccal mucosa fibroblasts

Cultures of human oral buccal mucosa fibroblasts and human tooth pulp fibroblasts were established and grown under standard routine conditions. The biological characteristics of cell proliferation, growth pattern, cell morphology and enzyme release (lactate dehydrogenase and acid phosphatase) were studied. Under the same standard in vitro conditions the two cell types demonstrated different growth patterns and different levels of enzyme activity. It is suggested that differences in biological characteristics should be considered when selecting appropriate cells for toxicological studies of dental materials.

Buccal mucosa fibroblasts and periodontal ligament cells perturbed by tensile stimuli in vitro

Human buccal mucosa fibroblasts and periodontal ligament cells grown in tissue culture were subjected to tensile forces approximating those used for orthodontic bodily tooth movement. The cells were synchronized into pre S phase and positively tested for response to nonmechanical physical stimuli. Two-dimensional gel analysis and immunohistochemical analysis of the three cytoskeletal components showed a lack of response. Similar negative results were found when the cells were perturbed in the presence of substance P. We hypothesize that perhaps these cells respond more readily to injury, a secondary effect of the forces of tooth movement, than to tensile forces.

Growth-regulatory factors for normal, premalignant, and malignant human cells in vitro

Normal human cells, cells from nonmalignant proliferative lesions, and primary and metastatic tumor cells can be maintained in vitro and analyzed for requirements for growth in chemically defined media. The human melanocytic cell system with normal melanocytes, precursor nevus cells, and primary and metastatic melanoma cells has been extensively studied for the phenotypic properties of the cells, including their requirements for exogenous growth factors and other mitogens. In high calcium-containing W489 medium, normal melanocytes require four supplements: IGF-I (or insulin); bFGF, TPA, and alpha-MSH. Nevus cells are largely independent of bFGF. Depletion of TPA from medium is not as detrimental to nevus cells as it is to melanocytes, but the phorbol ester is still essential for maintenance of the typical nevic phenotype. Primary melanoma cells require at least one growth factor, IGF-I (or insulin), for continuous proliferation. On the other hand, metastatic cells of melanoma as well as of carcinomas of colon and rectum, bladder, ovary, and cervix are able to proliferate after a short adaptation period in medium depleted of any growth factors and other proteins. Doubling times of metastatic tumor cells in protein-free medium are only 30-60% longer than in FCS-containing medium. The growth autonomy of human tumor cells is apparently due to the endogenous production of growth factors. Likely candidates for autocrine growth stimulation of human tumor cells are TGF-alpha, TGF-beta, and PDGF. Melanoma and colorectal carcinoma cells express functional EGF/TGF-alpha receptors, and produce TGF-alpha, indicating that this growth factor is produced for autocrine stimulation. In addition to the use of anti-growth factor antibodies, other strategies for the inhibition of autocrine growth stimulation include mAbs to growth factor receptors, soluble receptors, receptor-mimicking antiidiotype antibodies, and active immunization against growth factors. Whether any of these therapeutic approaches is clinically feasible will need to be determined in extensive preclinical investigations.

Proliferation and differentiation characteristics of normal human squamous mucosal cells of the upper aerodigestive tract

Normal human squamous mucosal cells of the soft palate, buccal surface, epiglottis, hypopharynx, floor of the mouth, and tongue were cultured in vitro in serum-free medium. In medium MCDB 153 containing epidermal growth factor, insulin, bovine pituitary extract, and 0.1 or 2.0 mmol/L Ca++, squamous mucosal cells double every 24 hours. These cells then can be induced to arrest their proliferation reversibly by treatment with transforming growth factor-beta or ethionine, and they can irreversibly growth-arrest during senescence or when cultured in growth factor-deficient medium containing 2 mmol/L Ca++. The latter medium also induces differentiation, as does culture of cells in serum-containing medium. Serum-containing medium furthermore promotes extensive cell stratification and the formation of multilayered squamous mucosal tissue specimens that can be removed intact by Dispase treatment. These specimens represent potential autogenous mucosal grafts that can be used in patients who require reconstructive surgery of the oral cavity and oropharynx. Normal human squamous mucosal cells therefore closely resemble keratinocytes derived from the epidermis in the mechanisms that regulate proliferation and differentiation. This model cell system should facilitate future studies on upper aerodigestive tract squamous mucosal cell physiology and pathophysiology.

