| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1999: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
1. We investigated glucocorticoid-induced osteoblastic or adipocytic differentiation of the culture-expanded human marrow stromal cells (HMSCs). Recombinant human bone morphogenetic protein-2 (rhBMP-2) increased alkaline phosphatase (ALP) activity in HMSCs, whereas it did not induce adipocytic differentiation at all. In the presence of dexamethasone (Dex), rhBMP-2 additively increased ALP activity and dramatically stimulated adipocytic differentiation. Peroxisome proliferator-activated receptor (PPAR)γ ligand, BRL49653, alone was not sufficient for adipogenesis. However, in the presence of Dex, PPAR γ ligand strongly stimulated adipogenesis. RT-PCR analysis showed that Dex induced the expression of PPAR γ 2 and lipoprotein lipase mRNAs. These mRNAs of the markers for adipogenesis were not detected in vehicle-, rhBMP-2-, or PPAR γ ligand-treated culture. These findings indicate that Dex is essential for in vitro adipocytic differentiation, and both rhBMP-2 and PPAR γ ligand stimulate Dex-induced adipocyte differentiation. These findings show that HMSCs are bipotential and can be manipulated by various factors.
2. We also investigated whether the in vivo bone-forming capacity of HMSCs could be enhanced by rhBMP-2. Passaged HMSCs from 7 donors exhibited the osteoblastic phenotype in vitro. For the in vivo assay, HMSCs were subcutaneously implanted in nude mice (xenograft) with or without rhBMP-2. Four weeks after implantation, correlated radiographic findings, histological observations, and in situ hybridization using species-specific probes showed that small amounts of HMSCs-derived bone tissue were detected at the periphery in 2 of 7 transplants of HMSCs alone. In contrast, 5 of 7 transplants of HMSCs with rhBMP-2 exhibited HMSCs-derived bone tissue. This study demonstrated that 1) culture-expanded HMSCs preserved the osteoblastic phenotype, and 2) the in vivo bone-forming capacity could be promoted by rhBMP-2.
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