Transport of D-glucose across cultured stratified cell layer of human oral mucosal cells

Corticosteroid delivery using oral mucosa equivalents for the treatment of inflammatory mucosal diseases

Oral lichen planus (OLP) is an immune‐mediated disease of the oral mucosa with idiopathic aetiology. It is frequently treated with topical corticosteroids (applied as gels, mouthwashes, or sprays); however, the mucosal exposure times of topical corticosteroids are short because of removal by the constant flow of saliva and mechanical forces. In this study we used cell monolayers, as well as oral mucosal equivalents (OMEs) containing activated T‐cells, to examine corticosteroid potency and delivery of clobetasol‐17‐propionate from a novel electrospun mucoadhesive patch. The OMEs displayed tight junctions, desmosomes, hemidesmosomes, and an efficient permeability barrier. Following application of corticosteroids to cells cultured as monolayers, the degree of cytotoxicity measured correlated to the level of potency recognized for each corticosteroid; by contrast, OMEs were largely unaffected by corticosteroid treatment. Permeation of clobetasol‐17‐propionate into and through the OMEs was time‐ and dose‐dependent, regardless of whether this corticosteroid was delivered in liquid form or from a mucoadhesive patch, and both liquid‐ and patch‐delivered clobetasol‐17‐propionate significantly reduced the secretion of interleukin‐2 by activated T‐cells. This study confirms that OMEs are more suitable models than cell monolayers for evaluating toxicity and drug delivery. After topical exposure, clobetasol‐17‐propionate accumulated in OMEs at a higher level than betamethasone‐17‐valerate and hydrocortisone‐17‐valerate, and exerted its immunosuppressive actions following application via the patch delivery system, highlighting the efficacy of this mode of drug delivery to treat OLP.

Cell culture models of oral mucosal barriers: A review with a focus on applications, culture conditions and barrier properties

Understanding the function of oral mucosal epithelial barriers is essential for a plethora of research fields such as tumor biology, inflammation and infection diseases, microbiomics, pharmacology, drug delivery, dental and biomarker research. The barrier properties are comprised by a physical, a transport and a metabolic barrier, and all these barrier components play pivotal roles in the communication between saliva and blood. The sum of all epithelia of the oral cavity and salivary glands is defined as the blood-saliva barrier. The functionality of the barrier is regulated by its microenvironment and often altered during diseases. A huge array of cell culture models have been developed to mimic specific parts of the blood-saliva barrier, but no ultimate standard in vitro models have been established. This review provides a comprehensive overview about developed in vitro models of oral mucosal barriers, their applications, various cultivation protocols and corresponding barrier properties.

Hollow optical-fiber based infrared spectroscopy for measurement of blood glucose level by using multi-reflection prism

A mid-infrared attenuated total reflection (ATR) spectroscopy system employing hollow optical fibers and a trapezoidal multi-reflection ATR prism has been developed to measure blood glucose levels. Using a multi-reflection prism brought about higher sensitivity, and the flat and wide contact surface of the prism resulted in higher measurement reproducibility. An analysis of in vivo measurements of human inner lip mucosa revealed clear signatures of glucose in the difference spectra between ones taken during the fasting state and ones taken after ingestion of glucose solutions. A calibration plot based on the absorption peak at 1155 cm(-1) that originates from the pyranose ring structure of glucose gave measurement errors less than 20%.

Towards a defined, serum- and feeder-free culture of stratified human oral mucosal epithelium for ocular surface reconstruction

PURPOSE

Ocular surface reconstruction with cultivated oral mucosal epithelial transplantation technique is a viable treatment option for severe ocular surface injuries and diseases with limbal stem cell deficiency. Currently, this technique is based on utilization of xenogenic, allogenic or undefined components such as murine 3T3 feeders, serum and amniotic membrane. In this study, we aimed to find a more defined culture method to generate stratified human oral mucosal epithelium.

METHODS

In this study, we have examined the formation of stratified cell sheets from human oral mucosal epithelial cells under serum-free culture environment both in the absence and presence of fibroblast-conditioned culture medium and elevated epidermal growth factor (EGF) concentration.

