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Our previous study has showed that co-grafted Schwann cells (SCs) promote proliferation and migration of the grafted oligodendrocyte precursor cells (OPCs). However, how the co-grafted SCs affect OPCs has not been clarified. In the present study, we confirmed that SC-induced proliferation and migration of OPCs were mediated by SC-secreted factors using SC-conditioned medium (SCM). Then, we detected several candidate factors, PDGF-AA, FGF-2, and IGF-1, in SCs and SCM, and their receptors in OPCs. Finally, by using the selective inhibitors, the effects of these candidate factors on proliferation and migration of OPCs were examined. Our results showed that SCM-stimulated proliferation and migration of OPCs could be markedly decreased by both AG1295 (the inhibitor of PDGFR) and PD173074 (the inhibitor of FGFR). Together, our study suggests that SCs affect proliferation and migration of OPCs through secreting PDGF-AA and FGF-2. Identity of these molecules not only contributes to understand the mechanism of SC-induced proliferation and migration of OPCs but also provides possible target for treatment of CNS diseases.

The conditioned medium from B104 neuroblastoma cells (B104CM) induces proliferation of oligodendrocyte progenitor cells (OPCs) in vitro. Our previous study showed that phosphorylation of extracellular signal-regulated protein kinase(s), not PI3K or p38, is key to B104CM-induced OPC proliferation. However, whether there are still other signaling pathways that are also involved in B104CM-induced proliferation remains unknown. In the present study, we evaluated the implication of c-Jun N-terminal kinase (JNK) signaling pathway in the B104CM-induced proliferation of OPCs using the specific inhibitor of JNK. We provided convincing evidence for the first time that the phosphorylation of JNK is necessary for OPC proliferation induced by B104CM in vitro. Moreover, the activation of JNK results in subsequent expressions of c-jun, c-fos, and c-myc, which initiates proliferation of OPCs. Collectively, these results suggest that JNK is also necessary for B104CM-induced OPC proliferation.

The conditioned medium from B104 neuroblastoma cells (B104CM) induces proliferation of οligodendrocyte precursor cells (OPCs) in vitro, which indicates that certain factors contained within B104CM give instructional signals that direct the proliferation of OPCs. However, the OPC-proliferative factors present in B104CM have yet to be identified. Platelet-derived growth factor AA (PDGF-AA), basic fibroblast growth factor (bFGF) and insulin-like growth factor-1 (IGF-1) have been reported to act as potent mitogens for OPC proliferation. This raises the possibility that B104CM induces proliferation of OPCs through secretion of PDGF‑AA, bFGF and/or IGF-1. In the present study, we detected the expression and levels of PDGF-AA, bFGF and IGF-1 in B104 cells and B104CM, and observed the expression of their receptors in OPCs. The results indicated that these growth factors were expressed in B104 cells and B104CM. All 3 receptors, PDGFR, FGFR2 and IGF-1R, were also detected in OPCs. Furthermore, B104CM-stimulated OPC proliferation could be markedly decreased by both AG1295 (an inhibitor of PDGFR) and PD173074 (an inhibitor of FGFR). However, the inhibition of IGF-1R with AG1204 did not affect the proliferation of OPCs. Our study suggests that the PDGF-AA and bFGF in B104CM are 2 key factors that stimulate OPC proliferation.

The conditioned medium from B104 neuroblastoma cells (B104CM) induces neural stem cells (NSCs) to differentiate into OPCs in vitro, which indicates that certain factor(s) contained within the B104CM must give instructional signals that direct OPC differentiation of NSCs. However, the OPC-inductive factor(s) present within the B104CM has not been well identified yet. Platelet-derived growth factor AA (PDGF-AA) was not only known to be a potent mitogen for OPC proliferation but also to act as a regulator of oligodendrocyte differentiation from multipotent embryonic NSCs. This raises the possibility that B104CM induces OPC differentiation of NSCs through secretion of PDGF-AA. In the present study, we detected the expression of PDGF-AA mRNA in B104 cells and the high level of PDGF-AA protein in B104CM. Most importantly, B104CM-induced OPC differentiation of NSCs could be completely blocked by AG1295, a specific inhibitor of PDGFR signal pathway, suggesting that the PDGF-AA in B104CM is the key factor that induces NSCs to differentiate into OPCs. Moreover, such B104CM-induced OPC differentiation appears to be mediated by the extracellular signal-regulated kinases 1 and 2 (Erk1/2), phosphatidylinositol-3 kinase (PI3K), and p38 signal pathway because B104CM elicited the activation of Erk1/2, PI3K, and p38, which could be markedly blocked by U0126, LY294002, and SB203580, several specific inhibitors of these signal pathway, respectively. These inhibitors also abolished OPC differentiation of NSCs completely. Together our study suggests that PDGF-AA contained in B104CM is the key regulating molecule that instructs OPC differentiation from embryonic NSCs through the activation of Erk, PI3K, and p38 signal pathway in vitro.

