Proliferation and differentiation properties of bipotent glial progenitor cell lines immortalized with the adenovirus E1A gene

Cyclosporin A increases recovery after spinal cord injury but does not improve myelination by oligodendrocyte progenitor cell transplantation

BACKGROUND

Transplantation of oligodendrocyte precursor cells (OPCs) is an attractive therapy for demyelinating diseases. Cyclosporin A (CsA) is one of the foremost immunosuppressive agents and has widespread use in tissue and cell transplantation. However, whether CsA affects survival and differentiation of engrafted OPCs in vivo is unknown. In this study, the effect of CsA on morphological, functional and immunological aspects, as well as survival and differentiation of engrafted OPCs in injured spinal cord was explored.

RESULTS

We transplanted green fluorescent protein (GFP) expressed OPCs (GFP-OPCs) into injured spinal cords of rats treated with or without CsA (10 mg/kg). Two weeks after cell transplantation, more GFP-positive cells were found in CsA-treated rats than that in vehicle-treated ones. However, the engrafted cells mostly differentiated into astrocytes, but not oligodendrocytes in both groups. In the CsA-treated group, a significant decrease in spinal cord lesion volume along with increase in spared myelin and neurons were found compared to the control group. Such histological improvement correlated well with an increase in behavioral recovery. Further study suggested that CsA treatment could inhibit infiltration of T cells and activation of resident microglia and/or macrophages derived from infiltrating monocytes in injured spinal cords, which contributes to the survival of engrafted OPCs and repair of spinal cord injury (SCI).

CONCLUSIONS

These results collectively indicate that CsA can promote the survival of engrafted OPCs in injured spinal cords, but has no effect on their differentiation. The engrafted cells mostly differentiated into astrocytes, but not oligodendrocytes. The beneficial effect of CsA on SCI and the survival of engrafted cells may be attributed to its neuroprotective effect.

Mesenchymal Stem Cells Instruct Oligodendrogenic Fate Decision on Adult Neural Stem Cells

Adult stem cells reside in different tissues and organs of the adult organism. Among these cells are MSCs that are located in the adult bone marrow and NSCs that exist in the adult central nervous system (CNS). In transplantation experiments, MSCs demonstrated neuroprotective and neuroregenerative effects that were associated with functional improvements. The underlying mechanisms are largely unidentified. Here, we reveal that the interactions between adult MSCs and NSCs, mediated by soluble factors, induce oligodendrogenic fate decision in NSCs at the expense of astrogenesis. This was demonstrated (a) by an increase in the percentage of cells expressing the oligodendrocyte markers GalC and myelin basic protein, (b) by a reduction in the percentage of glial fibrillary acidic protein (GFAP)-expressing cells, and (c) by the expression pattern of cell fate determinants specific for oligodendrogenic differentiation. Thus, it involved enhanced expression of the oligodendrogenic transcription factors Olig1, Olig2, and Nkx2.2 and diminished expression of Id2, an inhibitor of oligodendrogenic differentiation. Results of (a) 5-bromo-2'-deoxyuridine pulse-labeling of cells, (b) cell fate analysis, and (c) cell death/survival analysis suggested an inductive mechanism and excluded a selection process. A candidate factor screen excluded a number of growth factors, cytokines, and neurotrophins that have previously been shown to influence neurogenesis and neural differentiation from the oligodendrogenic activity derived from the MSCs. This work might have major implications for the development of future transplantation strategies for the treatment of degenerative diseases in the CNS.

Establishment and characterization of adenoviral E1A immortalized cell lines derived from the rat suprachiasmatic nucleus

