Evaluation of the Relationship Between Common Variants in the TLR-9 Gene and Hip Osteoarthritis Susceptibility

Abstract

Objective:

Hip osteoarthritis (HOA) is one of the most common types of osteoarthritis and affects nearly 10% of men and 18% of women who are >60 years of age worldwide. It has been demonstrated to be a genetic disease with a 50% heritability risk. Recently, the TLR-9 gene has been associated with knee OA in both Turkish and Chinese populations, but the relationship between the TLR-9 gene and HOA has not been evaluated. In this study, we aimed to evaluate the relationship between the common genetic variants in the TLR-9 gene and the predisposition of Han Chinese individuals to HOA.

Methods:

A total of 730 HOA patients and 1220 healthy controls were recruited in a hospital-based case-control study. Six common single nucleotide polymorphisms (SNPs) of the TLR-9 gene were selected for genotyping, and genetic association analyses were performed using both single-marker and haplotype-based methods.

Results:

The SNP rs187084 was found to be significantly associated with the risk of HOA after a Bonferroni correction (adjusted allelic p-values with age, gender, and body mass index [BMI] = 0.0008). The results indicated that the A allele of rs187084 is a risk allele for HOA and is likely to be a predisposing factor leading to an increased risk of HOA (adjusted odds ratio with age, gender, and BMI = 1.26, 95% confidence interval = 1.10-1.43). The results of the haplotype analyses confirmed a similar pattern to the SNP analyses.

Conclusions:

Our study provides strong evidence that variations in the TLR-9 gene are closely linked with genetic susceptibility to HOA in the Han Chinese population. This finding furthers the role of TLR-9 in the development and occurrence of OA in general.

Introduction

Osteoarthritis (OA) is a chronic degenerative joint disease that is characterized by articular cartilage loss, synovial inflammation and structural changes in the subchondral bone (Herrero-Beaumont et al., 2009). This type of derangement and destruction of joint integrity in OA occurs in the knee and hip in humans and exhibits clinical symptoms, such as joint pain, dysfunction, stiffness, activity limitations, and physical disabilities (Moskowitz, 1987). Primary osteoarthritis of the hip (HOA) is defined as the degeneration of the tissues of the hip joint, including hyaline cartilage, fibrocartilage, bone, and synovium (Hoaglund and Steinbach, 2001). According to the literature, HOA is virtually absent in black Africans, is consistently rare in non-Europeans but occurs at a rate of 3-6% in populations with European ancestry (Hoaglund, 2013). The crude prevalence of radiographic HOA in Chinese ages 60-89 years was 0.9% in women and 1.1% in men (Nevitt et al., 2002).

In addition to the interplay of obesity, joint injury, excessive occupational joint load, and sports activity as environmental factors in patients, HOA has been demonstrated to be a genetic disease with a 50% heritability risk that is caused by genetic variants through family, sibling, and twin studies (Hoaglund, 2013). However, at present, the etiology and pathogenesis of HOA has not been thoroughly elucidated. Therefore, it is urgent to discover the susceptibility genes that induce a higher risk of HOA in patients, which may then enhance diagnostic techniques and reduce the prevalence rate.

With the progression of differential gene expression analysis techniques, Toll-like receptors (TLRs) were found to be increased in OA cartilage lesions, thereby indicating that the modulation of TLR-mediated signaling as a therapeutic strategy may be feasible (Kim et al., 2006). These results can explain a small degree of the HOA heritability; however, at present, the molecular mechanisms of HOA remain largely unknown. Recently, two candidate-gene-based genetic association studies have demonstrated that TLR-9 is associated with knee OA (KOA) in both Turkish and Chinese populations (Su et al., 2012b; Balbaloglu et al., 2017). Therefore, it is reasonable to explore whether there is an association between TLR-9 and HOA.

