Cultures enriched in Schwann-like cells from dissociated nerve segments of the adult cat

Dispase rapidly and effectively purifies Schwann cells from newborn mice and adult rats

In the present study, Schwann cells were isolated from the sciatic nerve of neonatal mice and purified using dispase and collagenase. Results showed that after the first round of purification with dispase, most of the Schwann cells appeared round in shape and floated in culture solution after 15 minutes. In addition, cell yield and cell purity were higher when compared to the collagenase group. After the second round of purification, the final cell yield for the dispase group was higher than that for the collagenase group, but no significant difference was found in cell purity. Moreover, similar results in cell quantity and purity were observed in adult Sprague-Dawley rats. These findings indicate that purification with dispase can result in the rapid isolation of Schwann cells with a high yield and purity.

Repair of a myelin lesion by Schwann cells transplanted in the adult mouse spinal cord

In multiple sclerosis and experimental demyelination, oligodendrocytes and Schwann cells are able to repair myelin lesions of the central nervous system. However, spontaneous myelin repair is often insufficient. Several approaches to enhance remyelination have been considered and transplantation of myelin-forming cells has been proposed as one of them. In this paper, we present results which confirm the ability of transplanted Schwann cells to remyelinate an induced demyelinated lesion of the spinal cord. Schwann cells were either purified Schwann cells isolated from 1-2-day-old rat sciatic nerves, or immortalized Schwann cells (MSC80) arising from a purified culture of 7-day-old mouse sciatic nerves. They were transplanted into or at a distance from a lysolecithin-induced lesion of the Shiverer spinal cord. Labelling of the Schwann cells with the fluorochrome Hoechst 33342 enabled us to trace them after transplantation in their host and evaluate their ability to reach and to repair the demyelinated lesion. Using the Hoechst-Shiverer model, we show that when transplanted in the lesion, cultured Schwann cells, even immortalized, are able to remyelinate such a lesion efficiently. In addition, when transplanted at a distance from the lesion, they are able to reach and repair the lesion in time frames which allow them to compete actively with host oligodendrocytes.

Establishment and characterization of a mouse Schwann cell line which produces myelin in vivo

A Schwann cell line (MSC 80) was established from purified mouse Schwann cell cultures using large doses of serum. MSC 80 cell line is an aneuploid cell line which has a doubling time of 17 hr and has been maintained through more than 110 passages. Most of MSC 80 cells are of bipolar or stellate (3-5 processes) shape. A few others are irregular in shape, gigantic, and multinucleated. All MSC 80 cells express antigens of myelin-forming Schwann cells such as S-100, 224/58, laminin, and other glycoproteins of the extracellular matrix. However, they also express the non-myelin-forming Schwann cell antigen GFAP. By time-lapse cinematography, MSC 80 cells exhibit the Schwann cell characteristic rhythmical undulations. When induced to form aggregates in agar, they form intercellular junctions and basement membrane-like structures. In addition, after transplantation in or at a distance from a lysolecithin induced lesion, MSC 80 cells form myelin around the host demyelinated axons. MSC 80 cells thus express, when isolated in vitro, some of the normal myelin-forming Schwann cell phenotype. In addition, they present the major advantage of forming myelin when associated with axons in vivo.

Isolation and characterization of neonatal Schwann cells from cryopreserved rat sciatic nerves

