Objective: The objective of this study was to compare the effects of hyperosmolar sodium (Na+), lithium (Li+) and potassium (K+) on catabolic and inflammatory osteoarthritis (OA) markers and sulfated glycosaminoglycan (sGAG) loss in TNF-α-stimulated cartilage explants.
Methods: Explants from bovine stifle joints were stimulated with TNF-α for 1 day to induce cartilage degradation followed by supplementation with 50 mM potassium chloride (KCl), 50 mM lithium chloride (LiCl), 50 mM sodium chloride (NaCl), or 100 nM dexamethasone for an additional 6 days. We assessed the effect of TNF-α stimulation and hyperosmolar ionic treatment on sGAG loss and expression of OA-associated proteins: ADAMTS-5, COX-2, MMP-1, MMP-13, and VEGF.
Results: TNF-α treatment increased sGAG loss (P < 0.001) and expression of COX-2 (P = 0.018), MMP-13 (P < 0.001), and VEGF (P = 0.017) relative to unstimulated controls. Relative to activated controls, LiCl and dexamethasone treatment attenuated sGAG loss (P = 0.008 and P = 0.042, respectively) and expression of MMP-13 (P = 0.005 and P = 0.036, respectively). In contrast, KCl treatment exacerbated sGAG loss (P = 0.032) and MMP-1 protein expression (P = 0.010). NaCl treatment, however, did not alter sGAG loss or expression of OA-related proteins. Comparing LiCl and KCl treatment shows a potent reduction (P < 0.05) in catabolic and inflammatory mediators following LiCl treatment.
Conclusion: These results suggest that these ionic species elicit varying responses in TNF-α-stimulated explants. Cumulatively, these findings support additional studies of hyperosmolar ionic solutions for potential development of novel intraarticular injections targeting OA.
Keywords: cartilage explant; hyperosmolar solution; inflammation; lithium; osteoarthritis; potassium; sodium.