Characterization of human gingival keratinocytes cultured in a serum-free medium

Primary cultures of keratinocytes were established from gingival tissue explanted on the surface of type I collagen gels and fed a serum-containing medium. Cells could be routinely subcultured for at least five passages in a basal nutrient medium (MCDB 153) containing low calcium (0.1 mM), and supplemented with ethanolamine, phosphoethanolamine, hydrocortisone, insulin, epidermal growth factor and protein of bovine pituitary extract. Cells seeded at low densities doubled exponentially in number every 24-30 h and formed a confluent monolayer within 10-14 days. Phase-contrast light and transmission electron microscopy showed that the keratinocyte cultures had features typical of epithelial cells, including desmosomes and perinuclear tonofilament bundles. Immunofluorescent microscopy showed the presence of specific keratin proteins in basal cells of proliferating cultures. Gel electrophoresis of the insoluble cytosolic proteins of gingival and skin keratinocytes showed several differences. Suspension of dividing gingival keratinocytes in 1.3% methylcellulose medium induced greater than 50% cross-linked envelopes, suggesting the existence of a terminal differentiation pathway in gingival basal cells. Clonal growth experiments showed that both insulin and epidermal growth factor were required for optimal clonal growth. The growth of subcultures was arrested and the unstratified epithelial monolayer induced to form a stratified sheet by replacing the growth medium with basal MCDB 153 medium depleted of growth factors and containing 2 mM calcium. Sheets of stratified gingival epithelium formed on and later released from the dish by enzymatic treatment may be suitable for a variety of experimental and clinical uses.

A simple model for evaluating relative toxicity of root filling materials in cultures of human oral fibroblasts

Standardized test tubes filled with freshly mixed root filling materials (AH26, CRCS, N2, Kloroperka NO, ZOE cement and 2 experimental cements, ECI and ECII) were transferred into tissue culture flasks. Normal human oral fibroblasts were seeded in the flasks. Morphological cell changes were studied up to 15 days after seeding. The size of cell-free zones around the test tubes and the total cell number per culture flask were calculated after 5, 10 and 15 days. The findings showed N2 cement to be by far the most toxic material at all observation periods, whereas no toxic reactions could be seen in relation to tubes filled with Kloroperka NO. Compared with the 5-day observation period, some cell recovery was observed around test tubes with AH26 and ECII, whereas almost full cell recovery was found around test tubes with CRCS, ZOE and ECI. It was concluded that the present model, which allows long-term observations of human cellular reactions to dental materials, can be used as a simple and relatively cheap screening test for initial toxicity testing of dental materials.

Explants of human oral epithelium exposed to viruses and cancer chemotherapeutics

Cultures of proliferating epithelial cells were established from explants of normal human oral epithelium from healthy young volunteers. The epithelial cells were found permissive for herpes simplex virus type 1 and type 2, coxsackie virus A-4 and A-16, adenovirus type 5, measles vaccine, rubella and influenza type A virus-. Medium from DEAE-pretreated epithelial cultures infected with two subtypes of human immunodeficiency virus-1 showed an increasing content of virusprotein with time by antigen ELISA testing. In contrast there was no evidence of infection with coxsackie virus type B-2, cytomegalovirus, Epstein-Barr virus and varicella zoster virus. Treatment of the epithelial cells with a non-cytotoxic dose of cancer chemotherapeutic prior to or after infection with coxsackie virus A-4 or herpes simplex virus type 1 influenced the virus production dependent on both compound, mode of application, and virus. Adriamycin (doxorubicin) in low dose was found to stimulate the production of the two viruses.

Cultivation of ethmoidal sinus ciliated epithelia

Proceeding from the cultivation of human epidermal cells we succeeded in cultivating mucosal cells from ethmoidal sinuses and in characterizing them by scanning electron microscopy. In particular, the reaction of ciliated cells and goblet cells in vitro and their ability to reproduce were compared with the reaction of keratinocytes. Ethmoidal sinus cells show adhesion and spreading rates similar to those of skin cells; they proliferate faster (3 days up to monolayer) and differentiate in vitro to ciliated epithelia. It would seem possible to use them for lining of plastic prostheses for the respiratory tract.

Toxic effects of two dental materials on human buccal epithelium in vitro and monkey buccal mucosa in vivo

Confluent cultures of human buccal epithelial cells were exposed to graded dilutions of Gluma Bond or 3M Etching Liquid for 5 min. The cytotoxic effects induced by this treatment were observed (epithelial cell damage, growth inhibition). In vivo, monkey buccal mucosa was exposed to Gluma Bond or 3M Etching Liquid for 5 min. Biopsies were taken after 24 h, and the buccal epithelium processed for light microscopic examination. The toxic reactions to Gluma Bond were far more pronounced compared with the toxic reactions to 3M Etching Liquid in both models. Data obtained suggest that the in vitro model may be useful in assessing mucosal toxicity and in studying mechanisms of toxic action.

The Toxic Effects of Two Dental Materials on Human Buccal Epithelium In Vitro and Monkey Buccal Epithelium In Vivo

The aim of the present study was to compare the toxicity in vitro with the toxicity in vivo of two commercial chemicals marketed for use in the oral cavity (GLUMA BondR and 3M Etching LiquidR).

Confluent cultures of human buccal epithelial cells were exposed to graded concentrations of GLUMA Bond or 3M Etching Liquid for 5 minutes. The cytotoxic effects induced by this treatment were observed (cytomorphology, proliferation rate).

In vivo, monkey buccal epithelium was exposed to GLUMA Bond or 3M Etching Liquid for 5 minutes. Biopsies were taken after 24 hours, and the buccal epithelium processed for light microscopical examination.

In both models, the toxic reactions to GLUMA Bond were far more extensive than those caused by 3M Etching Liquid.