RESULTS

In all examined culture conditions, the cultivated oral epithelial cells formed a stratified tissue, which was positive for keratins K3/12, K4 and K13. The tissue-engineered oral epithelia also expressed proliferation and progenitor markers Ki67 and p63 in the basal layer of the cell sheets, suggesting that the epithelia still had regenerative capacity. The cultures presented expression of tight junction proteins ZO-1 and occludin and high transepithelial electrical resistance values.

CONCLUSION

In this culture method, we have been able to produce stratified cell sheets successfully without serum, conditioning of the medium or increased EGF concentration. We provide a novel protocol to produce tight multi-layered epithelium with proliferative potential, which can be easily adapted for cultivated oral mucosal epithelial transplantation.

Development of a new assay system for evaluating the permeability of various substances through three-dimensional tissue

A novel assay system with cell-dense three-dimensional (3D) tissue was developed for measuring the permeability of substances. In this paper, the permeabilities of various molecules containing nutrients, a cytokine, and a chemokine were examined and analyzed. A single-layered cell sheet was approximately 20 mum thick, and as the number of layers of these cell sheets increased, so did the total thickness of the tissue. The diffusion rates of glucose and pyruvic acid were reduced to approximately 30-40% by a single-layered cell sheet compared with the control without the cell sheet, and the diffusion of both substances were completely inhibited by a quadruple-layered cell sheet. The diffusion rate of creatinin was reduced to approximately 50% and 15-20% by a single-layered and by a quintuplet-layered cell sheet, respectively. On the other hand, the diffusion rate of stromal cell-derived factor 1alpha, vascular endothelial growth factor, beta2-microglobulin, and transferrin was reduced to approximately 10%, 5%, 20%, and 10%, by only a single-layered cell sheet, respectively. The diffusion of these substances were completely inhibited by a double-layered cell sheet. These results show that the permeability of substances through 3D tissue significantly decreased with the increase of the molecular weight. Therefore, the system could give a simulated living-tissue condition for measuring the permeability of substances. To our knowledge, this is the first report about measuring the permeability of substances through cell-dense 3D tissues without scaffolds. The assay system is believed to contribute to the progress of physiology, metabology, biochemistry, and pharmacokinetics. Further, the system may give some hints for developing a new dialysis membrane technology for an artificial kidney.

Chiral toxicology: it's the same thing...only different

Chiral substances possess a unique architecture such that, despite sharing identical molecular formulas, atom-to-atom linkages, and bonding distances, they cannot be superimposed. Thus, in the environment of living systems, where specific structure-activity relationships may be required for effect (e.g., enzymes, receptors, transporters, and DNA), the physiochemical and biochemical properties of racemic mixtures and individual stereoisomers can differ significantly. In drug development, enantiomeric selection to maximize clinical effects or mitigate drug toxicity has yielded both success and failure. Further complicating genetic polymorphisms in drug disposition, stereoselective metabolism of chiral compounds can additionally influence pharmacokinetics, pharmacodynamics, and toxicity. Optically pure pharmaceuticals may undergo racemization in vivo, negating single enantiomer benefits or inducing unexpected effects. Appropriate chiral antidotes must be selected for therapeutic benefit and to minimize adverse events. Enantiomers may possess different carcinogenicity and teratogenicity. Environmental toxicology provides several examples in which compound bioaccumulation, persistence, and toxicity show chiral dependence. In forensic toxicology, chiral analysis has been applied to illicit drug preparations and biological specimens, with the potential to assist in determination of cause of death and aid in the correct interpretation of substance abuse and "doping" screens. Adrenergic agonists and antagonist, nonsteroidal anti-inflammatory agents, SSRIs, opioids, warfarin, valproate, thalidomide, retinoic acid, N-acetylcysteine, carnitine, penicillamine, leucovorin, glucarpidase, pesticides, polychlorinated biphenyls, phenylethylamines, and additional compounds will be discussed to illustrate important concepts in "chiral toxicology."

