Mechanoreceptors in Alveolar Osteocyte

虽然众所周知，骨形成是由机械刺激加速的，但涉及的信号转导途径在很大程度上是未知的。根据E.Burger等人的研究，表明骨细胞对高水平和低水平的应力反应不同，我们比较了新生大鼠颅骨细胞从未成熟成骨细胞到成熟成骨细胞，再到骨细胞发育过程中对机械应力的反应。我们发现，对生理拉伸最敏感的细胞类型不是成骨细胞，而是年轻的骨细胞。这些细胞正在从成骨细胞向骨细胞过渡，表达低水平的碱性磷酸酶和高水平的骨钙素。它们还发育广泛的细胞突起，形成骨骼中的细胞网络。这些年轻的骨细胞因拉伸而停止增殖，并使基质矿化。结果表明，人牙槽骨中cAMP分泌，IGF-I和骨钙素表达上调。在人牙槽骨中，在分离细胞之前，不易清洗骨屑。这可能是我们不能获得像大鼠颅骨那样多的分化骨细胞的原因。然而，在这些少数成功的案例中，骨细胞对上述拉伸的反应与大鼠骨细胞的反应相似。换言之，RT-PCR方法表明，拉伸导致骨钙素的表达上调。我们的通道阻滞剂研究结果还表明，阿米洛利敏感通道(S)参与了他们对伸展的反应。

Although it is well known that bone formation is accelerated by mechanical stimuli, the signal transduction pathways involved are largely unknown. Suggested by the studies by E.Burger and others, which showed that bone cells respond to high-level and low-level stresses differently, we compared the response of newborn rat calvarial cells to mechanical stress during their development from immature osteoblasts to mature osteoblasts, further into osteocytes. We showed that the type of cells which is most sensitive to physiological stretching of less than 4,0000 mustrain is not osteoblast but young osteocyte. These cells are in transition from osteoblasts to osteocytes expressing low-level alkaline phosphatase and high-level osteocalcin. They also develop extensive cell processes which form a network of cells in bone. These young osteocytes stop proliferation in response to stretching and mineralize thir matrix. It was shown that cAMP is secreted and the expression of IGF-I and osteocalcin is induced in response to the stress.In human alveolar bone, it was not easy to clean the bone chips prior to the isolation of cells. That is probably why we could not obtain as many differentiated osteocytes as in rat calvaria. In those few successful cases, however, the response of osteocytes to the above mentioned stretching was similar to that of rat osteocytes. In other words, it was shown by RT-PCR method that osteocalcin expression was upregulated as a result of stretching. It was also suggested that amiloride sensitive channel (s) is involved in their response to stretching from our results of channel blocker studies measuringCa influx upon the exposure to lower osmotic conditions.