Faculty Bibliography

Neurofibromatosis is a disorder which predominantly involves cellular elements of peripheral neural sheaths. Little is known about the regulation of differentiation and proliferation of cells comprising neurofibromas. Because nerve growth factor-like activity may be present in neurofibromas and the cells comprising neurofibromas are neural crest derivatives, we have investigated whether nerve growth factor (NGF) receptors are present on cells from dissociated dermal neurofibromas. Using 125I-NGF to measure binding to cultured cells in suspension and for autoradiography, we identified a population of cells having characteristics of Schwann cells which exhibited saturable 125I-NGF binding. This binding is characteristic of the 'fast' (low affinity) NGF receptor, having a Kd of approximately 1 nM and a Bmax of at least 120 fmol/10(6) cells. Less than 20% of the bound 125I-NGF (5 ng/ml) is not displaced when transferred to 0 degrees C by an excess of unlabeled NGF (10 micrograms/ml) and is therefore bound to either 'slow' (high affinity) sites or is rapidly internalized. NGF receptors with characteristics of fast sites have recently been reported on Schwann-like cells from chick dorsal root ganglia [Zimmerman, A., and Sutter, A. Beta nerve growth factor (beta NGF) receptors on glial cells. Cell-cell interaction between neurones and Schwann cells in culture of chick sensory ganglia. EMBO J., 2: 879-885, 1983]. The identification of NGF receptors on both fetal chick dorsal root ganglia and neurofibroma Schwann-like cells suggests that NGF may have a role in the regulation of Schwann cell function in both normal development and in neurofibromatosis

Primary cultures prepared from dermal and plexiform neurofibromas contain Schwann-like cells and fibroblast-like cells. SLC are elongated and bipolar or multipolar. By indirect immunofluorescence light microscopy, living SLC bind antibodies against laminin and against nerve growth factor receptor to their surface, but not antibodies against fibronectin. In these respects, cultured SLC are indistinguishable from cultured human adult Schwann cells. FLC are flat and pleomorphic. By indirect immunofluorescence light microscopy, living FLC bind antibodies against fibronectin but not against laminin or NGFR. In these respects, cultured FLC are indistinguishable from cultured human adult endoneurial fibroblasts. Considerable purification of viable SLC from SLC/FLC mixed cultures can be achieved by flow cytofluorometry using a monoclonal anti-NGFR antibody. Tritiated thymidine radioautography indicated that mitosis of SLC in mixed SLC/FLC cultures prepared from dermal neurofibromas is infrequent in MEM with 10% calf serum, more frequent in RPMI 1640 medium with 15% fetal calf serum. Central nervous system axolemmal fragments (rat or human) elicited a greater than 10-fold SLC proliferative response in mixed SLC/FLC cultures from three of seven dermal neurofibromas (from six patients with neurofibromatosis), but had no effect on SLC mitosis in cultures from the other four dermal neurofibromas. SLC mitosis was inhibited by concentrations of cyclic adenosine 3',5'-monophosphate analogues known to stimulate proliferation of normal rat Schwann cells. Glial growth factor partially purified from bovine pituitaries stimulated SLC mitosis both in SLC/FLC mixed cultures and in cultures of purified SLC. The studies we have described indicate that neurofibroma SLC can be cultured, unequivocally identified in culture by morphological and immunohistological criteria, purified, and stimulated to proliferate by several Schwann cell mitogens. Further quantitative comparisons of the baseline and mitogen-stimulated rates of proliferation of SLC and age-matched control human Schwann cells are needed, however, to determine which of the two alternate pathogenetic mechanisms for formation of neurofibromas mentioned in the introduction is correct

NF is a relatively common genetic disorder which predisposes to a variety of clinical manifestations involving multiple body systems. NF poses important questions to researchers involved with developmental neurobiology, nerve regeneration and growth, the mechanism of malignant degeneration, and the use of molecular techniques to identify genetic disorders. It is hoped that this conference will bring together researchers who have developed new techniques in these areas and will encourage them to apply these techniques to the problem of NF