The TLR-9 gene is located on chromosome 3p21.2 and has two exon counts, and the TLR-9 ligands are DNA that contain bacterial and viral CpGs (Ahmed et al., 2013). TLR-9 belongs to the TLR family, which is a group of transmembrane proteins that act as the primary receptors of innate immunity. Owing to the interaction with proinflammatory pathways through TLRs, the development of inflammatory diseases may occur with diseases, including cardiovascular diseases and OA (Zheng et al., 2017). Moreover, two independent studies have found that there was an association between TLR-9 and KOA among the Chinese population (Su et al., 2012b; Zheng et al., 2017).

Although there is evidence of significant associations between TLR-9 and KOA in several populations, the contributions of TLR-9 to the risk of HOA in the Chinese population have not been thoroughly elucidated to date. However, there has been no study examining the association of TLR-9 with HOA to date; thus, we performed a hospital-based case-control study to further identify the associations of TLR-9 with the risk of HOA and to investigate the etiology and pathogenesis of HOA. From the results of this study, we will further understand the association between TLR-9 and HOA, which may ensure reductions in HOA-related morbidity and mortality from a genetic perspective.

Methods

Study subjects

A total of 1950 unrelated Han Chinese men and women, comprising 730 HOA patients and 1220 controls, were recruited from the Second Affiliated Hospital of Xi'an Jiaotong University. All of the patients with HOA were diagnosed according to the American College of Rheumatology, and HOA was confirmed through clinical examination and radiographic inspection. According to the Kellgren-Lawrence (KL) grading standard, patients with scores >2 were included in the study. The healthy controls had no symptoms of arthritis or any other joint-related disorders or family history of OA or other rheumatic diseases. All controls were recruited from healthy persons under routine health screening at the health checkup center of the same hospital.

The inclusion criteria were as follows: (1) patients without signs or symptoms of arthritis, or any other joint-related disorders, and (2) patients without inflammatory arthritis, post-traumatic or postseptic arthritis and skeletal or developmental dysplasia. Individuals with autoimmune diseases, cancer, systemic diseases, and other serious diseases were excluded from the study. All of the subjects were born in the local area. The subjects were randomly chosen unrelated Han Chinese individuals without migration histories, which ensure the genetic homogeneity in the study. Data on general characteristics and clinical information, including age, gender, body mass index (BMI), smoking status, drinking status, and KL grading, were obtained from the use of medical records or questionnaires (Table 1). Written informed consent was obtained from each of the subjects. This research was performed in accordance with the ethical guidelines of the Declaration of Helsinki (version 2002) and was approved by the ethics committee of Xi'an Jiaotong University.

Table 1.

Distributions of Selected Variables in the Subjects

Variables	Case (n = 730)	Control (n = 1220)	p-Value
Age (mean ± SD)	62.3 ± 7.65	61.9 ± 7.90	0.2913
Gender			0.8221
Men (%)	348 (47.7%)	588 (48.2%)
Women (%)	382 (52.3%)	632 (51.8%)
BMI (mean ± SD)	25.9 ± 1.33	25.7 ± 1.56	0.0014
Smoking/nonsmoking (%)	188/542 (25.8%/74.2%)	306/914 (25.1%/74.9%)	0.7419
Drinking/nondrinking (%)	201/529 (27.5%/72.5%)	331/889 (27.1%/72.9%)	0.8467
KL grading (%)
Grade 2	335 (45.9%)
Grade 3	287 (39.3%)
Grade 4	108 (14.8%)

BMI, body mass index; KL, Kellgren-Lawrence.

Single nucleotide polymorphism selection and genotyping

Single nucleotide polymorphisms (SNPs) located within the TLR-9 gene region with a minor allele frequency (MAF) >0.01 were searched in the 1000-genomes CHB database. Overall, six SNPs were selected for further genotyping (rs535746223, rs140122922, rs352140, rs352139, rs187084, and rs352144). Genomic DNA was extracted from peripheral blood leukocytes according to the manufacturer's protocol (Genomic DNA kit; Axygen Scientific, Inc., CA). The selected tagging SNPs were genotyped by using the high-throughput Sequenom MassARRAY platform (Sequenom, San Diego, CA), according to the manufacturer's protocol. The results were processed by using the Sequenom Typer 4.0 software (Guan et al., 2012a), to generate genotypic data. To maintain quality control, the disease status of each sample was unknown throughout the genotyping process. The final genotyping call rate for each SNP was >99%, and the overall genotyping call rate was 99.9%. Subsequently, we randomly selected 5% of the samples for regenotyping, and the results were determined to be identical to the previous results (Guan et al., 2012b).

