Effects of Olig2-overexpressing neural stem cells and myelin basic protein-activated T cells on recovery from spinal cord injury

The beneficial effect of α-lipoic acid on spinal cord injury repair in rats is mediated through inhibition of oxidative stress: A transcriptomic analysis

BACKGROUND

Oxidative stress is a crucial factor contributing to the occurrence and development of secondary damage in spinal cord injuries (SCI), ultimately impacting the recovery process. α-lipoic acid (ALA) exhibits potent antioxidant properties, effectively reducing secondary damage and providing neuroprotective benefits. However, the precise mechanism by which ALA plays its antioxidant role remains unknown.

METHODS

We established a model of moderate spinal cord contusion in rats. Experimental rats were randomly divided into 3 distinct groups: the sham group, the model control group (SCI_Veh), and the ALA treatment group (SCI_ALA). The sham group rats were exposed only to the SC without contusion injury. Rats belonging to SCI_Veh group were not administered any treatment after SCI. Rats of SCI_ALA group were intraperitoneally injected with the corresponding volume of ALA according to body weight for three consecutive days after the surgery. Subsequently, three days after SCI, spinal cord samples were obtained from three groups of rats: the sham group, model control group, and administration group. Thereafter, total RNA was extracted from the samples and the expression of three sets of differential genes was analyzed by transcriptome sequencing technology. Real-time PCR was used to verify the sequencing results. The impact of ALA on oxidative stress in rats following SCI was assessed by measuring their total antioxidant capacity and hydrogen peroxide (H2O2) content. The effects of ALA on rat recovery following SCI was investigated through Beattie and Bresnahan (BBB) score and footprint analysis.

RESULTS

The findings from the transcriptome sequencing analysis revealed that the model control group had 2975 genes with altered expression levels when compared to the ALA treatment group. Among these genes, 1583 were found to be upregulated while 1392 were down-regulated. Gene ontology (GO) displayed significant enrichment in terms of functionality, specifically in oxidative phosphorylation, oxidoreductase activity, and signaling receptor activity. The Kyoto encyclopedia of genes and genomes (KEGG) pathway was enriched in oxidative phosphorylation, glutathione metabolism and cell cycle. ALA was found to have multiple benefits for rats after SCI, including increasing their antioxidant capacity and reducing H2O2 levels. Additionally, it was effective in improving motor function (such as 7 days after SCI, the BBB score for SCI_ALA was 8.400 ± 0.937 compared to 7.050 ± 1.141 for SCI_Veh) and promoting histological recovery after SCI (The results of HE demonstrated that the percentage of damage area in was 44.002 ± 6.680 in the SCI_ALA and 57.215 ± 3.964 in the SCI_Veh at the center of injury.). The sequence data from this study has been deposited into Sequence Read Archive (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE242507).

CONCLUSION

Overall, the findings of this study confirmed the beneficial effects of ALA on recovery in SCI rats through transcriptome sequencing, behavioral, as well histology analyses.

Efficacy of growth factor gene-modified stem cells for motor function after spinal cord injury in rodents: a systematic review and meta‑analysis

The efficacy of growth factor gene-modified stem cells in treating spinal cord injury (SCI) remains unclear. This study aims to evaluate the effectiveness of growth factor gene-modified stem cells in restoring motor function after SCI. Two reviewers searched four databases, including PubMed, Embase, Web of Science, and Scopus, to identify relevant records. Studies on rodents assessing the efficacy of transplanting growth factor gene-modified stem cells in restoring motor function after SCI were included. The results were reported using the standardized mean difference (SMD) with a 95% confidence interval (95% CI). Analyses showed that growth factor gene-modified stem cell transplantation improved motor function recovery in rodents with SCI compared to the untreated (SMD = 3.98, 95% CI 3.26-4.70, I2 = 86.8%, P < 0.0001) and stem cell (SMD = 2.53, 95% CI 1.93-3.13, I2 = 86.9%, P < 0.0001) groups. Using growth factor gene-modified neural stem/histone cells enhanced treatment efficacy. In addition, the effectiveness increased when viral vectors were employed for gene modification and high transplantation doses were administered during the subacute phase. Stem cells derived from the human umbilical cord exhibited an advantage in motor function recovery. However, the transplantation of growth factor gene-modified stem cells did not significantly improve motor function in male rodents (P = 0.136). Transplantation of growth factor gene-modified stem cells improved motor function in rodents after SCI, but claims of enhanced efficacy should be approached with caution. The safety of gene modification remains a significant concern, requiring additional efforts to enhance its clinical translatability.

