Clinical manifestations of osteoarthritis and the role of silent information regulation 1 in the pathogenesis of osteoarthritis

doi:10.3969/j.issn.2095-4344.2017.12.022

Abstract

Abstract:

BACKGROUND: Functional changes of some functional genes have been showed to trigger osteoarthritis, among which, age may be a critical one.
OBJECTIVE: To summarize the clinical manifestations of osteoarthritis and the research process of silent information regulation 1 in the occurrence and development of osteoarthritis.
METHODS: A computer-based retrieval was performed in the databases of CNKI, PubMed, SpringerLink, and Elsevier Science Direct using the keywords of “osteoarthritis, silent information regulation 1 and cartilage” in Chinese and English, respectively. Finally 83 eligible literatures were enrolled for analysis.
RESULTS AND CONCLUSION: Deacetylation modification acts on the occurrence and development of osteoarthritis by regulating the expression and biological function of various cytokines. Silent information regulation 1 cannot only regulate body metabolism, inhibit cell apoptosis, repair DNA injury, delay senescence and resist to stress, but also play important roles in the epigenetic modification, gene silencing and signal transduction. Therefore, silent information regulation 1 is involved in the age-related diseases, such as osteoarthritis, osteoporosis, diabetes and Alzheimer’s disease. Furthermore, silent information regulation 1 is likely to be an important target of osteoarthritis drugs, and even reverses mechanical stress-induced cartilage injury in the early stage of osteoarthritis.

中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

Key words: Osteoarthritis, Gene Silencing, Cartilage, Tissue Engineering

CLC Number:

R318

Lei Ming1, Yu Fei2, Xiao De-ming1. Clinical manifestations of osteoarthritis and the role of silent information regulation 1 in the pathogenesis of osteoarthritis[J]. Chinese Journal of Tissue Engineering Research, 2017, 21(12): 1933-1939.

