Cassiede P, Dennis J E, Ma F, Caplan A I
Department of Biology, Case Western Reserve University, Cleveland, Ohio, USA.
J Bone Miner Res. 1996 Sep;11(9):1264-73. doi: 10.1002/jbmr.5650110911.
Mesenchymal progenitors cells can be isolated from rat bone marrow and mitotically expanded in vitro. When these cells, which we operationally call mesenchymal stem cells (MSCs), are placed in an appropriate environment, they have the capacity to differentiate into bone and/or cartilage. This capacity is called osteochondrogenic potential. In this study, preconfluent MSCs were exposed in vitro to 5 ng/ml transforming growth factor-beta 1 (TGF-beta 1) or platelet-derived growth factor, isoform BB (PDGF-BB) for a pulse of 48 h and assayed for cell proliferation, alkaline phosphatase activity, and osteochondrogenic potential; untreated MSC's served as controls. In these cell culture conditions, TGF-beta 1 or PDGF-BB had similar effects on proliferation and alkaline phosphatase activity. Both growth factors increased cell proliferation and decreased alkaline phosphatase activity of MSCs. Sister cultures of TGF-beta 1- or PDGF-BB-treated MSCs and untreated MSCs were trypsinized. For each type of culture, the trypsinised MSCs were split in two parts: one part was replated in an osteogenic medium to assess its in vitro osteogenic potential, whereas the other part was seeded into porous calcium phosphate ceramics and implanted subcutaneously in syngeneic rats to assess its in vivo osteochondrogenic potential. PDGF-pretreated MSCs showed no difference in in vivo and in vitro osteochondrogenesis from that of control MSCs, while TGF-beta 1 pretreatment blocked the osteochondrogenic potential of MSCs when assayed in vitro for bone nodule formation. However, when tested in vivo, TGF-beta 1-pretreated MSCs were able to form bone and cartilage. These data show that measurements of proliferation and alkaline phosphatase activity of preconfluent MSCs immediately after exposure to growth factor were not predictive of their subsequent osteochondrogenic potential. Moreover, the variation of the osteochondrogenic potential of MSCs after exposure to growth factor was further modulated by the environment in which the MSCs were assayed.
间充质祖细胞可从大鼠骨髓中分离出来，并在体外进行有丝分裂扩增。当这些细胞（我们在操作上称之为间充质干细胞（MSCs））置于合适的环境中时，它们有分化为骨和/或软骨的能力。这种能力称为骨软骨生成潜能。在本研究中，将未汇合的MSCs在体外暴露于5 ng/ml转化生长因子-β1（TGF-β1）或血小板衍生生长因子BB亚型（PDGF-BB）48小时进行脉冲处理，然后检测细胞增殖、碱性磷酸酶活性和骨软骨生成潜能；未处理的MSCs作为对照。在这些细胞培养条件下，TGF-β1或PDGF-BB对增殖和碱性磷酸酶活性有相似的影响。两种生长因子均增加了MSCs的细胞增殖并降低了其碱性磷酸酶活性。对经TGF-β1或PDGF-BB处理的MSCs和未处理的MSCs的姐妹培养物进行胰蛋白酶消化。对于每种类型的培养物，将经胰蛋白酶消化的MSCs分成两部分：一部分重新接种到成骨培养基中以评估其体外成骨潜能，而另一部分接种到多孔磷酸钙陶瓷中并皮下植入同基因大鼠体内以评估其体内骨软骨生成潜能。与对照MSCs相比，经PDGF预处理的MSCs在体内和体外骨软骨生成方面没有差异，而在体外检测骨结节形成时，TGF-β1预处理阻断了MSCs的骨软骨生成潜能。然而，在体内测试时，经TGF-β1预处理的MSCs能够形成骨和软骨。这些数据表明，在暴露于生长因子后立即测量未汇合MSCs的增殖和碱性磷酸酶活性并不能预测其随后的骨软骨生成潜能。此外，MSCs暴露于生长因子后骨软骨生成潜能的变化进一步受到检测MSCs时所处环境的调节。
