Osteoarthritis (OA) is the most prevalent form of arthritis and its multifactorial nature has been increasingly recognized. Genetic factors play an important role in OA etiology and estrogen receptor alpha (ESR1) gene polymorphisms may be involved. This study tried to explore whether the ESR1 gene single nucleotide polymorphisms (SNPs) were associated with primary knee OA in the Chinese Han population. Two SNPs, rs2234693 and rs9340799, were genotyped in 469 cases and 522 controls. Rs2234693 was associated with knee OA in the dominant genetic model (TT + TC versus CC)
Osteoarthritis (OA, OMIM#165720) is a multifactorial disorder characterized by progressive cartilage loss, osteophyte formation, and subchondral sclerosis, which accounts for a large amount of elderly individuals with pain and disability [
To date, several large-sample studies and genome-wide association studies (GWAS) have shed further light on potential chromosome regions that may carry OA susceptibility genes which have been subsequently confirmed by replication studies in different populations [
The human estrogen receptor has two isoforms: ESR1 and ESR2, which are members of the steroid/thyroid hormone superfamily of nuclear receptors and encoded by separate genes [
A total of 991 subjects were enrolled in this study. 469 patients with primary knee OA (357 females and 113 males) were recruited consecutively at the Center of Diagnosis and Treatment for Joint Disease, Drum Tower Hospital, affiliated to the Medical School of Nanjing University, and 522 age-matched healthy controls (124 females and 398 males) were consecutively selected in a plenty of more than 2000 individuals at the Center of Physical Examination. All subjects included in this study were Han Chinese living in and around Nanjing and no one dropped out. The study was approved by the ethics committee of the Medical School of Nanjing University, and informed consent was obtained from patients and control participants.
The inclusion criteria for both OA patients and controls were previously described by Jiang et al. [
The minor allele frequencies of both rs2234693 and rs9340799 were above 0.2 in the Chinese population, respectively. DNA samples were obtained from all the participants from peripheral blood adopting the Chelex-100 method [
Mean values were presented with their standard deviation (SD) and assessed by Students’
Baseline characteristics of all the subjects were shown in Table
Baseline characteristics of subjects.
Cases | Controls |
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Subjects, number | 469 | 522 | — |
Females, number (%) | 356 (75.9) | 120 (23.0) |
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Mean age, y (SD) |
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Mean BMI, kg/m2 (SD) |
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Kellgren-Lawrence grading | |||
Grade 2, number (%) | 255 (54.5) | 0 (0.0) | — |
Grade 3, number (%) | 119 (25.3) | 0 (0.0) | — |
Grade 4, number (%) | 95 (20.2) | 0 (0.0) | — |
No.: number; y: years; SD: standard deviation.
Genotype and allele frequencies of rs2234693 and rs9340799 of the ESR1 gene in the Han Chinese population.
Group | Number | rs2234693 | rs9340799 | |||||||||||
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Genotype (frequency) | Allele (frequency) | H-WE | Number | Genotype (frequency) | Allele (frequency) | H-WE | ||||||||
TT | TC | CC | T | C |
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AA | AG | GG | A | G |
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OA | ||||||||||||||
All | 469 | 167 (0.356) | 217 (0.463) | 85 (0.181) | 551 (0.587) | 387 (0.413) | 0.325 | 469 | 288 (0.614) | 152 (0.324) | 29 (0.062) | 728 (0.776) | 210 (0.224) | 0.144 |
Female | 356 | 119 (0.334) | 170 (0.478) | 67 (0.188) | 408 (0.573) | 304 (0.427) | 0.649 | 356 | 210 (0.590) | 122 (0.343) | 24 (0.067) | 542 (0.761) | 170 (0.239) | 0.280 |
Male | 113 | 48 (0.425) | 47 (0.416) | 18 (0.159) | 143 (0.633) | 83 (0.367) | 0.264 | 113 | 77 (0.682) | 30 (0.265) | 6 (0.053) | 184 (0.814) | 42 (0.186) | 0.192 |
Control | ||||||||||||||
All | 514 | 198 (0.385) | 242 (0.471) | 74 (0.144) | 638 (0.621) | 390 (0.379) | 0.997 | 522 | 348 (0.667) | 155 (0.297) | 19 (0.036) | 851 (0.815) | 193 (0.185) | 0.736 |
Female | 120 | 47 (0.392) | 61 (0.508) | 12 (0.100) | 155 (0.646) | 85 (0.0354) | 0.223 | 124 | 82 (0.661) | 40 (0.323) | 2 (0.016) | 204 (0.823) | 44 (0.177) | 0.242 |
Male | 394 | 151 (0.383) | 181 (0.459) | 62 (0.158) | 483 (0.613) | 305 (0.387) | 0.528 | 398 | 266 (0.668) | 115 (0.289) | 17 (0.043) | 647 (0.813) | 149 (0.187) | 0.314 |
No.: number; H-WE: Hardy-Weinberg Equilibrium.
