Effect of CD44 deficiency on in vitro and in vivo osteoclast formation
Effect of CD44 deficiency on in vitro and in vivo osteoclast formation
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DOI：
10.1002/jcb.20326
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发表时间：
2005-04-01
影响因子：
4
通讯作者：
Everts, V
中科院分区：
文献类型：
--
作者：
de Vries, TJ;Schoenmaker, T;Everts, V
体外研究表明，CD44参与破骨细胞前体细胞的融合过程。然而，体内研究并不支持这一点，因为尚未描述CD44敲除（CD44 k.o）小鼠的骨质疏松表型。这种差异可能表明CD44在融合中的作用可能取决于破骨细胞形成的微环境。通过分析野生型小鼠和CD44 k.o.小鼠长骨中破骨细胞的数量和大小，研究了野生型小鼠和CD44 k.o.小鼠在体外、塑料和骨上以及体内三种条件下破骨细胞的形成。分析了野生型和CD44 k.o.小鼠骨髓细胞在巨噬细胞集落刺激因子（M-CSF）和NF-kB配体受体激活剂（RANKL）存在下在塑料和骨上形成破骨细胞的能力。在塑料上，CD44 k.o.培养物中多核酒石酸盐抗性酸性磷酸酶（TRAP）阳性细胞的数量是野生型培养物的两倍。然而，在骨骼上，形成了相同数量的破骨细胞。有趣的是，两种基因型在骨上形成的破骨细胞总数均高于在塑料上形成的破骨细胞总数，这强烈表明破骨细胞的形成是由骨表面刺激的，并且在骨上形成破骨细胞并不需要CD44。功能分析表明，两种基因型的骨吸收相似。我们进一步研究了CD44阻断抗体存在下野生型骨髓细胞的破骨潜能。这些抗体不影响破骨细胞的发生，这进一步表明CD44不是形成多核细胞所必需的。最后，我们通过分析野生型和CD44 k.o.小鼠的长骨来分析破骨细胞的体内形成。形态计量学分析显示，破骨细胞数量、每个破骨细胞的细胞核数量或破骨细胞大小均无差异。我们对塑料的体外实验显示，在缺乏CD44的情况下，破骨细胞的形成增强，这表明CD44对破骨细胞的形成有抑制作用。然而，当在骨上产生破骨细胞时，在多核细胞数量和骨吸收方面没有发现差异。这些观察结果与体内破骨细胞的特征一致，在野生型和CD44 k.o.骨之间没有发现差异。因此，CD44在破骨细胞形成中的调节作用似乎取决于微环境。(c) 2004 Wiley-Liss, Inc。
In vitro studies have shown that CD44 is involved in the fusion process of osteoclast precursor cells. Yet, in vivo studies do not support this, since an osteopetrotic phenotype has not been described for CD44 knock-out (CD44 k.o.) mice. This discrepancy may suggest that the role of CD44 in fusion may depend on the microenvironment of osteoclast formation. We investigated osteoclast formation of CD44 k.o. and wild-type mice under three conditions: in vitro, both on plastic and on bone and in vivo by analyzing osteoclast number, and size in long bones from wild-type and CD44 k.o. mice. Bone marrow cells from wild-type and CD44 k.o. mice were analyzed for their capacity to form osteoclasts on plastic and on bone in the presence of macrophage colony stimulating factor (M-CSF) and receptor activator of NF-kB ligand (RANKL). On plastic, the number of multinucleated tartrate resistant acid phosphatase (TRAP) positive cells in CD44 k.o. cultures was twofold higher than in wild-type cultures. On bone, however, equal numbers of osteoclasts were formed. interestingly, the total number of osteoclasts formed on bone proved to be higher than on plastic for both genotypes, strongly suggesting that osteoclastogenesis was stimulated by the bone surface, and that CD44 is not required for osteoclast formation on bone. Functional analyses showed that bone resorption was similar for both genotypes. We further studied the osteoclastogenic potential of wild-type bone marrow cells in the presence of CD44 blocking antibodies. Osteoclastogenesis was not affected by these antibodies, a further indication that CD44 is not required for the formation of multinucleated cells. Finally, we analyzed the in vivo formation of osteoclasts by analyzing long bones from wild-type and CD44 k.o. mice. Morphometric analysis revealed no difference in osteoclast number, nor in number of nuclei per osteoclasts or in osteoclast size. Our in vitro experiments on plastic showed an enhanced formation of osteoclasts in the absence of CD44, thus suggesting that CD44 has an inhibitory effect on osteoclastogenesis. However, when osteoclasts were generated on bone, no differences in number of multinucleated cells nor in bone resorption were seen. These observations are in agreement with in vivo osteoclast characteristics, where no differences between wild-type and CD44 k.o. bones were encountered. Therefore, the modulating role of CD44 in osteoclast formation appears to depend on the microenvironment. (c) 2004 Wiley-Liss, Inc.