骨-软骨交互作用与骨关节炎的研究进展

郑　洁(综述) ，王瑞辉，寇久社(审校)

(1.陕西中医学院针灸推拿系,陕西 咸阳712046； 2.陕西中医学院第二附属医院康复针灸科，陕西 咸阳712046)



骨-软骨交互作用与骨关节炎的研究进展

郑洁1※(综述) ，王瑞辉1，寇久社2(审校)

(1.陕西中医学院针灸推拿系,陕西 咸阳712046； 2.陕西中医学院第二附属医院康复针灸科，陕西 咸阳712046)

摘要：骨关节炎(OA)进程中，为适应局部生化环境及生物信号的改变，由软骨及软骨下骨构成的关节功能单位经历了不可控制的分解及合成代谢的重构过程。软骨及软骨下骨信号分子的交互作用使两者在病理上相互影响、相互作用。新生血管及微裂隙的形成为骨-软骨间分子通讯提供结构基础。WNT、骨形态发生蛋白、转化生长因子β和丝裂原活化蛋白激酶等信号通路可能是构成OA中骨-软骨交互作用的分子基础。

关键词：骨关节炎；软骨；WNT信号；骨形态发生蛋白；丝裂原活化蛋白激酶

骨关节炎(osteoarthritis,OA)是以进行性关节软骨退变、骨赘形成及继发关节间隙变窄为主要特征的退行性关节疾病[1]。OA进程中，为适应关节局部生化环境的变化，关节软骨和软骨下骨都经历了分解及合成代谢的重构过程。软骨及软骨下骨的病理改变不只是OA的继发表现，更是加快OA进程的积极因素。OA关节骨-软骨新生血管和微裂隙的形成提示，骨-软骨之间可能存在信号分子的交互作用，引起骨-软骨病理上相互影响、相互作用，进而加速软骨退变、软骨下骨破坏及骨赘形成。现对调控关节内软骨及软骨下骨生化代谢的主要信号通路及骨-软骨间细胞通讯在OA进程中的作用予以综述。

1OA关节软骨与软骨下骨的相互作用

正常软骨与软骨下骨有一层钙化软骨相隔，两者很少存在功能上的相互作用。OA软骨下骨大量新生血管及微裂隙的形成提示，OA软骨细胞与软骨下骨细胞分泌的介质可能直接通过这些通道相互作用[2]。研究显示，OA软骨细胞可分泌调节因子介导破骨细胞生成，进而导致软骨下骨丢失[3]；同时，OA软骨下骨成骨细胞来源信号可介导软骨细胞出现肥大表型[4]；小鸡肥大软骨细胞可刺激成骨细胞分化及骨基质沉积[5]。以上结果表明，OA进程中软骨下骨与软骨之间存在着信号分子的密切交互作用。

