Article Text
PDF
Abstract
Background Interstitial lung disease (ILD) occasionally occurs in rheumatoid arthritis (RA) and confers a dismal prognosis. We previously reported that a single-nucleotide variant (SNV) of MUC5B was associated with ILD in RA. However, the pathogenesis of ILD in Japanese patients with RA could not be explained solely by this SNV because its frequency is extremely low in the Japanese population. Here, we examined whether a different idiopathic pulmonary fibrosis susceptibility SNV might be associated with ILD in Japanese patients with RA.
Methods Genotyping of rs2609255 (G/T) in FAM13A was conducted in 208 patients with RA with ILD and 420 without chronic lung disease using TaqMan assays.
Results A significant association with usual interstitial pneumonia (UIP) in RA was detected for rs2609255 under the allele model (p=0.0092, Pc=0.0276, OR 1.53, 95% CI 1.12 to 2.11) and recessive model for the G allele (p=0.0003, Pc=0.0009, OR 2.63, 95% CI 1.59 to 4.32). FAM13A rs2609255 was significantly associated with UIP in male patients with RA (p=0.0043, OR 3.65, 95% CI 1.52 to 8.73) under the recessive model.
Conclusions This study is the first to document an association of rs2609255 with ILD in Japanese patients with RA, implicating it in the pathogenesis of UIP, though studies on the function of rs2609255 are warranted.
- Rheumatoid Arthritis
- Inflammation
- Autoimmune Diseases
Data availability statement
Data are available upon reasonable request. Data supporting the findings of this study are presented in the paper and the supplementary file. Other data are available from the authors upon reasonable request. However, the clinical information and genotype data of each participant are not available under the conditions of informed consent mandated by the Act on the Protection of Personal Information.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
Statistics from Altmetric.com
WHAT IS ALREADY KNOWN ON THIS TOPIC
A single-nucleotide variant (SNV) of MUC5B was associated with interstitial lung disease (ILD) in rheumatoid arthritis (RA), but its frequency is extremely low in the Japanese population.
WHAT THIS STUDY ADDS
An association of FAM13A rs2609255 with ILD in Japanese RA was detected.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
The pathogenesis of ILD in Japanese RA could be explained by the SNV in FAM13A, though studies on the function of the SNV are warranted.
Introduction
Rheumatoid arthritis (RA) is a systemic autoimmune disease characterised by the destruction of the synovial joints. It is occasionally complicated by the development of interstitial lung disease (ILD) characterised by interstitial inflammation of the lung detected in about 10% of patients with RA.1 The prognosis of patients with RA with ILD is quite poor.2 Although the aetiology of RA is unclear, it is thought that disease susceptibility is associated with genetic factors, many of which have been reported for RA or idiopathic interstitial pneumonia. In contrast, only a few genetic analyses have been conducted for susceptibility to ILD in RA.
We previously reported that a single-nucleotide variant (SNV) in the MUC5B promoter was associated with ILD in a multiethnic study of RA.3 This SNV has the strongest association with susceptibility to idiopathic pulmonary fibrosis.4–8 However, the pathogenesis of ILD in Japanese patients with RA cannot be explained by this SNV because its frequency is extremely low in the Japanese population compared with European populations.3
RPA3-UMAD1 rs12702634 was reported to be associated with ILD in Japanese RA in a genome-wide association study (GWAS)9 but was not confirmed in our replication study in other Japanese populations.10 Another recent GWAS revealed that SNVs in MUC5B, TOLLIP, FAM13A and TERT genes were associated with ILD in European RA.11 In addition to MUC5B, an association of FAM13A with idiopathic pulmonary fibrosis has been reported in GWAS or candidate gene studies.4 7 8 12–14 FAM13A is also associated with ILD in European RA.11 Additionally, it was reported that FAM13A is associated with chronic obstructive pulmonary disease.15 16 FAM13A is expressed in the lung and is thought to be involved in the Wnt signalling pathway,17 18 which is activated in idiopathic pulmonary fibrosis.19 20 Thus, FAM13A could be a candidate susceptibility gene for ILD in RA. Accordingly, the present study was conducted to determine whether SNVs in FAM13A are associated with ILD in Japanese RA.
Material and methods
Patients
Patients with RA fulfilled American College of Rheumatology criteria for RA21 or Rheumatoid Arthritis Classification Criteria22 and were recruited at the institutes of research groups organised by Tokyo National Hospital and Sagamihara National Hospital. The patients with RA were native Japanese living in Japan. Patients with RA were diagnosed with usual interstitial pneumonia (UIP), non-specific interstitial pneumonia (NSIP) or no chronic lung disease (CLD) based on chest conventional or high-resolution CT,23 as follows: UIP: irregular linear opacities and honeycombing, NSIP: bilateral ground-glass attenuation patterns predominantly in subpleural and basal regions, and CLD (−): no abnormalities in CT images. A total of 208 patients with RA with ILD (94 with UIP and 114 with NSIP) and 420 patients with RA without CLD were enrolled (table 1). The allele frequency of FAM13A rs2609255 in the Japanese population was extracted from the 38KJPN panel of the Japanese Multi Omics Reference Panel (https://jmorp.megabank.tohoku.ac.jp/202206/).24
Characteristics of the patients with RA
Genotyping
Genotyping of rs2609255 (G/T) in the FAM13A gene was performed using a TaqMan assay (assay ID: C__15906608_10; Thermo Fisher Scientific, Waltham, Massachusetts, USA) on a 7500 Fast Real-Time PCR System (Thermo Fisher Scientific), according to the manufacturer’s instructions. Conditions for thermal cycling were denaturation at 95°C for 20 s, followed by 40 cycles of 95°C for 3 s and 60°C for 30 s.
