Pathak Janak L, Bravenboer N, Luyten Frank P, Verschueren Patrick, Lems Willem F, Klein-Nulend Jenneke, Bakker Astrid D
Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
Calcif Tissue Int. 2015 Aug;97(2):169-78. doi: 10.1007/s00223-015-9999-z. Epub 2015 May 13.
Multiple factors contribute to bone loss in inflammatory diseases such as rheumatoid arthritis (RA), but circulating inflammatory factors and immobilization play a crucial role. Mechanical loading prevents bone loss in the general population, but the effects of mechanical loading in patients with RA are less clear. Therefore, we aimed to investigate whether mechanical stimuli reverse the stimulatory effect of RA serum on osteocyte-to-osteoclast communication. Human primary osteocytes were pretreated with 10 % RA serum or healthy control serum for 7 days, followed by 1 h ± mechanical loading by pulsating fluid flow (PFF). Nitric oxide (NO) and prostaglandin E2 were measured in the medium. Receptor activator of nuclear factor-kappaB ligand (RANKL), osteoprotegerin (OPG), interleukin-6 (IL-6), cyclooxygenase-2 (COX2), matrix-extracellular phosphoglycoprotein (MEPE), cysteine-rich protein 61 (CYR61), and SOST gene expression was quantified by qPCR. Osteoclast precursors were cultured with PFF-conditioned medium (PFF-CM) or static-conditioned medium (stat-CM), and osteoclast formation was assessed. RA serum alone did not affect IL-6, CYR61, COX2, MEPE, or SOST gene expression in osteocytes. However, RA serum enhanced the RANKL/OPG expression ratio by 3.4-fold, while PFF nullified this effect. PFF enhanced NO production to the same extent in control serum (2.6-3.5-fold) and RA serum-pretreated (2.7-3.6-fold) osteocytes. Stat-CM from RA serum-pretreated osteocytes enhanced osteoclastogenesis compared with stat-CM from control serum-pretreated osteocytes, while PFF nullified this effect. In conclusion, RA serum, containing inflammatory factors, did not alter the intrinsic capacity of osteocytes to sense mechanical stimuli, but upregulated osteocyte-to-osteoclast communication. Mechanical loading nullified this upregulation, suggesting that mechanical stimuli could contribute to the prevention of osteoporosis in inflammatory disease.
多种因素导致类风湿关节炎（RA）等炎症性疾病中的骨质流失，但循环炎症因子和制动起着关键作用。机械负荷可防止普通人群骨质流失，但机械负荷对RA患者的影响尚不清楚。因此，我们旨在研究机械刺激是否能逆转RA血清对骨细胞与破骨细胞通讯的刺激作用。将人原代骨细胞用10%RA血清或健康对照血清预处理7天，然后通过脉动流体流（PFF）进行1小时±机械负荷处理。测量培养基中的一氧化氮（NO）和前列腺素E2。通过qPCR定量核因子κB受体活化剂配体（RANKL）、骨保护素（OPG）、白细胞介素-6（IL-6）、环氧化酶-2（COX2）、基质细胞外磷酸糖蛋白（MEPE）、富含半胱氨酸蛋白61（CYR61）和SOST基因表达。将破骨细胞前体与PFF条件培养基（PFF-CM）或静态条件培养基（stat-CM）一起培养，并评估破骨细胞形成。单独的RA血清不影响骨细胞中IL-6、CYR61、COX2、MEPE或SOST基因表达。然而，RA血清使RANKL/OPG表达比值提高了3.4倍，而PFF消除了这种作用。PFF在对照血清预处理的骨细胞（2.6 - 3.5倍）和RA血清预处理的骨细胞（2.7 - 3.6倍）中同等程度地增强了NO产生。与对照血清预处理的骨细胞的stat-CM相比，RA血清预处理的骨细胞的stat-CM增强了破骨细胞生成，而PFF消除了这种作用。总之，含有炎症因子的RA血清并未改变骨细胞感知机械刺激的内在能力，但上调了骨细胞与破骨细胞的通讯。机械负荷消除了这种上调，表明机械刺激可能有助于预防炎症性疾病中的骨质疏松症。
