Everts V, Beertsen W, Schröder R
Laboratory of Histology and Cell Biology, Faculty of Medicine, University of Amsterdam, The Netherlands.
Calcif Tissue Int. 1988 Sep;43(3):172-8. doi: 10.1007/BF02571316.
To determine the possible involvement of cysteine-proteinases in bone matrix degradation by osteoclasts, the effects of the proteinase inhibitors leupeptin and E-64 were studied in an in vitro system using mouse bone explants. It was observed that in explants treated with the drugs, the amount of demineralized matrix opposing the ruffled border of the osteoclasts increased about 20-fold within 6 hours. This suggests that demineralization had proceeded whereas matrix degradation had been retarded. It was further noticed that in 12 of 287 osteoclasts, cytoplasmic vacuoles were present containing collagen fibrils that could not be distinguished from those in cartilage or bone. Their intracellular localization was proved by the study of serial sections. Finally, a significant reduction was shown as to the relative surface density of electron-translucent vacuoles; this would seem to suggest reduced endocytic activity of the cells. Our observations support the view that cysteine-proteinases play an important role in osteoclastic bone resorption. It was further noticed that the in vitro effects of leupeptin and E-64 in certain respects resemble ultrastructural features of pycnodysostosis, an osteopetrosislike bone disorder. The data are in line with the hypothesis that this disease is caused by insufficient activity of osteoclastic cysteine-proteinases.
为了确定半胱氨酸蛋白酶是否可能参与破骨细胞对骨基质的降解，我们在一个使用小鼠骨外植体的体外系统中研究了蛋白酶抑制剂亮抑酶肽和E-64的作用。观察到在用这些药物处理的外植体中，与破骨细胞褶皱缘相对的脱矿质基质的量在6小时内增加了约20倍。这表明脱矿质过程已经进行，而基质降解受到了抑制。还进一步注意到，在287个破骨细胞中有12个存在含有胶原纤维的细胞质空泡，这些空泡与软骨或骨中的胶原纤维无法区分。通过连续切片研究证实了它们的细胞内定位。最后，电子透明空泡的相对表面密度显示出显著降低；这似乎表明细胞的内吞活性降低。我们的观察结果支持这样一种观点，即半胱氨酸蛋白酶在破骨细胞性骨吸收中起重要作用。还进一步注意到，亮抑酶肽和E-64的体外作用在某些方面类似于致密性骨发育不全（一种类似骨质石化的骨疾病）的超微结构特征。这些数据与该疾病是由破骨细胞半胱氨酸蛋白酶活性不足引起的这一假设一致。
