Dickkopf-3 (DKK3) Signaling in IL-1α-Challenged Chondrocytes: Involvement of the NF-κB Pathway

Objective: Osteoarthritis (OA) is an age-related biomechanical and low-grade inflammometabolic disease of the joints and one of the costliest and disabling forms of arthritis. Studies on matrix-degrading enzymes such as metalloproteases, which are implicated in the increased catabolism of extracellular matrix, are of paramount relevance. DKK3 is a member of DKK family and is best known for its role in cancer. Although there is some information about the participation of DKK3 in cartilage pathophysiology and on metalloproteases regulation, in particular, little is known about DKK3 signaling mechanisms. Thus, the aim of this study is to explore how DKK3 regulates matrix metalloproteinase-13 (MMP-13) expression. Design: Gene, protein expression and protein phosphorylation in primary human chondrocytes and ATDC5 mouse cells were assessed by RT-qPCR and Western blot analysis. Further studies on DKK3 activity were performed by targeting DKK3 gene with a specific siRNA. Results: DKK3 expression was found to be higher in OA human chondrocytes than healthy cells, being its expression decreased in interleukin-1? (IL-1?)-stimulated cells. DKK3 knockdown increased the induction of MMP-13 elicited by IL-1? in human and mouse chondrocytes and after the analysis of different signalling pathways, we observed that NF-?B pathway was involved in the regulation of MMP-13 expression by DKK3. Conclusions: Herein we have demonstrated, for the first time, that DKK3 gene silencing exacerbated NF-?B activation, resulting in an increased IL-1?-driven induction of MMP-13. Our results further confirm that DKK3 may play a protective role in OA by attenuating NF-?B activation and the subsequent production of metalloproteases. Funding: OG and FL are Staff Personnel of Xunta de Galicia (Servizo Galego de Saude, SERGAS) through a research-staff stabilization contract (ISCIII/SERGAS). JC is “Miguel Servet” Researcher “CP19/00172 (ISCIII/FEDER), MS and VF are currently “Sara Borrell” Researchers funded by ISCIII and FEDER (CD16/00111). RG is a “Miguel Servet” Researcher funded by Instituto de Salud Carlos III (ISCIII) and FEDER. CR is a predoctoral research scholar funded by ISCIII and FEDER (Exp. 18/00188). OG, RG, and MAGG are members of RETICS Programme, RD16/0012/0014 (RIER: Red de Investigación en Inflamación y Enfermedades Reumáticas) via Instituto de Salud Carlos III (ISCIII) and FEDER. FL is a member of CIBERCV (Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares). The work of OG and JP (PI17/00409), RG (PI16/01870 and CP15/00007) and FL (PI15/00681 PI18/00821 and CB16/11/00226) was funded by Instituto de Salud Carlos III and FEDER. OG is a beneficiary of a project funded by Research Executive Agency of the European Union in the framework of MSCA-RISE Action of the H2020 Programme (Project number 734899). OG is beneficiary of a project funded by Xunta de Galicia, Consellería de emprego e industria (GAIN) (IN607B2019/10). RG is beneficiary of a project funded by Mutua Madrileña 2018. AM wishes to acknowledge financial support from the European Structural and Social Funds through the Research Council of Lithuania (Lietuvos Mokslo Taryba) according to the activity ‘Improvement of researchers’ qualification by implementing world-class R&D projects’ of Measure No. 09.3.3-LMT-K-712 (grant application code: 09.3.3-LMT-K-712-01-0157, agreement No. DOTSUT-215) and the new funding programme: Attracting Foreign Researchers for Research Implementation (2018–2022).