Fig. 4. PAI1 stimulates fibronectin-matrix assembly in osteosarcoma and osteoblast cells. (A) Cells (HOS, Saos-2, hFOB) were pre-incubated for 20 minutes with PAI1 (20 nM), or for 45 minutes with the cyclic peptide RGDfV (20 µM) or its inactive analog RADfV (20 µM); cells were then incubated with [¹²⁵I]fibronectin (Fn) for 6 hours. Cell layers were extracted in 1% DOC, and [¹²⁵I]fibronectin that had been incorporated into the detergent-insoluble matrix was recovered by centrifugation and measured by -scintillation. This experiment is representative of three separate experiments. Data are the mean ± s.e. of two different experiments performed in duplicate. ^*P<0.05 (n=4), significantly different than control cells (t-test). (B) Same as A only under conditions of uPAR stimulation with 50 µM P25. This experiment is representative of three separate experiments. Data are the mean ± s.e. of two experiments performed in duplicate. ^*P<0.05 (n=4), significantly different than P25-treated cells (t-test).