Differential effect of molecular size HA in mouse chondrocytes stimulated with PMA

Background: Hyaluronan (HA) fragments elicit the expression of inflammatory mediators through a mechanism involving the CD44 receptor. This study investigated the effects of HA at different molecular weights on PMA-induced inflammation in mouse chondrocytes. Methods: mRNA and related protein levels were measured for CD44, PKC delta, PKC epsilon, TNF-alpha, IL-1 beta, MMP-13, and NOS in chondrocytes, untreated or PMA treated. with and without the addition of HA. The level of NF-kB activation was also assayed. Results: CD44, PKC delta. and PKC epsilon mRNA expression resulted higher than controls in chondrocytes treated with PMA. PMA also induced NF-kB up-regulation and increased TNF-alpha, IL-1 beta, MMP-13, and NOS expression. HA treatment produced different effects: low MW HA up-regulated CD44 expression, increased PKC delta and PKC epsilon levels, and enhanced inflammation in untreated chondrocytes; while in PMA-treated cells it increased CD44. PKC delta, PKC epsilon, NF-kB, TNF-alpha, IL-1 beta, MMP-13, and iNOS expression and enhanced the effects of PMA; medium MW HA did not exert action: high MW HA had no effect on untreated chondrocytes; however, it reduced PKC delta, PKC epsilon. NF-kB activation and inflammation in PMA-stimulated cells. Specific CD44 blocking antibody was utilised to confirm CD44 as the target of HA modulation. General Significance: These data suggest that HA via CD44 may modulate inflammation via its different molecular mass. (C) 2009 Elsevier B.V. All rights reserved.