Correlation between ABCB1 and OLIG2 polymorphisms and the severity and prognosis of patients with cerebral infarction

This study investigated the relationship between ATP-binding cassette sub-family B member 1 (ABCB1) and OLIG2 single nucleotide polymorphism (SNP) and neurological injury severity and outcome in cerebral infarction (CI). The neurological injury severity of 298 CI patients was evaluated by the National Institutes of Health Stroke Scale. The prognosis of CI patients at 30 days after admission was evaluated by the modified Rankin Scale. And 322 healthy people were selected as the control group. The SNPs of the ABCB1 gene (rs1045642) and OLIG2 gene (rs1059004 and rs9653711) were detected by TaqMan probe PCR, and the distribution of SNPs genotype was analyzed. SNP rs9653711 was correlated with CI. Recessive models of rs1045642 and rs9653711 were correlated with CI. The genotypes of rs1045642 and rs9653711 and genetic models were associated with CI severity. rs1045642 had no correlation with CI prognosis, while rs9653711 had less correlation. The genotype distribution and recessive model were associated with CI prognosis. SNP rs1059004 was not associated with CI severity and prognosis. Alcohol consumption, hypertension, diabetes, hyperlipidemia, and high levels of homocysteine (HCY) were independent risk factors for CI, while hypertension, hyperlipidemia, and HCY were associated with poor prognosis of CI. ABCB1 rs1045642 and OLOG2 rs9653711 are associated with CI severity.

Genetically engineered neural stem cells (NSCs) therapy for neurological diseases; state-of-the-art

Neural stem cells (NSCs) are multipotent stem cells with remarkable self-renewal potential and also unique competencies to differentiate into neurons, astrocytes, and oligodendrocytes (ODCs) and improve the cellular microenvironment. In addition, NSCs secret diversity of mediators, including neurotrophic factors (e.g., BDNF, NGF, GDNF, CNTF, and NT-3), pro-angiogenic mediators (e.g., FGF-2 and VEGF), and anti-inflammatory biomolecules. Thereby, NSCs transplantation has become a reasonable and effective treatment for various neurodegenerative disorders by their capacity to induce neurogenesis and vasculogenesis and dampen neuroinflammation and oxidative stress. Nonetheless, various drawbacks such as lower migration and survival and less differential capacity to a particular cell lineage concerning the disease pathogenesis hinder their application. Thus, genetic engineering of NSCs before transplantation is recently regarded as an innovative strategy to bypass these hurdles. Indeed, genetically modified NSCs could bring about more favored therapeutic influences post-transplantation in vivo, making them an excellent option for neurological disease therapy. This review for the first time offers a comprehensive review of the therapeutic capability of genetically modified NSCs rather than naïve NSCs in neurological disease beyond brain tumors and sheds light on the recent progress and prospect in this context.

The role of immune cells and associated immunological factors in the immune response to spinal cord injury

Spinal cord injury (SCI) is a devastating neurological condition prevalent worldwide. Where the pathological mechanisms underlying SCI are concerned, we can distinguish between primary injury caused by initial mechanical damage and secondary injury characterized by a series of biological responses, such as vascular dysfunction, oxidative stress, neurotransmitter toxicity, lipid peroxidation, and immune-inflammatory response. Secondary injury causes further tissue loss and dysfunction, and the immune response appears to be the key molecular mechanism affecting injured tissue regeneration and functional recovery from SCI. Immune response after SCI involves the activation of different immune cells and the production of immunity-associated chemicals. With the development of new biological technologies, such as transcriptomics, the heterogeneity of immune cells and chemicals can be classified with greater precision. In this review, we focus on the current understanding of the heterogeneity of these immune components and the roles they play in SCI, including reactive astrogliosis and glial scar formation, neutrophil migration, macrophage transformation, resident microglia activation and proliferation, and the humoral immunity mediated by T and B cells. We also summarize findings from clinical trials of immunomodulatory therapies for SCI and briefly review promising therapeutic drugs currently being researched.

Olig2 Ablation in Immature Oligodendrocytes Does Not Enhance CNS Myelination and Remyelination

