Blavier L, Delaissé J M
Laboratoire de Chimie Physiologique (Connective Tissue Group), Université de Louvain, Bruxelles, Belgium.
J Cell Sci. 1995 Dec;108 ( Pt 12):3649-59. doi: 10.1242/jcs.108.12.3649.
A key event in bone resorption is the recruitment of osteoclasts to future resorption sites. We follow here the migration of preosteoclasts from the periosteum to the developing marrow cavity of fetal mouse metatarsals in culture, and investigate the role of proteinases and demineralization in this migration. Our approach consisted in testing inhibitors of proteinases and demineralization on the migration kinetics. Migration was monitored by histomorphometry and the (pre)osteoclasts were identified by their tartrate resistant acid phosphatase (TRAP) activity. At the time of explantation, TRAP+ cells (all mononucleated) are detected only in the periosteum, and the core of the diaphysis (future marrow cavity) consist of calcified cartilage. Upon culture, TRAP+ cells (differentiating progressively into multinucleated osteoclasts) migrate through a seam of osteoid and a very thin and discontinuous layer of mineral, invade the calcified cartilage and transform it into a "marrow' cavity; despite the passage of maturing osteoclasts, the osteoid develops into a bone collar. The migration of TRAP+ cells is completely prevented by matrix metalloproteinase (MMP) inhibitors, but not by a cysteine proteinase inhibitor, an inhibitor of carbonic anhydrase, or a bisphosphonate. The latter three drugs inhibit, however, the resorptive activity of mature osteoclasts at least as efficiently as do the MMP inhibitors, as assessed in cultures of calvariae and radii. Furthermore, in situ hybridizations reveal the expression of 2 MMPs, gelatinase B (MMP-9 or 92 kDa type IV collagenase) in (pre)osteoclasts, and interstitial collagenase (MMP-13) in hypertrophic chondrocytes. It is concluded that only MMPs appear obligatory for the migration of (pre)osteoclasts, and that this role is distinct from the one MMPs may play in the subosteoclastic resorption compartment. We propose that this new role of MMPs is a major component of the mechanism that determines where and when the osteoclasts will attack the bone.
骨吸收过程中的一个关键事件是破骨细胞被募集到未来的吸收部位。我们在此追踪培养的胎鼠跖骨中前破骨细胞从骨膜迁移至发育中的骨髓腔的过程，并研究蛋白酶和脱矿作用在这一迁移过程中的作用。我们的方法是测试蛋白酶和脱矿作用的抑制剂对迁移动力学的影响。通过组织形态计量学监测迁移情况，并通过抗酒石酸酸性磷酸酶（TRAP）活性鉴定（前）破骨细胞。在植入时，仅在骨膜中检测到TRAP+细胞（均为单核细胞），骨干的核心（未来的骨髓腔）由钙化软骨组成。培养后，TRAP+细胞（逐渐分化为多核破骨细胞）穿过类骨质缝和一层非常薄且不连续的矿物质层，侵入钙化软骨并将其转化为“骨髓”腔；尽管成熟破骨细胞通过，但类骨质仍发育成骨环。TRAP+细胞的迁移完全被基质金属蛋白酶（MMP）抑制剂阻断，但不受半胱氨酸蛋白酶抑制剂、碳酸酐酶抑制剂或双膦酸盐的影响。然而，后三种药物抑制成熟破骨细胞的吸收活性至少与MMP抑制剂一样有效，这在颅骨和桡骨培养物中得到评估。此外，原位杂交显示在（前）破骨细胞中表达2种MMP，即明胶酶B（MMP-9或92 kDa IV型胶原酶），在肥大软骨细胞中表达间质胶原酶（MMP-13）。得出的结论是，只有MMPs对于（前）破骨细胞的迁移似乎是必不可少的，并且这一作用不同于MMPs在破骨细胞下吸收区可能发挥的作用。我们提出MMPs的这一新作用是决定破骨细胞何时何地攻击骨骼的机制的一个主要组成部分。
