Background/Purpose: Infiltration of inflammatory cells, including monocytes, into the organs is a major process leading to fibrosis, remodelling and organ dysfunction in systemic sclerosis (SSc). Adhesion is a key process for cell infiltration. However, its pathomechanisms in SSc remain elusive.

CD52 protein is highly expressed on CD4⁺ T-cells and plays an important role in the modulation of T-cell receptor signalling. Nevertheless, the function of this protein on monocytes is not completely understood.

We aimed to investigate the process of monocyte adhesion in SSc with a special focus on the influence of CD52 expression.

Methods: Biopsies from the heart, lungs and skin of SSc patients (n=11, 7, 7, respectively) and healthy controls (HC) (n=10, 7, 9, respectively) were analysed by immunohistochemistry for the presence of CD14⁺ cells. RNAseq of CD14⁺ blood monocytes of lcSSc (n=5, age=54.4±6.7), dcSSc patients (n=5, age=51.8±7.2) and age- and sex-matched HC (n=5, age=50.8±9.7) was performed. Differentially expressed genes were computed using DeSEQ2 algorithm. Gene ontology and pathway analysis were performed using Metacore software and ShinyApp. Expression of adhesion molecules was confirmed by flow cytometry (HC n=16, SSc n =76). Adhesion of CD14⁺ monocytes to ICAM1 and TNFα-stimulated endothelial cells was checked using the 96-well plate adhesion assay (HC n=12, SSc n=40). CD52 regulation in CD14⁺ monocytes from HC (n=4) was analysed on mRNA level upon stimulation with LPS, IFNγ, IL-4 and IL-13. Adhesion under the physiological shear flow of THP-1 cell lines with overexpression and silencing of CD52 was investigated (n=4).

Results: Immunohistochemistry confirmed higher infiltration of CD14+ cells in the heart (p< 0.01), lung (p< 0.05) and skin (p< 0.001) of SSc patients. 1440 differentially expressed genes were detected between dcSSc vs HC and 225 between lcSSc and HC (p≤0.01; log2 ratio≥0.5). Pathway analysis revealed significant alterations in adhesion and chemotaxis pathways. Flow cytometry confirmed upregulation of adhesion molecules CD11b (p< 0.01) and CD18 (p< 0.05). In contrast, expression of CD52 was downregulated in SSc patients (p< 0.05). SSc CD14⁺ monocytes exhibited increased adhesion both to ICAM1-coated plates (p< 0.01) and to TNFα-stimulated endothelial cells (p< 0.05). CD52 mRNA was increased in a dose-dependent manner after IL-4 and IL-13 stimulation and decreased after LPS and IFNγ stimulation (p< 0.05). Overexpression of CD52 in THP-1 monocytes decreased adhesion to TNFα-stimulated endothelial cells (p< 0.01) under the shear flow conditions. Accordingly, silencing of CD52 increased adhesion of THP-1 monocytes (p< 0.01).

Conclusion: Here we pointed to an increased adhesion of peripheral blood CD14⁺ monocytes to ICAM1 and endothelial cells in SSc. Our results suggest the primary activation of monocytes in peripheral blood, which may translate into higher organ infiltration in SSc patients. Finally yet importantly, we characterised a novel function of the CD52 molecule on monocytes and its possible contribution during the course of the disease.

« Back to 2019 ACR/ARP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/altered-expression-of-cd52-facilitates-adhesion-of-circulating-cd14-monocytes-in-systemic-sclerosis/