Background/Purpose: CTLA4-Ig interacts with the cell surface costimulatory molecule CD86 and can downregulate the target cell activation [1]. Circulating fibrocytes (CFs) express markers of both hematopoietic cells (CD45, MHC class II) and stromal cells (collagen I and III), together with the chemokine receptors, which regulate their migration into inflammatory lesions (CXCR4, CCR2, CCR7) [2]. CFs can migrate into systemic sclerosis (SSc)-affected tissues and can differentiate into fibroblasts/myofibroblasts [2]. Skin fibroblasts (SFs) are involved in the excessive production of extracellular matrix (ECM) proteins which characterizes fibrosis in SSc [3].

The aim of the study was to compare CD86 expression on CFs, SFs and human macrophages (M) from SSc patients and to study the effects of CTLA4-Ig/CD86 interaction on SSc cultured CFs and SFs.

Methods: Peripheral blood CFs and M together with SFs were obtained from 8 “limited” cutaneous SSc patients (treated only with vasodilators, mainly cyclic prostanoids), after patient informed consent and local Ethics Committee approval for skin biopsies.

CFs and M were characterized by fluorescence-activated cell sorter analysis (FACS), for CD45, collagen type I (COL I), CXCR4, CD14, CD86, and HLA-DRII expression. After 8 days (T8) of culture, CFs were treated for 3 hrs and SFs were treated for 24 and 48 hrs, in the absence or in the presence of CTLA4-Ig (10, 50, 100 and 500 micrograms/ml). Quantitative real-time polymerase chain reaction (qRT-PCR) for CD86 on CFs, SFs and M were performed. In addition, after CTLA4-Ig treatment, qRT-PCR for CD86, COL I, IL1beta, TGFbeta, αphaSMA, S100A4, CXCR2, CXCR4, CD11a was performed. The statistical analysis was carried out by the nonparametric Mann-Whitney U test.

Results: At gene level, SSc M highly expressed CD86 molecule. Notably, T8-cultured SSc CFs showed significantly higher CD86 gene expression, compared to SSc M (p<0.05). On the contrary, SSc SFs showed a very low CD86 gene expression, compared to both M and CFs (both p<0.01). After 3 hrs-CTLA4-Ig treatments, qRT-PCR of SSc CFs showed αlphaSMA, COL I and CD11a gene expression significantly decreased (p<0.01, p<0.05 and p<0.05 respectively), whereas S100A4 gene expression resulted significantly increased (p<0.01), compared to untreated cells (CNT). CD86 and CXCR4 gene expression resulted decreased (not significantly) only after treatment with CTLA4-Ig 500 micrograms/ml. Otherwise, SSc CFs did not show any significant variations in TGFbeta, IL1beta and CXCR2 gene expressions, compared to CNT. SSc SFs treated with CTLA4-Ig did not show any significant modulation in the gene expression levels of CD86, compared to CNT.

Conclusion: In conclusion, CD86 expression on M and CFs in SSc patients might support their earlier and intensive activation in this disease when compared to resident SFs in the same patients. Therefore, SSc CFs seem to be more responsive to CTLA4-Ig treatment than SFs, thus a new therapeutic option for abatacept in SSc treatment should be taken into consideration based on its possible anti-fibrotic effect.

References: 1. Cutolo M et al. Arthritis Res Ther 2009;11:176-85; 2. Bucala R. Mol Med 2015;2:S3-5; 3. Asano Y. J Dermatol 2017; Epub ahead of print. Review.

« Back to 2018 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/ctla4-ig-cd86-interaction-on-cultered-human-fibrocytes-and-fibroblasts-from-systemic-sclerosis-patients/