Statistical analyses

The distributions of the demographic characteristics between the cases and the controls were examined by using χ² tests or Student's t-tests. Hardy-Weinberg equilibrium (HWE) tests for each SNP were performed through Haploview v4.2. Genotypic and allelic association analyses were performed for each SNP in a logistic model, with adjustments of age, gender, and BMI, by using Plink v1.9. Bonferroni corrections were applied, to address multiple comparisons. For single-marker-based association analyses, the Bonferroni correction was applied to avoid multiple comparison problems; therefore, the threshold used for significance was a p-value of 0.05/6 ≈ 0.0083.

Linkage disequilibrium (LD) blocks were constructed by using Haploview v4.2, based on the algorithm proposed by Gabriel et al. (2002). The haplotype frequencies were estimated by using GENECOUNTING v2.2, and haplotype-based analyses, including a likelihood ratio test followed by permutation testing, were then performed for the LD blocks that contained a significantly associated SNP. The global p-value was calculated based on the distributions of the haplotypic frequencies between the cases and the controls. In addition, the correlations of the associated SNPs with disease severity measurements from the KL grade scale were examined through χ² tests. We used PGA v2.0 to perform the power calculations. The sample size used in this study could detect SNP associations with 85% power at an MAF of 0.1 and a false positive rate of 0.05.

Results

The general characteristics and clinical information of the subjects are presented in Table 1. As shown, there was a significant difference in the distribution of BMI between HOA cases and healthy controls (p = 0.0014), but the other factors, including age, gender, smoking status, and alcohol drinking status, were well matched between both groups (p > 0.05). The distributions of the allelic and genotypic frequencies of SNPs, as well as the HWE, were tested in all subjects, and the results are presented in Table 2 and Supplementary Table S1. The results of the HWE showed that the SNPs that were selected in this study were highly polymorphic in both the case and control groups. Moreover, the genotype distributions of these SNPs met HWE requirements in both cases and controls (p > 0.05), which further confirmed that the randomly selected subjects in this study were demographically representative (Table 2 and Supplementary Table S1).

Table 2.

Results of Single Nucleotide Polymorphism Association Analyses

SNP affection	HWE p-value	Allele number (%)		Allelic p-value^a	OR ^a 95% CI	Genotype number (%)			Genotypic p-value^a
rs352140		C	T	0.0449		CC	CT	TT	Codominant model	0.0471
Case	0.124	873 (59.8)	587 (40.2)		1.14	251 (34.3)	371 (50.8)	108 (14.9)	Dominant model	0.0137
Control	0.699	1379 (56.5)	1061 (43.5)		1.00-1.31	393 (32.2)	593 (48.6)	234 (19.2)	Recessive model	0.0216
rs187084		A	G	0.0008		AA	AG	GG	Codominant model	0.0016
Case	0.146	911 (62.4)	549 (37.6)		1.26	275 (37.7)	361 (49.4)	94 (12.9)	Dominant model	0.0008
Control	0.847	1389 (56.9)	1051 (43.1)		1.10-1.43	397 (32.5)	595 (48.8)	228 (18.7)	Recessive model	0.0003

Risk allele and significant p-values are in bold italics, and the threshold used for significance of p-value was 0.05/6 ≈ 0.0083.

OR refers to the risk allele odds ratio in both groups.

p-Values with adjustments for covariants (age, gender, and BMI).

CI, confidence interval; HWE, Hardy-Weinberg equilibrium; OR, odds ratio.

