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

目前，移植受者在其余生中都需要免疫抑制药物，尽管这些治疗方法有许多副作用。急性骨质疏松症就是其中之一，通过给大鼠注射免疫抑制剂FK506，已经建立了一种可重复性的骨质疏松症模型。研究表明，这种骨质疏松症是由于破骨细胞异常增殖，改变了骨重建过程而引起的。然而，目前还不清楚FK506诱导破骨细胞增殖的原因，以及这一过程是通过细胞因子的变化还是骨吸收因子的增加来介导的。因此，对破骨细胞分化因子(ODF)和破骨细胞生成抑制因子(OCIF)的最新发现进行了研究。这些因素导致了破骨细胞分化/成熟机制的阐明。大鼠肌肉注射FK506(1 mg/kg)，连续28天建立骨质疏松模型。FK506组骨小梁吸收程度低于软骨骨化，抗酒石酸酸性磷酸酶(TRAP)染色显示软骨骨化部位破骨细胞较对照组明显增多。逆转录聚合酶链式反应(RT-PCR)和原位杂交(ISH)显示对照组和治疗组之间OCIF的表达差异很小。反转录-聚合酶链式反应显示治疗组ODF表达明显增加。在使用ISH的治疗组，ODF的表达也增加。这在组织学上与破骨细胞增殖区低于软骨骨化相一致。本研究结果支持FK506介导的骨质疏松症是通过药物作用于破骨细胞，促进ODF mRNA表达，从而促进破骨细胞分化成熟而发生的假说。

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.