2OA关节软骨与软骨下骨相互作用的信号机制

2.1WNT(wingless-type)信号机制与骨-软骨交互作用WNT信号不仅在软骨细胞、成骨细胞和破骨细胞生物学中发挥重要作用，而且可能是关节软骨与软骨下骨相互作用的关键信号分子。研究发现，WNT信号通路参与维持成熟小鼠关节软骨表型，可抑制软骨细胞凋亡、延长其存活时间及防止软骨细胞向肥大表型转化[6-8]。脂蛋白受体相关蛋白5(lipoprotein receptor-related protein 5,LRP5)(LRP5是WNTs的共受体)基因剔除OA小鼠软骨细胞凋亡率显著高于野生型OA小鼠[9]，表明WNT信号可促进软骨细胞存活、抑制其凋亡，可作为软骨细胞存活的标志物。然而也有研究发现，WNT信号的高表达可诱发关节软骨基质金属蛋白酶(matrix metalloproteinases，MMPs)和聚蛋白多糖酶等软骨分解代谢因子的表达，导致软骨降解[9]。分泌性卷曲相关蛋白3(secreted frizzled-related protein 3,sFRP3,Frzb)是一种WNT信号拮抗剂，研究发现，sFRP3缺陷小鼠不会出现自发性关节炎，但药物诱导的sFRP3缺陷OA小鼠模型软骨退变程度较野生型对照组OA小鼠更加严重[10]。除调节软骨细胞活动，WNT信号还参与调节骨发育及骨稳态的维持[11]。在胚胎发育后期及生后发育过程中，关节软骨下松质骨形成高度依赖生长板低肥厚区软骨细胞中β联蛋白的表达，而肥厚软骨细胞β联蛋白的表达对调节核因子κB受体活化因子配体表达,进而调控软骨下生长板破骨细胞活动十分必要[12]。研究发现，WNT信号高表达可诱导骨硬化[13]。WNT拮抗剂或受体的基因剔除可激活WNT信号通路，导致成骨过程活跃，骨质变厚变硬[6，9-10]。OA进程中，软骨下皮质骨和松质骨广泛重构，软骨下骨终板增厚，软骨机械负载环境改变，退化过程加快；OA关节中多种内源性WNT激动剂和拮抗剂的表达水平均出现上调。研究发现，OA患者关节软骨FRP、DKK(dickkopf)1和Gremlin1等WNT信号拮抗剂的表达明显上调[14-15]；DKK1表达下调可延缓膝OA关节软骨细胞凋亡、软骨降解及软骨下骨骨量丢失[16]，提示拮抗剂介导的WNT信号抑制可能会诱发软骨细胞合成分解代谢酶及软骨下骨重构。此外，OA患者关节软骨中WNT1诱导信号通路蛋白1(WNT信号激动剂)也呈高表达；OA关节中内源性WNT激动剂的大量分泌可直接刺激软骨细胞分泌MMPs和聚蛋白多糖酶，加速软骨退变[17]；与此同时，软骨下骨重构过程加快，导致关节内骨赘形成[18]。由此可见，WNT信号通路对关节软骨及软骨下骨稳态发挥着重要的调节作用，OA关节软骨与软骨下骨病理上的相互作用可能涉及WNT信号通路的异常活动，软骨及软骨下骨分泌的WNT信号激动剂和拮抗剂可能是OA骨-软骨相互作用的效应分子。

2.2转化生长因子β(transforming growth factor-β，TGF-β)/骨形态发生蛋白(bone morphogenetic protein，BMP)信号机制与骨-软骨交互作用TGF-β和BMP在胚胎发育、组织稳态和多种疾病的发病机制中起着关键作用。BMP是具有调节骨骼系统细胞外基质合成和骨重构等多种功能的高度保守的蛋白。BMP通过经典Smad信号通路介导骨诱导，促进软骨内成骨及软骨特异性Smad1、5基因缺失小鼠出现严重的软骨发育异常[19]。BMP-2、BMP-4、BMP-5、BMP-6、BMP-11和生长分化因子5(growth differentiation factor 5,GDF5)在正常及OA患者软骨均有表达[20]。局部分泌的BMPs在软骨生物学中的具体作用还不明确，但有研究发现，BMPs参与调节蛋白多糖和蛋白聚糖的合成，在软骨保护及修复中发挥作用[21-22]。BMPs信号通路除促进软骨基质合成外，还可促进软骨细胞终末分化，导致MMP-13大量分泌，软骨降解[23]。同时，BMPs也是强有力的成骨刺激因子，可调节体内外成骨细胞和破骨细胞活动[24]。GDF5(BMP信号通路激活因子)单缺陷小鼠可出现软骨下骨密度下降及骨组织胶原纤维排列紊乱[25]，证明BMP信号通路在软骨下骨重构中具有重要的调节作用。伴随BMPs，TGF-β在维持关节完整及代谢平衡中也发挥着不可或缺的作用。TGF-β是细胞外基质合成的强诱导剂，TGF-β 的缺失可导致蛋白多糖丢失和软骨降解[26]。内源性TGF-β1活性抑制可阻抑OA大鼠关节内骨赘形成，但同时也可加快软骨降解过程[27]。除调节软骨稳态外，TGF-β1还参与骨吸收过程，并诱导骨髓间充质干细胞向骨吸收区迁移形成新骨[28]。OA损伤软骨大量分泌TGF-β[29]，软骨下骨TGF-β 活性显著提高[30]，提示TGF-β可能是OA骨-软骨相互影响的信号机制之一。此外，骨-软骨之间可能存在WNT信号通路与TGF-β信号通路的交联。OA患者软骨中经典WNT信号激活后可诱导软骨分泌WNT诱导信号蛋白1[17]，WNT诱导信号蛋白1 可通过增强成骨细胞分化促进成骨过程[31]，提示OA中WNT诱导信号蛋白1 可能通过诱导软骨下骨成骨过程加速软骨下骨OA样变化。

