Buccal cell cultures

The use of buccal cell cultures for assessing the permeability of the buccal mucosa has attracted recent attention (see Chap. 7 for a more extensive summary). In order to culture buccal epithelial cells, the cells must be harvested from an appropriate source and cultured under specific conditions using an appropriate growth medium, temperature, and humidity [46], Cell cultures have been successfully grown from hamster cheek pouch. These cultured cells, however, did not differentiate to form a complete keratinized surface as seen in the normal hamster cheek pouch, and they consequently displayed a greater permeability to compounds when compared with keratinized hamster cheek pouch mucosa [134], Therefore, the cultured hamster cheek cells more closely mimicked the human buccal mucosa due to their lack of keratinization, and so this may be an appropriate model for predicting permeability through the human buccal mucosa. 

Recently, a cell culture derived from biopsies of healthy human buccal mucosa has been developed with remarkably similar morphology, membranecoating granule structure and appearance, and lipid composition to intact buccal tissue [102], The barrier nature of this cell culture model is similar to intact buccal mucosa, and so this cell culture may be an alternative model to the 

TR146 cell culture. With the development of tissue culture techniques, it is anticipated that various cell culture models may be developed with similar morphological and barrier properties to normal intact buccal mucosa. Such models may be very useful in assessing the buccal permeability and metabolism of many compounds. 

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The advantages of the in vitro approaches described above also apply to buccal cell culture systems. In addition, other aspects such as cell growth and differentiation can be studied in these systems in detail. Also, once the source is established, a continuous supply of cell lines can be obtained, which obviates the need for expensive animal or human tissues that are often difficult to obtain in large quantities. 

Nielsen HM, Rassing MR (2000a) TR146 cells grown on filters as a model of human buccal epithelium V. Enzyme activity of the TR146 cell culture model, human buccal epithelium and porcine buccal epithelium, and permeability of leu-enkephalin. Int J Pharm 200 261-270... 

Nielsen HM, Rassing MR (2002) Nicotine permeability across the buccal TR146 cell culture model and porcine buccal mucosa in vitro Effect of pH and concentration. Eur J Pharm Sci 16 151-157... 

Portero A, Remunan-Lopez C, and Nielsen HM (2002) The potential of chitosan in enhancing peptide and protein absorption across the TR146 cell culture model—An in vitro model of the buccal mucosa. Pharm. Res. 19 169-174. 

Of the different types of oral mucosal cell cultures that have been used [47,48], the most commonly used ones are explants of primary cultures. Small pieces of excised buccal or sublingual tissue are placed in a support system and fed with culture medium. The outgrowths obtained from these tissue explants are then transferred and grown in appropriate media. For example, outgrowths of fibroblasts [49] thus obtained have been described. Gibbs and Ponec [50] reconstructed the epithelium of mucosal tissue by placing a tissue biopsy (with the epithelial side upwards) onto a fibroblast-populated collagen gel. The explants obtained were cultured immediately at the air liquid interface until the epithelium had expanded over the gel (2-3 weeks). These explant cultures may retain many of the in vivo tissue characteristics. 

Quadros E, Cassidy JP, and Leipold H. Buccal Tissues and Cell Culture. Chapter 7. In Borchardt RT (ed.). Models for Assessing Drug Absorption and Metabolism. Plenum Press, New York, 1996. 

In addition, the cultured HeLa cells display a strong additional protein band in the second derivative spectra at about 1645 cm that is totally absent in the second derivative spectra of the buccal cells. In the original studies [45], the S/N... 

Freshly excised buccal or sublingual tissues have also been used to generate dissociated cells. Hedberg et al. [49] used one such culture to measure the expression of alcohol dehydrogenase-3 in cultured cells from human oral mucosal tissue. Human buccal tissue was incubated with 0.17% trypsin in phosphate-buffered saline (PBS) at 4°C for 18 to 24 h to obtain dissociated primary keratinocytes, and subsequently these keratinocytes were seeded onto fibronectin and collagen-coated dishes in serum-free epithelial medium. 

Autrup, H., et al. 1985. Metabolism of benzo[a]pyrene by cultured rat and human buccal mucosa cells. Carcinogenesis 6 1761. 

Sundqvist, K., et al. 1991. Growth regulation of serum-free cultures of epithelial cells from normal human buccal mucosa. In Vitro Cell Dev Biol 27A 562. 

XXX Type of Trisomy. Patients have been observed with duplicate sex chromatin bodies in the cells of the buccal mucosa, with resistant amenorrhea, infantile external genitalia, underdeveloped breasts, and high levels of urinary gonadotropins. Chromosome studies on cultured bone marrow cells demonstrated the presence of 47 chromosomes with the XXX type of trisomy. 

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