Two SNPs (rs352140 and rs187084) were found to be associated with HOA risk (adjusted allelic p-values with age, gender, and BMI = 0.0449 and 0.0008, respectively) (Table 2). However, only rs187084 obtained a significant association signal with the risk of HOA after a Bonferroni correction (Table 2). Furthermore, the results of the overall analyses indicated that the A allele of rs187084 is a risk allele of HOA and is likely to be a predisposing factor that leads to an increased risk of HOA (adjusted odds ratio with age, gender and BMI = 1.26, 95% confidence interval = 1.10-1.43). We performed association analyses of the genotypic distributions with the adjustments of age, gender, and BMI. The results indicated similar patterns with those of the allelic analyses. When considering the other four SNPs, whether they were analyzed in the allele or genotype distributions, we found no evidence of an association between these four SNPs and HOA risk (Supplementary Table S1).

The LD structures of the six SNPs were constructed by using the genotype data. As indicated in Figure 1, one LD block (rs352140-rs352139-rs187084) was found. Haplotype-based analyses were conducted to evaluate the association of the LD block with the risk of HOA. As shown in Table 3, the significant global p-value (p < 0.0001) was identified in the LD block. It is worth noting that two haplotypes (HAP3 and HAP4) in the LD block were positively correlated with the risk of HOA (Table 3).

FIG. 1.

LD structure based on genotype data sets. The LD blocks are indicated as shaded matrices. The darker the color of the block, the higher the value of D'. LD, linkage disequilibrium.

Table 3.

Results of Haplotype-Based Association Analyses

No.	Haplotype	Haplotype frequencies (%)
		Case	Control	p-Value^a
		rs352140-rs352139-rs187084
HAP1	CTA	56.5	55.6	0.5662	<0.0001
HAP2	TCG	36.9	41.9	0.0013
HAP3	CCA	2.7	0.5	<0.0001
HAP4	TCA	2.7	0.5	<0.0001

Significant haplotypes and p-values are in italic bold. Rare haplotypes are not shown, if the frequency <0.5%.

Based on 10,000 permutations.

Based on comparison of frequency distribution of all haplotypes for the combination of SNPs.

When considering the risk haplotypes, the frequencies of HAP3 and HAP4 increased almost fourfold in the case group compared with the control group, and the fact that they all contained the A allele of rs187084 also confirmed that the significant association signal of HOA risk is most likely from rs187084. Haplotype HAP2 suggested a certain protective effect because there was a higher frequency of HAP2 in the control group (Table 3). However, when testing the associated SNPs of rs352140 and rs187084 for their correlations with the severity of HOA that was measured through KL grade scaling in the case group, we found no association between these SNPs and the severity of HOA (Table 4).

Table 4.

Relationship of Two Nominally Associated Single Nucleotide Polymorphisms with KL Grading Scale in Hip Osteoarthritis Patients

SNP	KL grading scale (%)				χ²	p-Value
rs352140		CC (n = 251)	CT (n = 371)	TT (n = 108)
	KL-2	116 (46.2%)	169 (45.5%)	50 (46.3%)
	KL-3	97 (38.7%)	146 (39.4%)	44 (40.7%)
	KL-4	38 (15.1%)	56 (15.1%)	14 (15.0%)	0.0533	0.9737
rs187084		AA (n = 275)	AG (n = 361)	GG (n = 94)
	KL-2	122 (44.4%)	173 (47.9%)	40 (42.6%)
	KL-3	109 (39.6%)	137 (38.0%)	41 (43.6%)
	KL-4	44 (16.0%)	51 (14.1%)	13 (13.8%)	1.2282	0.5413

SNP, single nucleotide polymorphism.

Discussion

With the rapid development of high-throughput sequencing, although more and more susceptibility variants of complex diseases have been identified (Guan et al., 2013, 2014, 2016a, 2016b, 2016c; Liu et al., 2014; Zhang et al., 2018a). In recent years, researchers have identified strong association signals between the TLR-9 gene and the risk of KOA in both Han Chinese and Turkish populations (Su et al., 2012a; Balbaloglu et al., 2017; Zheng et al., 2017). For HOA, an important aspect of OA (the relationship of TLR-9 to the risk of HOA) remains largely unknown. To the best of our knowledge, we have reported, for the first time, the association of the common variants in the TLR-9 gene with HOA susceptibility in this study. The SNP of rs187084 in the TLR-9 gene was shown to be significantly associated with the susceptibility of HOA in the Han Chinese population, and patients with HOA showed much higher frequencies of the A allele than did the normal controls.