The oligodendrocyte (OL) lineage transcription factor Olig2 is expressed throughout oligodendroglial development and is essential for oligodendroglial progenitor specification and differentiation. It was previously reported that deletion of Olig2 enhanced the maturation and myelination of immature OLs and accelerated the remyelination process. However, by analyzing multiple Olig2 conditional KO mouse lines (male and female), we conclude that Olig2 has the opposite effect and is required for OL maturation and remyelination. We found that deletion of Olig2 in immature OLs driven by an immature OL-expressing Plp1 promoter resulted in defects in OL maturation and myelination, and did not enhance remyelination after demyelination. Similarly, Olig2 deletion during premyelinating stages in immature OLs using Mobp or Mog promoter-driven Cre lines also did not enhance OL maturation in the CNS. Further, we found that Olig2 was not required for myelin maintenance in mature OLs but was critical for remyelination after lysolecithin-induced demyelinating injury. Analysis of genomic occupancy in immature and mature OLs revealed that Olig2 targets the enhancers of key myelination-related genes for OL maturation from immature OLs. Together, by leveraging multiple immature OL-expressing Cre lines, these studies indicate that Olig2 is essential for differentiation and myelination of immature OLs and myelin repair. Our findings raise fundamental questions about the previously proposed role of Olig2 in opposing OL myelination and highlight the importance of using Cre-dependent reporter(s) for lineage tracing in studying cell state progression.SIGNIFICANCE STATEMENT Identification of the regulators that promote oligodendrocyte (OL) myelination and remyelination is important for promoting myelin repair in devastating demyelinating diseases. Olig2 is expressed throughout OL lineage development. Ablation of Olig2 was reported to induce maturation, myelination, and remyelination from immature OLs. However, lineage-mapping analysis of Olig2-ablated cells was not conducted. Here, by leveraging multiple immature OL-expressing Cre lines, we observed no evidence that Olig2 ablation promotes maturation or remyelination of immature OLs. Instead, we find that Olig2 is required for immature OL maturation, myelination, and myelin repair. These data raise fundamental questions about the proposed inhibitory role of Olig2 against OL maturation and remyelination. Our findings highlight the importance of validating genetic manipulation with cell lineage tracing in studying myelination.

Clemastine Promotes Differentiation of Oligodendrocyte Progenitor Cells Through the Activation of ERK1/2 via Muscarinic Receptors After Spinal Cord Injury

The recovery of spinal cord injury (SCI) is closely associated with the obstruction of oligodendrocyte progenitor cell (OPC) differentiation, which ultimately induces the inability to generate newly formed myelin. To address the concern, drug-based methods may be the most practical and feasible way, possibly applying to clinical therapies for patients with SCI. In our previous study, we found that clemastine treatment preserves myelin integrity, decreases the loss of axons, and improves functional recovery in the SCI model. Clemastine acts as an antagonist of the muscarinic acetylcholine receptor (muscarinic receptor, MR) identified from a string of anti-muscarinic drugs that can enhance oligodendrocyte differentiation and myelin wrapping. However, the effects of clemastine on OPC differentiation through MRs in SCI and the underlying mechanism remain unclear. To explore the possibility, a rat model of SCI was established. To investigate if clemastine could promote the differentiation of OPCs in SCI via MR, the expressions of OPC and mature OL were detected at 7 days post injury (dpi) or at 14 dpi. The significant effect of clemastine on encouraging OPC differentiation was revealed at 14 dpi rather than 7 dpi. Under pre-treatment with the MR agonist cevimeline, the positive role of clemastine on OPC differentiation was partially disrupted. Further studies indicated that clemastine increased the phosphorylation level of extracellular signal–regulated kinase 1/2 (p-ERK1/2) and the expressions of transcription factors, Myrf and Olig2. To determine the relationship among clemastine, ERK1/2 signaling, specified transcription factors, and OPC differentiation, the ERK1/2 signaling was disturbed by U0126. The inhibition of ERK1/2 in SCI rats treated with clemastine decreased the expressions of p-ERK 1/2, Myrf, Olig2, and mature OLs, suggesting that ERK1/2 is required for clemastine on promoting OPC differentiation and that specified transcription factors may be affected by the activity of ERK1/2. Moreover, the impact of clemastine on modulating the level of p-ERK 1/2 was restricted following cevimeline pre-injecting, which provides further evidence that the role of clemastine was mediated by MRs. Altogether, our data demonstrated that clemastine, mediated by MRs, promotes OPC differentiation under the enhancement of Myrf and Olig2 by activating ERK1/2 signaling and suggests a novel therapeutic prospect for SCI recovery.

Growth Factor Gene-Modified Cells in Spinal Cord Injury Recovery; a Systematic Review

BACKGROUND

Numerous pre-clinical studies have been performed in recent years on the effects of growth factor gene-modified cells' administration in spinal cord injury (SCI). However, findings of these studies are contradictory.

OBJECTIVE

The present study aims to conduct a systematic review and meta-analysis on animal studies evaluating the effects of growth factor gene-modified cells' administration on locomotion recovery following SCI.

METHODS

A search of the Medline, Embase, Scopus and Web of Science databases was conducted, including all animal studies until the end of 2020. Two researchers screened search results, summarized relevant studies and assessed risk of bias, independently.