Genotype and allele frequencies of rs2234693 and rs9340799 of the ESR1 gene with a stratification by K/L grades.
K/L grading | Number | rs2234693 | rs9340799 | ||||||||||
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Genotype (frequency) | Allele (frequency) | H-WE | Genotype (frequency) | Allele (frequency) | H-WE | ||||||||
TT | TC | CC | T | C |
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AA | AG | GG | A | G |
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Grade 2 | 255 | 82 (0.321) | 120 (0.471) | 53 (0.208) | 284 (0.557) | 226 (0.443) | 0.458 | 156 (0.612) | 81 (0.318) | 18 (0.070) | 393 (0.771) | 117 (0.229) | 0.105 |
Grade 3 | 119 | 46 (0.387) | 54 (0.454) | 19 (0.159) | 146 (0.613) | 92 (0.387) | 0.638 | 74 (0.622) | 42 (0.353) | 3 (0.025) | 190 (0.798) | 48 (0.202) | 0.295 |
Grade 4 | 95 | 39 (0.410) | 43 (0.453) | 13 (0.137) | 121 (0.637) | 69 (0.363) | 0.834 | 57 (0.600) | 29 (0.305) | 9 (0.095) | 143 (0.753) | 47 (0.247) | 0.079 |
K/L: Kellgren-Lawrence; No.: number; H-WE: Hardy-Weinberg Equilibrium.
In the association study, for rs2234693, we did not observe any significant difference in any comparison as a whole (Table
Association of the rs2234693 with knee OA in the Chinese Han population with a stratification by gender.
Groups compared | TT versus TC + CC | TT + TC versus CC | T allele versus C allele | All genotyped* | ||||||
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OR | 95% CI |
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OR | 95% CI |
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OR | 95% CI |
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All patients ( |
1.133 | 0.874–1.469 | 0.345 | 1.316 | 0.937–1.850 | 0.113 | 1.149 | 0.959–1.377 | 0.133 | 0.259 |
Female patients ( |
1.282 | 0.836–1.967 | 0.254 | 2.087 | 1.086–4.009 |
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1.359 | 1.003–1.840 |
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0.073 |
Male patients ( |
0.917 | 0.599–1.405 | 0.690 | 0.954 | 0.538–1.691 | 0.871 | 0.943 | 0.693–1.283 | 0.709 | 0.923 |
OR: Odds Ratio; CI: confidence interval.
With respect to rs9340799, A allele was relevant to a higher risk of knee OA in all the patients and controls (OR = 1.272; 95% CI, 1.022–1.583;
Association of the rs9340799 with knee OA in the Chinese Han population with a stratification by gender.
Groups compared | AA versuss AG + GG | AA + AG versus GG | A allele versus G allele | All genotyped* | ||||||
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OR | 95% CI |
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OR | 95% CI |
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OR | 95% CI |
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All patients ( |
1.257 | 0.969–1.630 | 0.085 | 1.745 | 0.965–3.156 | 0.063 | 1.272 | 1.022–1.583 |
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0.084 |
Female patients ( |
1.357 | 0.885–2.082 | 0.161 | 4.410 | 1.027–18.938 |
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1.454 | 1.006–2.102 |
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0.069 |
Male patients ( |
0.801 | 0.510–1.256 | 0.332 | 1.125 | 0.433–2.925 | 0.809 | 0.869 | 0.594–1.271 | 0.468 | 0.817 |
OR: Odds Ratio; CI: confidence interval.