Much of our knowledge about the development and maintenance of the peripheral nervous system has been learned through studying the interaction of neurons, or their isolated membranes, with Schwann cells (SC), in tissue culture. Numerous approaches have been employed to obtain an adequate quantity of SC, but all have been limited by either the uncertainty of obtaining a sufficient amount of starting material, the time and expertise required to isolate the SC, or by the limited number of SC that can be generated. We have developed a procedure to isolate SC from cryopreserved sciatic nerves. This procedure allows for sciatic nerves to be pooled until adequate numbers of nerves are obtained, yet still produces cells that retain the functional abilities of SC isolated from fresh nerves. Sciatic nerves were isolated from 2 day old rat pups, placed in either DME media and used fresh or placed in a freezing solution containing DME media (25%), DMSO (25%), fetal calf serum (50%), frozen at -70 degrees C and stored in liquid nitrogen. The frozen nerves were rapidly thawed to 37 degrees C and single cells were prepared from both fresh and frozen nerves using enzymatic and mechanical disruption as previously described (Brockes et al., Brain Res 165: 105-118, 1979). Comparable cell yields were obtained for SC isolated from both frozen and fresh nerves. Immunohistochemical staining of both fresh and frozen SC produced similar staining patterns with antibodies to GFAP, laminin, CNPase, S100, MBP, and P0 protein. Addition of axolemmal enriched membrane fractions to both the frozen and fresh SC gave a similar dose response curve of 3H-thymidine incorporation, with SC from frozen sciatic nerves responding even better than fresh sciatic nerves at higher doses (50 micrograms and 100 micrograms of protein/ml). As demonstrated by the cell yield, immunohistochemical staining and responses to axolemmal mitogens, this procedure produces SC from frozen sciatic nerves with similar characteristics to those isolated from fresh nerves. This procedure will allow the production and utilization of a large number of SC, which will be critical in further studies on the development and maintenance of the peripheral nervous system.

Age-related changes in attachment and proliferation of mouse Schwann cells in vitro

Schwann cells can be cultured readily from the peripheral nerves of the neonatal animal but not from the adult. To correlate the physiological properties of Schwann cells relevant to such a difference, we examined age-related changes in attachment and proliferation of mouse Schwann cells in vitro. The capacity of Schwann cells to attach to polylysine-coated coverslips at 1 day in vitro declined rapidly between 3 and 30 days of age, followed by a more gradual decrease with age. Attachment of Schwann cells from younger mice (but not older mice) was enhanced by precoating coverslips with laminin or to a lesser degree with fibronectin, suggesting an age-dependent decrease in receptors for these substrates. Indeed, the staining for fibronectin receptor could be demonstrated in vivo, and was more intense and diffuse in neonatal sciatic nerves. In vitro, although staining of Schwann cells and fibroblasts was clear, there was no age-related difference for the intensity or distribution of the staining. Proliferation, as assessed by thymidine incorporation at 1 day in vitro, was high when Schwann cells were isolated from younger mice but declined as a function of the age of mice from which cells were prepared. Removal of axonal and myelin debris from cultures 3 h after plating resulted in a reduction of thymidine uptake by Schwann cells from 30-day-old mice, but much less from 10-day-old mice. Schwann cell growth was faster in the cells from younger mice than older ones, thus leading to early confluency and cell-contact inhibition in the former. In addition, evidence is presented that in medium supplemented with fetal bovine serum, thymidine uptake by Schwann cells from mice at 3-30 days of age was three times higher than that by Schwann cells from age-matched rats. These results indicate that the methodology usually used for purification of rat Schwann cells involving antimitotics is not suitable for highly proliferating mouse Schwann cells.

Adhesion and proliferation are enhanced in vitro in Schwann cells from nerve undergoing Wallerian degeneration

Proliferation of Schwann cells during nerve degeneration or regeneration is well documented in vivo. We investigated whether the proliferative response of Schwann cells to injury is retained in vitro. Using 5-month-old male C57BL mice, Schwann cells were isolated from sciatic nerves under 3 experimental conditions: (1) uninjured, (2) after permanent nerve-transection, or (3) after nerve-crush, which permits axonal regeneration. Schwann cells rarely attached to polylysine-coated coverslips when isolated from uninjured or 1 day posttransection/crush nerves. The number of adherent cells increased when Schwann cells were isolated 3 days after nerve-transection or -crush. When cells were isolated from transected nerves, cell adhesion reached a peak 2 weeks after the injury and then declined. Maximal attachment of Schwann cells occurred when the cells were isolated 2-4 weeks after nerve-crush. The percentage of Schwann cells with spreading processes corresponded closely with the number of thymidine-labeled cells at 1 day in vitro. The in vitro capacity of cells to spread and incorporate thymidine reached maximal levels at 5 days posttransection/crush. Capacity of cells to spread and incorporate thymidine subsequently decreased with time following transection. However, a biphasic elevation in cell spreading and thymidine incorporation was observed in Schwann cells isolated from crushed nerves. Maximal growth of Schwann cells in vitro occurred at 1-2 weeks posttransection and at 1-4 weeks postcrush. Adhesion and spreading of Schwann cells were promoted by coating coverslips with laminin or fibronectin. Preincubation of Schwann cells with soluble laminin or fibronectin prevented the initial cell attachment induced by the corresponding protein. Our results suggest that Schwann cells from injured nerves possess binding sites for laminin and fibronectin, which are, in part, responsible for the enhanced adhesion of Schwann cells in vitro. This study provides a new method for preparation of Schwann cells from peripheral nerves of adult mice.