RESULTS

Thirty-three studies were included in the final analysis. Transplantation of growth factor gene-modified cells in the injured spinal cord resulted in a significant improvement in animals' locomotion compared with non-treated animals [standardized mean difference (SMD)=1.86; 95% CI: 1.39-2.33; p<0.0001)] and non-genetically modified cells treated animals (SMD=1.30; 0.80-1.79; p<0.0001). Transplantation efficacy of these cells failed to achieve significance in moderate lesions (p=0.091), when using modified neural stem/progenitor cells (p=0.164), when using synthetic neurotrophins (p=0.086) and when the number of transplanted cells was less than 1.0 × 10⁵ cells per animal (p = 0.119).

CONCLUSION

The result showed that transplantation of growth factor gene-modified cells significantly improved locomotion in SCI animal models. However, there is a major concern regarding the safety of genetically modified cells' transplantation, in terms of overexpressing growth factors. Further studies are needed before any effort to perform a translational and clinical study.

Hematogenous Macrophages: A New Therapeutic Target for Spinal Cord Injury

Spinal cord injury (SCI) is a devastating disease leading to loss of sensory and motor functions, whose pathological process includes mechanical primary injury and secondary injury. Macrophages play an important role in SCI pathology. According to its origin, it can be divided into resident microglia and peripheral monocyte-derived macrophages (hematogenous Mφ). And it can also be divided into M1-type macrophages and M2-type macrophages on the basis of its functional characteristics. Hematogenous macrophages may contribute to the SCI process through infiltrating, scar forming, phagocytizing debris, and inducing inflammatory response. Although some of the activities of hematogenous macrophages are shown to be beneficial, the role of hematogenous macrophages in SCI remains controversial. In this review, following a brief introduction of hematogenous macrophages, we mainly focus on the function and the controversial role of hematogenous macrophages in SCI, and we propose that hematogenous macrophages may be a new therapeutic target for SCI.

Active and Passive Immunization with Myelin Basic Protein as a Method for Early Treatment of Traumatic Spinal Cord Injury; a Meta-Analysis

Introduction:

Traumatic spinal cord injury (SCI), as a dangerous central nervous system damage, continues to threaten communities by imposing various disabilities and costs. Early adjustment of the immune system response using Myelin Basic Protein (MBP) immunization may prevent the SCI-related secondary damages. As a result, the current study is designed to review and analyse the evidence on active and passive immunization with MBP for treatment of traumatic SCI.

Methods:

Medline, Embase, Scopus, and Web of Science databases were systematically searched until the end of 2020. Criteria for inclusion in the current study included pre-clinical studies, which performed passive (injection of MBP-activated T cells) or active (administration of MBP or MBP-modified peptides) immunization with MBP after traumatic SCI. Exclusion criteria was defined as lack of a non-treated SCI group, lack of evaluation of locomotion, review studies, and combination therapy. Finally, analyses were conducted using STATA software, and a standardized mean difference (SMD) with a 95% confidence interval (CI) were reported.

Results:

Data from 17 papers were included in the present study. Finally, analysis of these data showed that passive immunization (SMD=0.87; 95%CI: 0.19-1.55; p=0.012) and active immunization (SMD=2.08, 95%CI: 1.42-2.73; p<0.001) for/with MBP both have good efficacy in improving locomotion following traumatic SCI. However, significant heterogeneity was observed in both of them. The most important sources of heterogeneity in active immunization were differences in SCI models, route of administration, time interval between SCI and transplantation, and type of vaccine used. In passive immunization, however, these sources were the model of SCI and the time interval between SCI and transplantation. Although, there was substantial heterogeneity among studies, subgroup analysis showed that active immunization improved locomotion after traumatic SCI in all tested conditions (with differences in injury model, severity of injury, method of administration, different time interval between SCI to vaccination, etc.).

Conclusion:

The results of the present study demonstrated that immunization with MBP, especially in its active form, could significantly improve motor function following SCI in rats and mice. Therefore, it could be considered as a potential treatment in acute settings such as emergency departments. However, the safety of this method is still under debate. Therefore, it is recommended for future research to focus on the investigation of safety of MBP immunization in animal studies, before conducting human clinical trials.

