Austin V Stone1, Richard F Loeser2, Michael F Callahan3, Margaret A McNulty4, David L Long5, Raghunatha R Yammani5, Sara Bean6, Kadie Vanderman5, Susan Chubinskaya7, Cristin M Ferguson3. 1. Division of Sports Medicine, Department of Orthopaedic Surgery & Sports Medicine, University of Kentucky, Lexington, KY, USA. 2. Division of Rheumatology, Allergy and Immunology and the Thurston Arthritis Research Center, University of North Carolina, Chapel Hill, NC, USA. 3. Division of Sports Medicine, Department of Orthopaedic Surgery, Wake Forest School of Medicine, Winston-Salem, NC, USA. 4. Department of Anatomy, Cell Biology, & Physiology, Indiana University School of Medicine, Indianapolis, IN, USA. 5. Division of Molecular Medicine, Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA. 6. University of Kentucky School of Medicine, Lexington, KY, USA. 7. Department of Pediatrics, Rush University Medical Center, Chicago, IL, USA.
Abstract
OBJECTIVE: Meniscus injury and the hypoxia-inducible factor (HIF) pathway are independently linked to osteoarthritis pathogenesis, but the role of the meniscus HIF pathway remains unclear. We sought to identify and evaluate HIF pathway response in normal and osteoarthritic meniscus and to examine the effects of Epas1 (HIF-2α) insufficiency in mice on early osteoarthritis development. METHODS: Normal and osteoarthritic human meniscus specimens were obtained and used for immunohistochemical evaluation and cell culture studies for the HIF pathway. Meniscus cells were treated with pro-inflammatory stimuli, including interleukins (IL)-1β, IL-6, transforming growth factor (TGF)-α, and fibronectin fragments (FnF). Target genes were also evaluated with HIF-1α and HIF-2α (Epas1) overexpression and knockdown. Wild-type (n = 36) and Epas1+/- (n = 30) heterozygous mice underwent destabilization of the medial meniscus (DMM) surgery and were evaluated at 2 and 4 weeks postoperatively for osteoarthritis development using histology. RESULTS: HIF-1α and HIF-2α immunostaining and gene expression did not differ between normal and osteoarthritic meniscus. While pro-inflammatory stimulation significantly increased both catabolic and anabolic gene expression in the meniscus, HIF-1α and Epas1 expression levels were not significantly altered. Epas1 overexpression significantly increased Col2a1 expression. Both wild-type and Epas1+/- mice developed osteoarthritis following DMM surgery. There were no significant differences between genotypes at either time point. CONCLUSION: The HIF pathway is likely not responsible for osteoarthritic changes in the human meniscus. Additionally, Epas1 insufficiency does not protect against osteoarthritis development in the mouse at early time points after DMM surgery. The HIF pathway may be more important for protection against catabolic stress.
OBJECTIVE: Meniscus injury and the hypoxia-inducible factor (HIF) pathway are independently linked to osteoarthritis pathogenesis, but the role of the meniscus HIF pathway remains unclear. We sought to identify and evaluate HIF pathway response in normal and osteoarthritic meniscus and to examine the effects of Epas1 (HIF-2α) insufficiency in mice on early osteoarthritis development. METHODS: Normal and osteoarthritic human meniscus specimens were obtained and used for immunohistochemical evaluation and cell culture studies for the HIF pathway. Meniscus cells were treated with pro-inflammatory stimuli, including interleukins (IL)-1β, IL-6, transforming growth factor (TGF)-α, and fibronectin fragments (FnF). Target genes were also evaluated with HIF-1α and HIF-2α (Epas1) overexpression and knockdown. Wild-type (n = 36) and Epas1+/- (n = 30) heterozygous mice underwent destabilization of the medial meniscus (DMM) surgery and were evaluated at 2 and 4 weeks postoperatively for osteoarthritis development using histology. RESULTS: HIF-1α and HIF-2α immunostaining and gene expression did not differ between normal and osteoarthritic meniscus. While pro-inflammatory stimulation significantly increased both catabolic and anabolic gene expression in the meniscus, HIF-1α and Epas1 expression levels were not significantly altered. Epas1 overexpression significantly increased Col2a1 expression. Both wild-type and Epas1+/- mice developed osteoarthritis following DMM surgery. There were no significant differences between genotypes at either time point. CONCLUSION: The HIF pathway is likely not responsible for osteoarthritic changes in the human meniscus. Additionally, Epas1 insufficiency does not protect against osteoarthritis development in the mouse at early time points after DMM surgery. The HIF pathway may be more important for protection against catabolic stress.
Authors: Meredith A Rowe; Lindsey R Harper; Margaret A McNulty; Anthony G Lau; Cathy S Carlson; Lin Leng; Richard J Bucala; Richard A Miller; Richard F Loeser Journal: Arthritis Rheumatol Date: 2017-02 Impact factor: 10.995