Transforming growth factor-beta and gamma-interferon have dual effects on growth of peripheral glia

The influence of transforming growth factor-beta (TGF-beta) and gamma-interferon on DNA synthesis in Schwann cells and enteric glia in culture has been studied. TGF-beta stimulated the DNA synthesis of short-term (less than 2 weeks in culture) Schwann cells, whereas gamma-interferon was ineffective. The stimulatory effect of TGF-beta was additive to the stimulation of DNA synthesis due to axonal membrane fragments. In contrast to their effect on short-term Schwann cells, both TGF-beta and gamma-interferon inhibited DNA synthesis in enteric glial cells and in long-term (over 3 months in culture) Schwann cells. When short-term Schwann cells were stimulated to divide by axolemma or glial growth factor, gamma-interferon did not inhibit this enhanced DNA synthesis although it suppressed DNA synthesis induced by cAMP analogues. These results raise the possibility that TGF-beta and gamma-interferon might have a role in controlling glial proliferation during development and/or regeneration of the peripheral nervous system.