Biomaterial Strategies to Bolster Neural Stem Cell-Mediated Repair of the Central Nervous System

Stem cell therapies have the potential to not only repair, but to regenerate tissue of the central nervous system (CNS). Recent studies demonstrate that transplanted stem cells can differentiate into neurons and integrate with the intact circuitry after traumatic injury. Unfortunately, the positive findings described in rodent models have not been replicated in clinical trials, where the burden to maintain the cell viability necessary for tissue repair becomes more challenging. Low transplant survival remains the greatest barrier to stem cell-mediated repair of the CNS, often with fewer than 1-2% of the transplanted cells remaining after 1 week. Strategic transplantation parameters, such as injection location, cell concentration, and transplant timing achieve only modest improvements in stem cell transplant survival and appear inconsistent across studies. Biomaterials provide researchers with a means to significantly improve stem cell transplant survival through two mechanisms: (1) a vehicle to deliver and protect the stem cells and (2) a substrate to control the cytotoxic injury environment. These biomaterial strategies can alleviate cell death associated with delivery to the injury and can be used to limit cell death after transplantation by limiting cell exposure to cytotoxic signals. Moreover, it is likely that control of the injury environment with biomaterials will lead to a more reliable support for transplanted cell populations. This review will highlight the challenges associated with cell delivery in the CNS and the advances in biomaterial development and deployment for stem cell therapies necessary to bolster stem cell-mediated repair.

VX-765 reduces neuroinflammation after spinal cord injury in mice

Inflammation is a major cause of neuronal injury after spinal cord injury. We hypothesized that inhibiting caspase-1 activation may reduce neuroinflammation after spinal cord injury, thus producing a protective effect in the injured spinal cord. A mouse model of T9 contusive spinal cord injury was established using an Infinite Horizon Impactor, and VX-765, a selective inhibitor of caspase-1, was administered for 7 successive days after spinal cord injury. The results showed that: (1) VX-765 inhibited spinal cord injury-induced caspase-1 activation and interleukin-1β and interleukin-18 secretion. (2) After spinal cord injury, an increase in M1 cells mainly came from local microglia rather than infiltrating macrophages. (3) Pro-inflammatory Th1Th17 cells were predominant in the Th subsets. VX-765 suppressed total macrophage infiltration, M1 macrophages/microglia, Th1 and Th1Th17 subset differentiation, and cytotoxic T cells activation; increased M2 microglia; and promoted Th2 and Treg differentiation. (4) VX-765 reduced the fibrotic area, promoted white matter myelination, alleviated motor neuron injury, and improved functional recovery. These findings suggest that VX-765 can reduce neuroinflammation and improve nerve function recovery after spinal cord injury by inhibiting caspase-1/interleukin-1β/interleukin-18. This may be a potential strategy for treating spinal cord injury. This study was approved by the Animal Care Ethics Committee of Bengbu Medical College (approval No. 2017-037) on February 23, 2017.

CRID3, a blocker of apoptosis associated speck like protein containing a card, ameliorates murine spinal cord injury by improving local immune microenvironment

Background

After spinal cord injury (SCI), destructive immune cell subsets are dominant in the local microenvironment, which are the important mechanism of injury. Studies have shown that inflammasomes play an important role in the inflammation following SCI, and apoptosis-associated speck-like protein containing a card (ASC) is the adaptor protein shared by inflammasomes. Therefore, we speculated that inhibiting ASC may improve the local microenvironment of injured spinal cord. Here, CRID3, a blocker of ASC oligomerization, was used to study its effect on the local microenvironment and the possible role in neuroprotection following SCI.

Methods

Murine SCI model was created using an Infinite Horizon impactor at T9 vertebral level with a force of 50 kdynes and CRID3 (50 mg/kg) was intraperitoneally injected following injury. ASC and its downstream molecules in inflammasome signaling pathway were measured by western blot. The immune cell subsets were detected by immunohistofluorescence (IHF) and flow cytometry (FCM). The spinal cord fibrosis area, neuron survival, myelin preservation, and functional recovery were assessed.

Results

Following SCI, CRID3 administration inhibited inflammasome-related ASC and caspase-1, IL-1β, and IL-18 activation, which consequently suppressed M1 microglia, Th1 and Th1Th17 differentiation, and increased M2 microglia and Th2 differentiation. Accordingly, the improved histology and behavior have also been found.

Conclusions

CRID3 may ameliorate murine SCI by inhibiting inflammasome activation, reducing proinflammatory factor production, restoring immune cell subset balance, and improving local immune microenvironment, and early administration may be a promising therapeutic strategy for SCI.

Effects of neural stem cell transplantation on the motor function of rats with contusion spinal cord injuries: a meta-analysis

Objective

To judge the efficacies of neural stem cell (NSC) transplantation on functional recovery following contusion spinal cord injuries (SCIs).

Data sources

Studies in which NSCs were transplanted into a clinically relevant, standardized rat model of contusion SCI were identified by searching the PubMed, Embase and Cochrane databases, and the extracted data were analyzed by Stata 14.0.

