Biomolecular Analysis on Decorin associated with Ossification of the Longitudinal Ligament

我们检测了从OPLL患者和脊髓型颈椎病患者收集的脊髓韧带中tgf - β和decorin的表达，但没有观察到显著差异。然后，我们对此前已指出硬度异常的OPLL患者颈部皮肤进行了同样的对比研究。结果发现，OPLL患者表皮tgf - β免疫染色倾向于比对照患者稍强。OPLL患者表皮的decorin染色明显增高。进一步用原位杂交法检测decorin mRNA的表达。然后，在OPLL患者中，decorin mRNA的表达也增强。考虑到OPLL患者皮肤硬度异常，这些结果强烈提示OPLL患者皮肤细胞外基质异常。为了研究decorin在骨形成中的作用，我们还在大鼠骨折模型中检测了tgf - β和decorin的免疫组织化学表达。在软骨成骨部位，tgf - β和decorin的定位相反，提示decorin在软骨成骨过程中以某种形式对tgf - β起调节作用。去皮素在韧带骨化中的作用尚未明确。然而，这些结果与先前报道的血清纤维连接蛋白升高一致，反映了OPLL患者易发生系统性骨化，并证实了细胞外基质异常的存在。细胞外基质与生长因子在细胞的增殖和分化过程中起着局部的重要作用。因此，我们推测细胞外基质的异常在异位骨化的发生或进展中发挥了一些额外的作用。

In spinal ligaments collected from patients with OPLL and those with cervical spondylotic myelopathy, we examined the expressions of TGF-beta and decorin, but no significant differences were observed. Then, we made the same comparative study in the nuchal skin of OPLL patients in which hardness abnormality had been pointed out since befor. As a result, it was found that the immunostaining for TGF-beta in epidermis of OPLL patinets tended to show somewhat stronger than those of control patients. The staining of decorin in the epidermis of OPLL patients increased significantly. We further examined mRNA of decorin by in situ hybridization. Then, the expression of decorin mRNA was also enhanced in OPLL patients. Considering the hardness abnormality in the skin of OPLL patients, these results strongly suggest an abnormality in extracellular matrix of the skin of OPLL patients. To study the roles of decorin in bone formation, we also examined expression of TGF-beta and decorin immunohistochemically in rat fracture models. At the site of enchondral ossification, localization of TGF-beta and decorin were opposite to each other, suggesting that decorin works as a regulatory factor in some form against TGF-beta in the process of enchondral ossification. The action of decorin on the ossification of ligament has been not clarified yet. However, these results are consistent with an increase in serum fibronectin as previously reported, reflect OPLL patients' predisposition to systemic ossification and substantiate the presence of an abnormality in extracellular matrix. Extracellular matrix plays an important role locally, together with the growth factor, in proliferation and differentiation of the cells. Therefore, it is presumed that the abnormality in extracellular matrix has playd some additional role in the initiation or progression of heterotopic ossification.