PC12 cells overexpressing tissue plasminogen activator regenerate neurites to a greater extent and migrate faster than control cells in complex extracellular matrix.

PC12 cells were stably transfected with expression vectors containing rat tissue plasminogen activator (tPA) under control of either a cytomegalovirus or rous sarcoma virus promoter. Cell lines were characterized using protease assays, ELISAs, immunoblots, northern blots, and Southern blots. Control PC12 cells or cells containing vectors alone released about 1 pg tPA/cell/24 h, whereas cells stably transfected with a tPA cDNA released 2-5 pg tPA/cell/24 h. A strong correlation existed between the amount of tPA released and the ability of cells to degrade extracellular matrix. Experiments with protease inhibitors and antibodies against tPA and plasminogen indicated that degradation of matrix involved tPA-generated plasmin and that the amount of matrix degraded was dependent on the amount of tPA released. Cells expressing high levels of tPA migrated on a three-dimensional matrix about twice as fast as control cells and regenerated neurites within three-dimensional gels of Matrigel to a greater extent than control cells. Antibodies that inhibited tPA and plasminogen decreased migration and neurite regeneration, indicating that tPA was involved in both events, PC12 cells overexpressing tPA should provide a useful model system for investigating neural functions of tPA including its role in migration and regeneration.