Oligodendrocyte precursor cells (OPCs) are bipotential progenitor cells that can differentiate into myelin-forming oligodendrocytes or functionally undetermined type II astrocytes. Transplantation of OPCs is an attractive therapy for demyelinating diseases. However, due to their bipotential differentiation potential, the majority of OPCs differentiate into astrocytes at transplanted sites. It is therefore important to understand the molecular mechanisms that regulate the transition from OPCs to oligodendrocytes or astrocytes. In this study, we isolated OPCs from the spinal cords of rat embryos (16 days old) and induced them to differentiate into oligodendrocytes or type II astrocytes in the absence or presence of 10% fetal bovine serum, respectively. RNAs were extracted from each cell population and hybridized to GeneChip with 28,700 rat genes. Using the criterion of fold change > 4 in the expression level, we identified 83 genes that were up-regulated and 89 genes that were down-regulated in oligodendrocytes, and 92 genes that were up-regulated and 86 that were down-regulated in type II astrocytes compared with OPCs. The up-regulated genes, such as activating transcription factor 3 and myelin basic protein in oligodendrocytes or claudin 11 in type II astrocytes, might contribute to OPC differentiation and represent constitutive components of oligodendrocytes or type II astrocytes. The down-regulated genes in both oligodendrocytes and type II astrocytes, such as transcription factor 19, might be involved in maintaining self-renewal and/or represent the property of OPCs. These results provide new insights into the elucidation of the molecular mechanisms, by which OPCs differentiate to oligodendrocytes or type II astrocytes.

Oligodendrocyte precursor cells (OPCs) can differentiate into oligodendrocytes or astrocytes, depending on cellular microenvironments. OPCs, cultured in medium supplemented with 10% (v/v) fetal bovine serum (FBS), give rise to type II astrocytes that express glial fibrillary acidic protein and a cell surface ganglioside that is recognized by A2B5 monoclonal antibody. However, the factors in FBS that direct the astrocyte differentiation are not determined. Moreover, bone morphogenetic proteins (BMPs) have been reported to be involved in astrocyte differentiation of neural progenitor cells. We therefore examined whether BMPs are responsible for the serum-mediated astrocyte differentiation from OPCs. OPCs were isolated from the spinal cords of Wistar rat embryos (at day 14) using the A2B5 antibody. We measured the concentrations of BMP-2 and BMP-4 in FBS and rat and human sera and the expression of mRNAs for three types of BMP receptors (BMPRIa, Ib and II) in OPCs by RT-PCR. The serum samples of the three species contained BMP-2 and BMP-4, as judged by ELISA with each monoclonal antibody, and the BMP receptor mRNAs are expressed in OPCs. When OPCs were cultured in the medium containing 10% FBS, cells (more than 95%) differentiated into type II astrocytes. However, when OPCs were pretreated with noggin, a soluble antagonist of BMP action, the degree of astrocyte differentiation was markedly decreased from 95.39 to 38.36%. Taken together, these results suggest that BMP signaling may be responsible for the serum-mediated astrocyte differentiation of OPCs. Our findings provide new insights into the molecular basis of differentiation of OPCs.

Demyelination contributes to the functional deficits after spinal cord injury (SCI). Therefore, remyelination may be an important strategy to facilitate repair after SCI. Oligodendrocyte precursor cells (OPCs) are immature oligodendrocytes and can differentiate into myelin-forming cells of central nervous system under certain conditions. OPC transplantation is an attractive approach for the treatment of demyelinating diseases. In this study, we transplanted OPCs expressing green fluorescent protein (GFP-OPCs) into normal and injured rat spinal cords to evaluate the differentiation of transplanted OPCs in vivo. Unfortunately, the grafted GFP-OPCs, in spinal cord whether normal or injured, were all differentiated into astrocytes, but not oligodendrocytes. Our further study indicated that inflammatory environment might not be the key factor influencing the differentiation of OPCs. Some spinal cord components, such as bone morphogenetic proteins (BMPs), were the major factors that induced OPCs to differentiate into astrocytes. The three types of BMP receptor (BMPRIA, IB and II) could all be detected in OPCs, and the astroglial differentiation of OPCs induced by spinal cord homogenate extract (SCHE) in vitro could be blocked partly by noggin, an antagonist of BMP. These results suggested that the BMPR signal transduction pathway might be one of the key factors which determine the differentiation direction of engrafted OPCs in spinal cord., (Copyright © 2010 International Society of Differentiation. Published by Elsevier B.V. All rights reserved.)

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.

