| Summary: | 博士 === 國立臺灣大學 === 醫學工程學研究所 === 106 === An ideal in vitro drug screening model is important for the drug development. In addition to monoculture systems, coculture systems have been used to mimic the in vivo tumor tissues because cell-cell and cell-extracellular matrix interactions can be studied. In this study, suspension core/shell coculture multicellular spheroids on chitosan are developed. Based on the characteristic of chitosan inhibiting cell adhesion, SW620 (colon cancer cell line), 3A6 (mesenchymal stem-like cell line) and Hs68 (foreskin fibroblast line) cells can aggregate to form 3D coculture spheroids with intimate cell contacts. CD44 is extensively expressed within adult bone marrow and has been considered as an important marker for cancer stem cells in some types of tumors. Therefore, it is used to understand the variations of stem cells and cancer cells when cells culturing on chitosan firstly. When cells are cocultured on chitosan, 3A6 and Hs68 cells always locate in the core of spheroids and are completely enveloped by SW620 cells following the differential adhesion hypothesis. Moreover, the core cells can stimulate the shell SW620 cells to enhance activity and resistance against the cytotoxicity effect of chemotherapy drugs. Therefore, based on the specificity of the core/shell coculture multicellular spheroids, a novel in vitro tumor model is proposed.
Fibroblasts have been extensively used as a model to study cellular senescence. The second purpose of this study is to investigate whether the human foreskin fibroblast aging process can be regulated by using the chitosan. Senescent cells are collected and seeded on chitosan to form multicellular spheroids. The protein expression of senescence-associated secretory phenotypes (SASPs) and senescence-associated molecular markers of these cells in multicellular spheroids are downregulated significantly. Following chitosan treatment, fibroblasts reseed on TCPS show lower SA β-gal activity, and higher cellular motility and proliferation ability. Cells can form suspending multicellular spheroids on many biomaterials, but only chitosan is capable of delaying senescence of fibroblasts. Therefore, in addition to the structure of multicellular spheroids, chitosan itself should play an important role in delaying fibroblast senescence. In addition to the intracellular TGF-β expression, the extracellular TGF-β expression is also downregulated by chitosan. TGF-β signaling pathway is involved in the chitosan-mediating fibroblast senescence process. Finally, whether the senescence-delaying effect of chitosan can be applied to other cells, such as human synovial membrane derived cells (SCs) and anterior cruciate ligament fibroblasts (ACLs) is examined. From the studied data, we find that chitosan not only delays the senescence but also enhances the functions of SCs and ACLs, which is benefit for chitosan applying on the cell therapy.
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