Characterization of Chitosan in Tissue Engineering f Salivary Gland Morphogenesis
Date Issued
2008
Date
2008
Author(s)
Yang, Tsung-Lin
Abstract
Salivary gland is an exocrine gland that is responsible for saliva production, absorption, and regulation. In histology, salivary is a ramified tissue formed by interconnecting branches and ducts. The arborized architecture, which is formed by the developmental process of branching morphogenesis, is essential for salivary function. Branching morphogenesis is an efficient and ubiquitous process for creating a larger cellular area for metabolic requirement in developing many glandular organs. To regenerate the glandular organ, such as salivary glands, recapitulation of branching processes may be requisite. At present, though with the progress in preserving phenotypes and promoting differentiation of salivary cells for regenerative purpose, to facilitate the morphogenesis of salivary tissue by tissue-engineering approaches has never been thoroughly explored. In this study, the possibility of promoting salivary gland morphogenesis is explored by tissue-engineering approach step by step, and the way that the chitosan-based biomaterial affects salivary tissue morphogenesis is characterized. or the purpose of recapitulating salivary gland morphogenesis, the interaction between epithelia and mesenchyme is required. During the development of ectodermal organ, the epithelium interacts with the surrounding mesenchyme to form specific phenotypes by receiving the guiding morphogenetic information. We first use murine fetal submandibular gland (SMG) model and the biomaterials which had been explored for salivary cells regeneration to study the biomaterial effects on epithelial-mesenchymal interaction and salivary morphogenesis. It is found that viability, migratory ability, and tissue interaction of salivary tissue are largely affected by different biomaterials. When salivary tissue is cultured on an appropriate substratum, the epithelial-mesenchymal interaction and the tissue-specific morphogenesis could be induced. ext, we perform global screening to find out the best cultured biomaterial which is capable of promoting morphogenesis of salivary tissue. It shows that the biomaterial effects still exist when whole salivary progenitor tissues are used in the survey. Numerous biomaterials, including synthetic, natural, biodegradable, non-biodegradable, and biological-origin polymers have been investigated. It is found that the cell behaviors as well as the tissue morphogenesis of salivary origin are biomaterial-dependent. Among them, chitosan shows a superior morphogenesis-promoting capacity, which maintains tissue viability and promotes an appropriate tissue interaction for morphogenesis. hen chitosan is prepared in the membranous form, it is capable of providing a more preferential environment for salivary gland branch formation. After culturing SMG explants on chitosan membranes, secreted extracellular matrices distribute in a reticular manner and form thicker fibers beyond the extents of cell attachment, which are not found in other biomaterials. In addition, the conditioned chitosan membranes are able to further enhance SMG branching. The fact that the promoting effects are eliminated with collagenase treatment and that type I and III collagen are identified within the adherent fibrillar extracellular matrix raise the possibility that the stimulating factors are collagen-originated. Furthermore, when chitosan is prepared in a soluble form, the morphogenesis-promoting effects are also observed. This result indicates that chitosan is a bioactive substratum for salivary tissue morphogenesis which enables active interaction between cultured salivary tissue and biomaterial. Next, the specificity of chitosan’s morphogenesis-promoting effects is further investigated. It is found that chitosan is able to promote SMG branching in a dose-dependent manner. The effect is chitosan-specific and is not reproduced by substrates with similar chemical structures or by other polymeric molecules of natural or synthetic origin. Furthermore, the branch-promoting effect is molecular weight-dependent. In addition, following digestion with lysozyme, chitinase, or chitosanase, digested chitosan is unable to reproduce the similar effects. This study clarifies the specificity and preferential activity of chitosan in enhancing branching morphogenesis of progenitor salivary tissue. ith chitosan, the morphogenesis-promoting effects of mesenchymal tissue on SMG are further enhanced. Chitosan is also competent to induce recombined SMG epithelium to form branches in the serum-free condition. In the presence of chitosan, the morphogenetic efficacy of mesenchyme-derived growth factors responsible for epithelial morphogenesis increases. The specific epithelial phenotype induced by individual growth factor is promoted by chitosan as well. Moreover, the proliferative and the chemotactic properties of these growth factors toward SMG epithelia are also reinforced by chitosan. Therefore, in orchestrating and intensifying the essential mesenchyme-derived growth factors, chitosan is versatile in mediating SMG epithelium to form a predetermined phenotype more efficiently and comprehensively. n all, the current study demonstrates that the morphogenesis of salivary tissue could be regulated by tissue-engineering approaches. It is suggested that, for salivary tissue, chitosan is a morphogenesis-regulating biomaterial. We design a novel methodology to facilitate salivary tissue morphogenesis by enhancing branch formation. The results provide a novel insight into the role of chitosan in salivary tissue morphogenesis and highlight the potential for future application in salivary tissue investigation and regeneration.
Subjects
Chitosan
Salivary gland
Morphogenesis
Branching
Type
thesis
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