2.3丝裂原活化蛋白激酶(mitogen-activated protein kinases，MAPKs)信号机制与骨-软骨交互作用MAPKs包括三大类激酶，即细胞外信号调节激酶(the extracelluar signal-regulated kinases，ERKs)、c-Jun氨基末端激酶(c-Jun N-terminal kinases，JNKs)和p38激酶。这三类激酶不仅在骨、软骨生物学中具有重要调节作用，而且也涉及OA病理过程。ERK和p38的激活是关节软骨退变的上游关键信号，ERK和p38信号的激活是MMPs表达和活化的必要条件，而ERK激活是聚蛋白多糖酶介导的软骨退变的必须条件[32]。机械应变可诱导成骨细胞内ERK信号的激活，导致成骨细胞合成MMP-13[33]，提示OA进程中机械应变可诱导软骨下骨中的成骨细胞合成MMP-13，促进软骨退变。体外研究发现，正常软骨细胞可抑制软骨下成骨细胞分化，而OA软骨细胞可促进软骨下成骨细胞分化，后者与ERK的激活密不可分[34]。ERK-1/2磷酸化和p38去磷酸化可介导OA软骨细胞与软骨下骨细胞的病理性相互作用，导致软骨细胞呈现肥大表型[35]。还有研究发现，OA软骨或软骨下骨可释放一些未知可溶性因子，这些因子通过激活正常或OA软骨或软骨下骨ERK信号通路介导蛋白聚糖酶和MMPs的释放[36]。以上研究结果表明，OA软骨与软骨下骨存在异常细胞间通讯并借此相互影响，MAPKs信号通路很可能是其物质基础。

3小结

滑膜关节内，结构上的紧密联系使关节软骨与软骨下骨得以通过分子间相互作用并借此在组织结构和功能上相互影响。OA软骨下骨新生血管向软骨层的入侵以及软骨和软骨下骨微裂隙的形成为骨-软骨间分子交互作用提供了结构基础。由软骨及软骨下骨分泌的多种生物因子在OA病理生理中发挥重要的调控作用，其中尤以WNT、BMP、TGF-β和MAPK等关节稳态相关信号分子较为突出，可能是OA骨-软骨交互作用的分子基础。

参考文献

[1]Castaneda S,Roman-Blas JA,Largo R,etal.Subchondral bone as a key target for osteoarthritis treatment[J].Biochem Pharmacol,2012,83(3):315-323.

[2]Fransès RE,McWilliams DF,Mapp PI,etal.Osteochondral angiogenesis and increased protease inhibitor expression in OA[J].Osteoarthritis Cartilage,2010,18(4):563-571.

[3]Jiao K,Niu LN,Wang MQ,etal.Subchondral bone loss following orthodontically induced cartilage degradation in the mandibular condyles of rats[J].Bone，2011,48(2):362-371.

[4]Moreno-Rubio J,Herrero-Beaumont G,Tardio L,etal.Nonsteroidal antiinflammatory drugs and prostaglandin E2 modulate the synthesis of osteoprotegerin and RANKL in the cartilage of patients with severe knee osteoarthritis[J].Arthritis Rheum,2010,62(2):478-488.

[5]Nurminskaya M,Magee C,Faverman L,etal.Chondrocyte-derived transglutaminase promotes maturation of preosteoblasts in periosteal bone[J].Dev Biol，2003,263(1):139-152.

[6]Zhu M,Tang D,Wu Q,etal.Activation of β-catenin signaling in articular chondrocytes leads to osteoarthritis-like phenotype in adult β-catenin conditional activation mice[J].J Bone Miner Res,2009,24(1):12-21.

[7]Zhu M,Chen M,Zuscik M,etal.Inhibition of β-catenin signaling in articular chondrocytes results in articular cartilage destruction[J].Arthritis Rheum,2008,58(7):2053-2064.

[8]Nalesso G,Sherwood J,Bertrand J,etal.WNT-3A modulates articular chondrocyte phenotype by activating both canonical and noncanonical pathways[J].J Cell Biol,2011,193(3):551-564.

