Introduction:
MiR-101 rs7536540 may influence the expression of miR-101 and another polymorphism, rs2227513, which in turn affects the expression of IL-22, . However, studies on the combined effect of these polymorphisms are still scarce.

Material and methods:
Quantitative real-time PCR was performed to analyze the expression of miR-101 and IL-22 mRNA. ELISA and Western blot were carried out to examine the expression of IL-22 protein. MTT assay and flow cytometry were used to assess the cellular proliferation and apoptosis . Immunofluorescence was performed to measure the expression of p-STAT3. Luciferase assay was carried out to explore the inhibitory role of miR-101 in the expression of IL-22.

Results:
The severity of RA was progressively increased in patients with rs7536540 GG + rs2227513 AA, rs7536540 GG + rs2227513 AG, rs7536540 CC/CG + rs2227513 AA and rs7536540 CC/CG + rs2227513 AG genotypes. The CC/CG alleles at rs7536540 were correlated with up-regulated miR-101 expression in the serum and SF of RA patients, whereas both CC/CG alleles at rs7536540 and AG alleles at rs2227513 were correlated with elevated expression of IL-22. Incubation of FLS with SF isolated from RA patients carrying the CC/CG alleles at rs7536540 and AG alleles at rs2227513 remarkably increased the cell proliferation and inhibited the apoptosis of FLS. Luciferase assay demonstrated that the expression of IL-22 was notably suppressed by miR-101 in THP-1 cells.

Conclusions:
Our study revealed the combined effect of polymorphisms rs7536540 and rs2227513 on the expression of IL-22 and the proliferation of FLS as well as their association with the severity of RA