软骨细胞线粒体功能异常对骨关节炎发病机制的研究

骨关节炎(osteoarthritis, OA)主要是关节软骨退变导致的慢性炎症性关节疾病，病因及发病机制复杂，最新研究发现，软骨细胞中的线粒体功能异常与OA发病机制密切相关。线粒体通过调控软骨细胞衰老、凋亡、氧化应激、炎症抑制，参与OA发病进程。此外，线粒体相关信号通路AMPK/SIRT3对于调节软骨细胞的代谢过程很重要，表明这些可能是OA治疗的目标。因此，该文论述软骨细胞线粒体功能异常与OA的发病机制的相关性。     

CALM1基因及钙调素与骨关节炎

骨关节炎(OA)以进行性关节软骨丢失、骨赘形成等退行性变为主要特征。多功能受体蛋白钙调素(CaM)在真核细胞Ca~(2 )信号转导通路中发挥重要作用。关节软骨内Ca~(2 )-CaM信号对软骨细胞的分化形成具有重要作用;给予关节软骨适当的压力负荷刺激能诱导软骨基质合成增加,而这一反应似乎必须依赖于Ca~(2 )-CaM信号通路。软骨细胞内Ca~(2 )-CaM信号通路一旦发生异常,可能会引起软骨细胞分化形成、软骨细胞粘附能力、关节软骨修复及对压力负荷刺激的反应性等方面的异常,进而促进OA的发生、发展。近期研究表明,编码CaM的CaM基因之一CALM1的单核苷酸多态性与OA易感性相关,这一发现从基因和分子转录水平提示CaM及Ca~(2 )-CaM信号通路异常在OA发病机制中的作用。     

Wnt信号通路对软骨和软骨下骨双靶向调控及其在骨关节炎进展中的作用

目的综述Wnt信号通路在骨关节炎(osteoarthritis,OA)发生发展中的活性变化,及其对软骨、软骨下骨的双靶向调控和两者间信息交流对OA进程的影响和机制。方法查阅近年在体内外实验研究及临床研究中,OA和非OA状态下Wnt信号通路对关节软骨、软骨下骨调控作用及软骨与软骨下骨间信息交流的相关文献,并对其作用机制进行分析总结。结果 Wnt信号可通过依赖β-catenin的经典或不依赖β-catenin的非经典Wnt信号通路及其与其他信号通路的交联,调控软骨细胞、成骨细胞的分化和功能,进而影响软骨及骨的代谢。过度激活Wnt信号可加重软骨OA样退变,并且Wnt信号通路可激活下游蛋白Wnt1诱导的信号通路蛋白1调控OA进展,还可通过软骨及软骨下骨中不同细胞间建立的缝隙连接,直接进行分子交流调控OA的发生发展。关节腔内注射Wnt信号通路抑制剂SM04690可以抑制OA进程;在成骨细胞中过表达Wnt信号通路抑制剂Dickkopf可以拮抗VEGF对软骨细胞的作用,并抑制其基质的分解代谢。结论 Wnt信号通路及其与其他信号分子的交互作用,可调控软骨和软骨下骨的代谢和功能及两者间信息交流,因此在OA的发生发展中发挥重要作用,有望成为OA治疗的新靶点。     

骨关节炎关节软骨细胞凋亡的研究进展

骨关节炎(OA)是由肥胖、劳损、老化、创伤等一系列因素所致的炎性病症。研究发现,OA软骨细胞凋亡可直接导致关节软骨退变甚至钙化,影响关节功能。本文对OA中软骨细胞凋亡涉及的炎症介质、信号通路、靶点调控三方面进行综述,探讨软骨细胞凋亡在OA发生发展中的作用机制,为OA的预防及早期治疗提供理论基础。     

Wnt信号通路对软骨细胞影响研究进展

软骨细胞病变是关节软骨退行性变的重要病理因素之一,软骨细胞存活状态和软骨基质代谢平衡状态直接影响软骨相关性疾病的发生发展。大量研究显示,Wnt信号通路参与软骨细胞的增殖、分化、迁移、凋亡及稳态维持等过程,在参与软骨细胞生长发育过程中与其他信号通路相互作用、相互影响,共同介导软骨细胞生长发育。全面研究和认识Wnt信号通路调控途径和机制,对软骨相关疾病治疗具有重要意义。     

