Wakikawa T, Shioi A, Hino M, Inaba M, Nishizawa Y, Tatsumi N, Morii H, Otani S
Department of Biochemistry, Osaka City University Medical School, Osaka, Japan.
Endocrinology. 1997 Oct;138(10):4160-6. doi: 10.1210/endo.138.10.5438.
To determine whether thrombopoietin (TPO) can modulate the osteoclastic differentiation from hematopoietic stem cells, we investigated the effect of TPO on in vitro osteoclastogenesis by using the coculture of murine bone marrow cells with the stromal cell line (ST2) in the presence of 1alpha,25-dihydroxyvitamin D3 and dexamethasone. Recombinant human TPO inhibited the formation of tartrate-resistant acid phosphatase-positive multinucleated cells in a dose-dependent manner (0.02-200 ng/ml). The effect of TPO on differentiation of bone-resorbing capacity was investigated by pit assay. TPO dose dependently decreased the areas oftoluidine blue-stained resorption pits (2.0-200 ng/ml). To identify the cellular target of TPO, we used a variety of bone marrow/stromal cell coculture methods. Initially, we found that TPO mainly exerted its effect on the early stage of osteoclastic differentiation in delayed addition experiments. Consequently, the majority of TPO's inhibition of osteoclastic cell formation was due to its effect on bone marrow cells. Finally, we examined whether transforming growth factor-beta (TGFbeta) and platelet-derived growth factor (PDGF), major cytokines produced by megakaryocytes, mediate the inhibitory effect of TPO. The addition of either anti-TGFbeta or anti-PDGF antibody to bone marrow cell culture completely antagonized the effect of TPO on osteoclastogenesis. Furthermore, treatment of bone marrow cells with TGFbeta or PDGF mimicked the inhibitory effect of TPO. These data suggest that TPO inhibits osteoclastogenesis through stimulating thrombopoiesis and that TGFbeta and PDGF mediate the effect of TPO by impacting on macrophage-lineage cells as osteoclast precursors.
为了确定血小板生成素（TPO）是否能够调节造血干细胞向破骨细胞的分化，我们在1α,25-二羟基维生素D3和地塞米松存在的情况下，利用小鼠骨髓细胞与基质细胞系（ST2）共培养，研究了TPO对体外破骨细胞生成的影响。重组人TPO以剂量依赖方式（0.02 - 200 ng/ml）抑制抗酒石酸酸性磷酸酶阳性多核细胞的形成。通过凹坑试验研究了TPO对骨吸收能力分化的影响。TPO剂量依赖性地减少了甲苯胺蓝染色的吸收凹坑面积（2.0 - 200 ng/ml）。为了确定TPO的细胞靶点，我们使用了多种骨髓/基质细胞共培养方法。最初，我们发现在延迟添加实验中，TPO主要在破骨细胞分化的早期发挥作用。因此，TPO对破骨细胞形成的大部分抑制作用是由于其对骨髓细胞的作用。最后，我们研究了巨核细胞产生的主要细胞因子转化生长因子-β（TGFβ）和血小板衍生生长因子（PDGF）是否介导TPO的抑制作用。向骨髓细胞培养物中添加抗TGFβ或抗PDGF抗体完全拮抗了TPO对破骨细胞生成的作用。此外，用TGFβ或PDGF处理骨髓细胞模拟了TPO的抑制作用。这些数据表明，TPO通过刺激血小板生成来抑制破骨细胞生成，并且TGFβ和PDGF通过影响作为破骨细胞前体的巨噬细胞系细胞来介导TPO的作用。