Figures/Tables 1

2.1 骨关节炎的概述国内外的流行病学研究显示，骨关节炎的总体患病率约为15%，整体的致残率为2%-6%[3-4]。在中国陕西省境内的7 126名农村居民中，有983人患有膝骨关节炎[5]，而黑龙江省内一个普通社区的骨关节炎患病率高达16.05%[6]。另一方面，随着年龄的增长骨关节炎患病率也显著增加。在中国，40岁人群的患病率为10%-17%，65岁以上的人群约为60%，75岁以上人群约为80%，全国大约有6 500万以上的人患有此病，致残率可高达53%，严重影响了人类的健康[7-11]。另外一项研究显示患骨关节炎的女性和男性比例分别是34%和31%[8]，说明女性患骨关节炎的概率明显高于男性[9]。骨关节炎所导致的残疾仅次于心血管疾病居世界第二[7，12-13]。因此探讨骨关节炎的发病原因及发病机制，寻找有效预防及治疗骨关节炎的方法对于骨关节炎的防治尤为重要。 2.2 骨关节炎的临床治疗目前骨关节炎尚无完全治愈的手段，在关节形态与功能达到严重损害前多采用对症治疗。临床上多数患者前来就诊时已处于中晚期，并且对该病的进展变化缺乏明显的生物学指标进行跟踪随访，而不同部位的骨关节炎可能有着不同的易感因素和始发机制，且不同层次的软骨对应激的反应也不尽一致，这一系列的难题极大的限制了对该病发生发展的认识。临床上大多采用药物和非药物相结合的方式来治疗，具体需要结合患者自身情况，如性别、年龄、病变部位的程度等制定合适的个体化治疗方案，以达到减轻患者病痛，矫正畸形，改善关节功能，提高患者生活质量的目的[14-15]。目前各种非类固醇类抗炎药物、葡萄糖胺和硫酸软骨素、抗骨质疏松药物和神经生长因子拮抗剂、肿瘤坏死因子抑制剂的口服，透明质酸或糖皮质激素在关节腔内注射以及多种侵入性，包括手术在内的治疗方式或有着不同程度的副反应，或患者不能长期耐受，依从性不高或价格昂贵等诸多缺点，治疗效果也不确定甚至导致症状加重[1，16-27]。一般来讲，对于初次患病且症状较轻的骨关节炎患者，多选用理疗康复训练的治疗方式，如针灸、按摩、热疗，超声波、关节功能训练和肌力训练等[28-30]。若上述治疗无效或效果不佳，就需要选用合适药物进行治疗，如对乙酰氨基酚、非类固醇类抗炎药物、阿片类镇痛剂、抗骨质疏松药物和神经生长因子拮抗剂、肿瘤坏死因子抑制剂等[17-27]。传统的镇痛药物对于疼痛的缓解和关节功能的改善优于安慰剂，在缓解关节僵直方面无明显差异，但在治疗早期的骨关节炎能改善僵直的关节功能[17]。在缓解骨关节炎急性发作症状，曲马多-双氯芬酸钠或曲马多-扑热息痛这两种联合用药均能显著的缓解疼痛，耐受性亦较好[18]。长期使用非类固醇类抗炎药物需注意心血管方面的风险，塞来昔布相对安全且有效[19]。葡萄糖胺及硫酸软骨素等疗效不确切，不同品牌作用不一，缺乏一致性，但最新的一项多中心、双盲的研究显示联合使用葡萄糖胺和硫酸软骨素在改善膝关节功能，减轻肿胀，缓解疼痛上不亚于塞来昔布[20]。在一项为期28周的治疗膝关节骨关节炎的随机双盲安慰剂对照实验中，抗肿瘤药物氨甲蝶呤能有效的减少疼痛，改善关节功能[21]。在欧洲的一项临床双盲对照试验中，有学者选择对止痛药物非类固醇类抗炎药物不敏感的手骨关节炎患者作为研究对象，他们发现对于疼痛症状的缓解方面，肿瘤坏死因子抑制剂——阿达木单抗并不优于安慰剂[22]。另一项为期3年利用抗骨质疏松药物——雷奈酸锶应用于关节骨关节炎的临床试验研究中发现雷奈酸锶能缓解症状，改善关节功能[23]，同时亦有研究发现二膦酸盐类等抑制破骨细胞的抗骨质疏松药物对早期骨关节炎有降低疼痛评分的效果[24]。在采用抗神经生长因子单抗缓解骨关节炎症状的一项研究指出对非类固醇类抗炎药物缓解疼痛有效的患者，单一使用他尼珠单抗可能更有止痛效果，但不良反应增加[25]，不推荐两者联合使用[26]。另一种抗神经生长因子单抗药物Fasinumab耐受性更好，且明显优于安慰剂[27]。此外，关节腔内注射透明质酸钠或糖皮质激素，运用关节镜(内窥镜)和开放手术等有创的外科干预方式对于骨关节炎的治疗同样在临床广泛应用[28]。 2.3 骨关节炎的病因及发病过程骨关节炎可简单分为原发性和继发性两种：原发性骨关节炎无明确病因，可能是多种因素综合作用的结果，如遗传、老年、肥胖等。继发性骨关节炎常常由于过度使用、机械与外伤、内分泌紊乱或炎症等明确致病因素引起[31]。在上述这些全身因素与局部因素的综合作用下，关节软骨的受损、关节滑膜的病变，以及软骨下骨反应性增生被认为是骨关节炎发病过程中的重要病理特征[32]。作为一种与年龄、遗传易感性密切相关的多因素疾病，骨关节炎主要病理变化是关节软骨进行性的退变、丢失和继发性的骨质增生(骨赘形成和软骨下骨硬化等)，年龄、肥胖、性别、遗传因素等均起着重要作用[1-2]。