MAPK信号通路在骨关节炎发病机制中的研究进展

丝裂原活化蛋白激酶（mitogen—activated proteinkinase,MAPK）真核细胞信号传递的重要途径之一,在调节控制细胞结构和功能活动中发挥关键作用。在真核生物中MAPK信号通路包括p38、ERK、JNK、ERK5等多个亚家族。随着研究的不断深入,发现p38、ERK、JNK信号转导途径的活化与骨关节炎（osteoarthritis,OA）软骨损伤密切相关,诱导软骨细胞产生基质金属蛋白酶,加速关节软骨病理性降解,并参与软骨细胞增殖、凋亡与分化等一系列反应,明确MAPK信号通路在OA中的发生发展机制已成为研究的新热点。     

表皮生长因子受体信号通路对骨折愈合的生物学作用

骨折愈合过程中,骨髓间充质干细胞、软骨细胞、成骨细胞及破骨细胞都有各自特定的作用,任何一类细胞的功能异常都会影响骨折愈合。目前一些研究显示,EGFR信号通路参与调节骨髓间充质干细胞、软骨细胞、成骨细胞及破骨细胞的增殖、分化及凋亡等多种生物学过程,在此,作者对EGFR信号通路对骨折愈合过程中相关骨组织细胞的影响做一综述。     

软骨细胞线粒体氧化应激在骨关节炎发病机制中的研究进展

骨关节炎（OA）是老年人最常见的关节疾病之一,同时也是导致残疾的重要因素。软骨细胞是成熟软骨中唯一的细胞,软骨细胞的稳定和正常功能的维持对延缓OA进展有重要作用。近年来的研究发现,软骨细胞线粒体氧化应激与OA关系密切。本文综述了软骨细胞线粒体氧化应激在OA发病过程中的相关机制,为OA的相关研究提供一定参考。     

甲状旁腺激素和甲状旁腺激素相关蛋白在正常及骨性关节炎软骨中作用机制的研究进展

目的综述在正常和骨性关节炎(osteoarthritis,OA)的关节软骨及软骨下骨中,甲状旁腺激素(parathyroid hormone,PTH)和甲状旁腺激素相关蛋白(parathyroid hormone-related protein,PTHrP)的作用机制研究进展。方法广泛查阅近年来有关PTH和PTHrP对正常和OA关节软骨作用机制的文献,并进行总结与分析。结果 PTH和PTHrP可抑制OA软骨细胞的肥大分化及凋亡,促进其增殖,从而对OA软骨细胞起到保护作用;OA软骨下骨成骨细胞对PTH的反应下降。结论 PTH、PTHrP可能通过多种信号通路参与软骨降解和软骨下骨重塑,并对OA进展起到延缓和保护作用。     

柚皮苷抑制骨关节炎软骨细胞凋亡实验研究

目的研究柚皮苷在炎症环境下对人骨关节炎（OA）软骨细胞凋亡的影响和可能的作用机制。方法采用不同浓度（0、0．1、1、10、100 mg／L）柚皮苷对 OA 软骨细胞进行预处理2 h 后,加入或不加入炎症因子混合液（白细胞介素-1β5 ng／ml 和肿瘤坏死因子-α20 ng／ml）共作用24 h。首先检测柚皮苷对炎症环境下软骨细胞活性和凋亡的影响,然后检测软骨细胞在柚皮苷作用下的一氧化氮（NO）水平及半胱氨酸天冬氨酸特异性蛋白酶（caspase）-3、caspase-8活性变化情况。结果柚皮苷预处理后软骨细胞在炎症因子刺激下发生凋亡显著减轻,且其抑制细胞凋亡作用具有浓度依赖性。进一步分子生物学检测显示,柚皮苷对 NO 生成及激活的 caspase 信号转导通路具有明显抑制作用。结论柚皮苷能有效抑制人 OA 软骨细胞凋亡,其作用机制可能是柚皮苷阻断了 NO 产生并抑制了下游的 caspase 信号通路,有望应用于 OA 治疗新药的研发。     

EGFR Signaling Is Required for Maintaining Adult Cartilage Homeostasis and Attenuating Osteoarthritis Progression

