Novel neurotrophic factor secreted by amniotic epithelial cells.

By virtue of expressions of glial and neural surface markers and capability of neurotransmitter metabolism, amniotic epithelial cells are considered as candidate cell type for transplantation strategies to treat neurological disorders. Previously, we have reported neurotrophism exhibited by human amniotic epithelial cells when transplanted after spinal cord injury in bonnet monkeys. Amniotic epithelial cells were believed to secrete an "Epidermal Growth Factor (EGF)-like" factor and exact identification was not made. At this juncture, through the present study it was found that, chicken neural retinal cells when grown alone failed to survive and contrarily when either co-cultured with chicken amniotic epithelial cells/cultured in amniotic epithelial cell conditioned medium not only survived but also showed extensive differentiation. Fibroblast Growth Factor-2 (FGF-2) plays a critical role in retinal development especially in chicken neural retinal development. However, immunoassay using western blot did not revealed the presence of any already known isoforms of FGF-2 in the medium. It is interesting to note that while factor secreted by amniotic epithelial cells resembles EGF and/or FGF-2 in its biological action, known isoforms of them were not detected. Considering the biological closeness between EGF and FGF-2, results indicate the possibility of a novel isoform of these growth factors secreted by amniotic epithelial cells. Further studies will establish the nature of this novel factor which will enhance the application of this interesting cell type for neural transplantations.