Primary cultured cells from the presumptive anlage of the rat suprachiasmatic nucleus (SCN) were immortalized by infection with a retroviral vector encoding the adenovirus 12S E1A gene. After drug selection, the resulting neural cell lines (SCN1.4 and SCN2.2) displayed (a) extended growth potential without evidence of transformed or tumorigenic properties, (b) expression of E1A protein within all cell nuclei, and (c) heterogeneous cell types in various stages of differentiation. A large proportion of the SCN1.4 and SCN2.2 cells were characterized by gliallike morphologies, but showed limited expression of corresponding cell type-specific antigens. In addition, both lines exhibited a stable population of cells with neuronlike characteristics. When treated so as to enhance differentiation, these cells were often distinguished by fine, long processes and immunocytochemical expression of neuronal markers and peptides found within SCN neurons in situ. Observations on SCN neuropeptide immunostaining, content, release, and mRNA expression followed a concordant pattern in which somatostatin and vasopressin cells were the most and least common peptidergic phenotypes in both lines, respectively. Since these results indicate that constituents of E1A-immortalized lines derived from the primordial SCN can differentiate into cells with phenotypes resembling parental peptidergic neurons, it will be critical to explore next whether these lines also retain the distinctive function of the SCN to generate circadian rhythms. Cloning of immortalized cell types could subsequently yield useful tools for studying the development of SCN glial and peptidergic cell types and delineating their distinct roles in mammalian circadian time-keeping.

Immunocytochemical and biochemical characterization of glial phenotypes in normal and immortalized cultures derived from 3-day-old chick embryo encephalon

We examined properties of glia derived from very early neurogenesis in the chick embryo, as well as their behavior in response to extended cell passages and at various periods in culture. Primary cultures derived from the telencephalic region of 3-day-old chick embryo (stage 19) exhibited intense staining for vimentin (Vim; indicative of immature glial phenotypes) throughout the 17-day culture period, transitioning to Vim-positive/glial fibrillary acidic protein (GFAP)-positive astroblasts after a single cell passage at 13 days in vitro (DIV). With subsequent passage (P; through P6), cell continued to coexpress Vim/GFAP with the occasional appearance of fibronectin (Fib). By P11, Vim staining was faint, whereas GFAP staining gained in intensity, indicating the presence of mature astrocytes. These cultures also featured significant activity of glutamine synthetase (GS), which increased slightly with both cell passage and days in culture, correlating well with immunocytochemical findings. The activity of 2'3'-cyclic nucleotide 3'-phosphohydrolase (CNP) remained low, indicating a low percentage of mature oligodendrocytes. Thus, embryonic day (E)3H glia cultures mature into astrocytes given sufficient time in culture. To obtain a stable population of glia at various stages of astrocytic differentiation, we immortalized and subcloned homogenous colonies of E3H glia precursors at specific stages of development. A cell suspension was electroporetically transfected with the pSV40neo gene for large T antigen (E3H.SV5). After 5 passages, the parent colonies consisted of a heterogeneous population of cells, most of which were vim and GFAP positive. Following subcloning, one line (colony 7) displayed the staining pattern of mature astrocytes. However, with advancing age in culture, staining for both vim and GFAP became increasingly faint. Compared with control (normal) cultures, transfected cells exhibited a significantly lower activity of GS that did not fluctuate with days in culture but decreased with advancing cell passage. Furthermore, CNP activity in E3H.SV5 colony 7 was approximately double that observed in normal cultures at the same cell passage. This observation suggests that the phenotype of transfected glia was less stable than that observed in normal glial cultures.

Physiological relevance and functional potential of central nervous system-derived cell lines

Central nervous system (CNS)-derived neural cell lines have proven to be extremely useful for delineating mechanisms controlling such diverse phenomena as cell lineage choice and differentiation, synaptic maturation, neurotransmitter synthesis and release, and growth factor signalling. In addition, there has been hope that such lines might play pivotal roles in CNS gene therapy and repair. The ability of some neural cell lines to integrate normally into the CNS following transplantation and to express foreign, often corrective gene products in situ might offer potential therapeutic approaches to certain neurodegenerative diseases. Five general strategies have evolved to develop neural cell lines: isolation and cloning of spontaneous or mutagenically induced malignancies, targeted oncogenesis in transgenic mice, somatic cell fusion, growth factor mediated expansion of CNS progenitor or stem cells, and retroviral transduction of neuroepithelial precursors. in this article, we detail recent progress in these areas, focusing on those cell lines that have enabled novel insight into the mechanisms controlling neuronal cell lineage choice and differentiation, both in vitro and in vivo.