Vaes G, Delaissé J M, Eeckhout Y
Laboratoire de Chimie Physiologique (Connective Tissue Group), Université de Louvain, Bruxelles, Belgium.
Matrix Suppl. 1992;1:383-8.
Both lysosomal cysteine-proteinases and collagenase appear to be necessary for the resorption of actively growing, immature woven bone, but their relative roles are not yet clearly elucidated. The present evidence indicates that, during bone resorption, the osteoclast first solubilizes the mineral by a secretion of acid and then removes the exposed demineralized collagen by the action of secreted lysosomal collagenolytic cysteine-proteinases. Collagenase in bone seems to be mainly a product of osteoblasts and related cells, not osteoclasts. Its role could be limited in the removal of any non-mineralized collagen layers which could be covering mineralized bone surfaces and which seem to prevent the activation of osteoclasts and thus their action; such a "shield" of unmineralized osteoid is well-established at the surface of actively growing woven bone, although not on the resorbing surfaces of mature lamellar bone. Moreover, some osteoblast-derived procollagenase is stored in the mineralized bone matrix from which it can be released by demineralization. It is therefore possible that it may also contribute to the degradation of demineralized bone collagen once it has been released and activated by lysosomal cysteine-proteinases under the osteoclast.
溶酶体半胱氨酸蛋白酶和胶原酶似乎对于活跃生长的未成熟编织骨的吸收都是必需的，但其相对作用尚未明确阐明。目前的证据表明，在骨吸收过程中，破骨细胞首先通过分泌酸来溶解矿物质，然后通过分泌的溶酶体胶原分解半胱氨酸蛋白酶的作用去除暴露的脱矿质胶原。骨中的胶原酶似乎主要是成骨细胞和相关细胞而非破骨细胞的产物。其作用可能局限于去除可能覆盖矿化骨表面且似乎会阻止破骨细胞激活及其作用的任何非矿化胶原层；这种未矿化类骨质的“屏障”在活跃生长的编织骨表面已得到充分证实，尽管在成熟板层骨的吸收表面不存在。此外，一些成骨细胞衍生的前胶原酶储存在矿化骨基质中，脱矿质作用可使其释放。因此，一旦它被破骨细胞下的溶酶体半胱氨酸蛋白酶释放并激活，它也有可能促进脱矿质骨胶原的降解。
