外源性骨强化蛋白对强直性脊柱炎小鼠的疗效研究

Treatment of a mouse model of ankylosing spondylitis with exogenous sclerostin

目的评估外源性骨强化蛋白(sclerostin,SOST)治疗强直性脊柱炎的疗效。方法 BALB/c IL-4小鼠每隔2周皮下注射2mg人蛋白多糖,8周后诱导脊柱炎(PGISp)模型,PGISp小鼠体内SOST表达下调。随后将PGISp小鼠根据治疗方案,分为SOST组与阳性对照组。SOST组注射2.5μg重组SOST(recombinant SOST,rSOST),持续8周。阳性对照组注射同剂量外源性Wnt通路抑制因子Dickkopf1(DKK-1),同样持续8周。使用双能X线骨密度仪(DEXA)检测2组小鼠组织学和骨骼变化,评估外周关节及中轴骨疾病的发展状况。结果 SOST组外周或轴向疾病发展,骨质密度或疾病严重程度均无改善。rSOST注射8h达到峰值,注射24h后血浆SOST质量浓度水平较高,导致循环系统SOST血清水平累积。免疫组化法检查骨细胞水平,阳性对照组中未受累关节内骨细胞水平显著低于受累关节内骨细胞水平;SOST组小鼠不同关节之间的骨细胞水平无差异。组间未受累关节进行比较,阳性对照组优于SOST组。结论 rSOST未能降低关节内的骨细胞水平,但其具有生物活性。今后需要改变剂量,提高骨靶向能力,从而影响骨生成;目前外源性骨强化蛋白疗效不及DKK-1。

mObjective To evaluate the curative effect of exogenous bone strengthening protein（sclerostin,SOST）for the treatment of ankylosing spondylitis.Methods The proteoglycan（2 mg）-induced spondylitis（PGISp）mouse model in which we previously demonstrated down regulated SOST expression,was used for this study.Mice were injected with 2.5μg rSOST/day for a period of 8weeks following induction of disease.Same dose Dickkopf1（DKK-1）was injected in control group,also 8weeks.Axial skeleton disease development was assessed by histology and skeletal changes examined using DEXA.Results SOST treatment had no effect on peripheral or axial disease development,bone density or disease severity.Injected rSOST was stable over 8hand residual levels were evident 24 hafter injection,resulting in a cumulative increase in SOST serum levels over the treatment time course.Immunohistochemical examination of SOST levels within the joints in control group showed a significant decrease in the percentage of positive osteocytes in the unaffected joints compared to the affected joints,while no difference was observed in SOST treated mice.This suggests that rSOST treatment increases the number of SOST-positive osteocytes in unaffected joints but not affected joints,despite of having no impact on the number of joints affected by disease.Conclusions Although not disease-modifying,rSOST treatment did appear to regulate SOST levels in the joints suggesting biological activity.Further dose response studies are required and SOST may require modifications to improve its bone targeting ability in order to affect tissue formation to a meaningful level in this model.The curative effect is inferior to DKK-1.