Previously, all of the candidate gene association studies that have examined the relationship between TLR-9 and KOA found a significant relationship between rs187084 and the risk of KOA. Zheng et al. (2017) and Balbaloglu et al. (2017) both demonstrated that the CC genotype at rs187084 had a higher risk for KOA in Han Chinese individuals and Turks. However, a two-stage case-control study found that the TT genotype at rs187084 had a higher risk for KOA in a Han Chinese population from Taiwan (Su et al., 2012a).

In this study, although rs187084 in the TLR-9 gene was also strongly associated with HOA, the risk allele was demonstrated to be the A allele, which is a similar result observed in the study of Su et al. (2012a). The difference may be due to the different phenotypes of OA (KOA and HOA) or the genetic heterogeneity of different ethnic populations (Liu et al., 2013). Although it is difficult to draw convincing conclusions only from SNP-based association analysis (Yang et al., 2013; Chen et al., 2015; Guan et al., 2015, 2016d; Zhang et al., 2015, 2018b; Jia et al., 2016; Han et al., 2018), further haplotype association analyses confirmed the similar association pattern. These positive results indicated that rs187084 in the TLR-9 gene is associated with both KOA and HOA in the Han Chinese population, which suggests that TLR-9 may play an essential role in the etiology of OA.

The SNP rs187084 is located on the promoter region of TLR-9, and a mutation in this region may have an effect on the expression of TLR-9 (Gaffney, 2013). As a key molecule of the immune system, the TLR-9 gene has been relevant to various immune-related diseases, such as cancer (Wan et al., 2014), rheumatoid arthritis (RA) (Lee et al., 2013), systemic lupus erythematosus (Huang et al., 2012), and OA. Researchers have demonstrated that TLR-9 is upregulated in RA and systemic lupus erythematosus patients (Lyn-Cook et al., 2014; Lacerte et al., 2016).

Moreover, in a recent study, TLR-1, TLR-2, TLR-4, and TLR-9 were observed to be increased with the progression of OA in synovial cartilage tissues (Magnusson et al., 2006). Synovial injection of the ligands for TLR-2, -3, -4, or -9 induces or exacerbates arthritis in experimental models (Zhang et al., 2008). Hence, we hypothesize that the rs187084 SNP in TLR-9 may enhance the promoter transcription efficiency, which may then lead to the overexpression of TLR-9 in OA patients.

Although OA is not a traditional inflammatory joint disease, there are data that show the incidences of synovial inflammation, prostaglandin production, and cytokine production in OA articular tissues (Mukundan et al., 2011). As an important part of the innate immune system, TLRs can induce robust proinflammatory cytokine production in response to ligand activation (Brown et al., 2011). Previous studies have demonstrated that the cartilage damage of OA is aggravated by the binding of TLRs and endogenous ligands that release large amounts of cytokines and inflammatory mediators (Li et al., 2014). For example, OA causes the upregulation of double-stranded RNA (dsRNA) release in damaged articular chondrocytes; the dsRNA can then bind to TLR-3 and induce IL-33 elevation, which can ultimately lead to cartilage degeneration (Li et al., 2017a).

Moreover, mRNA levels of TLR-4 are significantly higher within the damaged cartilage of OA patients than in controls (Kim et al., 2006). The activation of TLR-4 in human chondrocyte cultures can also induce increases in IL-1β and MMP expressions (Kim et al., 2006). Furthermore, TLR-4−/− mice were resistant to IL-1β-overexpression-mediated cartilage destruction (Abdollahi-Roodsaz et al., 2009). Therefore, we hypothesize that the upregulated TLR-9 may also initiate an inflammatory cascade and eventually lead to cartilage degeneration and OA. In addition, the NF-κB signaling pathway is a major catabolic pathway in OA joints (Rigoglou and Papavassiliou, 2013). The activated NF-κB molecules trigger the expression of an array of genes that induce destruction of the articular joint, thus leading to the onset and progression of OA (Pulai et al., 2005).