Distribution of anthocyanins delivered from a bioadhesive black raspberry gel following topical intraoral application in normal healthy volunteers

PURPOSE

Results from our oral cavity chemoprevention trial demonstrated appreciable interpatient variations regarding chemopreventive efficacy of a freeze dried black raspberry (FBR) gel. We speculated these data reflected individual patient-related differences in absorption, target tissue uptake and local compound metabolism of key FBR compounds (anthocyanins). Accordingly, this study assessed the distribution of anthocyanins from the 10% (w/w) FBR gel in saliva, oral tissues and plasma.

METHODS

Human subject participation entailed collection of: (1) saliva, tissue and plasma (5 min following gel application, keratinized tissues), (2) saliva and plasma (5 min after sublingual gel application), (3) saliva and plasma at 1, 2, and 4 h post gel application (keratinized tissues), and (4) saliva (cyanidin 3-rutinoside incubations). Levels of FBR anthocyanins in the respective samples were analyzed by LC/MS/MS.

RESULTS

Our data show: significantly higher anthocyanin levels in saliva and oral tissues relative to matched plasma samples, marked donor-specific variations in anthocyanin uptake, sustainability of anthocyanins at the target site, pH affects anthocyanin penetration and intraoral anthocyanin decomposition and/or metabolism.

CONCLUSIONS

No previous oral cavity chemoprevention trials evaluated compound distribution at the treatment site. Our data, which demonstrate a local delivery-derived pharmacologic advantage, provide insights which could advance oral cavity chemoprevention strategies.

Sublingual Delivery of Insulin: Effects of Enhancers on the Mucosal Lipid Fluidity and Protein Conformation, Transport, and in Vivo Hypoglycemic Activity

The purposes of this study were to evaluate effects of enhancers for sublingual delivering insulin on the mucosal lipid fluidity and protein conformation, transport, and in vivo hypoglycemic activity in normal rats. The effects on sublingual mucosa, and aggregation states of insulin were estimated using fluorescence polarization, and circular dichroism method, respectively. The human immortalized oral epithelial cell monolayer was used for evaluating transport of insulin. Hydroxylpropyl-beta-cyclodextrin (HP-beta-CD), chitosan, polyethylene-polypropylene glycol, polyoxyethylene lauryl ether, polysorbate 80, egg lecithin, or oleic acid, was used as a penetration enhancer, respectively. The fluidity of sublingual mucosal lipid was markedly reduced by these enhancers excluding polysorbate 80, and the secondary structure of the mucosal proteins was also influenced by these enhancers. The hexamers of insulin were dissociated to monomers only by chitosan, polyoxyethylene lauryl ether, and egg lecithin. Nonetheless, plasma glucose levels in normal rats were significantly lowered after sublingual administration of insulin with an enhancer compared with those without an enhancer at the same time-point. The enhancing effects may be due to one or multiple factors: increasing the mucosal lipid fluidity, directly loosing the tight junction of epithelia, and dissociating the hexamers of insulin to monomers. Among these, the opened tight junction may correlate most with the enhancing effect in the mucosal permeability. Because the aggregates of insulin exist, the dissociation of the aggregates by an enhancer would benefit the permeability.

Actin microfilaments et al.--the many components, effectors and regulators of epithelial cell endocytosis

The aim of this review is to introduce the advances made over the past several years regarding the participation of actin and actin-associated proteins in clathrin-mediated endocytosis in simple cell models, and then to consider the evidence for the involvement of these effectors in apical clathrin-mediated endocytosis in epithelial cells. Basic mechanisms of clathrin-mediated endocytosis are initially addressed, followed by a detailed description of the actin cytoskeleton: its organization, function and, most importantly, the essential role played by proteins and signaling pathways responsible for the regulation of actin filament dynamics. Our focus then shifts to the GTPase, dynamin and its pivotal role as a bridge between various components of the clathrin endocytic machinery and the actin cytoskeleton. Mechanisms and effectors of dynamin-dependent endocytosis are then described, with a particular emphasis on novel proteins, which link dynamin to actin filaments. We consider additional effectors proposed to interact with actin to facilitate clathrin-mediated endocytosis in a dynamin-independent manner. The multiple roles which actin filaments are thought to play in endocytosis are addressed followed by a more detailed characterization of actin filament participation specifically in apical endocytosis. We conclude by discussing how these concepts may be integrated to improve drug internalization at the apical plasma membrane of epithelial cells.