一般认为反复性的机械应力损伤、遗传易感性和年龄因素共同触发了骨关节炎的初始阶段，激活一种以软骨细胞为主，滑膜细胞和软骨下骨参与的应答反应，继而软骨细胞外基质、软骨细胞及软骨下骨三者的合成代谢发生紊乱。这种紊乱造成合成代谢与分解代谢之间的失衡，具体表现为基质降解酶类的产生和软骨修复的抑制，但同时也发现无论是在骨关节炎的早期还是晚期，软骨细胞都表现为整体合成能力的提高，其中包括Ⅱ型胶原在内的Ⅳ型、Ⅸ型、Ⅺ型胶原，以及肥大软骨细胞特异性的X型胶原均有不同程度的表达增加，这些应答模式极为类似在肢体发育中软骨发生逐渐被骨组织替代的过程[1，16，33]，提示在骨关节炎发生发展过程中，软骨细胞的这种表型改变可能是一种具有“记忆”的调节，但两者后果却完全不同：肢体发育中分化的软骨细胞虽然不断发生肥大、凋亡继而被骨组织替代，但长骨的远端依然保留一定厚度的关节软骨，这在一定程度上可能是由于处于骺板的软骨细胞比较“幼稚”，在增生的同时还能产生大量软骨基质的缘故[33]。在骨关节炎发病人群中，骨骺已经闭合，而那些处于终末分化状态的软骨细胞由于衰老、遗传等因素，已经没有足够能力扭转这种过度的基质降解和软骨丢失，因此推测骨关节炎的始发可能在青春发育完毕后就已缓慢开始，在后期快速进展。在骨关节炎发病进程中，软骨基质出现降解破坏，软骨细胞的表型、细胞周期发生改变并最终发生去分化、衰老凋亡继而诱导软骨基质逐步钙化的一系列形态学改变，受累关节完整性和稳定性遭到破坏，加之关节周围组织的退变和废用性萎缩更加加速了后期的病理进程。最新文献表明它还伴随着不同程度的炎症应答和免疫趋化反应，并在滑膜、软骨下骨、半月板、关节周围肌肉、韧带以及关节囊等的共同参与下形成病理性的适应[34]。软骨的损伤和退化是骨关节炎发生与发展过程中的一个关键环节，而软骨细胞是成熟软骨组织内唯一的细胞类型，因此在骨关节炎的发病过程中发挥着关键的作用[35]。在正常情况下，软骨细胞数量少且很少发生分裂，并且在发生凋亡后不易被吞噬细胞清除。随着年龄的增长，凋亡细胞数目增多进一步累积导致软骨组织损伤加重[36]。与此同时，与衰老密切关联的氧化应力和炎症反应影响软骨细胞的染色体端粒的长短，并参与软骨细胞向终末表型分化的过程[37-38]。此外，软骨基质也是软骨组织的重要组成部分，其主要成分Ⅱ型胶原和聚集蛋白聚糖等同样受到衰老的影响[39]。随着机体的老化，Ⅱ型胶原发生高级糖基化的终末产物在软骨组织内大量蓄积，引发胶原间广泛的交联，造成软骨硬度增加，脆性加大，更易受到疲劳性应力的损伤，也更易被基质金属蛋白酶类降解[37]。研究表明，软骨细胞和软骨基质在生化、组成结构和代谢上发生的不同程度的改变，直接参与软骨的软化、破溃和局部剥脱等关节软骨损伤的过程，并引发关节僵硬变形、肿胀疼痛等多种相应的临床症状，促进了骨关节炎的病程进展[40-41]。关节滑膜的病变在骨关节炎发病过程中也起着重要作用，譬如关节滑液的缺失导致关节骨骼缺少必要的保护，因此更容易受到外界炎性因子的侵入，而且在机械应力作用下关节也更易发生损伤，最终导致了骨关节炎的发生发展[42]。此外，关节滑膜的另一种常见的病变滑膜炎症是软骨基质降解产物引起的继发性改变，同样参与了骨关节炎的发病过程[43-44]。软骨下骨反应性增生同样是骨关节炎发生发展的的主要成因之一。研究表明，在骨关节炎患者关节的软骨下骨表现为骨小梁数目增加，密度增高，间距变小，骨小梁方向与关节表面更垂直，进而出现骨质象牙化、骨囊肿和骨赘形成等病理变化[45-46]。因此，软骨，滑膜和软骨下骨的改变在骨关节炎的发病过程中都起到了非常重要的作用，一方面关节软骨发生形态学的改变和功能损伤，另外一方面关节滑膜发生病变以及软骨下骨出现反应性增生，而衰老引起的一系列内环境的改变则加剧了这些进程，同时进一步揭示出年龄因素在骨关节炎中的重要地位。 2.4 SIRT1 2.4.1 SIRT1基本特征 SIRT1相关酶类(sirtuins)是一种保守的烟酰胺腺嘌呤二核苷酸(NAD+)依赖的组蛋白去乙酰化酶，广泛地存在于原核与真核生物中[47]。在人类的sirtuins 中，存在7个同源蛋白，分别命名为沉默信息调节因子1-7 (SIRT1-7)[48-49]。在sirtuins所有家族成员中，SIRT1与sirtuins的同源性最高[50]。SIRT1含有一个保守的核心催化结构域，并结合NAD+作为辅酶，该核心结构域具有脱乙酰基酶的活性的作用，而且SIRT1的COOH端和NH2端增强了核心结构域的催化效率和脱乙酰基酶活性[51]。 2.4.2 SIRT1功能概述 Kim等[52]研究发现当高糖诱导肾小球系膜细胞发生损伤时，SIRT1的活性降低，氧化应激以及细胞凋亡加剧，这说明SIRT1在调节线粒体代谢能量，氧化应激，以及细胞凋亡中具有重要作用。