Overexpression of mutant COMP decreases the viability of chondrocytes. (a) Monolayer cells were transduced with different infectious titers of adenovirus, and viable cells were quantified 3 days later. Viable cells are indicated relative to untransduced control cultures. Filled circles, cultures expressing mutant COMP; open circles, cultures expressing wild-type COMP. The composite result of two independent experiments is shown, with each point representing nine measurements. Error bars indicate 1 SD; **P < 0.01 in the two-sided student t test. (b) The supernatants of cultures were analyzed for LDH activity 3 days after gene transfer with 200 MOI. Values were corrected for the background activity of the culture medium and related to the LDH activity of a total cell lysate obtained by sonication of an equivalent cell number. Measurements were performed in triplicate, error bars indicate 1 SD. NS, no significant difference; *P < 0.05 in the two-sided student t test. Mu, cultures overexpressing mutant COMP; Wt, cultures overexpressing wild-type COMP; C, untransduced control cultures.