Association of the rs2234693 with knee OA in the Chinese Han population with a stratification by the severity of OA.
Groups compared | TT versus TC + CC | TT + TC versus CC | T allele versus C allele | All genotyped* | ||||||
---|---|---|---|---|---|---|---|---|---|---|
OR | 95% CI |
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OR | 95% CI |
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OR | 95% CI |
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Mild OA (255 patients versus 514 controls) | 1.322 | 0.963–1.815 | 0.084 | 1.560 | 1.056–2.304 |
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1.302 | 1.050–1.615 |
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Severe OA (214 patients versus 514 controls) | 0.951 | 0.686–1.318 | 0.763 | 1.045 | 0.667–1.638 | 0.846 | 0.986 | 0.782–1.245 | 0.908 | 0.910 |
OR: Odds Ratio; CI: confidence interval.
Association of the rs9340799 with knee OA in the Chinese Han population with stratification by the severity of OA.
Groups compared | AA versus AG + GG | AA + AG versus GG | A allele versus G allele | All genotype* | ||||||
---|---|---|---|---|---|---|---|---|---|---|
OR | 95% CI |
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OR | 95% CI |
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OR | 95% CI |
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Mild OA (255 patients versus 522 controls) | 1.269 | 0.930–1.732 | 0.132 | 2.011 | 1.036–3.902 |
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1.312 | 1.013–1.701 |
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0.073 |
Severe OA (214 patients versus 522 controls) | 1.267 | 0.911–1.762 | 0.159 | 1.573 | 0.750–3.299 | 0.227 | 1.258 | 0.954–1.658 | 0.103 | 0.261 |
OR: Odds Ratio; CI: confidence interval.
To our best knowledge, this case-control study firstly described a compelling association of ESR1 SNPs (rs2234693 and rs9340799) and primary knee OA in a Chinese Han population with a complete exclusion of those who had hypertension previously or currently. Significant differences were found between 469 patients and 522 control subjects in the two SNPs. Summarily, we herein suggested the leading roles of T allele of rs2234693 and A allele of rs9340799 in the pathogenesis of primary knee OA, especially for female patients and those subjects with mild disease. For these patients, a potential individualized prevention and treatment of knee OA may be practicable.
Until now, a relative lack of consistency or reproducibility of the association between ESR1 gene (rs2234693 and rs9340799) polymorphisms and OA still exists. Previously, Ushiyama et al. [
Noteworthy, the C allele frequency of rs2234693 and the G allele frequency of rs9340799 in controls were 0.379 and 0.185, respectively, which were similar to those observed in the Japanese and Korean populations [
The lack of difference in male participants in this study may be due to the limited sample number, despite a large sex bias of OA incidence in females [
Estrogens act on the skeleton through the binding to ESRs (ESR1 and ESR2), and ESR1 has been increasingly deemed as a mediator of considerable importance in the signal transduction pathway [
OA has been seen as a chronic inflammatory disease which could affect the cartilage, the synovium, the subchondral bone, and the other joint tissues [
Our study still has a few limitations. The relatively limited sample size and unmatched gender in patients and controls may influence the statistical power of any existing association. We failed to systematically obtain X-rays of the knee in control subjects to avoid the interference of asymptomatic OA. Also, we only evaluate the risk of knee OA and ESR1 gene polymorphisms, and the results cannot be well generalized to other joint sites. Nevertheless, there is reason to believe that the findings are of considerable credibility and veracity. Given the fact that genetic factors may vary with disease pattern and severity and according to individuals’ characteristics such as gender and age [
In conclusion, we suggested an association of the polymorphisms of rs2234693 and rs9340799 in the ESR1 gene and susceptibility to primary knee OA in the Chinese Han population. This association remained in female patients and those who had mild OA. Future investigations should focus on sex-specific mechanisms on the etiology of knee OA and determine whether there are genetic factors which can be targeted through prevention and therapy strategies to mitigate the seemingly increased prevalence of knee OA.
The authors declare that there is no conflict of interests regarding the publication of this paper.
Xiaoyu Dai and Chao Wang were considered to contribute equally to this work.
This paper was supported by National Science Foundation for Distinguished Youth Scholars of China (81125013).