Periostin may act on monocytes and monocyte-derived macrophages with a pro-fibrotic phenotype in patients with systemic sclerosis (SSc)

Background: Circulating periostin levels are increased in systemic sclerosis (SSc) patients and correlates positively with disease severity. Additionally, monocytes/macrophages are one of the key cells in SSc pathogenesis. However, the effect of periostin on immune cells, particularly monocytes and macrophages, has not been well investigated. Objectives: To examine the effect of periostin on monocytes and monocyte-derived macrophages (MDMs) in SSc. Methods: Monocytes were purified from blood samples of nine diffuse cutaneous SSc patients and five healthy controls (HCs) and were differentiated into macrophages. Cell surface markers were assessed by flow cytometry. RNA sequencing analysis was performed on recombinant periostin-stimulated monocytes from three HCs. Cytokine/chemokine and extracellular matrix (ECM) protein expressions in MDMs differentiated supplemented with recombinant periostin were assessed by quantitative real-time polymerase chain reaction and bead-based immunoassays in six HCs. Moreover, we evaluated whether periostin was involved in monocyte migration by Transwell assay. Results: The modified Rodnan total skin thickness score correlated positively with the proportion of CD80-CD206+ M2 cells. The M2 macrophage proportion was reduced in rPn-stimulated MDMs in HCs, but not in SSc patients. mRNA expression levels of pro-fibrotic cytokine, chemokine, and ECM protein genes were significantly upregulated in recombinant periostin-stimulated monocytes and MDMs as compared to those from control monocytes and MDMs. Similar trends for their protein levels were also observed in MDMs. Moreover, the ratio of migrated cells in recombinant periostin-stimulated monocytes was significantly higher than that in control monocytes. We performed gene expression profiling analysis using data obtained from RNA-seq of recombinant periostin-stimulated monocytes from three healthy controls.