Endocrinology and Metabolism

Original Articles

Retrovirus Mediated Gene Transfer of RANK-Fc Ameliorates Bone Loss in a Mouse Ovariectomy Model of Osteoporosis.: Dohee Kim, Chan Soo Shin; J Korean Endocr Soc. 2006;21(3):192-203. Published online June 1, 2006; DOI: https://doi.org/10.3803/jkes.2006.21.3.192

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BACKGROUND
Interactions between the receptor activator of the NF-kappaB ligand (RANKL) and its receptor, RANK, are important in the terminal differentiation and activation of osteoclasts. In the current investigation, we examine the feasibility of using genetically modified mesenchymal stem cells (MSCs), C3H10T1/2 cells as a platform for the sustained systemic delivery of therapeutic proteins into the circulation in an osteoporosis model, and investigate retroviral-mediated gene therapy of RANK-Fc as a means of ameliorating ovariectomy (OVX)-induced bone resorption. METHODS: C3H10T1/2 cells were transduced with a MSCV-based retroviral vector containing cDNA of a fusion protein combining the extracellular domain of murine RANK with the human immunoglobulin constant domain (MSCV-RANK-Fc-eGFP). Young adult female mice were subjected to OVX or sham surgery, followed by treatment with transduced cells or PBS 4 weeks later. The expression of RANK-Fc by these cells was assessed, both in vitro and in vivo. Total bone mineral density (BMD) was measured and GFP expression was examined. RESULTS: Transduced cells produced biologically active RANK-Fc in vitro and in vivo. Mice that were subjected to OVX followed by treatment with cells transduced with MSCV-RANK-Fc-eGFP 4 weeks later contained no significant but higher total BMD than either the control vector or PBS-treated mice after 8 weeks. Higher GFP expression was attained in the liver, spleen, and intra-abdominal fat of mice treated with MSCV-RANK-Fc-eGFP. CONCLUSION: The data collectively indicate that C3H10T1/2 cells are effectively transduced with a MSCV-based retrovirus, and are capable of secreting biologically active RANK-Fc in vitro and in vivo. Moreover, gene therapy facilitating the sustained delivery of RANK-Fc may be an effective method to reverse OVX-induced osteoporosis.

Citations

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RANK-Fc Gene Therapy in Mouse Model of Osteoporosis
Ho Yeon Chung
Journal of Korean Endocrine Society.2006; 21(3): 189. CrossRef

Search for "Proximal Histidine" of Thyroperoxidase Using Site Directed Mutagenesis.: Won Bae Kim, Young Kee Shong; J Korean Endocr Soc. 2003;18(4):371-378. Published online August 1, 2003

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Abstract PDF: BACKGROUND
Thyroperoxidase (TPO), a transmembrane heme containing glycoprotein, catalyzes iodide organification and thyroid hormone synthesis. It is a single peptide making a loop with more than one disulfide bond. The tertiary conformational structure is essential for its enzymatic activity and immunogenicity. The proximal histidine is thought to play a major role in enzymatic activity since it is linked to the iron center of the heme. The crystal structure of TPO has not yet been reported, but some have suggested histidine 407 be a putative proximal histidine based on comparison of a.a. sequence for TPO and that for myeloperoxidase. METHODS: The putative histidine 407 and nearby histidine 414 were mutated to arginine to verify their role as the proximal histidine. Using site directed mutagenesis of wild type, human TPO cDNA, mutants H407R and H414R were made. Mutant cDNAs were transiently transfected into COS-7 cells, and the TPO enzyme activities were measured by guaiacol assay. Four cysteine residues around the putative proximal histidines were mutated to serine and their enzymatic activities were measured to check if they were involved in the formation of intra-molecular disulfide bonds. RESULTS: TPO protein expression of H407R- and H414R- transfected cells was confirmed by Western blot, using Hashimoto's IgG as primary antibody. Both the mutants H407R and H414R showed significant peroxidase enzymatic activity, although lower than those of the wild type. None of the cysteine mutants, C375S, C389S, C598S, and C655S, were detected by Hashimoto's IgG ordisplayed any enzymatic activity. CONCLUSION: These data suggest that neither histidine 407 nor histidine 414 functions as the "proximal histidine" in human TPO. All the cysteine residues checked (375, 389, 598, 655) might be involved in the formation of disulfide bonds in TPO molecules, but this hypothesis could not be confirmed. A further search for the other putative histidine residues using the same strategy is needed to define the structure-function relationship in the human TPO molecule.

The Effects of Aging on the Proliferation and Differentiation of Osteoblasts from Human Mesenchymal Stem Cells.: Ki Hyun Baek, Hyun Jung Tae, Ki Won Oh, Won Young Lee, Chung Kee Cho, Soon Yong Kwon, Moo Il Kang, Bong Yun Cha, Kwang Woo Lee, Ho Young Son, Sung Koo Kang, Choon Choo Kim; J Korean Endocr Soc. 2003;18(3):296-305. Published online June 1, 2003

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Abstract PDF: BACKGROUND
Osteoblasts originate from osteoprogenitor cells in bone marrow stroma, termed mesenchymal stem cells (MSCs) or bone marrow stromal cells. Each MSC forms colonies (colony forming units-fibroblasts [CFU-Fs]) when cultured ex vivo. There are some reports about the age-related changes of the number and osteogenic potential of osteoprogenitor cells, but any relationship has not been clearly established in humans. In this study, we counted MSCs using CFU-Fs count and examined the proliferative capacity and differentiation potential of osteoprogenitor cells. Finally, we analyzed how these parameters varied with donor age. METHODS: Bone marrow was obtained from the iliac crest of young (n=6, 27.2+/-8.6 years old) and old (n=10, 57.4+/-6.7 years old) healthy donors. Mononuclear cells, including MSCs, were isolated and cultured in osteogenic medium. In primary culture, we compared the colony-forming efficiency of MSCs between the two groups and determined the matrix calcification. When primary culture showed near confluence, the cells were subcultured. Alkaline phosphatase activity, osteocalcinexpression by RT-PCR and proliferative potential by MTT assay were examined by the time course of secondary culture. RESULTS: At the 15th day of primary culture, the mean number of CFU-Fs was significantly higher in the younger donors (young: 148.3+/-28.9, old: 54.3+/-9.1, p=0.02) and the mean size of CFU-Fs was also larger in the younger donors than the older donors. However, matrix calcification was not different between the two groups (young: 103.6+/-50.6, old: 114.0+/-56.5, p=NS). In secondary culture, alkaline phosphatase activities were significantly lower in the older donors. The younger donors showed peak alkaline phosphatase activity at day 10, while the older donors didn't showed a remarkable peak (young: 935.5+/-115.0U/mg, old: 578.4+/-115.7U/mg, p<0.05). Total cell number as a proliferative index increased progressively during the secondary culture and a significantly greater cell number was noted in the younger donors. Osteocalcin expression was generally upregulated in the younger donors, but this was not statistically significant. CONCLUSION: Our study shows that the number of osteoprogenitor cells is decreased during aging and that the proliferative capacity and differentiation potential of osteoprogenitor cells seem to be reduced during aging.

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