Biological activity of a new neuronal growth factor from injured peripheral nerve

In response to transection injury, the distal nerve segment produces a soluble neurite promoting factor (SN). In this study, the ability to support neuronal survival and differentiation have been studied. Embryonic rat dorsal root ganglion (DRG) neurons were plated out on collagen substrates and incubated in medium containing either SN or nerve growth factor (NGF). The number of surviving neurons was counted after 1, 2, 4, 7, and 15 days in vitro. After fixation and staining, the diameter of the surviving neurons was measured. During the period of observation, 60.8 +/- 5.8% of plated neurons survived in the presence of NGF and 90.5 +/- 12.9% survived with SN (P less than 0.05). The mean of median neuronal cell diameter was 28 +/- 2.7 microns with NGF and 34.2 +/- 3.7 microns with SN, (P less than 0.01). This increased diameter was due to enhanced survival of 30-50 microns diameter neurons. In parallel experiments, the degree of myelination of DRG neurons by Schwann cells was assessed morphometrically. In the presence of SN there was an 86% increased in myelination compared with NGF which indicates that not only is the survival of neurons increased but they are able to become fully differentiated in the presence of SN.

A simple method for the Schwann cell preparation from newborn rat sciatic nerves

We have developed a simple and relatively rapid method for obtaining a sufficient number of Schwann cells with a favorable purification ratio from newborn rat sciatic nerves. Perineurium-free nerves were torn into small fascicles of approximately 150-200 microns in diameter and explanted twice on type I collagen gel every 2 days of the culture period in order to reduce the number of contaminant fibroblasts. The last explanted tissues were fed with Dulbecco's modified Eagle medium supplemented with 10% fetal bovine serum and 100 micrograms/ml bovine pituitary extract for 10 days. More than 10 X 10(4) Schwann cells (greater than 95% purity) were obtained from newborn rat sciatic nerves.

Localization of dynorphin gene product-immunoreactivity in neurons from spinal cord and dorsal root ganglia

Using spinal cord and dorsal root ganglion cell cultures, we have studied the immuno-histochemical distribution of several peptide products of the dynorphin gene. With antibody directed toward the midregion of dynorphin A, peptide-immunoreactivity was found exclusively in the cell bodies of spinal cord neurons. Antibody directed toward the amino- or carboxy-terminus of dynorphin A revealed peptide-immunoreactivity in the neurites, as well as perikarya. Spinal cord neurons also expressed dynorphin B- and alpha-neo-endorphin-immunoreactivities in both cell bodies and neurites. Dorsal root ganglion neurons cultured from embryonic tissue expressed dynorphin A-(1-13)-, dynorphin A-(9-17)- and dynorphin B-immunoreactivities in their perikarya. Sensory neurons obtained from dissociated adult ganglia similarly expressed dynorphin-immunoreactivity immediately upon inoculation into culture. Embryonic and adult murine sensory ganglia from the sacral region more frequently expressed dynorphin than did cells obtained from other spinal levels. Expression of dynorphin-immunoreactivity by sensory neurons was not influenced by elevated levels of Nerve Growth Factor or spinal cord conditioned medium. These data indicate that intrinsic spinal cord neurons may modulate sensory and spinal function in rather subtle ways via the expression of several different opioid peptide products of the dynorphin gene, in addition to the opioid peptides produced by the proenkephalin A gene. Beyond this, the observation of dynorphin-related peptides in dorsal root ganglion neurons suggests that these opioid peptides may have a specialized role in primary afferent neurotransmission.