Statistical analysis
Associations of the variants were analysed to compare RA with ILD to RA without CLD by Fisher’s exact test using 2×2 contingency tables under the allele model or recessive model. The Bonferroni method was used for the adjustment of multiple comparisons; that is, p values were multiplied by the number of tests used for the calculation of corrected p values (Pc). Statistical power of 80% was obtained when the OR was 1.59 (UIP vs CLD (−)), 1.54 (NSIP vs CLD (−)) and 1.41 (ILD vs CLD (−)) or higher under the allele model. It was also calculated to be 2.19 (UIP vs CLD (−)), 2.08 (NSIP vs CLD (−)) and 1.82 (ILD vs CLD (−)) under the recessive model for the G allele of rs2609255 (http://biostat.mc.vanderbilt.edu/wiki/Main/PowerSampleSize).25 Meta-analysis in the allele model for ILD in RA was performed with EZR under the fixed effect model (http://www.jichi.ac.jp/saitama-sct/SaitamaHP.files/statmed.html).26
Results
Association of FAM13A rs2609255 with UIP or ILD in RA
FAM13A rs2609255 was genotyped in the patients with RA. No deviation from the Hardy-Weinberg equilibrium was observed (p=0.7683). It was investigated whether FAM13A rs2609255 was associated with UIP, NSIP or ILD in RA. A significant association with UIP was detected for FAM13A rs2609255 under the allele model (p=0.0092, Pc=0.0276, OR 1.53, 95% CI 1.12 to 2.11; table 2) and the recessive model for the G allele (p=0.0003, Pc=0.0009, OR 2.63, 95% CI 1.59 to 4.32). However, no association with NSIP was detected. FAM13A rs2609255 was also significantly associated with ILD in RA (p=0.0039, Pc=0.0117, OR 1.83, 95% CI 1.22 to 2.73) under the recessive model for the G allele. To exclude any effects resulting from differences in the male:female ratio between UIP and CLD (−) groups, the association of FAM13A rs2609255 was analysed solely in male patients with RA. It was found that FAM13A rs2609255 was significantly associated with UIP in male patients with RA (p=0.0088, OR 3.37, 95% CI 1.43 to 7.95; table 3) under the recessive model for the G allele, but it was not associated with ILD. FAM13A rs2609255 was also significantly associated with UIP in patients with RA older than 65 (p=0.0016, OR 2.62, 95% CI 1.46 to 4.72; table 3) under the recessive model. FAM13A rs2609255 was also significantly associated with UIP in male patients with RA older than 65 (p=0.0407, OR 3.29, 95% CI 1.10 to 9.84; table 3) under the recessive model. Thus, an association of FAM13A rs2609255 with UIP was detected in Japanese RA and a role for this variant especially in male and older patients with RA was suggested. Meta-analysis of data from previous reports3 11 and our data confirmed a significant association with ILD in RA (p=0.0168, OR 1.24, 95% CI 1.04 to 1.49). The lack of heterogeneity was confirmed in these data (p = 0.0674). Finally, we tested whether FAM13A rs2609255 is associated with RA itself and found that it is (p=0.0375, OR 1.13, 95% CI 1.01 to 1.26; online supplemental table S1).
Supplemental material
Genotype frequencies of FAM13A rs2609255 in the patients with RA in this study
Genotype frequencies of FAM13A rs2609255 in the subpopulations of patients with RA
Discussion
Here, we found that rs2609255G is a risk allele for UIP or ILD in Japanese RA. It was also determined that FAM13A rs2609255 was significantly associated with UIP in male and older patients with RA, as well as an association of FAM13A rs2609255 generally with RA. This had already been reported in European populations,11 but to the best of our knowledge, the present study is the first in Asian populations.
MUC5B rs35705950 was reported to be associated with ILD in RA.3 However, the frequency of the rs35705950T risk allele is extremely low in Japanese. The predominant pathogenesis of ILD in Japanese RA therefore cannot be explained by this SNV. Other genetic factors were suspected to be associated with ILD in Japanese RA. RPA3-UMAD1 rs12702634 was reported to be associated with ILD in the GWAS of Japanese RA,9 but the association described in that study was not confirmed in our replication study in other Japanese populations,10 suggesting heterogeneity of ILD in RA. The confirmation of the results of genetic association studies by replication is important to establish their validity. The present study indicated that FAM13A rs2609255 is associated with UIP in Japanese RA. FAM13A rs2609255 was apparently associated with UIP in male and older patients with RA. However, FAM13A rs2609255 was not associated with NSIP in Japanese RA. Additionally, older men are predominant in RA with UIP but not in RA with NSIP.23 27 These data suggest that the pathogenesis of ILD in RA is heterogeneous.
