Figure 7.

Effect of purified human lubricin on the in vitro growth of Prg4^–/– synoviocytes. (A) Growth curves of adherent Prg4^–/– synoviocytes that were plated overnight in serum-containing media and then switched to growth media (red) or growth media with 60 μg/ml of purified lubricin (blue). Total cell number (± 1 SEM) was determined 48 hours after addition of growth media or growth media with 60 μg/ml of purified lubricin and every 24 hours thereafter. No significant difference in growth was observed between the 2 groups. (B) Growth curves of adherent Prg4^–/– synoviocytes that were plated overnight in serum-free media and then switched to growth media (red) or growth media with 60 μg/ml of purified lubricin (blue). Total cell number (± 1 SE) was determined 48 hours after addition of growth media or growth media with 60 μg/ml of purified lubricin and every 24 hours thereafter. When plates were not pre-exposed to serum-containing media, Prg4^–/– synoviocyte growth was significantly inhibited by growth media supplemented with 60 μg/ml of purified lubricin. (C–E) Prg4^–/– synoviocyte growth on tissue culture plates that were pretreated with control media, lubricin media, or 60 μg/ml of purified lubricin, respectively. Portions of tissue culture plates (to the right of the blue line) were incubated with control media, lubricin media, or 60 μg/ml of purified lubricin overnight at 37–C. After washing off the media with several changes of PBS, we added Prg4^–/– synoviocytes to the culture dishes and allowed them to proliferate in growth media for 7 days. Note that few synoviocytes were able to adhere to the lubricin-media or purified lubricin treated plates (magnification, ×100). Also note that synoviocytes on the untreated portion of the plate did not proliferate onto the lubricin-treated portion.