Rosemary extract slows down cartilage degeneration in bovine articular cartilage explants

Abstract

Background: Osteoarthritis (OA) is a common disabling degenerative joint condition that involves the breakdown of articular cartilage, which results in pain and prevents the whole joint from functioning properly, There are no drug treatments available apart from painkillers (with associated side‐effects such as stomach ulcers with high and long‐term use). OA is receiving more attention and that dietitians will be increasingly asked to advice. Many studies indicate that some plant extracts provide symptom relief to osteoarthritic patients and slow down cartilage degeneration in vitro and/or in animal models [Ameye & Chee, 2006]. The aim of the study was to investigate the in vitro effects of rosemary, an herb frequently used in Mediterranean cuisine, and of carnosol, one of its main antioxidant, on cartilage breakdown after catabolic stimulation.Methods: In study one (n = 3), radioactive 35S‐labelled bovine articular cartilage explants were cultured for 3 days with interleukin (IL)‐1β in the presence or absence of various doses of rosemary extract or carnosol (50, 25, 10, 5 μg mL−1 for both). Cell viability was assessed by the release of lactate dehydrogenase. Glycosaminoglycan degradation was measured by quantifying the amount of 35S released in the culture media. In study two (n = 1), bovine articular cartilage explants were cultured for 21 days with oncostatin and tumour necrosis factor (TNF)‐α in the presence or absence of various doses of rosemary extract (100, 50, 10 μg mL−1) or carnosol (3.31, 1.66, 0.33 μg mL−1 corresponding to 10, 5 and 1 μM). Cell viability was assessed by the AlamarBlue assay. Matrix metalloproteinases (MMP) mediated collagen and glycosaminoglycan degradation were assessed by measuring the amounts of CTX‐II and 342FFGVG epitopes (Karsdal, 2008) released in the culture media over the 21 days of culture. Aggrecanase mediated aggrecan degradation was assessed by measuring the amount of 374ARGSV epitope (Karsdal, 2008) released in the culture media over the first 9 days of culture. For statistical analysis, analysis of variance followed by t‐tests were performed using Microsoft Excel (Microsoft Corp. Redmond, WA, USA).Results: Rosemary extract, at doses ranging from 50 down to 5 μg mL−1, and carnosol, at the doses of 10 and 5 μg mL−1, inhibited IL‐1β induced S35 release (P < 0.05) without affecting cell viability. At the highest doses of 50 and 25 μg mL−1, carnosol decreased cell viability. In the second set of experiments, rosemary extract at the lowest tested dose (10 μg mL−1) strongly inhibited the MMP‐mediated degradation of aggrecan and of type II collagen induced by oncostatin and TNF‐α without affecting the aggreganase mediated aggrecan degradation. At this low dose, rosemary extract did not affect cell viability, contrary to the two highest tested doses (50 and 100 μg mL−1). Conversely, the two lowest tested doses of carnosol (1.66, 0.33 μg mL−1) decreased the aggrecanase mediated aggrecan degradation without affecting the MMP mediated degradation of aggrecan and type II collagen. The highest tested dose of carnosol (3.31 g mL−1) decreased cell viability.Discussion: Taken together, these results suggest that rosemary extract slows down cartilage degeneration in vitro by inhibiting MMP activity. Preliminary observations suggest that the effects of rosemary extract on cartilage degeneration are not solely mediated by its carnosol content because the anti‐catabolic effects of carnosol and rosemary extract on articular cartilage only partly overlap.Conclusions: These findings provide a rationale for the in vivo testing of rosemary extract in human osteoarthritis.References Ameye, L.G. & Chee, W.S.S. (2006) Osteoarthritis and nutrition. From nutraceuticals to functional foods: a systematic review of the scientific evidence. Arthritis Res. Ther.8, R127 (Doi: 10.1186/ar2016).Karsdal, M.A., Madsen, S.H., Christiansen, C., Henriksen, K., Fosang, A.J. & Sondergaard, B.C. (2008) Cartilage degradation is fully reversible in the presence of aggrecanase but not matrix metalloproteinase activity. Arthritis Res. Ther.10, R63.