In a recent GWAS, FAM13A was associated with ILD in European RA.11 This SNV had already been tested in a previous study in European and Mexican populations3; it was not associated with ILD in RA. In the present study, this association was confirmed in Japanese populations, establishing a clear genetic association. It was reported that FAM13A is expressed in the lungs,17 and expression quantitative trait loci analysis in the Genotype-Tissue Expression portal database revealed an association of FAM13A rs2609255 with the expression of the gene in lung or tibial artery (https://gtexportal.org/home/snp/rs2609255).28 It was reported that FAM13A modulated Wnt signalling,17 18 which is thought to be involved in the pathogenesis of idiopathic pulmonary fibrosis.19 20 Thus, FAM13A rs2609255 would be a candidate for pathogenicity in the development of ILD in RA.
To the best of our knowledge, this is the first report of an association of FAM13A rs2609255 with ILD in Asian RA. The study does have several limitations. The sample size was modest and the study was based on the results solely from Japanese populations. This study did not include replications in other Asian populations, though this is the replication of the European report.11 Thus, larger scale multiethnic studies with other populations including other Asians should be performed to validate the aetiology of ILD in RA. Future studies on the function of FAM13A rs2609255 on ILD in RA are warranted to reveal the causality. The associations of FAM13A rs2609255 with the severity, progression or prognosis of ILD in patients with RA should be focused in future analyses, though it was not able to be assessed in the present study. This study established an association of FAM13A rs2609255 with ILD in RA, especially in older men, suggesting an explanation for the pathogenesis of ILD in Japanese RA.
Data availability statement
Data are available upon reasonable request. Data supporting the findings of this study are presented in the paper and the supplementary file. Other data are available from the authors upon reasonable request. However, the clinical information and genotype data of each participant are not available under the conditions of informed consent mandated by the Act on the Protection of Personal Information.
Ethics statements
Patient consent for publication
Ethics approval
This study involves human participants and was approved by the research ethics committee of Tokyo National Hospital (190010), Sagamihara National Hospital and all other institutes participating in the present study. Written informed consent was obtained from all participants. This study was conducted in accordance with the principles expressed in the Declaration of Helsinki.
References
Supplementary materials
Supplementary Data
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Footnotes
Deceased Dr. Okamoto is deceased.
Contributors HF and STo designed the study. TH, SO and HF conducted the experiments. TH and HF analysed the data. HF, KSh, STs, SI, AO, MK, KSa, SS, TM, KM, SN and STo contributed to the collection of clinical information and materials. TH, HF and STo wrote the manuscript. HF is the guarantor
Funding The work was supported by research grants from the following pharmaceutical companies: Teijin Pharma, Takeda Pharmaceutical Company, Pfizer Japan, Merck Sharp and Dohme, Mitsuibishi Tanabe Pharma Corporation, Eisai Co., Chugai Pharmaceutical Co., Astellas Pharma, Abbott Japan Co. and Bristol-Myers K.K; RA clinical Investigation grant from Bristol-Myers Squibb Co.; research Grants from Mitsui Sumitomo Insurance Welfare Foundation, Takeda Science Foundation, the Nakatomi Foundation, Daiwa Securities Health Foundation and Japan Research Foundation for Clinical Pharmacology; grants-in-aid for clinical research from the National Hospital Organization, the Practical Research Project for Allergic Diseases and Immunology (Research on Allergic Diseases and Immunology) from Japan Agency for Medical Research and Development, Health and Labour Science Research Grants from the Ministry of Health, Labour, and Welfare of Japan, Scientific Research (B, C) (26293123, 22591090, 15K09543 and 18K08402) from the Japan Society for the Promotion of Science.
Competing interests STo received honoraria from Pfizer Japan, Ono Pharmaceutical Co., Mitsubishi Tanabe Pharma Corporation, Chugai Pharmaceutical Co., Astellas Pharma, AbbVie GK and Asahi Kasei Pharma Corporation, and was supported by research grants from Teijin Pharma, Takeda Pharmaceutical Company, Pfizer Japan, Mitsubishi Tanabe Pharma Corporation, Merck Sharp and Dohme, Eisai Co., Chugai Pharmaceutical Co., Astellas Pharma and Abbott Japan Co. HF received honoraria from Takeda Pharmaceutical Company, Pfizer Japan, Luminex Japan Corporation, Dainippon Sumitomo Pharma Co., Daiichi Sankyo Co., Ayumi Pharmaceutical Corporation and Ajinomoto Co., and was supported by research grants from Bristol-Myers-Squibb Co., Mitsui Sumitomo Insurance Welfare Foundation established by Mitsui Sumitomo Insurance Co., Daiwa Securities Health Foundation established by Daiwa Securities Group, Nakatomi Foundation established by Hisamitsu Pharmaceutical Co., Takeda Science Foundation supported by Takeda Pharmaceutical Company and Japan Research Foundation for Clinical Pharmacology run by Daiichi Sankyo.
Provenance and peer review Not commissioned; externally peer reviewed.
Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.