Data selection

Inclusion criteria were that NSCs were used in in vivo animal studies to treat contusion SCIs and that behavioral assessment of locomotor functional recovery was performed using the Basso, Beattie, and Bresnahan lo-comotor rating scale. Exclusion criteria included a follow-up of less than 4 weeks and the lack of control groups.

Outcome measures

The restoration of motor function was assessed by the Basso, Beattie, and Bresnahan locomotor rating scale.

Results

We identified 1756 non-duplicated papers by searching the aforementioned electronic databases, and 30 full-text articles met the inclusion criteria. A total of 37 studies reported in the 30 articles were included in the meta-analysis. The meta-analysis results showed that transplanted NSCs could improve the motor function recovery of rats following contusion SCIs, to a moderate extent (pooled standardized mean difference (SMD) = 0.73; 95% confidence interval (CI): 0.47-1.00; P < 0.001). NSCs obtained from different donor species (rat: SMD = 0.74; 95% CI: 0.36-1.13; human: SMD = 0.78; 95% CI: 0.31-1.25), at different donor ages (fetal: SMD = 0.67; 95% CI: 0.43-0.92; adult: SMD = 0.86; 95% CI: 0.50-1.22) and from different origins (brain-derived: SMD = 0.59; 95% CI: 0.27-0.91; spinal cord-derived: SMD = 0.51; 95% CI: 0.22-0.79) had similar efficacies on improved functional recovery; however, adult induced pluripotent stem cell-derived NSCs showed no significant efficacies. Furthermore, the use of higher doses of transplanted NSCs or the administration of immunosuppressive agents did not promote better locomotor function recovery (SMD = 0.45; 95% CI: 0.21-0.70). However, shorter periods between the contusion induction and the NSC transplantation showed slightly higher efficacies (acute: SMD = 1.22; 95% CI: 0.81-1.63; subacute: SMD = 0.75; 95% CI: 0.42-1.09). For chronic injuries, NSC implantation did not significantly improve functional recovery (SMD = 0.25; 95% CI: -0.16 to 0.65).

Conclusion

NSC transplantation alone appears to be a positive yet limited method for the treatment of contusion SCIs.

Stem Cell Therapies: A Way to Promising Cures

Stem cells carry the remarkable ability to differentiate into different cell types while retaining the capability to self-replicate and maintain the characteristics of their parent cells, referred to as potency. Stem cells have been studied extensively to better understand human development and organogenesis. Because of advances in stem cell-based therapies, regenerative medicine has seen significant growth. Ophthalmic conditions, some of which are leading causes of blindness worldwide, are being treated with stem cell therapies. Great results have also been obtained in the treatment of oral and maxillofacial defects. Stem-cell-based therapies have great potential in the treatment of chronic medical conditions like diabetes and cardiomyopathy. The unique property of stem cells to migrate towards cancer cells makes them excellent vectors for the transportation of bioactive agents or for targeting cancer cells, both primary and metastatic.

While these therapeutic strategies are extremely promising, they are not without limitations. Failure to completely eradicate the tumor and tumor relapse are some of those concerns. Stem cells share some characteristics with cancer stem cells, raising concerns for increasing the risk of cancer occurrence. Ethical concerns due to the fetal origin of stem cells and cost are other major obstacles in the large-scale implementation of such therapies.

Olig2-expressing Mesenchymal Stem Cells Enhance Functional Recovery after Contusive Spinal Cord Injury

Background and Objectives

Glial scarring and inflammation after spinal cord injury (SCI) interfere with neural regeneration and functional recovery due to the inhibitory microenvironment of the injured spinal cord. Stem cell transplantation can improve functional recovery in experimental models of SCI, but many obstacles to clinical application remain due to concerns regarding the effectiveness and safety of stem cell transplantation for SCI patients. In this study, we investigated the effects of transplantation of human mesenchymal stem cells (hMSCs) that were genetically modified to express Olig2 in a rat model of SCI.

Methods

Bone marrow-derived hMSCs were genetically modified to express Olig2 and transplanted one week after the induction of contusive SCI in a rat model. Spinal cords were harvested 7 weeks after transplantation.

Results

Transplantation of Olig2-expressing hMSCs significantly improved functional recovery in a rat model of contusive SCI model compared to the control hMSC-transplanted group. Transplantation of Olig2-expressing hMSCs also attenuated glial scar formation in spinal cord lesions. Immunohistochemical analysis showed that transplanted Olig2-expressing hMSCs were partially differentiated into Olig1-positive oligodendrocyte-like cells in spinal cords. Furthermore, NF-M-positive axons were more abundant in the Olig2-expressing hMSC-transplanted group than in the control hMSC-transplanted group.

