The role of Dickkopf-1 in joint remodeling and fibrosis: A link connecting spondyloarthropathies and scleroderma?

Background: Dickkopf-1 (Dkk-1) is a soluble inhibitor of the canonical Wnt pathway, which plays critical roles in embryonic development. Evidence suggests that this molecule regulates several aspects of both bone biology and fibrosis.
Objectives: To provide an overview of our current knowledge of the role of Dkk-1 in joint remodeling and fibrosis.
Methods: We performed an electronic search (Medline) using the following key words: Dickkopf-1 (or Dkk-1), new bone formation, joint remodeling, ankylosing spondylitis, systemic sclerosis (or scleroderma), and fibrosis, supplemented by a manual search of references from retrieved articles.
Results: Dkk-1 is a master regulator of joint remodeling in animal models of arthritis shifting the balance toward new bone formation when its expression is decreased and toward erosion/joint destruction when its expression is increased. In humans, evidence suggests that Dkk-1 may be dysfunctional in patients with ankylosing spondylitis, a prototype bone forming disease. Moreover, data from animal models indicate that Dkk-1 has a protective role against fibrosis in several organs. Recent data suggest that inhibiting the canonical Wnt pathway by overexpression of Dkk-1 could be a way to target TGF-β signaling in fibrotic diseases. Finally, B-cell depletion therapy in systemic sclerosis may exert its effects through TGF-β dependent upregulation of Dkk-1.
Conclusions: Dkk-1 appears to play a crucial role in both joint remodeling/ectopic ossification and fibrosis, and may be a prospective therapeutic modality for fibrotic diseases or diseases characterized by pathologic joint remodeling.
(Copyright © 2017 Elsevier Inc. All rights reserved.)