Screening of female rheumatoid arthritis associated circRNA
To explore female RA associated circRNAs, we firstly collected total RNA of PBMC samples from four RA patients and control healthy subjects with gender and age matched. Then, we performed RNA sequencing analysis and compared circRNAs expression between rheumatoid arthritis patients and healthy control group. We identified 162 significantly differentially expressed circRNAs with a fold change ≥ 1.5 and a p-value ≤ 0.05 (Fig. 1A, Supplemental Table 1). Next, we used cluster screening to analyze the effect of gender against the background of female healthy samples and male rheumatoid arthritis samples (Fig. 1B,C, Supplemental Table 2,3). This enabled us to further identify female RA associated circRNAs. As shown in the Venn diagram, we identified three circRNAs (hsa_circ_0140271, hsa_circ_0105101 and hsa_circ_0010474) (Fig. 1D). Among those circRNAs, we were interested in hsa_circ_0140271, which were generated from MED14 gene located on X chromosome and highly expressed in three paired comparisons (Supplemental Table 4). To further explore the role of hsa_circ_0140271 in female RA, we designed specific primer to target hsa_circ_0140271, and then performed Sanger sequencing analysis and RT-qPCR. As the results shown, we identified the back-splice junction of hsa_circ_0140271 through Sanger sequencing analysis, and also found hsa_circ_0140271 was resistant to RNase R. While the liner RNA of MED14 was significantly decreased (Fig. 1E,F). These results confirmed the primer correctly amplified hsa_circ_0140271.
hsa_circ_0140271 was highly expressed in female rheumatoid arthritis patients’ PBMC
In order to further analyze hsa_circ_0140271 expression in female rheumatoid arthritis patients’ PBMC, we recruited PBMC totally from 47 RA patients and 47 healthy control donors. These two cohorts were also gender and age matched. The total RNA was also extracted and quantified hsa_circ_0140271 expression by RT-qPCR. As expected, hsa_circ_0140271 was significantly highly expressed in RA samples (Fig. 2A). To assess whether hsa_circ_0140271 would be specifically expressed in female RA samples, we stratified RA and healthy control samples according to gender. Consistent with previous results, hsa_circ_0140271 was also significantly highly expressed in female RA samples comparing to that in female healthy samples or male RA samples (Fig. 2B). However, it was not observed any difference in expression of mRNA of MED14 between RA and control group (Fig. 2C).
Next, we analyzed whether hsa_circ_0140271 expression was correlated with clinical status of female RA patients. According to DAS28 scores, we divided female RA patients into Remission group (DAS28 < 2.6) and Active group (DAS28 > 2.6). RT-qPCR results showed hsa_circ_0140271 expression was significantly higher in the Remission group and Active group comparing to that in female healthy group, while there was no difference between Remission group and Active group (Fig. 2C). We also analyzed effect of RA duration on hsa_circ_0140271 expression. We found that hsa_circ_0140271 expression was significantly higher in the female early RA (ERA) group (< 6 months) and RA group (> 6 months), but there was also no difference between ERA and RA group (Fig. 2D). Finally, we examined hsa_circ_0140271 expression in female RA-associated interstitial lung disease (ILD). Among female RA patients, there were four patients who suffered ILD. And hsa_circ_0140271 expression from those patients was not different to that from non-ILD patients (Fig. 2E). These data confirmed that hsa_circ_0140271 was specifically expressed in PBMC from female RA patients and its expression was independent with disease activity, duration and ILD.
hsa_circ_0140271 serves as a potential diagnostic biomarker for female RA
Based on the results showing that hsa_circ_0140271 was specifically highly expressed in PBMC of female RA patients, we established ROC curve analysis to explore the potential utility of hsa_circ_0140271 as a diagnostic biomarker of female RA. According to ROC analysis, the area under curve (AUC) for hsa_circ_0140271 was up to 0.704 (sensitivity = 0.419, specificity = 1), respectively (Fig. 3A, Table 2). We also performed ROC analysis by combining hsa_circ_0140271 and anti-cyclic citrullinated peptide (anti-CCP). The data suggested that the AUC and sensitivity were increased to 0.818 and 0.806, while the specificity was decreased to 0.742 (Fig. 3B, Table 2). These results implied that hsa_circ_0140271 was highly specificity for female RA and combination with anti-CCP improved its predictive value.
Table 2
ROC curve Validates the diagnostic value of differentially expressed hsa_circ_0140271 from female patients with RA.