TLR-9 is primarily associated with the NF-κB pathway and the TLR pathway (Pulai et al., 2005). Many studies have shown that TLR-9 is required for MAPK/NF-κB activation in the inflammatory reaction (Gomes et al., 2016; Li et al., 2017b), which suggests that TLR-9 may activate the NF-κB signaling pathway, to induce chronic inflammation in the joints. To some extent, these results suggest that TLR-9 may enhance the risk of OA by activating cytokines and inflammatory cascade pathways; however, these hypotheses require further studies to confirm.

However, there are still several limitations in the study that may affect our conclusions. First, we did not exclude other confounding factors, such as occupation, smoking habits, weight, and height, which may have a certain degree of interference with these results. Second, we solely focused on the association between HOA and the TLR-9 gene and neglected the aspects of the functional study of the TLR-9 gene in OA patients. Third, this study was performed at a single center, which may potentially limit the generalizability of these findings. Therefore, a well-designed study, based on the different populations that are associated with TLR-9 and OA, is required to fully elucidate the exact molecular mechanisms of the TLR-9 gene in the risk of HOA.

In summary, our study provides strong evidence that the TLR-9 gene is closely linked to the genetic susceptibility of HOA in the Han Chinese population, which further proves that TLR-9 is involved in the development and occurrence of OA. Our results also add credence to the relationship between the pathogenic mechanisms of OA and inflammation, which could lead to the development of novel therapeutic strategies for OA.

Footnotes

Acknowledgment

This study was totally supported by National Natural Science Youth Funds of China (No. 81601955). The funding source had no role in the design of this study; the collection, analysis, and interpretation of data; the writing of the report; or the decision to submit the article for publication.

Author Disclosure Statement

No competing financial interests exist.

Supplementary Material

References

Abdollahi-Roodsaz

, Joosten

LAB

, Koenders

, et al. (2009) Local interleukin-1-driven joint pathology is dependent on toll-like receptor 4 activation. Am J Pathol, 175:2004-2013.

Ahmed

, Redmond

, Wang

(2013) Links between Toll-like receptor 4 and breast cancer. Oncoimmunology, 2:e22945.

Balbaloglu

, Ozcan

, Korkmaz

, et al. (2017) Promoter polymorphism (T-1486C) of TLR-9 gene is associated with knee osteoarthritis in a Turkish population. J Orthop Res, 35:2484-2489.

Brown

, Wang

, Hajishengallis

, et al. (2011) Critical reviews in oral biology & medicine: TLR-signaling networks: an integration of adaptor molecules, kinases, and cross-talk. J Dent Res, 90:417-427.

Chen

, Guan

, Lin

, et al. (2015) Genetic analysis of common variants in the HDAC2 gene with schizophrenia susceptibility in Han Chinese. J Hum Genet, 60:479-484.

Gabriel

, Schaffner

, Nguyen

, et al. (2002) The structure of haplotype blocks in the human genome. Science, 296:2225-2229.

Gaffney

(2013) Global properties and functional complexity of human gene regulatory variation. PLoS Genet, 9.

Gomes

, Campos

, Pereira

, et al. (2016) TLR9 is required for MAPK/NF-kappa B activation but does not cooperate with TLR2 or TLR6 to induce host resistance to Brucella abortus. J Leukoc Biol, 99:771-780.

Guan

, Li

, Qiao

, et al. (2015) Evaluation of genetic susceptibility of common variants in CACNA1D with schizophrenia in Han Chinese. Sci Rep, 5:12935.

10.

Guan

, Niu

, Zhang

, et al. (2016a) Two-stage association study to identify the genetic susceptibility of a novel common variant of rs2075290 in ZPR1 to type 2 diabetes. Sci Rep, 6:29586.

11.

Guan

, Wei

, Feng

, et al. (2012a) Association study of a new schizophrenia susceptibility locus of 10q24.32-33 in a Han Chinese population. Schizophr Res, 138:63-68.

