Selective culture of mitotically active human Schwann cells from adult sural nerves

The role of the Schwann cell in trophic support and regeneration

Schwann cells show remarkable versatility in undertaking a broad repertoire of functions. Ensheathment and myelination are specifically regulated by contact with axons, and the Schwann cell is centrally involved in extracellular matrix production in the peripheral nerve trunk. Additional Schwann cell functions include the promotion of both peripheral and central nervous system regeneration, provision of a versatile source of trophic factors, the capacity to remyelinate central nervous system axons, and the restoration of electrophysiological conduction. Since it is now possible to isolate Schwann cells both from neonatal and adult human peripheral nerve, their ability to promote regenerative efforts by many central neurons suggests a role for Schwann cell autografts in influencing central nervous system repair.

Characterization of Schwann cells from normal nerves and from neurofibromas in the bicolour damselfish

Schwann cells are an important component of neurofibromas, one of the primary lesions encountered in neurofibromatosis type 1 in man. A central question in studies of neurofibromatosis type 1 has been whether the Schwann cells present in these tumours are intrinsically abnormal or exhibit abnormal phenotypes in response to stimuli from other cell types in these tumours. Damselfish neurofibromatosis is a naturally occurring disease in a species of marine fish, the bicolour damselfish, that is being developed as an animal model of neurofibromatosis type 1. Affected fish exhibit multiple neurofibromas and neurofibrosarcomas (malignant schwannomas). The present study compares the morphology, antigen expression and proliferative capacity in vitro of Schwann cells derived from peripheral nerves of normal, healthy fish with cells isolated from both spontaneously occurring and experimentally induced neurofibromas. Schwann cells from normal nerves expressed S100 antigens but not fibronectin or glial fibrillary acidic protein antigens and were similar in morphology and proliferative capacity to Schwann cells isolated from mammalian peripheral nerves. Tumour-derived cultures contained variable proportions (27-79%) of S100-positive cells that were identified as Schwann cells based on this feature. These tumour-derived Schwann cells exhibited a different morphology than normal Schwann cells, usually exhibited an increased reactivity to anti-S100 antibodies and were able to proliferate in vitro without added mitogens. Repeated subculturing of tumour-derived cultures led to the production of six cell lines all of which were composed exclusively of Schwann cells as indicated by S100 expression. These findings show that Schwann cells are an important component of tumours in Damselfish neurofibromatosis and that these cells are morphologically and physiologically altered in this disease. Observations of cell lines also suggest that tumour-derived Schwann cells are intrinsically abnormal and that this phenotype is not a result of stimuli from other cell types in the tumours.

Peripheral myelin protein-22 expression in Charcot-Marie-Tooth disease type 1a sural nerve biopsies

Peripheral myelin protein-22 (PMP22) is expressed in myelinating Schwann cells and shows significant homology to murine growth arrest-specific gene gas3. Charcot-Marie-Tooth disease type 1a (CMT1a) is a common hereditary demyelinating neuropathy. Recently it was demonstrated that the gene for PMP22 is duplicated in CMT1a patients. A gene dosage mechanism has been postulated to cause CMT1a. According to this hypothesis, the increase in copy number of PMP22 gene would lead to an elevated expression of PMP22 and thereby cause the demyelinating phenotype of CMT1a. In the present communication we analyzed PMP22 mRNA and protein expression in sural nerve biopsies from CMT1a patients and normal controls. We show that PMP22 mRNA expression in CMT1a is not uniform. We found both elevated as well as normal PMP22 mRNA levels in patients. Interestingly, the highest PMP22 mRNA level was found in the least affected patient. In contrast to the mRNA levels, PMP22 was clearly reduced in all CMT1a patients as shown by immunohistochemistry. Thus the CMT1a phenotype may not be strictly correlated with increased PMP22 mRNA and protein expression. Possible roles of PMP22 in the pathogenesis of CMT1a are discussed.

Role for the stem cell factor/KIT complex in Schwann cell neoplasia and mast cell proliferation associated with neurofibromatosis

Schwann cells are the primary cell type in the disfiguring lesions associated with neurofibromatosis type 1 (NF-1). These lesions also contain abnormally high numbers of mast cells, a cell type which develops in response to stem cell factor. We report here that neonatal and adult rat and human Schwann cells, as well as a transfected rat Schwann cell line and a human Schwannoma line derived from an NF-1 patient, all produced stem cell factor mRNA and protein. In coculture experiments, surface expression of stem cell factor by neonatal rat Schwann cells was profoundly downregulated by contact with dorsal root ganglion neurites. The receptor for stem cell factor, KIT, was not expressed in normal Schwann cells but was expressed in the human Schwannoma line, suggesting that aberrant KIT expression may form an autocrine loop in certain Schwann cell neoplasias.

Expanding roles for the Schwann cell: ensheathment, myelination, trophism and regeneration

Schwann cells show remarkable versatility in undertaking a broad repertoire of functions. It is now clear that the well known functions of ensheathment and myelination are specifically regulated by contact with axons, that the Schwann cell is centrally involved in extracellular matrix production in the peripheral nerve trunk, and that the Schwann cell plays a critical role in promoting axonal regeneration in the peripheral nervous system. The Schwann cell's ability to promote regenerative efforts in many central neurons has led to an increasing interest in using Schwann cell autografts for central nervous system repair.