I O Thompson

A comparative light-microscopic, electron-microscopic and chemical study of human vaginal and buccal epithelium.

The scarcity of sizeable specimens of normal oral mucosa for experimental purposes has hampered research on oral epithelium. Because large specimens of viable human vaginal mucosa are readily available and because vaginal and buccal epithelia are microscopically similar, vaginal mucosa has been used successfully to establish a human cyst model in experimental animals. The ultrastructure and distribution of keratin filaments in these epithelia are also similar, as is their permeability to water and a number of chemical substances. Therefore, if vaginal mucosa could be substituted for buccal mucosa it would expedite research on the epithelium of buccal mucosa. To strengthen further the concept that vaginal epithelium could replace buccal epithelium in certain experimental studies, the thickness of these epithelia, their patterns of surface keratinization, the presence or absence of intercellular lipid lamellae and their lipid contents were now compared. Thirty-three specimens of vaginal mucosa from postmenopausal women and 36 of buccal mucosa were investigated. To compare the thickness of the epithelial layers the number of cell layers in sections of 20 vaginal and 20 buccal mucosal specimens were counted in the three thickest and three thinnest regions of each specimen. Surface keratinization was evaluated on sections stained with the Picro-Mallory method. To demonstrate lipid lamellae two vaginal and two buccal mucosa specimens were examined electron microscopically after normal fixation and postfixation in ruthenium tetroxide. Following solvent extraction of 11 vaginal and 14 buccal epithelia, quantitative lipid analyses were performed using thin-layer chromatography. No statistically significant differences were found between the maximum and minimum number of epithelial cell layers. The patterns of surface keratinization and the distribution and appearance of the lipid lamellae in the intercellular spaces were similar. The lipid composition of the two epithelia corresponded, except for the cholesterol esters and glycosylceramides, which were higher in buccal epithelium. Ceramides for vaginal epithelium and triglycerides for buccal epithelium were not determined. Based on structural similarities, a similar lipid composition and earlier findings, it is concluded that vaginal epithelium can be used as a substitute for buccal epithelium in certain in vitro, and possibly for in vivo, studies.

Oral carriage of Candida in healthy and HIV-seropositive persons.

The prevalence of oral colonization with Candida species was studied in 28 HIV-seropositive and 28 healthy persons. Candida was cultured from 75% and 68% of HIV-positive and control persons, respectively, with a significantly higher density carriage in the HIV-seropositive group. Positive smears were seen in 39% of all patients. Candida albicans was the most frequently isolated species with Biotype 1 accounting for 56% of the isolates. Resistance to antifungal agents was seen in Candida strains isolated from both groups.

Permeation of 17β-estradiol through human vaginal and buccal mucosa

Because of the relative scarcity of fresh human oral mucosa specimens for permeability studies, we investigated the use of human vaginal mucosa as a model of the former. In a previous study we demonstrated the comparable diffusion rate of water across human vaginal and buccal mucosa and proposed the use of the former as a suitable model of the latter for in vitro drug permeability studies. To further evaluate the human vaginal/buccal mucosa model, we decided to compare these two tissues with respect to their permeability to 17beta-estradiol. Clinically healthy human vaginal and buccal mucosa specimens were obtained during vaginal hysterectomies and different oral surgical procedures. The permeability of each tissue specimen to 17beta-estradiol was determined through the use of a continuous flow-through diffusion system. Specimens were examined histologically before and after experiments. Mean flux values for 17beta-estradiol across human buccal mucosa tended to be slightly higher than those observed for vaginal tissue, but no statistically significant differences could be demonstrated. The results from this study further support our hypothesis that human vaginal mucosa may be a suitable model of human buccal mucosa for in vitro drug permeability studies.

Penetration of human vaginal and buccal mucosa by 4.4-kd and 12-kd fluorescein-isothiocyanate-labeled dextrans

In a previous study we demonstrated that human vaginal mucosa was as permeable to water as was buccal mucosa. Water, however, is a very small molecule with a molecular weight of 18 d. To further explore similarities between these two types of mucosa with respect to permeability, it was decided to investigate the passage of two large, hydrophilic molecules across these epithelia. Specimens of fresh, clinically healthy human vaginal and buccal mucosa were taken from excised tissue obtained during vaginal hysterectomies and various oral surgical procedures. Seven biopsy materials from each specimen were mounted in flow-through diffusion cells (exposed area, 0.039 cm2), and their permeability to 4.4- and 12-kd fluorescein-isothiocyanate-labeled dextrans was determined through use of a continuous flow-through perfusion system. Dextran was detected by means of a fluorospectrophotometric method at excitation and emission wave lengths of 498 and 520 nm, respectively. Specimens were examined histologically before and after permeability experiments, and similarities between vaginal and buccal tissues were verified. No statistically significant differences between the flux values of the 4.4-kd dextran across vaginal and buccal mucosa were found. However, for the 12-kd dextran the flux rate across buccal mucosa was significantly higher than the rate across vaginal mucosa. These results demonstrate that human vaginal mucosa is for practical purposes as permeable as buccal mucosa to 4.4-kd hydrophilic molecules. This further supports the hypothesis that vaginal mucosa may be a useful model for studying the passage across buccal mucosa of chemical compounds and therapeutic agents that are less than approximately 4.4 kd in molecular mass. For a 12-kd dextran the flux rate across buccal mucosa is significantly higher than the flux rate across vaginal mucosa, and the model becomes inaccurate.