Background/Purpose: Systemic sclerosis (SSc) is a systemic autoimmune connective tissue disease, characterized by microvascular damage, alteration of immune response and progressive fibrosis of skin and internal organs, including lungs (1). The lung involvement, either interstitial lung disease (ILD) or pulmonary arterial hypertension, contributes to the highest mortality of SSc patients (1).

Macrophages, primarily alternatively activated (M2) macrophages, seem to have a profibrotic role in SSc, being fundamental cells of the immune inflammatory infiltrate of skin and lungs (3).

M2 macrophages express specific surface markers such as mannose receptor (CD206), macrophage scavenger receptors (CD204 and CD163), and functional markers, including the MER proto-oncogene tyrosine kinase (MerTK). Moreover, they release profibrotic cytokines and growth factors, including interleukin-10 (IL10) and transforming growth factor-β1 (TGFβ1) (2).

Nintedanib is an intracellular tyrosine kinase inhibitor targeting several fibrotic mediators such as the receptors of platelet-derived growth factor, fibroblast growth factor, vascular endothelial growth factor, and colony-stimulating factor 1 (3).

To investigate the capability of nintedanib to downregulate the profibrotic M2 phenotype of cultured monocyte-derived macrophages (MDMs) obtained from SSc-ILD patients.

Methods: Monocytes isolated from the peripheral blood of nine female SSc-ILD patients (mean age 64±14 years) were differentiated into MDMs with phorbol myristate acetate (5ng/ml). Cultured SSc-ILD MDMs were maintained in growth medium without any other stimulation (untreated cells) or treated with nintedanib (0.1 and 1μM) for 3, 16 and 24 hours. SSc-ILD patients fulfilled the 2013 ACR/EULAR criteria for SSc diagnosis (during their standard diagnostic procedures and untreated with nintedanib, glucocorticoids or tocilizumab) and were enrolled after obtaining patients informed consent and Ethical Committee approval.

Gene and protein expression of CD204, CD163, CD206, MerTK and IL10 were evaluated by quantitative RT-PCR and Western blotting. TGFβ1 level was evaluated in the conditioned medium by ELISA.

The statistical analysis was carried out using non-parametric Wilcoxon test.

Results: In cultured SSc-ILD MDMs, nintedanib 0.1 and 1μM significantly downregulated the gene expression of CD204, CD206, CD163 and MerTK after 24 hours of treatment compared to untreated cells. Nintedanib also significantly downregulated gene expression of MerTK and IL10 after 16 hours of treatment compared to untreated cells.

In cultured SSc-ILD MDMs, nintedanib 0.1 and 1μM significantly reduced the protein synthesis of CD204, CD206, CD163, MerTK and the TGFβ1 production after 24 hours of treatment compared to untreated cells.

Conclusion: Nintedanib seems to downregulate the M2 phenotype and the profibrotic activity of cultured MDMs obtained from SSc-ILD patients, through the reduction of the gene expression and protein synthesis of CD206, CD163, MerTK, TGFβ1 and IL10.

References. 1 Cutolo M, et al. Expert Rev Clin Immunol. 2019;15:753-64. 2 Lescoat A, et al. Curr Opin Rheumatol. 2021;33:463-70. 3Hilberg F, et al. Cancer Res. 2008;68:4774–82.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/nintedanib-downregulates-the-profibrotic-m2-phenotype-of-macrophages-obtained-from-systemic-sclerosis-patients-affected-by-interstitial-lung-disease/