Ab0771 Enhanced Expression of Mrna for Interferon Signature Genes in Cd34+ Cells of the Bone Marrow in Rheumatoid Arthritis

Background: Proliferation of fibroblast-like synoviocytes (FLS) have been shown to play role in the pathogenesis of rheumatoid arthritis (RA). We have previously demonstrated that bone marrow (BM) CD34+ cells from RA patients have abnormal capacity to respond to TNF-α and to differentiate into FLS-like cells. Of note, we have also disclosed that RA BM CD34+ cells showed enhanced expression of NFkB1 (p50), silencing of which resulted in prevention of FLS-like cells differentiation. On the other hand, interferon-alpha (IFNα) has been implicated in the pathogenesis of RA. Indeed, enhanced expression of various IFNα-stimulated genes (ISGs) has been recently reported in peripheral blood mononuclear cells in RA. However, the mechanisms involved remain unclear. Nor has its relationship with NFkB1 mRNA expression not been addressed. Objectives: In the present study, we investigated the expression of ISGs in RA BM CD34+ cells and its relevance with NFkB1 mRNA expression. Methods: BM samples were obtained from 50 RA patients and 32 OA patients, who gave informed consent, during joint operations via aspiration from iliac crest. CD34+ cells were purified from BM mononuclear cells using magnetic beads. The expression of mRNA for IFI44L, PARP9, DTX3L and MX1 was examined by quantitative RT-PCR. The results are shown as the ratio of the copy numbers to those of β-actin mRNA. Results: Expression of IFI44L, PARP9 and DTX3L mRNA was significantly upregulated in BM CD34+ cells from RA patients compared to OA patients. MX1 mRNA expression also appeared to be higher in RA, although this difference did not reach the statistical significance (Figure 1). There was no difference in ISGs mRNA expression in BM CD34+ cells with or without methotrexate or glucocorticoid. There was also no significant correlation between the mRNA expression of ISGs in BM CD34+ cells and serum CRP levels. There was a significant correlation between the mRNA levels of the four ISGs in BM CD34+ cells with each other, but particularly with PARP9 mRNA and DTX3LmRNA (r=0.949, p<0.0001). PARP9 mRNA and DTX3L mRNA levels were also significantly correlated with NFkB1 mRNA levels (r=0.366, p=0.010 and r=0.355, p=0.014, respectively) in BM CD34+ cells from RA patients (Figure 2). Conclusion: The results indicate that the expression of ISGs mRNAs was upregulated in BM CD34+ cells from RA patients, particularly PARP9 mRNA and DTX3LmRNA,, accounting for its upregulation in peripheral blood. These correlate with increased expression of NFkB1 mRNA, which may also be related to the abnormal reactivity of BM CD34+ cells to TNFα to differentiate into FLS-like cells. REFERENCES: [1] Hirohata S, Miura Y, Tomita T, Yoshikawa H, Ochi T, Chiorazzi N. Enhanced expression of mRNA for nuclear factor kappaB1 (p50) in CD34+ cells of the bone marrow in rheumatoid arthritis. Arthritis Res Ther. 2006;8(2): R54. [2] Zhu H, Wu LF, Mo XB, Lu X, et al. Rheumatoid arthritis-associated DNA methylation sites in peripheral blood mononuclear cells. Ann Rheum Dis. 2019;78(1): 36-42 Acknowledgements: NIL. Disclosure of Interests: None declared.