OA07 Clinical and pathogenic significance of S100A4 overexpression in systemic sclerosis
Authors: Denton Christopher P , Xu Shiwen , Maclean Rory H , Clark Kristina E , Borchert Signe , Hussain Rizwan , Klingelhöfer Jorg , Hallén Jonas , Ong Voon H 
Published: April 2023

Abstract

Background/Aims
Preclinical studies suggest that the S100A4, a Damage Associated Molecular Pattern (DAMP) protein upregulated upon stress or injury, may be a target for antifibrotic therapy. We have studied expression and function of S100A4 in systemic sclerosis (SSc) to further explore its relevance as a driver of fibroblast activation.

Methods
S100A4 protein concentration was measured by ELISA (Cusabio, USA) in serum of SSc (n = 94) and healthy controls (n = 15). Association of serum level with major organ complications and skin score (mRSS) was determined. S100A4 protein expression in supernatant and cell layer of skin fibroblast cultures from diffuse cutaneous SSc (SScF, n = 6) and healthy controls (NF, n = 6) was assessed. Recombinant S100A4 and a high affinity anti-S100A4 neutralising monoclonal antibody (AX-202) were used to investigate activation of profibrotic molecular and functional phenotype in SSc and control fibroblasts.

Results
Median [range] S100A4 (ng/ml) was higher in serum of SSc (89.9 [15.0-240.0]) than healthy controls (71.4 [7.9-131.8]; p = 0.027). There was significant association with SSc-ILD (p = 0.025, n = 55), scleroderma renal crisis (p = 0.026, n = 4) and trend of increase in pulmonary hypertension (p = 0.075, n = 7). There was a trend for S100A4 to fall in longer disease duration (r=-0.18, p = 0.09) and a weak (r = 0.28, p = 0.07) correlation with current mRSS but not peak mRSS in dcSSc. Median [range] S100A4 (ng/ml) was higher in culture supernatants of SScF (4.19 [0.52-8.42]) than NF controls (0.28 [0.02-3.29]; p &lt; 0.0001) and SSc cell layer had increased levels by Western blot analysis (mean [sd] RDU NF = 0.50 [0.91]; SScF 8.16 [2.49]; p &lt; 0.0001). S100A4 induced a fibrotic phenotype in NF with concentration dependent increased in Col1, SMA and CTGF expression, and promotion of migration (scratch wound assay) and 3D type I collagen gel contraction that was attenuated by AX-202. AX-202 also reduced the constitutive profibrotic gene and protein expression phenotype of SScF. The effect of S100A4 was significantly attenuated by SB431524, a specific inhibitor of ALK5 (p &lt; 0.0001 ANOVA) using qPCR assays across treatment groups for Col1, SMA and CTGF. Gene expression data (qPCR) confirmed protein expression. Genome-wide RNAseq analysis identified an S100A4 activated signature in NF overlapping the hallmark gene expression signature of SScF. Thus, 464 differentially expressed genes (FDR&lt;0.001 and FC &gt; 1.5) induced in NF by S100A4 were also constitutively overexpressed in SScF, and significantly downregulated by AX-202. Pathway mapping of these S100A4 dependent transcripts in SSc showed the most significant enriched Kegg® pathways (FDR&lt;0.001) were regulation of stem cell pluripotency (4.6-fold) and metabolic pathways (1.9-fold).

Conclusion
Our findings provide compelling evidence supporting a profibrotic role for S100A4 in fibroblast activation in SSc and suggest that serum level may be a biomarker of major organ manifestations and disease severity. Studies to elucidate the therapeutic potential of targeting S100A4 in SSc are warranted.
Disclosure
C.P. Denton: None. S. Xu: None. R.H. Maclean: None. K.E. Clark: None. S. Borchert: Corporate appointments; Employee of ARXX Therapeutics. R. Hussain: Corporate appointments; Employee of ARXX Therapeutics. J. Klingelhöfer: Corporate appointments; Employee of ARXX Therapeutics. J. Hallén: Corporate appointments; Employee of ARXX Therapeutics. V.H. Ong: None.