Examination mechanism of bone absorption by immunosuppressant FK506 and bone graft In molecular biology

免疫抑制剂药物目前需要移植受者的余生，尽管与这些治疗相关的许多不良反应。急性骨质疏松症就是这样一种效应，并且已经通过在大鼠中施用免疫抑制剂药物FK 506建立了可再现的骨质疏松症模型。研究表明，这种骨质疏松症是由于破骨细胞异常增殖，改变了骨重建的过程。然而，目前还不清楚为什么FK 506诱导破骨细胞增殖，以及这一过程是否是由细胞因子的变化或骨吸收因子的增加介导的。因此，进行了调查，重点是最近发现的破骨细胞分化因子（ODF）和破骨细胞生成抑制因子（OCIF）。这些因素导致破骨细胞分化/成熟机制的阐明。采用连续28天肌肉注射FK 506（1 mg/kg）的方法在大鼠中建立骨质疏松症模型。在FK 506组中观察到小梁骨吸收劣于软骨内骨化，并且抗酒石酸酸性磷酸酶（TRAP）染色显示，相对于对照组，软骨内骨化部位的破骨细胞明显增加。逆转录聚合酶链反应（RT-PCR）和原位杂交（ISH）显示，对照组和治疗组之间的OCIF表达差异极小。然而，RT-PCR显示治疗组中ODF表达明显增加。在使用ISH的治疗组中，ODF表达也显示出增加。这在组织学上与破骨细胞增殖低于内软骨骨化的区域一致。本研究结果支持FK 506介导的骨质疏松症通过药物对破骨细胞的作用，促进ODF mRNA的表达，从而促进破骨细胞分化和成熟而发生的假设。

Immunosuppressant drugs are currently required by transplant recipients for the remainder of their lives, despite the many adverse effects associated with these therapies. Acute osteoporosis is one such effect, and a reproducible osteoporosis model has been established through the administration of the immunosuppressant drug FK506 in rats. It has been demonstrated that this osteoporosis was caused by abnormal osteoclast proliferation, altering the process of bone remodeling. However, it has been unclear why FK506 induces osteoclast proliferation and whether this process is mediated by cytokine changes or an increase in bone resorption factors. An investigation was therefore conducted focusing on the recent discoveries of osteoclast differentiation factor (ODF) and osteoclastogenesis inhibitory factor (OCIF). These factors led to elucidation of the osteoclast differentiation/maturation mechanism. An osteoporosis model was produced in rats utilizing intramuscular FK506 injection (1 mg/kg) for 28 consecutive days. Trabecular bone resorption was observed inferior to enchondral ossification in the FK506 group, and tartrate resistant acid phosphatase (TRAP) staining revealed a clear increase in osteoclasts at the site of enchondral ossification, relative to the control group. Reverse transcriptase polymerase chain reaction (RT-PCR) and in situ hybridization (ISH) demonstrated minimal differences in OCIF expression between control and the treatment groups. However, RT-PCR revealed clearly increased ODF expression in the treatment group. ODF expression was also shown to be increased in the treatment group using ISH. This was histologically consistent with a region of osteoclast proliferation inferior to enchondral ossification. The results of this study support the hypothesis that FK506-mediated osteoporosis occurs by action of the drug on osteoclasts, promoting expression of ODF mRNA and thus prompting osteoclast differentiation and maturation.