Axolemma is a mitogen for human Schwann cells.

The mechanisms responsible for the induction of Schwann cell proliferation in peripheral nerves undergoing wallerian degeneration and segmental demyelination are not understood. To determine whether contact with axolemma stimulates mitosis of human Schwann cells, cultured Schwann cells from spinal roots obtained postmortem and from sural nerve biopsy specimens were incubated with axolemmal fractions prepared from human spinal cord or from adult rat central nervous system. Schwann cell proliferation was estimated by autoradiographic assay of tritiated thymidine incorporation. Schwann cell labeling indices after exposure to human or rat axolemmal fractions ranged from 26.7 to 59.9%; labeling indices of Schwann cells cultured without axolemmal fraction were 9.8 to 22.4%. The stimulation index, or ratio of Schwann cell labeling index with axolemmal fraction to that without axolemmal fraction, ranged from 1.97 to 3.40. This study demonstrates that both human and rat axolemma are capable of stimulating human Schwann cell replication in vitro.