Survival, proliferation and morphological specialization of mouse Schwann cells in a serum-free, fully defined medium

Neonatal mouse dorsal root ganglionic (DRG) cell dissociates were cultured in a synthetic medium with horse serum or the serum-free supplement N1 (insulin, transferrin, progesterone, putrescine, selenium). Serum-supplemented cultures with added nerve growth factor (NGF) yielded neurons, small flat and spindle cells (Schwann) and large flat cells (fibroblastic elements). However, in serum-free, N1-supplemented medium plus exogenous NGF, neurons and Schwann cells predominated, with very few large flat cells. In the N1 medium most Schwann cells assumed a typical spindle shape and were associated with neuritic processes when neurons were present. Upon addition of serum, virtually all of the Schwann cells appeared to abandon physical contact with the neurites and develop a more flattened morphology. In N1 medium without NGF (no neurites), most Schwann cells still assumed a spindle shape and formed characteristic chain-like associations. Autoradiographic techniques, as well as numerical analyses, demonstrated that in N1 medium Schwann cells were able to proliferate when associated with neurites but only slightly so in their absence. These Schwann cells showed a marked increase in proliferation when serum was added regardless of the presence or absence of neurites. The above observations may provide a basis for the preparation of purified Schwann cells, alone or in combination with their neurons.