12.

Guan

, Wei

, Zhang

, et al. (2013) A population-based association study of 2q32.3 and 8q21.3 loci with schizophrenia in Han Chinese. J Psychiatr Res, 47:712-717.

13.

Guan

, Zhang

, Yan

, et al. (2014) MIR137 gene and target gene CACNA1C of miR-137 contribute to schizophrenia susceptibility in Han Chinese. Schizophr Res, 152:97-104.

14.

Guan

, Zhang

, Wei

, et al. (2012b) Association of PDE4B polymorphisms and schizophrenia in Northwestern Han Chinese. Hum Genet, 131:1047-1056.

15.

Guan

, Zhang

, Li

, et al. (2016b) Two-stage replication of previous genome-wide association studies of AS3MT-CNNM2-NT5C2 gene cluster region in a large schizophrenia case-control sample from Han Chinese population. Schizophr Res, 176:125-130.

16.

Guan

, Lin

, Chen

, et al. (2016c) Evaluation of association of common variants in HTR1A and HTR5A with schizophrenia and executive function. Sci Rep, 6:38048.

17.

Guan

, Zhang

, Liu

, et al. (2016d) Evaluation of voltage-dependent calcium channel gamma gene families identified several novel potential susceptible genes to schizophrenia. Sci Rep, 6:24914.

18.

Han

, Zhang

, Ni

, et al. (2018) Relationship of common variants in CHRNA5 with early-onset schizophrenia and executive function. Schizophr Res S0920-9964(18) 30613-3 [Epub ahead of print]; DOI: 10.1016/j.schres.2018.10.011.

19.

Herrero-Beaumont

, Roman-Blas

, Castaneda

, et al. (2009) Primary osteoarthritis no longer primary: three subsets with distinct etiological, clinical, and therapeutic characteristics. Semin Arthritis Rheumat, 39:71-80.

20.

Hoaglund

, Steinbach

(2001) Primary osteoarthritis of the hip: etiology and epidemiology. J Am Acad Orthop Surg, 9:320.

21.

Hoaglund

(2013) Primary osteoarthritis of the hip: a genetic disease caused by European genetic variants. J Bone Joint Surg Am, 95:463-468.

22.

Huang

, Huang

, Chen

, et al. (2012) Association of toll-like receptor 9 gene polymorphism in Chinese patients with systemic lupus erythematosus in Taiwan. Rheumatol Int, 32:2105-2109.

23.

Jia

, Zhang

, Li

, et al. (2016) Two-stage additional evidence support association of common variants in the HDAC3 with the increasing risk of schizophrenia susceptibility. Am J Med Genet B Neuropsychiatr Genet, 171:1105-1111.

24.

Kim

, Cho

, Choi

, et al. (2006) The catabolic pathway mediated by Toll-like receptors in human osteoarthritic chondrocytes. Arthritis Rheum, 54:2152-2163.

25.

Lacerte

, Brunet

, Egarnes

, et al. (2016) Overexpression of TLR2 and TLR9 on monocyte subsets of active rheumatoid arthritis patients contributes to enhance responsiveness to TLR agonists. Arthritis Res Ther, 18:10.

26.

Lee

, Bae

, Song

(2013) Meta-analysis demonstrates association between TLR polymorphisms and rheumatoid arthritis. Genet Mol Res, 12:328-334.

27.

, Chen

, Kang

, et al. (2017a) Double-stranded RNA released from damaged articular chondrocytes promotes cartilage degeneration via Toll-like receptor 3-interleukin-33 pathway. Cell Death Dis, 8:e3165.

28.

, Xie

, et al. (2014) Calcitonin treatment is associated with less severe osteoarthritis and reduced toll-like receptor levels in a rat model. J Orthop Sci, 19:1019-1027.

29.

, Liu

, Zuo

, et al. (2017b) TLR9 regulates the NF-kappa B-NLRP3-IL-1 beta pathway negatively in Salmonella-induced NKG2D-mediated intestinal inflammation. J Immunol, 199:761-773.