[9]Lodewyckx L,Luyten FP,Lories RJ.Genetic deletion of low-density lipoprotein receptor-related protein 5 increases cartilage degradation in instability-induced osteoarthritis[J].Rheumatology,2012,51(11):1973-1978.

[10]Lories RJ,Peeters J,Bakker A,etal.Articular cartilage and biomechanical properties of the long bones in Frzb-knockout mice[J].Arthritis Rheum,2007,56(12):4095-4103.

[11]Baron R,Kneissel M.WNT signaling in bone homeostasis and disease:from human mutations to treatments[J].Nat Med,2013,19(2):179-192.

[12]Golovchenko S,Hattori T,Hartmann C,etal.Deletion of beta catenin in hypertrophic growth plate chondrocytes impairs trabecular bone formation[J].Bone,2013,55(1):102-112.

[13]Jenkins ZA,van Kogelenberg M,Morgan T,etal.Germline mutations in WTX cause a sclerosing skeletal dysplasia but do not predispose to tumorigenesis[J].Nat Genet,2009,41(1):95-100.

[14]Chan BY,Fuller ES,Russell AK,etal.Increased chondrocyte sclerostin may protect against cartilage degradation in osteoarthritis[J].Osteoarthritis Cartilage,2011,19(7):874-885.

[15]Leijten JC,Emons J,Sticht C,etal.Gremlin 1,frizzled-related protein,and Dkk-1 are key regulators of human articular cartilage homeostasis[J].Arthritis Rheum,2012,64(10):3302-3312.

[16]Weng LH,Wang CJ,Ko JY,etal.Control of Dkk-1 ameliorates chondrocyte apoptosis,cartilage destruction,and subchondral bone deterioration in osteoarthritic knees[J].Arthritis Rheum,2010,62(5):1393-1402.

[17]Blom AB,Brockbank SM,van Lent PL,etal.Involvement of the WNT signaling pathway in experimental and human osteoarthritis:Prominent role of WNT-induced signaling protein 1[J].Arthritis Rheum,2009,60(2):501-512.

[18]Kuliwaba JS,Findlay DM,Atkins GJ,etal.Enhanced expression of osteocalcin mRNA in human osteoarthritic trabecular bone of the proximal femur is associated with decreased expression of interleukin-6 and interleukin-11 mRNA[J].J Bone Miner Res,2000,15(2):332-341.

[19]Retting KN,Song B,Yoon BS,etal.BMP canonical Smad signaling through Smad1 and Smad5 is required for endochondral bone formation[J].Development,2009,136(7):1093-1104.

[20]Chen AL,Fang C,Liu C,etal.Expression of bone morphogenetic proteins,receptors,and tissue inhibitors in human fetal,adult,and osteoarthritic articular cartilage[J].J Orthop Res,2004,22(6):1188-1192.

[21]Blaney Davidson EN,Vitters EL,van Lent PL,etal.Elevated extracellular matrix production and degradation upon bone morphogenetic protein-2 (BMP-2) stimulation point toward a role for BMP-2 in cartilage repair and remodeling[J].Arthritis Res Ther,2007,9(5):R102.

[22]Lories RJ,Daans M,Derese I,etal.Noggin haploinsufficiency differentially affects tissue responses in destructive and remodeling arthritis[J].Arthritis Rheum,2006,54(6):1736-1746.

[23]van der Kraan PM,Blaney Davidson EN,van den Berg WB.Bone morphogenetic proteins and articular cartilage:To serve and protect or a wolf in sheep clothing′s?[J].Osteoarthritis Cartilage,2010,18(6):735-741.

[24]Wang EA,RosenV,D′Alessnadro JS,etal.Recombinant human bone morphogenetic protein induced bone formation[J].Proc Natl Acad Sci U S A,1990,87(6):2220-2224.

[25]Daans M,Luyten FP,Lories RJ.GDF5 deficiency in mice is associated with instability-driven joint damage,gait and subchondral bone changes[J].Ann Rheum Dis,2011,70(1):208-213.

[26]Yang X,Chen L,Xu X,etal.TGF-β/Smad3 signals repress chondrocyte hypertrophic differentiation and are required for maintaining articular cartilage[J].J Cell Biol,2001,153(1):35-46.

