Characterization of molecular mechanism regulating bone mineralization during osteogenic differentiation of mesenchymal stem cells

• Main Authors: Yu-Tzu Tsao, 曹祐慈
• Other Authors: Oscar Kuang-Sheng Lee
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/y3r4up

博士 === 國立陽明大學 === 臨床醫學研究所 === 105 === There is a growing interest in cell therapies using mesenchymal stromal cells (MSCs) for repairing bone defects. MSCs have the ability to differentiate into osteoprogenitors and osteoblasts as well as to form calcified bone matrix. However, the molecular mechanisms governing mineralization during osteogenic differentiation remain unclear. Non-collagenous proteins in the extracellular matrix are believed to control different aspects of the mineralization. Since osteocalcin is the most abundant non-collagenous bone matrix protein, the purpose of this study is to investigate the roles of osteocalcin in mineral species production during osteogenesis of MSCs. Using Raman spectroscopy, we found that the maturation of mineral species was affected by osteocalcin expression level. After osteocalcin was knocked down, the mineral species maturation was delayed and total hydroxyapatite was lower than the control group. In addition, the expression of osteogenic marker genes, including RUNX2, alkaline phosphatase, type I collagen, and osteonectin, was downregulated during osteogenic differentiation compared to the control group; whereas gene expression of osterix was upregulated after the knockdown. Together, osteocalcin plays an essential role for the maturation of mineral species and modulates osteogenic differentiation of MSCs. The results offer new insights into the enhancement of new bone formation, such as for the treatments of osteoporosis and fracture healing. Magnesium exists mostly in bone and the amount of magnesium is dynamically regulated by skeletal remodeling. Accelerating bone mass loss occurs when magnesium intake is insufficient; whereas high magnesium could lead to mineralization defects. In the present study, the effects of high extracellular magnesium concentration on osteogenic differentiation of mesenchymal stromal cells (MSCs) were investigated. Our results showed that in high concentration of magnesium, early osteogenic marker genes of MSCs were downregulated and late marker genes were upregulated. siRNA treatment targeting SLC41A1, a member of solute carrier family, not only ameliorated the inhibition of mineralization caused by high concentration of magnesium but accelerated the mineralization process. Results also indicated that Wnt signaling is involved in SLC41A1-mediated regulation. Together, tissue-specific SLC41A1 could be a potential treatment for bone mineral disease; in addition, in CKD patients, caution should be taken regarding the use of formulated supplement with magnesium for bone health and biodegradable magnesium alloys for implantation.