Abstract Objectives WNT5A is a noncanonical WNT ligand that is overexpressed in autoimmune systemic sclerosis (SSc). While the pathogenic effects of WNT5A have been established in SSc fibroblasts, its contribution to profibrotic SSc macrophage activation is unknown. The goal of this study was to determine the effects of WNT5A on fibrotic macrophage activation. Methods Human monocyte-derived macrophages were cultured in the presence of recombinant WNT5A and assessed for changes in immunophenotype, STAT3 phosphorylation, and cytokine secretion. The ability of WNT5A-treated macrophages to induce healthy donor and SSc patient fibroblast activation was evaluated in the presence or absence of macrophage-specific pSTAT3 inhibition. Results WNT5A significantly increased surface levels of profibrotic markers CD163 and CD16, and the secretion of CCL2, TNF, IL-10, and IL-6, which are characteristic of profibrotic SSc macrophage activation. WNT5A also increased the percentage of pSTAT3+ macrophages as well as overall STAT3 phosphorylation levels, which we have shown in prior work are basally activated in SSc macrophages. Moreover, SSc macrophages treated with WNT5A induced SSc patient but not healthy donor fibroblast activation, which was significantly attenuated by inhibition of STAT3. Conclusions Collectively, these results indicate that WNT5A mediates profibrotic macrophage activation through a pSTAT3-dependent mechanism. As SSc fibroblasts secrete elevated levels of WNT5A, our experiments suggest that in addition to autocrine functions, paracrine WNT5A may also contribute to pathological macrophage activation in SSc.
Morris et al. (Tue,) studied this question.