Biochemical Analysis of the Proteins Secreted by Schwann Cells and Schwann Cell-Derived Neurotrophic Substances

The dissociated Schwann cells (SCs) taken from the adult rat sciatic nerve undergoing Wallerian degeneration were cultured in serum-free medium. The SCs serum-free conditioned medium (SC-SF-CM) was collected, ultrafiltrated and concentrated. The proteins secreted by SCs in SC-SF-CM ultrafiltrated-concentrated solution were analyzed by SDS-PAGE. It was found that there were 14 protein bands, which molecular weight were from more than 94 KDa to less than 43 KDa, with their main band at 65 KDa. By immunoblotting (Western Blot) for anti-2.5S NGF antibody, NGF was identified to exist in the proteins secreted by SCs. SC-SF-CM ultrafiltrated-concentrated solution was also separated by Disc-PAGE at 4°C, then electroluted, concentrated and collected. By biological activity examination for motor neuro-trophic substances, one protein zone (B+) of these was identified to have motor NTF activity, which contain five protein bands from 65 KDa to 34 KDa.