The development of human fetal dorsal root ganglia in vitro: the first 20 days.

Human fetal dorsal root ganglia aged from 8 to 12 weeks post-menstrual were grown in vitro for up to 20 days. Outgrowth of Schwann cells, axons and fibroblasts occurred after 4 h. By the 7th day in vitro Schwann cells enclosed bundles of axons and after 10 days some Schwann cells were seen to enclose individual axons. By the 20th day in vitro there was still a predominance of Schwann cells enclosing axonal bundles, but there were more individual axons ensheathed by three or four turns of Schwann cells. This arrangement mimics the early development in vivo of human dorsal root ganglia and provides the potential for an experimental system utilizing human nervous tissue rather than non-human animal models.