Reduced neuronotrophic activity of fibroblasts from individuals with dysautonomia in cultures of newborn mouse sensory ganglion cells

The neuronotrophic activity of human skin fibroblast cell lines from two normal individuals and 3 individuals with Familial Dysautonomia (FD) was compared in terms of their ability to support neuron survival and neurite regeneration in cultures of newborn mouse sensory neurons. Neuronotrophic activity was assayed by culturing dissociated sensory neurons from newborn mice: (1) on fibroblast 'cell beds' consisting of monolayer cultures of living fibroblasts, (2) with medium that had been conditioned by monolayer fibroblast cultures and (3) with extracts of the cultured fibroblasts. Neurite regeneration was compared by determining the percentage of neurons that had regenerated neurites after 24 or 48 h in culture. Neuron survival was determined by counts at 48 h, 7 days and 14 days after culture initiation. Neurite regeneration and neuron survival was found to be significantly less on FD cell beds or with FD-conditioned medium than in replicate cultures with normal fibroblasts or their conditioned medium. The reduced neuronotrophic activity of FD fibroblasts or conditioned medium was still observed in the presence of antibody sufficient to block the neuronotrophic effects of purified nerve growth factor (NGF). Thus, fibroblasts from individuals with FD exhibit reduced neuronotrophic activity for newborn mouse sensory neurons that appears to be due to factor(s) other than NGF.

The use of cultured autologous Schwann cells to remyelinate areas of persistent demyelination in the central nervous system

Areas of persistent demyelination were created in the dorsal columns of the cat spinal cord by injecting ethidium bromide into white matter which had previously been exposed to 40 Grays of X-irradiation. In the centre of such lesions demyelinated axons occurred in a glial-free area while axons next to normal tissue were separated by astrocyte processes. No remyelination occurs in such lesions (Blakemore 1984). Autologous Schwann cells and fibroblasts cultured from a peripheral nerve biopsy were injected into such lesions and the extent of Schwann cell remyelination examined. Only lesions injected with viable cells showed remyelination by Schwann cells; in no lesion were all the demyelinated axons remyelinated. Three forms of association of Schwann cell with axons were detected. In the centre of the lesions Schwann cells either remyelinated axons around or near to blood vessels, or lay next to demyelinated axons and did not form myelin. Schwann cell remyelination was also detected in the astrocyte-containing areas around the edges of some lesions. It was concluded that the extent of Schwann cell remyelination was influenced by the mode of entry of the cells into the lesion and by the architecture of the lesion. The presence or absence of stable extracellular matrix is believed to be the prime factor which influenced Schwann cell remyelination. The relevance of these observations to artificial repair of the lesions of multiple sclerosis is discussed.

Schwann cells cultured from adult rats contain a cytoskeletal protein related to astrocyte filaments

Cells that bound antibody to the astrocyte intermediate filament protein were cultured from adult rat sciatic nerve. The antigen was intracellular, finely filamentous, and formed perinuclear caps in response to colchicine, all properties of intermediate filaments. Cytoskeletal proteins of these cultures were separated by SDS-gel electrophoresis, transferred to nitrocellulose paper, and shown to bind the glial-specific antiserum to a protein of 50,000 daltons. All the cells that bound this serum had a Schwann cell surface antigen, Ran-1, whereas fibroblasts from the nerve had Thy-1 surface antigen and did not contain the astrocyte filament antigen. These results prove that some Schwann cells from adult nerve, in contrast to fibroblasts or immature Schwann cells, have an intermediate filament protein that shares antigenic determinants with, or may be identical to, the astrocyte filament protein.