Previous studies have shown that a cell-intrinsic timer might determine when oligodendrocyte progenitor cells (OPCs) isolated from the central nervous system (CNS) stop dividing and initiate differentiation in a defined environment. In this report, the proliferation and differentiation of OPCs induced from neural precursor cells (NPCs) were analyzed by flow cytometry combined with carboxyfluorescein diacetate succinimidyl ester labeling and propidium iodide staining, respectively. When OPCs were cultured in OPC-medium, more than 30% of cells were in S- and G2/M-phases, and continuously self-renewed without differentiation. After exposure to thyroid hormone, there was an obvious decrease in the fraction of cells in both S- and G2/M-phases (<10%). Furthermore, the OPCs no longer proliferated, but differentiated into oligodendrocytes. The dynamic proliferation and differentiation characteristics of OPCs induced from NPCs and analyzed by flow cytometry were similar to those of OPCs isolated from the CNS and analyzed by other methods. These studies indicated that the proliferation and differentiation of OPCs can be followed simply and rapidly by flow cytometry., ((c) 2008 International Society for Advancement of Cytometry)

Previous studies by our group have demonstrated that the transplantation of exogenous platelet-derived growth factor (PDGF)-AA-overexpressing oligodendrocyte progenitor cells (OPCs) promotes tissue repair and recovery of neurological function in a rat model of spinal cord injury (SCI). However, it remains unclear whether treatment with PDGF-AA also affects endogenous oligodendrocytes (OLs) or even neurons, thus promoting further functional recovery after SCI. In the present study, we evaluated the therapeutic potential of PDGF-AA treatment by direct subcutaneous injection of PDGF-AA immediately after SCI. We demonstrated that PDGF-AA injection resulted in increased tissue sparing, myelination and functional recovery in rats following SCI. Further experimentation confirmed that PDGF-AA increased the survival of endogenous OPCs and OLs, and promoted the proliferation of OPCs and their differentiation into OLs. Moreover, PDGF-AA also protected motor neurons from death in the injured spinal cord. These results indicated that PDGF-AA administration may be an effective treatment for SCI. [ABSTRACT FROM AUTHOR]

Interferon-induced transmembrane protein 1 (IFITM1) is a member of the IFITM family that is associated with some acute-phase cytokine-stimulated response. Recently, we demonstrated that IFITM1 was significantly upregulated in the injured spinal cords at the mRNA level. However, its expression and cellular localization at the protein level is still unclear. Here, a rat model of spinal cord injury (SCI) was performed to investigate the spatio-temporal expression of IFITM1 after SCI. IFITM1 mRNA and protein were assessed by quantitative reverse transcription-PCR and western blot, respectively. IHC was used to identify its cellular localization. We revealed that IFITM1 could be found in sham-opened spinal cords and gradually increased after SCI. It reached peak at 7 and 14 days postinjury (dpi) and still maintained at a relatively higher level at 28 dpi. IHC showed that IFITM1 expressed in GFAP+ and APC+ cells in sham-opened spinal cords. After SCI, in addition to the above-mentioned cells, it could also be found in CD45+ and CD68+ cells, and its expression in CD45+, CD68+, and GFAP+ cells was increased significantly. These results demonstrate that IFITM1 is mainly expressed in astrocytes and oligodendroglia in normal spinal cords, and could rapidly increase in infiltrated leukocytes, activated microglia, and astrocytes after SCI. [ABSTRACT FROM AUTHOR]

The conditioned medium from B104 neuroblastoma cells (B104CM) induces proliferation of oligodendrocyte progenitor cells (OPCs) in vitro. However, the molecular events that occur during B104CM-induced proliferation of OPCs has not been well clarified. In the present study, using OPCs immunopanned from embryonic day 14 Sprague-Dawley rat spinal cords, we explored the activation of several signaling pathways and the expression of several important immediate early genes (IEGs) and cyclins in OPCs in response to B104CM. We found that B104CM can induce OPC proliferation through the activation of the extracellular signal-regulated kinases 1 and 2 (Erk1/2), but not PI3K or p38 MAPK signaling pathways in vitro. The IEGs involved in B104CM-induced OPC proliferation include c-fos, c-jun and Id2, but not c-myc, fyn, or p21. The cyclins D1, D2 and E are also involved in B104CM-stimulated proliferation of OPCs. The activation of Erk results in subsequent expression of IEGs (such as c-fos, c-jun and Id-2) and cyclins (including cyclin D1, D2 and E), which play key roles in cell cycle initiation and OPC proliferation. Collectively, these results suggest that the phosphorylation of Erk1/2 is an important molecular event during OPC proliferation induced by B104CM. [ABSTRACT FROM AUTHOR]

Oligodendrocyte (OL) replacement is a promising treatment strategy for spinal cord injury (SCI). However, the poor survival of transplanted OLs or their precursors and inhibition of axonal regeneration are two major challenges with this approach. Our previous study showed that Schwann cells (SCs) promoted survival, proliferation, and migration of transplanted OL progenitor cells (OPCs) and neurological recovery. Remyelination is an important basis for functional recovery following spinal cord injury. It has been reported that myelin gene regulatory factor (MRF), a transcriptional regulator which specifically is expressed in postmitotic OLs within the CNS, is essential for OL maturation and CNS myelination. In the present study, we investigated whether co-transplantation of MRF-overexpressing OPCs (MRF-OPCs) and SCs could improve functional recovery in a rat model of contusional SCI. MRF overexpression had no effect on OPC survival or migration, but stimulated the differentiation of OPCs both in vitro and in vivo. Co-transplantation of MRF-OPCs and SCs increased myelination and tissue repair after SCI, leading to the recovery of neurological function. These results indicate that co-transplantation of MRF-OPCs and SCs may be an effective treatment strategy for SCI. [ABSTRACT FROM AUTHOR]