Search

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., (Copyright © 2016 Elsevier Inc. All rights reserved.)

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.

Neural stem cell (NSC) transplantation is a major focus of current research for treatment of spinal cord injury (SCI). However, it is very important to promote the survival and differentiation of NSCs into myelinating oligodendrocytes (OLs). In this study, myelin basic protein-activated T (MBP-T) cells were passively immunized to improve the SCI microenvironment. Olig2-overexpressing NSCs were infected with a lentivirus carrying the enhanced green fluorescent protein (GFP) reporter gene to generate Olig2-GFP-NSCs that were transplanted into the injured site to differentiate into OLs. Transferred MBP-T cells infiltrated the injured spinal cord, produced neurotrophic factors, and induced the differentiation of resident microglia and/or infiltrating blood monocytes into an "alternatively activated" anti-inflammatory macrophage phenotype by producing interleukin-13. As a result, the survival of transplanted NSCs increased fivefold in MBP-T cell-transferred rats compared with that of the vehicle-treated control. In addition, the differentiation of MBP-positive OLs increased 12-fold in Olig2-GFP-NSC-transplanted rats compared with that of GFP-NSC-transplanted controls. In the MBP-T cell and Olig2-GFP-NSC combined group, the number of OL-remyelinated axons significantly increased compared with those of all other groups. However, a significant decrease in spinal cord lesion volume and an increase in spared myelin and behavioral recovery were observed in Olig2-NSC- and NSC-transplanted MBP-T cell groups. Collectively, these results suggest that MBP-T cell adoptive immunotherapy combined with NSC transplantation has a synergistic effect on histological and behavioral improvement after traumatic SCI. Although Olig2 overexpression enhances OL differentiation and myelination, the effect on functional recovery may be surpassed by MBP-T cells.

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.

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.