Background/Purpose: Interstitial lung disease associate with Systemic Sclerosis(SSc-ILD) is one of the leading causes of mortality. We analyzed the gene expression of lung tissue in a prospective cohort of SSc-ILD compared to control lungs and to two prospective clinical parameters in order to understand molecular pathways implicated in progressive lung disease.

Methods: Lung tissue was obtained by open lung biopsy in 28 consecutive SSc-ILD patients and 4 controls. High-resolution computerized tomography(HRCT) and pulmonary function tests(PFTs) were performed on baseline and 2-3 years after treatment that was based on lung histologic classification. SSc lung RNA was available from 11 diffuse and 10 limited SSc patients. Microarray analysis was performed and the results correlated (Pearson’s) with changes in HRCT score(FibMax) and PFTs values. Quantitative polymerase chain reaction(qPCR) and immunohistochemistry(IHC) were used to confirm differential levels of mRNA and protein levels. Interferon receptor alpha-1(IFNAR) deficient mice were submitted to a systemic bleomycin-lung fibrosis murine model. The study was approved by the Institutional Review Boards from both universities (Brazil and USA).

Results: Despite treatment, cyclophosphamide for non-specific interstitial pneumonia(NSIP) and intense anti-reflux treatment for centrilobular fibrosis(CLF), most of SSc-ILD patients progressed based on delta FibMax(p< 0.01). Lung microarray data distinguished SSc-ILD from healthy controls. Macrophage markers, chemokines, collagen, TGF-beta- and interferon-regulated genes that were upregulated in SSc-NSIP were strongly correlated to the delta FibMax. IHC confirmed the collagen(Col1a1), interferon(OAS1 and IFI44), and macrophage(CCL18 and CD163) signatures and the positive correlation with delta FibMax was confirmed by qPCR in a larger group of SSc-NSIP patients: Col1a1 (r²=0.39; p<0.01); IFI44 (r²=0.44; p<0.01); OAS1 (r²=0.36; p<0.01); CD163 (r²=0.24; p<0.03), and CCL18 (r²=0.42; p<0,01). Several genes were correlated with both the delta FibMax (r>0.4) and delta %FVC (r<-0.1), including interferon and macrophage markers; chemokines; and heat-shock proteins. IFNAR-deficient compared to wild-type mice exposed systemically to bleomycin developed a milder fibrotic score at day 21^st. Several profibrotic genes, such as SPP1(osteopontin), LOX(protein-lysin oxidase), and PAI-1(serpine-1); macrophage markers (arginase-1 and chitinase-3) were blocked or partially blocked in IFNAR-deficient mice.

Conclusion: These results highlight the major pathogenic pathways relevant to progressive pulmonary fibrosis in SSc-ILD: macrophage activation, and upregulation of TGF-beta- and IFN-regulated genes. The importance of IFN was further supported here in a murine systemic lung-fibrotic model. These findings support the notion that blocking one or more of these pathways may be the best treatment approach for SSc-ILD.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/key-roles-for-interferon-and-macrophage-activation-in-progressive-lung-fibrosis-associated-with-systemic-sclerosis/