Variables
|
AUC
|
SEM
|
P value
|
95%CI
|
Sensitivity
|
Specificity
|
Cutoff value
|
hsa_circ_0140271
|
0.704
|
0.067
|
0.006
|
0.572–0.837
|
0.419
|
1.000
|
0.110
|
Anti-CCP
|
0.738
|
0.738
|
0.001
|
0.609–0.867
|
0.581
|
0.903
|
40.719
|
Anti-CCP + hsa_circ_0140271
|
0.818
|
0.054
|
< 0.001
|
0.699–0.904
|
0.806
|
0.742
|
NA
|
Since some cytokines, like IL-1α, IL-1β, IL-6, IL-8, TNF-α and INF-γ and so on, were contributed to pathology of RA[16], we analyzed the relation between hsa_circ_0140271 and those cytokines. Based on Cutoff values of hsa_circ_0140271 ROC analysis, we divided female RA patients into hsa_circ_0140271 positive group (> 0.110) and negative group (< 0.110). Then we detected IL-1α, IL-1β, IL-6, IL-8, TNF-α and INF-γ expression in serum from both groups. Unfortunately, there was no difference in the level of those factors between two groups (Supplemental Fig. 1). However, when dividing female RA and female healthy donors according to Cutoff values, the results showed that IL-6, IL-8 and TNF-α expression were higher in hsa_circ_0140271 positive group (Fig. 4 ).
hsa_circ_0140271 possibly regulates fatty acid metabolism in female RA patients
Accumulating evidences have been shown that circRNAs play a role in pathogenesis of diseases through function of miRNA sponge[17, 18]. To elucidate the role of hsa_circ_0140271 in RA, we predicted hsa_circ_0140271 related miRNA using circBank database (http://www.circbank.cn/) and circular RNA Interactome database (https://circinteractome.nia.nih.gov/) (Fig. 5A). By analyzing those two databases, it was shown eight miRNAs might be closely related to hsa_circ_0140271, which were has-miR-600, has-miR-1244, has-miR-576-5p, hsa-miR-941, has-miR-657, has-miR-635, has-miR-574-5p, and has-miR-1305. Then, to further predict function of hsa_circ_0140271, we performed KEGG analysis based on predicted miRNAs using DIANA-mirPath (http://www.microrna.gr/miRPathv2) (Fig. 5B). According to analysis, we found 9 enriched KEGG terms. Among those terms, we found 3 terms were related to lipid metabolism, which were “Fatty acid biosynthesis”, “Pantothenate and CoA biosynthesis” and “Fatty acid metabolism”. This analysis indicated function of hsa_circ_0140271 might be associated with lipid metabolism. To verify our hypothesis, we checked laboratory characteristics of female RA patients. Although there was no correlation between hsa_circ_0140271 and lipid associated categories, such as TG, TC, HDL-C and LDL-C, it was found that expression of TG from female RA patients was lower than that from female control groups (Fig. 5C-F, Supplemental Table 5). Taken together, hsa_circ_0140271 might play a role in lipid metabolism in female RA patients through function of miRNA sponge.
hsa_circ_0140271 was a potential biomarkers in discriminating female RA from OA or AS
Since female is predominant in autoimmune diseases[3], we also analyzed hsa_circ_0140271 expression in PBMC from female osteoarthritis (OA) and Ankylosing spondylitis (AS) patients. We recruited 24 female OA patients and 7 female As patients and PBMC of those patients was also extracted to perform RT-qPCR. RT-qPCR analysis demonstrated that hsa_circ_0140271 expression from OA and AS was significantly lower than that from RA, even lower than that from healthy control (Fig. 6A). Then, we performed ROC curve analysis to evaluate the potential value of hsa_circ_0140271 discriminating RA from OA or AS. ROC curve from patients with RA and AS showed AUC area was 0.922 (sensitivity = 0.806, specificity = 1). When distinguish RA patients from OA patients, AUC area was 0.868 (sensitivity = 0.645, specificity = 1). It was also analyzed by combining OA and AS. By combination, AUC area was 0.881 (sensitivity = 0.645, specificity = 1) (Fig. 6B,C, Table 3). Those analyses implied that hsa_circ_0140271 was specifically expressed in female RA patients and might discriminate RA from OA or AS.
Table 3
ROC curve analysis of the confirmed hsa_circ_0140271 as RA female specific diagnosis.
Variables
|
AUC
|
SEM
|
P value
|
95%CI
|
Sensitivity
|
Specificity
|
Cutoff value
|
hsa_circ_0140271(RA vs AS)
|
0.922
|
0.045
|
< 0.001
|
0.787–0.984
|
1
|
0.806
|
0.034
|
hsa_circ_0140271(RA vs OA)
|
0.868
|
0.048
|
< 0.001
|
0.748–0.945
|
1
|
0.645
|
0.072
|
hsa_circ_0140271(RA vs AS + OA)
|
0.881
|
0.045
|
< 0.001
|
0.772–0.950
|
1
|
0.645
|
0.072
|