Choosing the right chondrocyte cell line: Focus on nitric oxide.

Nitric oxide (NO) has been considered a catabolic factor that contributes to OA pathology by inducing chondrocytes apoptosis, matrix metalloproteinases synthesis, and pro-inflammatory cytokines expression. Thus, the research on NO regulation in chondrocytes represents a relevant field which needs to be explored in depth. However, to date, only the murine ATDC-5 cell line and primary chondrocytes are well-established cells to study NO production in cartilage tissues. The goal of this study is to determine whether two commonly used human chondrocytic cell lines: SW-1353 and T/C-28a2 cell lines are good models to examine lipopolysaccharide and/or pro-inflammatory cytokine-driven NO release and iNOS expression. To this aim, we carefully examined NO production and iNOS protein expression in human T/C-28a2 and SW-1353 chondrocytes stimulated with LPS and interleukin (IL)-1 alone or in combination. We also use ATDC-5 cells as a positive control for NO production. NO accumulation has been determined by colorimetric Griess reaction, whereas NOS type II expression was determined by Western Blot analysis. Our results clearly demonstrated that neither human T/C-28a2 nor SW-1353 chondrocytes showed a detectable increase in NO production or iNOS expression after bacterial endotoxin or cytokines challenge with IL-1. Our study demonstrated that T/C-28a2 and SW-1353 human cell lines are not suitable for studying NO release and iNOS expression confirming that ATDC5 and human primary cultured chondrocytes are the best in vitro cell system to study the actions derived from this mediator.