30.

Liu

, Lewinger

, Gilliland

, et al. (2013) Confounding and heterogeneity in genetic association studies with admixed populations. Am J Epidemiol, 177:351-360.

31.

Liu

, Hou

, Yan

, et al. (2014) Dopamine D3 receptor-regulated NR2B subunits of N-methyl-d-aspartate receptors in the nucleus accumbens involves in morphine-induced locomotor activity. CNS Neurosci Ther, 20:823-829.

32.

Lyn-Cook

, Xie

, Oates

, et al. (2014) Increased expression of Toll-like receptors (TLRs) 7 and 9 and other cytokines in systemic lupus erythematosus (SLE) patients: ethnic differences and potential new targets for therapeutic drugs. Mol Immunol, 61:38-43.

33.

Magnusson

, Zare

, Tarkowski

, et al. (2006) Requirement of type I interferon signaling for arthritis triggered by double-stranded RNA. Arthritis Rheumat, 54:148-157.

34.

Moskowitz

(1987) Primary osteoarthritis: epidemiology, clinical aspects, and general management. Am J Med, 83:5-10.

35.

Mukundan

, Ilana

B-L

, Cheongeun

, et al. (2011) Increased interleukin-1β gene expression in peripheral blood leukocytes is associated with increased pain and predicts risk for progression of symptomatic knee osteoarthritis. Arthritis Rheumat, 63:1908-1917.

36.

Nevitt

, Xu

, Zhang

, et al. (2002) Very low prevalence of hip osteoarthritis among Chinese elderly in Beijing, China, compared with whites in the United States: the Beijing osteoarthritis study. Arthritis Rheum, 46:1773-1779.

37.

Pulai

, Chen

, Im

, et al. (2005) NF-kappa B mediates the stimulation of cytokine and chemokine expression by human articular chondrocytes in response to fibronectin fragments. J Immunol, 174:5781-5788.

38.

Rigoglou

, Papavassiliou

(2013) The NF-kappa B signalling pathway in osteoarthritis. Int J Biochem Cell Biol, 45:2580-2584.

39.

, Salter

, Lee

(2012a) The (S1486T/C) promoter polymorphism of the TLR-9 gene is associated with knee osteoarthritis in a Chinese population. Bone, 50:S110.

40.

, Yang

, Lee

, et al. (2012b) The (-1486T/C) promoter polymorphism of the TLR-9 gene is associated with end-stage knee osteoarthritis in a Chinese population. J Orthop Res, 30:9-14.

41.

Wan

, Cao

, Li

, et al. (2014) Associations between TLR9 polymorphisms and cancer risk: evidence from an updated meta-analysis of 25,685 subjects. Asian Pac J Cancer Prev, 15:8279-8285.

42.

Yang

, Zhang

, Zhu

, et al. (2013) 4q22.1 contributes to bone mineral density and osteoporosis susceptibility in postmenopausal women of Chinese Han population. PLoS One, 8:e80165.

43.

Zhang

, Guan

, Chen

, et al. (2015) Common variants in SLC1A2 and schizophrenia: association and cognitive function in patients with schizophrenia and healthy individuals. Schizophr Res, 169:128-134.

44.

Zhang

, Hui

, Davidson

, et al. (2008) Differential Toll-like receptor-dependent collagenase expression in chondrocytes. Arthritis Res Ther, 67:1633-1641.

45.

Zhang

, Liu

, Zhang

, et al. (2018a) Combining information from multiple bone turnover markers as diagnostic indices for osteoporosis using support vector machines. Biomarkers. 1-7.

46.

Zhang

, Zhu

, Ni

, et al. (2018b) Voltage-gated calcium channel activity and complex related genes and schizophrenia: a systematic investigation based on Han Chinese population. J Psychiatr Res, 106:99-105.

47.

Zheng

, Shi

, Zheng

, et al. (2017) Association between TLR-9 gene rs187084 polymorphism and knee osteoarthritis in a Chinese population. Bioscience Reports. 37.

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.02 MB