Tataria Monika, Quarto Natalina, Longaker Michael T, Sylvester Karl G
Pediatric Surgery Research Laboratory, Department of Surgery, Stanford University School of Medicine and Lucille Packard Children's Hospital, Stanford, CA 94305, USA.
J Pediatr Surg. 2006 Apr;41(4):624-32; discussion 624-32. doi: 10.1016/j.jpedsurg.2005.12.001.
Osteosarcoma arises predominantly in the metaphyseal growth plate of children during the growth spurt years. These tumors develop during physiological growth from an expanding cell population, suggesting that the transformed cell is a bone-forming progenitor. An absence of the p53 oncogene has been implicated in the origin and progression of osteosarcoma, and because mesenchymal stem cells (MSCs) are the physiological osteogenic progenitor cell population, we hypothesized that a p53-/- mutation would enhance bone differentiation of MSC in a mouse model of in vitro osteogenesis.
Clonal MSC populations were derived from p53-/- mice. P53-/- and wild-type cells were placed in osteogenic culture and assessed via Alizarin Red quantification and alkaline phosphatase staining. The osteogenic marker genes Cbfa1, osteopontin, and osteocalcin were assessed by quantitative real time polymerase chain reaction during differentiation.
Bone nodule formation and alkaline phosphatase staining was accelerated and enhanced in the p53-/- cells. The early and intermediate osteogenic markers, Cbfa1 and osteopontin, were upregulated in p53-/- MSCs compared with wild-type cells during osteogenesis. The terminal osteogenic marker gene osteocalcin was paradoxically lower in p53-/- MSCs indicating impaired terminal differentiation.
The p53-/- mutation enhances and accelerates early osteogenesis in MSCs, but prevents terminal differentiation toward a mature osteocyte phenotype. These findings may have important implications for the regulation of the MSC compartment during the derivation of osteosarcoma in children.
骨肉瘤主要发生在儿童生长加速期的干骺端生长板。这些肿瘤在生理生长过程中由不断扩大的细胞群体发展而来，提示转化细胞是成骨祖细胞。p53癌基因的缺失与骨肉瘤的发生和进展有关，由于间充质干细胞（MSC）是生理性成骨祖细胞群体，我们推测在体外成骨小鼠模型中，p53基因敲除突变会增强MSC的骨分化。
从p53基因敲除小鼠中获得克隆性MSC群体。将p53基因敲除细胞和野生型细胞置于成骨培养基中培养，通过茜素红定量和碱性磷酸酶染色进行评估。在分化过程中，通过定量实时聚合酶链反应评估成骨标记基因Cbfa1、骨桥蛋白和骨钙素。
p53基因敲除细胞中骨结节形成和碱性磷酸酶染色加速且增强。与野生型细胞相比，在成骨过程中，p53基因敲除的MSC中早期和中期成骨标记物Cbfa1和骨桥蛋白上调。矛盾的是，p53基因敲除的MSC中终末成骨标记基因骨钙素较低，表明终末分化受损。
p53基因敲除突变增强并加速了MSC的早期成骨，但阻止了向成熟骨细胞表型的终末分化。这些发现可能对儿童骨肉瘤发生过程中MSC区室的调控具有重要意义。