Conclusions

We suggest that Olig2-expressing hMSCs are a safe and optimal cell source for treating SCI.

Transcriptome profile of rat genes in bone marrow-derived macrophages at different activation statuses by RNA-sequencing

The underlying mechanisms of macrophage polarization have been detected by genome-wide transcriptome analysis in a variety of mammals. However, the transcriptome profile of rat genes in bone marrow-derived macrophages (BMM) at different activation statuses has not been reported. Therefore, we performed RNA-Sequencing to identify gene expression signatures of rat BMM polarized in vitro with different stimuli. The differentially expressed genes (DEGs) among unactivated (M0), classically activated pro-inflammatory (M1), and alternatively activated anti-inflammatory macrophages (M2) were analyzed by using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis. In this study, not only we have identified the changes of global gene expression in rat M0, M1 and M2, but we have also made clear systematically the key genes and signaling pathways in the differentiation process of M0 to M1 and M2. These will provide a foundation for future researches of macrophage polarization.

To Be or Not to Be: Environmental Factors that Drive Myelin Formation during Development and after CNS Trauma

Oligodendrocytes are specialized glial cells that myelinate central nervous system (CNS) axons. Historically, it was believed that the primary role of myelin was to compactly ensheath axons, providing the insulation necessary for rapid signal conduction. However, mounting evidence demonstrates the dynamic importance of myelin and oligodendrocytes, including providing metabolic support to neurons and regulating axon protein distribution. As such, the development and maintenance of oligodendrocytes and myelin are integral to preserving CNS homeostasis and supporting proper functioning of widespread neural networks. Environmental signals are critical for proper oligodendrocyte lineage cell progression and their capacity to form functional compact myelin; these signals are markedly disturbed by injury to the CNS, which may compromise endogenous myelin repair capabilities. This review outlines some key environmental factors that drive myelin formation during development and compares that to the primary factors that define a CNS injury milieu. We aim to identify developmental factors disrupted after CNS trauma as well as pathogenic factors that negatively impact oligodendrocyte lineage cells, as these are potential therapeutic targets to promote myelin repair after injury or disease.

Local injection of Lenti-Olig2 at lesion site promotes functional recovery of spinal cord injury in rats

AIMS

Olig2 is one of the most critical factors during CNS development, which belongs to b-HLH transcription factor family. Previous reports have shown that Olig2 regulates the remyelination processes in CNS demyelination diseases models. However, the role of Olig2 in contusion spinal cord injury (SCI) and the possible therapeutic effects remain obscure. This study aims to investigate the effects of overexpression Olig2 by lentivirus on adult spinal cord injury rats.

METHODS

Lenti-Olig2 expression and control Lenti-eGFP vectors were prepared, and virus in a total of 5 μL (10⁸ TU/mL) was locally injected into the injured spinal cord 1.5 mm rostral and caudal near the epicenter. Immunostaining, Western blot, electron microscopy, and CatWalk analyzes were employed to investigate the effects of Olig2 on spinal cord tissue repair and functional recovery.

RESULTS

Injection of Lenti-Olig2 significantly increased the number of oligodendrocytes lineage cells and enhanced myelination after SCI. More importantly, the introduction of Olig2 greatly improved hindlimb locomotor performances. Other oligodendrocyte-related transcription factors, which were downregulated or upregulated after injury, were reversed by Olig2 induction.

CONCLUSIONS

Our findings provided the evidence that overexpression Olig2 promotes myelination and locomotor recovery of contusion SCI, which gives us more understanding of Olig2 on spinal cord injury treatment.

Transplantation of PDGF-AA-Overexpressing Oligodendrocyte Precursor Cells Promotes Recovery in Rat Following Spinal Cord Injury

Our previous study showed that Schwann cells (SCs) promote survival, proliferation and migration of co-transplanted oligodendrocyte progenitor cells (OPCs) and neurological recovery in rats with spinal cord injury (SCI). A subsequent in vitro study confirmed that SCs modulated OPC proliferation and migration by secreting platelet-derived growth factor (PDGF)-AA and fibroblast growth factor-2 (FGF)-2. We also found that PDGF-AA stimulated OPC proliferation and their differentiation into oligodendrocytes (OLs) at later stages. We therefore speculated that PDGF-AA administration can exert the same effect as SC co-transplantation in SCI repair. To test this hypothesis, in this study we investigated the effect of transplanting PDGF-AA-overexpressing OPCs in a rat model of SCI. We found that PDGF-AA overexpression in OPCs promoted their survival, proliferation, and migration and differentiation into OLs in vivo. OPCs overexpressing PDGF-AA were also associated with increased myelination and tissue repair after SCI, leading to the recovery of neurological function. These results indicate that PDGF-AA-overexpressing OPCs may be an effective treatment for SCI.

