A new method for the rapid and long term growth of human neural precursor cells.

A reliable source of human neural tissue would be of immense practical value to both neuroscientists and clinical neural transplantation trials. In this study, human precursor cells were isolated from the developing human cortex and, in the presence of both epidermal and fibroblast growth factor-2, grew in culture as sphere shaped clusters. Using traditional passaging techniques and culture mediums the rate of growth was extremely slow, and only a 12-fold expansion in total cell number could be achieved. However, when intact spheres were sectioned into quarters, rather than mechanically dissociated, cell cell contacts were maintained and cellular trauma minimised which permitted the rapid and continual growth of each individual quarter. Using this method we have achieved a 1.5 million-fold increase in precursor cell number over a period of less than 200 days. Upon differentiation by exposure to a substrate, cells migrated out from the spheres and formed a monolayer of astrocytes and neurons. No oligodendrocytes were found to develop from these human neural precursor cells at late passages when whole spheres were differentiated. This simple and novel culture method allows the rapid expansion of large numbers of non-transformed human neural precursor cells which may be of use in drug discovery, ex vivo gene therapy and clinical neural transplantation.