进一步的研究表明，SIRT1通过对组蛋白、转录因子及其它蛋白的赖氨酸残基进行去乙酰化修饰，来调节基因的表达，进而在调控机体代谢，抑制细胞凋亡，延缓衰老，抵抗应激等过程中发挥出重要的调控作用[53-54]。SIRT1不仅能调节组蛋白如组蛋白H3第9位赖氨酸(H3K9)，组蛋白H4第16位赖氨酸(H4K16)，和组蛋白H1第26位赖氨酸(H1K26)的去乙酰化，还能使其他类蛋白如p53，FOXO，和PGC-1α等去乙酰化，进而参与多种生命过程的调控[55-57]。此外，SIRT1的活性和表达也受到多种因素的影响，譬如底物的有效性、组织和亚细胞的定位、转录因子和微小RNA(miRNA)蛋白表达的调控等因素[58-60]。SIRT1的活性也与其发生磷酸化，甲基化，亚硝基化等翻译后修饰有关[61-63]，更重要的是SIRT1和多种转录因子的基因调控通路之间的串扰影响着干细胞的扩增与分化[64]。 2.5 骨关节炎与SIRT1 鉴于SIRT1在许多新陈代谢和生理活动中的重要作用，特别是SIRT1可通过多种机制如调控基因表达，促进神经新生，修复DNA损伤和细胞凋亡等促进机体长寿这一作用，目前引起了广泛的关注，SIRT1成为了抗衰老药物研究的新靶点[65]。SIRT1可能同样在与年龄因素密切相关的骨关节炎中扮演着重要的作用。 2.5.1 SIRT1在骨关节炎的体外研究骨关节炎的主要病理特征是关节软骨的功能退化，研究表明SIRT1在骨关节炎的软骨中发挥出重要的调节作用[66]。Hong等[67]发现电离辐射能够抑制SIRT1的表达，从而诱导软骨细胞发生凋亡，这说明软骨细胞内SIRT1的表达与该细胞的凋亡相关。此外，也有研究表明SIRT1通过增强胰岛素样生长因子信号，降低p53的活性，从而影响软骨细胞的存活能力[68]。Kim等[69]研究发现，无论是在正常人还是骨关节炎患者的软骨细胞中，25 μmol/L和50 μmol/L的白藜芦醇均能显著上调SIRT1的表达，并且上调Ⅰ型胶原(COL1)、X型胶原(COL10)和成骨特异性转录因子2 (RUNX2) 的表达，进一步促进软骨细胞发生增生。一些新的分子机制还表明在肿瘤坏死因子α刺激下，SIRT1从细胞核转移到细胞质，会进一步诱发或加重软骨细胞的炎症反应[70-71]。此外，SIRT1还可调节多种软骨特异性基因的表达，如聚集蛋白聚糖，Ⅱ型和IX型胶原和软骨寡聚基质蛋白(COMP)，尤其是抑制了ADAMTS-5的表达和使SOX9去乙酰化，进而影响骨关节炎的病理进程[72-73]。Matsushita等[74]也检测了人软骨细胞中SIRT1的过表达对基质金属蛋白酶1，2，9，13等骨关节炎基因的影响，研究发现过表达SIRT1能抑制这些基因的上调，对人软骨细胞产生保护作用。另外一方面，软骨功能障碍与多种因素相关，而白细胞介素1β则是降低软骨细胞的合成代谢酶活性，诱导软骨功能发生紊乱的重要因素之一。有研究发现SIRT1通过调控NF-κB信号通路，从而抑制白细胞介素1β诱导的软骨降解酶的表达[74]，进而改善软骨功能的退化。 2.5.2 SIRT1对骨关节炎的体内研究除了体外的研究，体内的研究也发现SIRT1在维持软骨功能，进一步抑制骨关节炎的发生和恶化的过程中发挥出了重要的作用[75]。在骨关节炎模型鼠中，每周关节内注射白藜芦醇通过激活SIRT1和沉默缺氧诱导因子2α显著减轻骨关节炎中软骨的退化[76]。另外一项研究也显示在氧化应激诱导的软骨细胞和兔骨关节炎模型中，褪黑激素(N-乙酰-5-甲氧基色胺)通过调控SIRT1通路发挥保护作用和抗炎效应[77]。目前运用基因突变小鼠来研究SIRT1在骨关节炎中的作用成为了一个新的研究方法，McBurney等[78]构建了含Sir2无效等位基因的菌株，进一步造模得到了携带无效Sir2等位基因的小鼠，研究发现此类小鼠体型小，表现出一定的发育迟缓，并且在出生后容易死亡。另外一项研究表明软骨细胞内SIRT1的缺失会加剧小鼠骨关节炎的恶化，说明SIRT1对骨关节炎的发展一定的预防作用[79]。进一步的研究也发现和野生型的小鼠相比，SIRT1敲除的小鼠表现出更小的体型和代谢紊乱，并且患骨关节炎的进程加快，这一现象可能与SIRT1参与小鼠软骨细胞的合成与凋亡途径有关[80-81]。Seifert等[82]则是将SIRT1催化结构域进行点突变，构建含有突变型SIRT1的小鼠，研究发现该结构域的催化活性对于维持机体代谢平衡是必需的，并影响了雄性小鼠的生育能力。最新研究表明，SIRT1敲除或者突变的小鼠比同窝的小鼠，其软骨功能更容易发展退化，患骨关节炎样疾病的速度更快，并伴有软骨基质蛋白的减少甚至凋亡[83]。"

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