Library

Notes: Summary Transplantation of oligodendrocytes or Schwann cells into the spinal cord of the newborn myelin-deficient (md) rat, an X-linked myelin mutant, was carried out and the extent of myelination of CNS axons studied. Dissociated glial cell suspensions, prepared from the spinal cords of female litter-mates, were injected into the lumbar spinal cord of 15 md rats and 5 normal litter-mates. In eight of the md rats examined 12 to 21 days post-transplantation patches of myelin produced by the transplanted oligodendrocytes were found in the dorsal or ventral columns. In two rats, small patches of myelination were found in more than one site. The myelin in these patches was positive on immunocytochemical staining for proteolipid protein. These observations were interpreted as evidence of the origin of this myelin from donor oligodendrocytes, as the md rat has an abnormality in synthesis of this protein. In addition, this myelin differed in its ultrastructure from host myelin, having a normal intraperiod line. Injection of cultured Schwann cells also resulted in extensive myelination of axons in the dorsal columns by these cells.

Notes: Summary We have recently reported the immortalization of primary Schwann cells isolated from sciatic nerves of normal neonatal rats. The cells were maintained under continuous mitogenic stimulation with glial growth factor and forskolin, achieving immortalization after 12 to 15 weeks without the use of viral infection, oncogene transformation or chemical carcinogens. The immortalized cells (1.17 cells) initially retain the capability to recognize and attach to peripheral neurons in culture as well as the ability to myelinate those neurons. The functional capacity of the cells gradually diminishes in culture, such that late passage cells can ensheath neurons but cannot form a myelin sheath. Both normal and immortalized cells secrete comparable amounts of autocrine growth factor activity in culture that can be regulated by extracellular matrix proteins. The difference between quiescent and immortalized Schwann cells seems to lie not in the production of growth factor but rather in the relative ability to respond to the factor(s). To test the potential of the immortalized Schwann cells for the ability to form tumoursin vivo, we injected equal numbers of primary or immortalized Schwann cells into the sciatic nerve of adult syngenic rats and allowed them to incubate there for 6 to 13 weeks, whereupon the injected nerves were inspected for tumour formation. In every case (N=3) the primary cells had no effect whereas every injection of immortalized cells (N=5) resulted in a solid cellular mass surrounding the injected nerve. The tumours were encapsulated masses of actively dividing Schwann-like cells that surrounded but did not invade the nerve fascicle. The cells in the tumour expressed the Schwann cell surface antigens laminin, 217C (Ran 1) and S-100 like the immortalized cells that had been injected. Within the tumour the cells were embedded in a collagenous matrix, were surrounded by basal lamina and occasionally attained an orientation comparable to the Antoni A or Antoni B patterns typical of human schwannomas. These data suggest that rat Schwann cells immortalizedin vitro by chronic mitogenic stimulation can provide an experimental animal model for human schwannomas and neurofibromas.