The uppermost superficial zone of articular cartilage is the first line of defense against the initiation of osteoarthritis (OA). We previously used Col2-Cre to demonstrate that epidermal growth factor receptor (EGFR), a tyrosine kinase receptor, plays an essential role in maintaining superficial chondrocytes during articular cartilage development. Here, we showed that EGFR activity in the articular cartilage decreased as mice age. In mouse and human OA samples, EGFR activity was initially reduced at the superficial layer and then resurged in cell clusters within the middle and deep zone in late OA. To investigate the role of EGFR signaling in postnatal and adult cartilage, we constructed an inducible mouse model with cartilage-specific EGFR inactivation (Aggrecan-CreER Egfr^Wa5/flox, Egfr iCKO). EdU incorporation revealed that postnatal Egfr iCKO mice contained fewer slow-cycling cells than controls. EGFR deficiency induced at 3 months of age reduced cartilage thickness and diminished superficial chondrocytes, in parallel to alterations in lubricin production, cell proliferation, and survival. Furthermore, male Egfr iCKO mice developed much more severe OA phenotypes, including cartilage erosion, subchondral bone plate thickening, cartilage degeneration at the lateral site, and mechanical allodynia, after receiving destabilization of the medial meniscus (DMM) surgery. Similar OA phenotypes were also observed in female iCKO mice. Moreover, tamoxifen injections of iCKO mice at 1 month post-surgery accelerated OA development 2 months later. In summary, our data demonstrated that chondrogenic EGFR signaling maintains postnatal slow-cycling cells and plays a critical role in adult cartilage homeostasis and OA progression. © 2022 American Society for Bone and Mineral Research (ASBMR).     

Alteration of matrix glycosaminoglycans diminishes articular chondrocytes' response to a canonical Wnt signal

OBJECTIVE: Although Wnt signaling is a key regulator of the chondrocyte life cycle during embryonic development, little is known about Wnt activity in articular cartilage. Recent studies have suggested an association between excess signaling through the canonical Wnt pathway and osteoarthritis (OA). Genetic and in vitro studies with Drosophila have shown that signaling by the orthologous protein, Wingless (Wg), is regulated by glycosaminoglycans (GAGs) found at the cell surface. The objective of this study was to determine whether alteration in GAG sulfation or matrix content, such as that occurs in OA cartilage, would affect articular chondrocytes' response to a canonical Wnt stimulus. METHODS: Cells were isolated from shoulder joints of young calves (bovine articular chondrocytes, bACs) and from human cartilage (human articular chondrocytes, hACs) discarded during total knee replacement for OA. Conditioned media from a cell line that is stably transfected with Wnt3a was used as a source of Wnt protein that activates the canonical signaling pathway. Conditioned media from the parental cell line was used as a control. beta-catenin levels were measured by immunoblot. In some experiments, chondrocyte cultures were treated with sodium chlorate (NaClO3) to inhibit GAG sulfation, or with chondroitinase ABC (ChABC) to digest chondroitin sulfate (CS) in the matrix. RESULTS: Cultured bACs showed low steady-state levels of beta-catenin that increased upon stimulation with Wnt3a. A decrease in either GAG sulfation or CS content diminished bACs' response to Wnt3a (approximately 40% and 37% of control, respectively). Similar effects on the response to Wnt3a via beta-catenin were observed for cultured hACs with undersulfation of GAGs (16% of control) and decreased CS content (20% of control). CONCLUSION: This study demonstrates that articular chondrocytes respond to canonical Wnt stimulation, and that reduced sulfation or CS content diminishes that response.     

β-连环蛋白在膝关节原发性骨关节炎关节软骨中的表达

目的通过检测β-连环蛋白(β-catenin)在膝关节原发性骨关节炎(osteoarthritis,OA)不同退变程度关节软骨中的表达,探讨其在原发性膝关节OA发生与发展中的作用。方法取2010年10月-2011年5月行人工全膝关节置换术的40例OA成年患者及10例创伤后行截肢术及股骨髁骨折成年患者自愿捐赠的膝关节软骨,于股骨髁切取包含全层软骨及少量软骨下骨组织块进行实验。组织切片行固绿-番红O染色,观察软骨退变情况,参照改良Mankin评分标准对软骨标本进行分级;行免疫组织化学染色及Western blot检测不同软骨组织中β-catenin表达。结果根据改良Mankin评分标准进行分级:正常软骨10例,轻度退变12例,中重度退变28例。组织学观察见轻度退变软骨浅表层裂隙形成,软骨细胞数减少,排列紊乱,潮线复制;中重度退变软骨深层裂隙形成,软骨细胞数目显著减少,成簇,甚至全层缺失。正常软骨中β-catenin表达呈阴性;OA软骨均有表达,主要位于细胞核,中重度退变软骨表达显著多于轻度退变软骨(P<0.05)。结论β-catenin与膝关节原发性OA发病机制及病情进展程度密切相关,其机制可能是Wnt/β-catenin信号通路活化后促进炎性基因转录,导致关节软骨破坏。     

