Studies on modeling of bone marrow niche under in vitro conditions

Mesenchymal stem cells (MSC) are the widely used stem cell type in preclinical research, clinical studies and investigational new drug applications. Isolation of MSC can be provided from bone marrow and adipose tissue, and the total isolated amount of MSC consists of 0.001-3% of nucleated cells. Thus, novel isolation techniques and resources are still needed. In the first section of this thesis, the suitability of the filter and bag systems, which are used during bone marrow transfer, were investigated. Those systems are removed as a medical waste, after the transfer, in routine. The current approach in stem cell-based therapy is using bioactive compounds named as "cell-free therapy" resourced from MSC, instead of applying MSC as systemically or locally. In the second stage of this study, the production of extracellular matrix (ECM) structure, which is constructed as bioactive compounds resourced from MSC, providing the basis of stem cell niche was carried out. The isolation of this structure was performed by using various decellularization techniques, as a current tissue engineering application was evaluated with microscopic studies, residual DNA and glycosaminoglycan content. Afterward, the structure was enlightened by using proteomics techniques. The results demonstrated the used filter and bags systems are an important source for isolation of MSC, which has a specific antigen expression and representing adipogenic, osteogenic and chondrogenic differentiation potential. Besides, after producing EM with osteogenic differentiation medium, human trabecular bone morphology-like MSC-dECM was isolated by using solution containing Triton X-100, NH4OH. Then, 2005 different protein structures were demonstrated by using nLC-MS/MS technique. The important proteins, which consist, associate and regulate EM structure, were detected by using Human Matrisome Database. Key Words: Regenerative medicine, bone marrow niche, mesenchymal stem cell, extracellular matrix, decellularization, tissue engineering (*) This work was supported by Scientific Research Coordination Unit of Hacettepe University (Project Number: THD-12181).