No abstract

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

The temperature dependence of CO-tolerant H2 oxidation reaction (HOR) activity at Pt, Pt-Co, and Pt-Ru electrodes in 0.1 M HClO4 solution was examined with a channel flow electrode at 30 to 90 degrees C. The kinetically controlled current density (j(K)) for the HOR at Pt decreased seriously at CO overage (theta(CO)) >0.6 in the whole temperature range examined. In contrast, the Pt-Ru alloy exhibited an excellent CO tolerance: only 15% reduction in j(K) even at theta(CO) = 0.6 and 30 degrees C. The Pt-Co alloy also showed moderate CO tolerance up to 70 degrees C. It was found for these alloys that the CO adsorption rate was much slower than that of Pt and the HOR sites were not so rigidly blocked by adsorbed CO due to its enhanced mobility, resulting from their modified electronic structure of surface Pt sites. The activation energies for the apparent rate constants for the HOR were as low as 3.0 and 5.3 kJ mol(-1) at Pt and Pt-Ru, respectively, indicating that the high-temperature operation increases CO-free HOR sites as well as enhancing the HOR kinetics.