الفهرس 
GENERAL INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Sjogren’s syndrome and radiotherapy for head and neck cancer result in irreversible loss of functional salivary acini; known as xerostomia, for which no adequate treatment is available. Our group has been testing different biomaterials, extracellular matrix proteins, and graft cells for the development of an orally implantable tissue-engineered artificial salivary gland device. The major hurdle we faced was to find a suitable graft cell type that must establish tight junctions (TJs) and exhibit an adequate transepithelial electrical resistance (TER) in addition to being functional acinar secretory cells. Therefore, the aim of this thesis was to isolate and characterize a suitable graft cell type. We determined the distribution of TJ proteins in human salivary tissue to serve as a reference for future studies to assess the presence of appropriate TJ proteins in the graft cells we are looking for. We have found that claudin-1 was expressed in ductal and ~25% of serous cells while claudin-2, -3, -4, JAM-A, occludin and ZO-1 were expressed in ductal and acinar cells. We characterized two candidate graft cells; human submandibular gland (HSG) cell line and primary human salivary gland (huSG) cells cultured individually on Matrigel (a basement membrane extract). Matrigel supported their morphogenesis and cytodifferentiation into 3-D polarized functional acinar units; expressing all TJ and acinar-specific proteins and exhibiting adequate TER. Thus, on Matrigel, both candidate cells showed ideal characteristics of suitable graft. However, neither Matrigel nor HSG would be used in clinical applications. Nevertheless, they would be implanted in animal models to further examine our envisioned artificial salivary gland device. Mesenchymal stem cells (MSCs) can differentiate into cells from all dermal lineages; carrying new promises and significant therapeutic implications. Importantly, MSCs have been isolated from different adult tissues including salivary glands, however; no reports localized such cells in situ. We localized CD44+ and CD166+ cells in human serous and mucous acini, respectively. Therefore, huSG tissue harbors MSCs, thus, these markers would be used; either to isolate MSCs or differentiated serous/mucous acini from huSGs. Implantation of autologous functional acini would be a major achievement to treat xerostomic patients, however, this would require the generation of a great number of such acini. Autologous MSCs would be expanded in vitro and induced to differentiate into functional salivary acini. MSCs were cocultured with huSG cells and analyzed afterward. Successfully, 40% of MSCs showed salivary acinar phenotype; expressed acinar-specific genes and proteins, exhibited a noticeable level of TER, and were able to secrete α-amylase into media. These results represent a proof-of-concept of full differentiation of MSCs guided by huSG into functional polarized acini. This supports the potential and feasibility of using MSCs in cell-based therapy. Therefore, MSCs would provide a novel alternative source of graft for an implantable artificial salivary gland device to treat xerostomic patients.