Dipartimento di Scienze Biomediche, Sezione di Morfologia umana-Istituti Anatomici, Università di Modena e Reggio Emilia, Via del Pozzo 71 (area Policlinico), 41125 Modena, Italy.
Calcif Tissue Int. 2012 Mar;90(3):211-8. doi: 10.1007/s00223-012-9569-6. Epub 2012 Jan 31.
Considering the pivotal role as bone mechanosensors ascribed to osteocytes in bone adaptation to mechanical strains, the present study analyzed whether a correlation exists between osteocyte apoptosis and bone remodeling in peculiar bones, such as human auditory ossicles and scleral ossicles of lower vertebrates, which have been shown to undergo substantial osteocyte death and trivial or no bone turnover after cessation of growth. The investigation was performed with a morphological approach under LM (by means of an in situ end-labeling technique) and TEM. The results show that a large amount of osteocyte apoptosis takes place in both auditory and scleral ossicles after they reach their final size. Additionally, no morphological signs of bone remodeling were observed. These facts suggest that (1) bone remodeling is not necessarily triggered by osteocyte death, at least in these ossicles, and (2) bone remodeling does not need to mechanically adapt auditory and scleral ossicles since they appear to be continuously submitted to stereotyped stresses and strains; on the contrary, during the resorption phase, bone remodeling might severely impair the mechanical resistance of extremely small bony segments. Thus, osteocyte apoptosis could represent a programmed process devoted to make stable, when needed, bone structure and mechanical resistance.
鉴于骨细胞作为骨机械感受器在骨对机械应变的适应中所起的关键作用，本研究分析了骨细胞凋亡是否与人类听觉小骨和较低等脊椎动物巩膜小骨等特殊骨骼中的骨重建有关，这些骨骼在生长停止后已经显示出大量的骨细胞死亡，但骨转换很少或没有。该研究采用 LM 下的形态学方法（原位末端标记技术）和 TEM 进行。结果表明，在达到最终大小后，听觉小骨和巩膜小骨中均发生大量的骨细胞凋亡。此外，没有观察到骨重建的形态学迹象。这些事实表明：（1）骨重建不一定由骨细胞死亡引发，至少在这些小骨中是这样；（2）骨重建不需要机械适应听觉小骨和巩膜小骨，因为它们似乎持续受到刻板的应力和应变；相反，在吸收阶段，骨重建可能严重损害极小骨段的机械阻力。因此，骨细胞凋亡可能代表一种程序性过程，旨在根据需要使骨结构和机械阻力稳定。
