Korkosz Mariusz, Czepiel Marcin, Guła Zofia, Stec Małgorzata, Węglarczyk Kazimierz, Rutkowska-Zapała Magdalena, Gruca Anna, Lenart Marzena, Baran Jarosław, Gąsowski Jerzy, Błyszczuk Przemysław, Siedlar Maciej
Department of Rheumatology, Jagiellonian University Medical College, 10 Sniadeckich Str., Krakow, Poland.
Department of Clinical Immunology, Institute of Paediatrics, Jagiellonian University Medical College, 265 Wielicka Str., 30-663, Krakow, Poland.
BMC Musculoskelet Disord. 2018 Dec 6;19(1):434. doi: 10.1186/s12891-018-2356-4.
Axial spondyloarthritis (axSpA) is characterized by significant bone loss caused by dysregulation of physiological bone turnover, possibly resulting from intensified differentiation of osteoclasts. The aim of this study was to reevaluate the levels of osteoclastogenesis-mediating factors: soluble RANKL, M-CSF, OPG and other cytokines in sera of untreated, with sDMARDs and/or bDMARDs, axSpA patients and to test whether these sera influence differentiation of healthy monocytes towards osteoclast lineage.
Bone remodeling molecules (RANKL, M-CSF, OPG, IL-6, OSM, IL-17A, TGFβ, and TNFα) were evaluated in 27 patients with axSpA and 23 age and sex-matched controls. Disease activity (BASDAI, ASDAS) and inflammatory markers (ESR, CRP) were assessed. Monocytes obtained from healthy individuals were cultured in vitro in presence of sera from 11 randomly chosen axSpA patients and 10 controls, with addition of exogenous M-CSF and/or RANKL or without. Osteoclastic differentiation was assessed analyzing osteoclast markers (cathepsin K and RANK at mRNA level) and with osteoclast-specific staining.
axSpA patients' sera levels of soluble RANKL were significantly lower and M-CSF, IL-6, OSM, IL-17A and TNFα significantly higher in comparison to controls, whereas of OPG and TGFβ were comparable in both groups. Numbers of generated in vitro osteoclasts and cathepsin K mRNA levels did not differ between cultures supplemented with sera of healthy and axSpA patients, both in the absence and presence of M-CSF. Instead, addition of exogenous RANKL boosted osteoclastogenesis, which was significantly higher in cultures with axSpA sera. Furthermore, sera from axSpA patients induced substantially higher levels of RANK mRNA, independently of M-CSF and RANKL stimulation.
We show that, paradoxically, serum levels of soluble RANKL observed in axSpA are in fact significantly lower in comparison to healthy blood donors. Our results indicate that sera of axSpA patients - in contrary to healthy subjects - contain circulating, soluble factors (presumably IL-6, OSM, IL-17A, TNFα and others) able to stimulate healthy monocytes responsiveness to even relative low RANKL serum levels, by inducing high RANK mRNA expression and - as a net effect - boosting their osteoclastogenic potential. We suggest also that locally produced RANKL in axSpA may induce overactive osteoclasts from their precursors.
中轴型脊柱关节炎（axSpA）的特征是生理性骨转换失调导致显著的骨质流失，这可能是由于破骨细胞分化增强所致。本研究的目的是重新评估未治疗、接受小分子抗风湿药物（sDMARDs）和/或生物制剂（bDMARDs）治疗的axSpA患者血清中破骨细胞生成介导因子：可溶性核因子κB受体活化因子配体（RANKL）、巨噬细胞集落刺激因子（M-CSF）、骨保护素（OPG）和其他细胞因子的水平，并测试这些血清是否影响健康单核细胞向破骨细胞谱系的分化。
对27例axSpA患者和23例年龄及性别匹配的对照者进行骨重塑分子（RANKL、M-CSF、OPG、白细胞介素-6（IL-6）、抑瘤素M（OSM）、白细胞介素-17A（IL-17A）、转化生长因子β（TGFβ）和肿瘤坏死因子α（TNFα））的评估。评估疾病活动度（巴斯强直性脊柱炎疾病活动指数（BASDAI）、强直性脊柱炎疾病活动评分（ASDAS））和炎症标志物（红细胞沉降率（ESR）、C反应蛋白（CRP））。从健康个体获取的单核细胞在体外与11例随机选择的axSpA患者和10例对照者的血清一起培养，添加外源性M-CSF和/或RANKL或不添加。通过分析破骨细胞标志物（组织蛋白酶K和RANK的mRNA水平）以及破骨细胞特异性染色来评估破骨细胞分化。
与对照组相比，axSpA患者血清中可溶性RANKL水平显著降低，而M-CSF、IL-6、OSM、IL-17A和TNFα水平显著升高，而两组间OPG和TGFβ水平相当。在添加健康人和axSpA患者血清的培养物中，无论是否存在M-CSF，体外生成的破骨细胞数量和组织蛋白酶K mRNA水平均无差异。相反，添加外源性RANKL可促进破骨细胞生成，在添加axSpA患者血清的培养物中破骨细胞生成显著更高。此外，axSpA患者的血清诱导的RANK mRNA水平显著更高，与M-CSF和RANKL刺激无关。
我们发现，矛盾的是，与健康献血者相比，axSpA患者血清中可溶性RANKL水平实际上显著降低。我们的结果表明，与健康受试者相反，axSpA患者的血清含有循环的可溶性因子（可能是IL-6、OSM、IL-17A、TNFα等），这些因子能够通过诱导高RANK mRNA表达，刺激健康单核细胞对相对较低的血清RANKL水平的反应性，并作为净效应增强其破骨细胞生成潜能。我们还认为，axSpA中局部产生的RANKL可能诱导其前体细胞产生过度活跃的破骨细胞。
