Effect of dimethylsulfoxide on articular cartilage proteoglycan synthesis and degradation, chondrocyte viability, and matrix water content

Objective—To determine the effects of dimethylsulfoxide (DMSO) exposure on cartilage proteoglycan (PG) synthesis, PG degradation, chondrocyte viability, and matrix water content. Study Design—Using a cartilage explant culture system, PG synthesis, PG degradation, matrix water content, and chondrocyte viablity were determined for cartilage exposed to DMSO daily for selected periods of time. Animals or Sample Population—Juvenile bovine (calf) carpometacarpal joint cartilage ex‐plants. Methods—PG synthesis: Explants (n = 30/group) were separated into 10 groups based on the time of daily exposure to 10% DMSO. Exposure time was repeated daily for 3 days. The control group was incubated in basal medium alone for 3 days, with daily medium changes. Once all DMSO exposure times were complete for the third day, PG synthesis was determined by analysis of incorporation of radiolabelled sulfate. Cell viability: Explants (n = 3/group) were subjected to an identical DMSO exposure protocol, and examined histologically. The percentage of viable cells/high power field (hpf) was calculated for each group. PG degradation: Explants (n = 21/group) were preincubated with radiolabelled sulfate, then subjected to a similar DMSO exposure protocol. The medium was collected from all explants daily and assayed for PG content. After 3 days, the explants were digested and total labelled PG content determined. Percent of total explant labelled PG content released into the medium daily was determined for each group. Water content: Explants (n = 21/group) were separated into three treatment groups, one of which had no treatments performed, whereas the other two groups were incubated in basal medium for 72 hours, one with, and one without, 10% DMSO. Wet and dry weights were determined, and percent water calculated, for all three groups. Separate 1‐way ANOVA were performed, with appropriate post hoc tests (p < .05). Results—PG synthesis was significantly lower than control for all time periods of DMSO exposure except for 1 and 3 hours, and decreased in a time‐dependent manner after the 1‐hour exposure time. The mean percentage of viable cells/hpf was significantly lower than control for the 1‐, 3‐, 9‐, 12‐, and 24‐hour treatment groups. There was no significant difference in PG degradation for any group compared with control for the first 2 days of incubation. All groups except the 24‐hour group had a significantly higher degradation compared with control for the third day of incubation. Car