van der Plas A, Aarden E M, Feijen J H, de Boer A H, Wiltink A, Alblas M J, de Leij L, Nijweide P J
Department of Cell Biology, University of Leiden, The Netherlands.
J Bone Miner Res. 1994 Nov;9(11):1697-704. doi: 10.1002/jbmr.5650091105.
Although the osteocyte is the most abundant among the highly differentiated cells of mature bone (osteocytes, lining cells, osteoblasts, and osteoclasts), its properties and functions are the least known and understood. Here we isolated osteocytes from mixed populations of bone cells liberated from fetal chick calvariae by alternate treatments with collagenase and EDTA. The osteocytes were removed from the bone cell populations by binding them via an osteocyte-specific antibody (MAb OB 7.3) to magnetic beads and removing the beads together with the coupled osteocytes from the population using a magnet. Isolated osteocytes were found to be highly differentiated, postmitotic cells that required their typical stellate morphology in culture. Osteocyte populations had alkaline phosphatase (ALP) activity somewhat lower than that of the osteoblast-like cell populations from which they were separated by the immunodissection procedure. On the single-cell level, the ALP activity was highly variable. Parathyroid hormone (PTH) receptors were found to be present on osteocytes as well as on osteoblast-like cells, but not on fibroblast-like cells of the outer periosteum. In response to PTH, osteocytes increased their intracellular levels of cAMP, as did the osteoblast-like cells. Osteocytes appeared to be somewhat more sensitive to PTH than osteoblasts. When seeded onto dentin slices, osteocytes did not corrode the dentin surface to any appraisable degree. We therefore found no evidence to support the notion that osteocytes play a role in the calcium homeostasis through osteocytic osteolysis. Whether osteocytes play an important role in perceiving and transducing hormonal and/or mechanical stimuli remains open for future research.
尽管骨细胞是成熟骨高度分化细胞（骨细胞、衬里细胞、成骨细胞和破骨细胞）中数量最多的，但对其特性和功能的了解却最少。在这里，我们通过用胶原酶和乙二胺四乙酸交替处理，从鸡胚颅骨中分离出的混合骨细胞群体中分离出骨细胞。通过一种骨细胞特异性抗体（单克隆抗体OB 7.3）将骨细胞与磁珠结合，然后用磁铁从群体中去除磁珠及与之结合的骨细胞，从而将骨细胞从骨细胞群体中分离出来。分离出的骨细胞被发现是高度分化的、有丝分裂后的细胞，在培养中需要保持其典型的星状形态。骨细胞群体的碱性磷酸酶（ALP）活性略低于通过免疫分离程序从其中分离出它们的成骨样细胞群体。在单细胞水平上，ALP活性变化很大。发现甲状旁腺激素（PTH）受体不仅存在于成骨样细胞上，也存在于骨细胞上，但不存在于外层骨膜的成纤维样细胞上。与成骨样细胞一样，骨细胞对PTH的反应是细胞内cAMP水平升高。骨细胞似乎比成骨细胞对PTH更敏感。当接种到牙本质切片上时，骨细胞并未对牙本质表面造成任何可评估程度的侵蚀。因此，我们没有发现证据支持骨细胞通过骨细胞性骨溶解在钙稳态中起作用这一观点。骨细胞在感知和转导激素和/或机械刺激方面是否发挥重要作用仍有待未来研究。
