Activation of latent TGF-β following transfection of Zf9.

BAEC cultures grown on 35-mm dishes were transfected with 1 μg of pCIneo or Zf9-pCIneo as described above. After a 36-hour incubation, medium was changed to serum-free αMEM containing 0.1% BSA, and cells were further incubated for 12 hours in the absence and presence of 50 μg/mL aprotinin (Apr). The concentration of active (panel A) and total (panel B) TGF-β in each conditioned medium was determined by the bioassays as described in “Materials and Methods.” Each value represents the average ± SD from triplicate determinations. Each experiment was repeated 3 times with similar results in all, and representative results are shown. Sample 1, pCIneo; sample 2, pCIneo with inclusion of aprotinin; sample 3,Zf9-pCIneo; sample 4, Zf9-pCIneo with inclusion of aprotinin. Points marked by an asterisk differ significantly (P < 0.05) from the control (sample 1).