Observation of cultured peripheral non-neuronal cells implanted into the transected spinal cord

We have previously reported that cultured peripheral non-neuronal cells could be used as an adjunct to spinal cord reconstruction with the delayed nerve graft technique. The cultured cells appeared to enhance axonal regeneration and with their use the time it took for axons from the spinal cord stumps to reach the nerve graft was reduced. To gain insight into the possible mechanisms through which peripheral non-neuronal cells can foster CNS regeneration, we have now investigated the behaviour of the peripheral non-neuronal cells after implantation into the spinal cord. Autologous mixed non-neuronal cell cultures were prepared from cat sciatic nerve biopsies and labeled in culture with tritiated thymidine. The labeled cells were implanted so as to completely fill the gap in the spinal cord produced by a narrow "slit transection". Light-and electron-microscopic autoradiography was used to identify the cells 3 and 7 days after implantation and to determine their proximity to, and possible interaction with, axons in the spinal cord stumps. The implanted peripheral cells were frequently found near spinal cord axons and axon terminals. Some of the labeled cells ensheathed axons in which case they displayed morphological characteristics of Schwann cells. Other labeled cells had characteristics of fibroblasts and were surrounded by an extracellular matrix rich in collagen fibrils. Many of the labeled cells contained phagocytosed myelin debris. These observations are consistent with the implanted cells acting to enhance regeneration in the spinal cord either by direct interaction with axons (ensheathment) or indirectly via the production of soluble neuronotrophic factors or a favorable extracellular matrix. The ability of the implanted cells to rapidly move into the spinal cord stumps and attain positions close to spinal cord axons would be an important factor for any of these mechanisms.

Purification of rat Schwann cells from cultures of peripheral nerve: an immunoselective method using surfaces coated with anti-immunoglobulin antibodies

We report a method for deriving purified rat Schwann cells by immunoselective removal of fibroblasts. Contaminating fibroblasts labeled with antibody against specific surface marker Thy 1.1 are bound on plastic surfaces coated with a second antibody. The efficacy of the method is demonstrated by flow cytometry and by specific Schwann cell Ran-1 immunofluorescence.

Growth properties and biochemical characterization of mouse Schwann cells cultured in vitro

Purified secondary cultures of mouse Schwann cells (less than 5% fibroblast contamination) have been obtained by taking advantage of the differential adhesion of Schwann cells and fibroblasts during trypsinization. The growth properties of the purified subcultures changed with time in culture. Cells passaged after 5 days in vitro (DIV) divided rapidly (doubling time 22 h), whereas cells that had been in vitro for longer periods progressively decreased their growth rate, becoming quiescent after 20 or more days. Schwann cells lacked the Thy 1.2 surface antigen, but were positively stained with antigalactocerebroside antibodies after prefixation. Biochemical analyses showed Schwann cells to be enriched in the activities of enzymes characteristic of the myelin-forming cells: 2'3'-cyclic nucleotide 3'-phosphodiesterase (CNP), cerebroside sulfotransferase (CST) and UDP-galactose: ceramide galactosyltransferase (CGalT).

Reconstruction of the contused cat spinal cord by the delayed nerve graft technique and cultured peripheral non-neuronal cells

Previously, surgical reconstruction of the transected dog spinal cord by the delayed nerve graft technique has been shown to result in reinnervation of the nerve graft by axons. In the present study, we compared the results of surgical reconstruction of the severely contused cat spinal cord by the delayed nerve graft technique alone to those after reconstruction with a similar nerve graft plus cultured peripheral non-neuronal cells implanted between the grafted nerve and the spinal cord stumps. The spinal cord-nerve graft junction was examined by light and electron microscopy. The cultured cells were prelabelled with tritiated thymidine and their location after implantation determined by autoradiography. By 3 days after spinal cord reconstruction, the prelabelled cells were present at the junction and had migrated into the nerve graft and also into the spinal cord stumps where they were observed near axons. By 7 days, physical connections were observed bridging the junction between the spinal cord and nerve graft and axons ensheathed by Schwann cells had already penetrated at least 1 mm into the nerve graft. Wound healing took at least a week longer in animals repaired with a nerve graft alone. At one year or later after reconstructive surgery, in both groups of animals, the grafted nerve was reinnervated with myelinated and unmyelinated axons. Thus, the severely contused cat spinal cord could be reconstructed with the delayed nerve graft technique alone but the use of the cultured cells appeared to enhance wound healing and decrease the time required for axon elongation into the nerve graft.