DEPTOR Prevents Osteoarthritis Development Via Interplay With TRC8 to Reduce Endoplasmic Reticulum Stress in Chondrocytes

Endoplasmic reticulum (ER) stress has been shown to promote chondrocyte apoptosis and osteoarthritis (OA) progression, but the precise mechanisms via which ER stress is modulated in OA remain unclear. Here we report that DEP domain-containing mTOR-interacting protein (DEPTOR) negatively regulated ER stress and OA development independent of mTOR signaling. DEPTOR is ubiquitinated in articular chondrocytes and its expression is markedly reduced along with OA progression. Deletion of DEPTOR in chondrocytes significantly promoted destabilized medial meniscus (DMM) surgery-induced OA development, whereas intra-articular injection of lentivirus-expressing DEPTOR delayed OA progression in mice. Proteomics analysis revealed that DEPTOR interplayed with TRC8, which promoted TRC8 auto-ubiquitination and degraded by the ubiquitin–proteasome system (UPS) in chondrocytes. Loss of DEPTOR led to TRC8 accumulation and excessive ER stress, with subsequent chondrocyte apoptosis and OA progression. Importantly, an inhibitor of ER stress eliminated chondrocyte DEPTOR deletion-exacerbated OA in mice. Together, these findings establish a novel mechanism essential for OA pathogenesis, where decreasing DEPTOR in chondrocytes during OA progression relieves the auto-ubiquitination of TRC8, resulting in TRC8 accumulation, excessive ER stress, and OA progression. Targeting this pathway has promising therapeutic potential for OA treatment. © 2020 American Society for Bone and Mineral Research (ASBMR).     

NF-κB信号通路在骨性关节炎发生发展中作用机制的研究

NF-κB( Nuclear Factor-κB)是广泛存在于真核细胞内的一个信号通路,它通过MAPKKK (Mitogen Activated Protein Kinase Kinase Kinase)或细胞膜受体级联激活,导致NIK( NF-κB inducing kinase-1)激活,进而活化IKK( IκB Kinase),磷酸化IκB(Inhibitory κB proteins),最终导致NF-κB向细胞核内转位指导目的基因表达.NF-κB在OA( Osteoarthritis)炎症反应及疾病发生发展过程中起到了至关重要的作用,最终导致软骨降解和关节损伤.NF-κB信号参与并调控软骨细胞的增殖、分化、凋亡,而NF-κB信号的失调在骨关节炎的发生、发展中扮演着十分重要的角色,这提示深入研究NF-κB信号在骨性关节炎发病机制中的确切作用将有助于骨性关节炎的靶向治疗,从而为骨性关节炎的治疗开辟更加广阔的前景.     

Homeostasis of the extracellular matrix of normal and osteoarthritic human articular cartilage chondrocytes in vitro

OBJECTIVE: In normal articular cartilage cells, the IGFRI/insulin-like growth factor 1 (IGF-1) autocrine pathway was shown to overrule the catabolic effects of the IL-1/IL-1RI pathway by up-regulation of the IL-1RII decoy receptor. The activity of the IGF-1/IGFR1 and IL-1/IL-1R pathways, and of the IL-1RII control mechanism in the synthesis and turnover of the extracellular matrix (ECM) by chondrocytes from normal and osteoarthritic (OA) articular cartilage was compared in order to identify possible therapeutic targets of this disease. METHODS: Phenotypically stable human articular cartilage cells were obtained from normal and OA cartilage of the same knee showing focal OA. The cells were cultured in alginate beads over 1 week to re-establish the intracellular cytokine and growth factors, to reexpress the respective plasma membrane receptors and to reach equilibrium in accumulated cell-associated matrix (CAM) compounds. Following liberation of the cells from the alginate beads, the levels of cell-associated matrix (CAM) aggrecan, type II collagen and fibronectin, of intracellular IGF-1, IL-1alpha and beta and of their respective plasma membrane-bound receptors, IGFR1, IL-1RI and the decoy receptor IL-1RII, were assayed using flow cytometry. RESULTS: Coordinated production and accumulation of CAM aggrecan and type II collagen under the effect of the IGFR1/IGF-1 autocrine pathway-as documented for chondrocytes from healthy controls-was absent when the chondrocytes had been obtained from OA joints. When compared with cells obtained from normal tissues, chondrocytes from fibrillated OA cartilage expressed significantly higher intracellular IGF-1 levels and plasma membrane-bound IGFR1. At the same time, significantly higher intracellular IL-1alpha and beta levels and upregulated plasma membrane-bound IL-1RI were observed. Plasma membrane-bound IL-1RII decoy receptor was downregulated in OA chondrocytes. The levels of CAM aggrecan, type II collagen and fibronectin were significantly reduced in the chondrocytes obtained from pathological tissue. CONCLUSION: Paired analysis of normal and OA chondrocytes from the same knee joint has shown an enhanced capacity of chondrocytes from OA cartilage to produce ECM macromolecules. However, the same cells have increased catabolic signalling pathways. As a consequence of this increased IL-1 activity and the reduced amounts of IL-1RII decoy receptor, less of the produced ECM macromolecules may persist in the CAM of the OA chondrocytes.     

