| Summary: | 博士 === 國立臺灣大學 === 醫學工程學研究所 === 103 === Salivary gland is an exocrine gland that is responsible for saliva production. The secretion of saliva contains digestive enzymes, growth factors, and antimicrobial agents. This function is crucial in the processes of digestion, lubrication, and protection in the body. Therefore, salivary gland hypofunction can result serious negative effects on the patients quality of life. Radiation therapy (RT) for head and neck cancer, and autoimmune diseases (such as Sjogren’s syndrome) can cause unavoidable coirradiation of surrounding normal tissues such as the salivary glands. This effect results in irreversible damage of salivary glands hence to significantly reduces salivary output. Salivary gland hypofunction and xerostomia lead to hindering of speech (dysphonia), difficulty of swallowing (dysphagia), influences on nutrition (dysnutritia) and others. Currently, there is no treatment available to permanently treat dysfunctional salivary glands. Constructing artificial salivary glands with tissue engineering may be a viable curative procedure to treat patients suffering from dry mouth.
Tissue engineering applications in salivary glands require a significant amount of salivary gland cells and an understanding of gland cell-related coordination and function. Many experimental induce the increase of salivary gland stem/progenitor cells with duct ligation or fluorescence-activated cell sorting by antibodies. This research establishes a simple and highly reproducible protocol for isolation and characterization of stem/progenitor cells obtained from human salivary glands. The percentage of CD49f and CD90 double-positive cells was increased at 14 days after seeding, and then decreased at 28 days. The gene expression levels of ALDH1A1 and ALDH1A3 were also at the highest at 14 days after seeding. Cultured cells can successfully differentiate into adipocytes and osteocytes. E-cadherin expression in cultured cells increased with time while vimentin expression gradually decreased to a very low level after prolonged culture, inferring a MET during the repopulation process of cell culture. Our study confirmed the existence of progenitor cells in cultured adult human parotid glands. This research was also established a simple culture method to obtain sufficient progenitor cells for further tissue engineering studies.
However, maintaining the expression levels of amylase in culturing salivary gland epithelial cells is important.Salivary gland cells in vivo are surrounded by a complex stromal environment, in which fibroblasts are the main cell type in proximity to the gland cells. An appropriate number of fibroblasts in contact with the parotid gland acinar cells (PGACs) is necessary to promote PGAC function. Fibroblast-secreted bFGF may play a paracrine signaling role in the regulation of α-amylase expression in PGACs. Interestingly, the effect of fibroblast conditioned medium from PVDF on the α-amylase expression of PGACs was obviously enhanced. By growth factor protein array assay, higher NT-4 expression was observed in PVDF-derived fibroblast conditioned medium. Fibroblasts might be reprogrammed into neural-like cells after cultured on appropriate biomaterials.
In these studies, the interaction between PGACs, fibroblasts, and biomaterials was investigated. This could be treated patients with xerostomia and applying directly by re-implantation of autologous salivary gland tissue engineering. The re-implantation treatment can be a major contribution to their quality of life.
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