Target organ expression and biomarker characterization of chemokine CCL21 in systemic sclerosis associated pulmonary arterial hypertension.

Systemic sclerosis (SSc) is a heterogenous disorder that appears to result from interplay between vascular pathologies, tissue fibrosis and immune processes, with evidence for deregulation of chemokines, which normally control immune trafficking. We recently identified altered levels of chemokine CCL21 in SSc associated pulmonary arterial hypertension (PAH). Here, we aimed to define target organ expression and biomarker characteristics of CCL21. To investigate target organ expression of CCL21, we performed immunohistochemistry (IHC) on explanted lung tissues from SSc-PAH patients. We assessed serum levels of CCL21 by ELISA and Luminex in two well-characterized SSc cohorts from Oslo (OUH, n=552) and Zurich (n=93) University hospitals and in 168 healthy controls. For detection of anti-CCl21 antibodies, we performed protein array analysis applying serum samples from SSc patients (n=300) and healthy controls. To characterize circulating CCL21 in SSc, we applied immunoprecipitation (IP) with antibodies detecting both full length and tailless and a custom-made antibody detecting only the C-terminal of CCL21. IP products were analyzed by SDS-PAGE/western blot and Mass spectrometry (MS). By IHC, we found that CCL21 was mainly expressed in the airway epithelial cells of SSc patients with PAH. In the analysis of serum levels of CCL21 we found weak correlation between Luminex and ELISA (r=0.515, p<0.001). Serum levels of anti-CCL21 antibodies were higher in SSc patients than in healthy controls (p<0.001), but only 5% of the SSc population were positive for anti-CCL21 antibodies in SSc, and we found no correlation between anti-CCl21 and serum levels of CCL21. By MS, we only identified peptides located within amino acid (aa) 23-102 of CCL21, indicating that CCL21 in SSc circulate as a truncated protein without the C-terminal tail. This study demonstrates expression of CCL21 in epithelial lung tissue from SSc patients with PAH, and indicate that CCL21 in SSc circulates as a truncated protein. We extend previous observations indicating biomarker potential of CCL21, but find that Luminex is not suitable as platform for biomarker analyses. Finally,

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Copyright © 2022 Didriksen, Molberg, Mehta, Jordan, Palchevskiy, Fretheim, Gude, Ueland, Brunborg, Garen, Midtvedt, Andreassen, Lund-Johansen, Distler, Belperio and Hoffmann-Vold.

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HF has received personal fees from Bayer and non-financial support <$10 000 from GSK and Actelion, outside the submitted work. ØMi has received honoraria from Boehringer Ingelheim and Jannsen. AA has a consultancy relationship with and has received travel support and honoraria from Jannsen. OD has a consultancy relationship with and/or has received research funding from and/or has served as a speaker for the following companies in the area of potential treatments for systemic sclerosis and its complications in the last three calendar years: Abbvie, Acceleron, Alcimed, Amgen, AnaMar, Arxx, AstraZeneca, Baecon, Blade, Bayer, Boehringer Ingelheim, Corbus, CSL Behring, 4P Science, Galapagos, Glenmark, Horizon, Inventiva, Janssen, Kymera, Lupin, Medscape, Miltenyi Biotec, Mitsubishi Tanabe, MSD, Novartis, Prometheus, Redxpharma, Roivant, Sanofi and Topadur. OD also has a patent issued “mir-29 for the treatment of systemic sclerosis” (US8247389, EP2331143). JB has received honoraria from Boehringer Ingelheim. A-MH-V has received grants, personal fees and non-financial support >$10 000 from Boehringer Ingelheim, and personal fees <$10 000 from Actelion, ARXX, Bayer, Jansen, Medscape, MSD and Roche outside the submitted work. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.