Since Sema3A is highly expressed in the cornea upon injury and does not inhibit the NGF induced growth on adult PNS neurons, we evaluated the effects of adding Sema3A alone to cultured neurons and compared to the NGF induced growth. (A) As described above DRG neurons responded well to NGF treatment. Surprisingly, Sema3A by itself is also a potent inducer of neuronal growth and similar neurite extension was observed at doses of 20 ng/ml Sema3A or higher. (B) Similarly, Sema3A is also a potent inducer of neuronal growth on TG neurons, and the number of TG neurons showing neurite growth was similar to that of neurons treated with NGF alone when incubated with Sema3A at 10 ng/ml or higher. (C) Sema3A from different sources, recombinant human or mouse, induced equally strong neuronal growth of TG neurons at equal concentrations. Values represent mean ± SD, experiments were performed in triplicate, each dish had an average of 200 neurons for DRG and 60 neurons for TG, and all neurons in a dish were evaluated. Neurite growth was evaluated at day 4 for DRG neurons and at day 3 for TG neurons. * indicate p<0.05 vs NGF. (R&D = from R&D Systems, m = murine, h = human, SB = Sino Biological Inc.).