Activation of β‐Catenin Signaling in Articular Chondrocytes Leads to Osteoarthritis‐Like Phenotype in Adult β‐Catenin Conditional Activation Mice

Osteoarthritis (OA) is a degenerative joint disease, and the mechanism of its pathogenesis is poorly understood. Recent human genetic association studies showed that mutations in the Frzb gene predispose patients to OA, suggesting that the Wnt/β‐catenin signaling may be the key pathway to the development of OA. However, direct genetic evidence for β‐catenin in this disease has not been reported. Because tissue‐specific activation of the β‐catenin gene (targeted by Col2a1‐Cre) is embryonic lethal, we specifically activated the β‐catenin gene in articular chondrocytes in adult mice by generating β‐catenin conditional activation (cAct) mice through breeding of β‐catenin^{fx(Ex3)/fx(Ex3)} mice with Col2a1‐CreER^T2 transgenic mice. Deletion of exon 3 of the β‐catenin gene results in the production of a stabilized fusion β‐catenin protein that is resistant to phosphorylation by GSK‐3β. In this study, tamoxifen was administered to the 3‐ and 6‐mo‐old Col2a1‐CreER^T2;β‐catenin^fx(Ex3)/wt mice, and tissues were harvested for histologic analysis 2 mo after tamoxifen induction. Overexpression of β‐catenin protein was detected by immunostaining in articular cartilage tissues of β‐catenin cAct mice. In 5‐mo‐old β‐catenin cAct mice, reduction of Safranin O and Alcian blue staining in articular cartilage tissue and reduced articular cartilage area were observed. In 8‐mo‐old β‐catenin cAct mice, cell cloning, surface fibrillation, vertical clefting, and chondrophyte/osteophyte formation were observed. Complete loss of articular cartilage layers and the formation of new woven bone in the subchondral bone area were also found in β‐catenin cAct mice. Expression of chondrocyte marker genes, such as aggrecan, Mmp‐9, Mmp‐13, Alp, Oc, and colX, was significantly increased (3‐ to 6‐fold) in articular chondrocytes derived from β‐catenin cAct mice. Bmp2 but not Bmp4 expression was also significantly upregulated (6‐fold increase) in these cells. In addition, we also observed overexpression of β‐catenin protein in the knee joint samples from patients with OA. These findings indicate that activation of β‐catenin signaling in articular chondrocytes in adult mice leads to the premature chondrocyte differentiation and the development of an OA‐like phenotype. This study provides direct and definitive evidence about the role of β‐catenin in the development of OA.     

The distribution of S-100 protein positive chondrocytes in the human articular cartilages under aging or diseased conditions]

There have been few reports on the localization of S-100 protein positive chondrocytes in the human articular cartilages. We studied 59 articular cartilages of the aged subjects, 65 osteoarthritic (OA) and 39 rheumatoid arthritic (RA) articular cartilages, to detect the histological localization of S-100 protein using immunoperoxidase method (ABC). The results obtained from normal cartilages demonstrated strongly positive cells representing hypertrophic chondrocytes in the perivascular areas of the neonatal articular cartilage and in the deep zone of the infant articular cartilage. The moderately positive cells were found in the intermediate zone of infant and adult articular cartilages. In mild OA, there were many positive chondrocytes in the intermediate zone with erosion of the surface layer, while in moderate or severe OA many strongly positive cells were found in clusters. The hypertrophic cells in the metaplastic cartilage arising from bone marrow in subjects with severe OA, or from pannus after RA were also positive. It is therefore, suggested that S-100 protein may be correlated with the metabolic activity of the cartilage matrix such as collagen and proteoglycan, as reported in the literature. S-100 protein further, appears to be useful for evaluating histologically the activity of cartilage repair in the pathologic human articular cartilages.