[27]Scharstuhl A,Glansbeek HL,van Beuningen,etal.Inhibition of endogenous TGF-β during experimental osteoarthritis prevents osteophyte formation and impairs cartilage repair[J].J Immunol,2002,169(1):507-514.

[28]Tang Y,Wu X,Lei W,etal.TGF-β1-induced migration of bone mesenchymal stem cells couples bone resorption with formation[J].Nat Med,2009,15(7):757-765.

[29]Mansell JP,Collins C,Bailey AJ.Bone,not cartilage,should be the major focus in osteoarthritis[J].Nat Clin Pract Rheumatol,2007,3(6):306-307.

[30]Zhen G,Wen C,Jia X,etal.Inhibition of TGF-β signaling in mesenchymal stem cells of subchondral bone attenuates osteoarth-ritis[J].Nat Med,2013,19(6):704-712.

[31]Inkson CA,Ono M,Kuznetsov SA,etal.TGF-β1and WISP-1/CCN-4 can regulate each other′s activity to cooperatively control osteoblast function[J].J Cell Biochem,2008,104(5):1865-1878.

[32]Sondergaard BC,Schultz N,Madsen SH,etal.MAPKs are essential upstream signaling pathways in proteolytic cartilage degradation-divergence in pathways leading to aggrecanase and MMP-mediated articular cartilage degradation[J].Osteoarthritis Cartilage,2010,18(3):279-288.

[33]Yang CM,Chien CS,Yao CC,etal.Mechanical strain induces collagenase-3 (MMP-13) expression in MC3T3-E1 osteoblastic cells[J].J Biol Chem,2004,279(21):22158-22165.

[34]Prasadam I,Friis T,Shi W,etal.Osteoarthritic cartilage chondrocytes alter subchondral bone osteoblast differentiation via MAPK signalling pathway involving ERK1/2[J].Bone,2010,46(1):226-235.

[35]Prasadam I,van Gennip S,Friis T,etal.ERK-1/2 and p38 in the regulation of hypertrophic changes of normal articular cartilage chondrocytes induced by osteoarthritic subchondral osteoblasts[J].Arthritis Rheum,2010,62(5):1349-1360.

[36]Prasadam I,Crawford R,Xiao Y.Aggravation of ADAMTS and matrix metalloproteinase production and role of ERK1/2 pathway in the interaction of osteoarthritic subchondral bone osteoblasts and articular cartilage chondrocytes-Possible pathogenic role in osteoarthritis[J].J Rheumatol,2012,39(3):621-634.

Research Progress of Cross Talk between Cartilage and Subchondral Bone in OsteoarthritisZHENGJie1,WANGRui-hui1,KOUJiu-she2.(1.DepartmentofAcupunctureandMoxibustion,ShaanxiUniversityofChineseMedicine,Xianyang712046，China； 2.DepartmentofAcupuncture&Rehabilitation,theSecondAffiliatedHospitalofShaanxiUniversityofChineseMedicine,Xianyang712046,China)

Abstract:During osteoarthritis(OA),functional units of joints comprising cartilage and subchondral bone undergo uncontrolled catabolic and anabolic remodeling processes to adapt to local biochemical and biological signals.There is interplay between articular cartilage and subchondral bone in OA pathology.Formation of vascularization and microcracks in joints contribute to molecular crosstalk between cartilage and subchondral bone during the process of OA.Wingless-type,bone morphogenic protein,transforming growth factor-β and mitogen-activated protein kinases signals may be the molecular basis for interaction of cartilage and subchondral bone in OA pathology.

Key words:Osteoarthritis； Cartilage； Wingless-type; Bone morphogenic protein； Mitogen-activated protein kinases

收稿日期：2014-10-10修回日期：2014-12-03编辑：郑雪

基金项目：陕西省中医康复学重点学科建设项目(陕中医药发〔2011〕46号)；陕西省教育厅科学研究项目(14JK1209)；陕西中医学院创新基金培育项目(14XJZR27)

doi：10.3969/j.issn.1006-2084.2015.14.005

中图分类号：R683

文献标识码：A

文章编号：1006-2084(2015)14-2507-03