Transcriptome profile of rat genes in injured spinal cord at different stages by RNA-sequencing

Background

Spinal cord injury (SCI) results in fatal damage and currently has no effective treatment. The pathological mechanisms of SCI remain unclear. In this study, genome-wide transcriptional profiling of spinal cord samples from injured rats at different time points after SCI was performed by RNA-Sequencing (RNA-Seq). The transcriptomes were systematically characterized to identify the critical genes and pathways that are involved in SCI pathology.

Results

RNA-Seq results were obtained from total RNA harvested from the spinal cords of sham control rats and rats in the acute, subacute, and chronic phases of SCI (1 day, 6 days and 28 days after injury, respectively; n = 3 in every group). Compared with the sham-control group, the number of differentially expressed genes was 1797 in the acute phase (1223 upregulated and 574 downregulated), 6590 in the subacute phase (3460 upregulated and 3130 downregulated), and 3499 in the chronic phase (1866 upregulated and 1633 downregulated), with an adjusted P-value <0.05 by DESeq. Gene ontology (GO) enrichment analysis showed that differentially expressed genes were most enriched in immune response, MHC protein complex, antigen processing and presentation, translation-related genes, structural constituent of ribosome, ion gated channel activity, small GTPase mediated signal transduction and cytokine and/or chemokine activity. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the most enriched pathways included ribosome, antigen processing and presentation, retrograde endocannabinoid signaling, axon guidance, dopaminergic synapses, glutamatergic synapses, GABAergic synapses, TNF, HIF-1, Toll-like receptor, NF-kappa B, NOD-like receptor, cAMP, calcium, oxytocin, Rap1, B cell receptor and chemokine signaling pathway.

Conclusions

This study has not only characterized changes in global gene expression through various stages of SCI progression in rats, but has also systematically identified the critical genes and signaling pathways in SCI pathology. These results will expand our understanding of the complex molecular mechanisms involved in SCI and provide a foundation for future studies of spinal cord tissue damage and repair.

The sequence data from this study have been deposited into Sequence Read Archive (http://www.ncbi.nlm.nih.gov/sra; accession number PRJNA318311).

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3532-x) contains supplementary material, which is available to authorized users.

Does the preclinical evidence for functional remyelination following myelinating cell engraftment into the injured spinal cord support progression to clinical trials?

This article reviews all historical literature in which rodent-derived myelinating cells have been engrafted into the contused adult rodent spinal cord. From 2500 initial PubMed citations identified, human cells grafts, bone mesenchymal stem cells, olfactory ensheathing cells, non-myelinating cell grafts, and rodent grafts into hemisection or transection models were excluded, resulting in the 67 studies encompassed in this review. Forty five of those involved central nervous system (CNS)-derived cells, including neural stem progenitor cells (NSPCs), neural restricted precursor cells (NRPs) or oligodendrocyte precursor cells (OPCs), and 22 studies involved Schwann cells (SC). Of the NSPC/NPC/OPC grafts, there was no consistency with respect to the types of cells grafted and/or the additional growth factors or cells co-grafted. Enhanced functional recovery was reported in 31/45 studies, but only 20 of those had appropriate controls making conclusive interpretation of the remaining studies impossible. Of those 20, 19 were properly powered and utilized appropriate statistical analyses. Ten of those 19 studies reported the presence of graft-derived myelin, 3 reported evidence of endogenous remyelination or myelin sparing, and 2 reported both. For the SC grafts, 16/21 reported functional improvement, with 11 having appropriate cellular controls and 9/11 using proper statistical analyses. Of those 9, increased myelin was reported in 6 studies. The lack of consistency and replication among these preclinical studies are discussed with respect to the progression of myelinating cell transplantation therapies into the clinic.

Differential effects of myelin basic protein-activated Th1 and Th2 cells on the local immune microenvironment of injured spinal cord

Myelin basic protein (MBP) activated T cells (MBP-T) play an important role in the damage and repair process of the central nervous system (CNS). However, whether these cells play a beneficial or detrimental role is still a matter of debate. Although some studies showed that MBP-T cells are mainly helper T (Th) cells, their subtypes are still not very clear. One possible explanation for MBP-T immunization leading to conflicting results may be the different subtypes of T cells are responsible for distinct effects. In this study, the Th1 and Th2 type MBP-T cells (MBP-Th1 and -Th2) were polarized in vitro, and their effects on the local immune microenvironment and tissue repair of spinal cord injury (SCI) after adoptive immunization were investigated. In MBP-Th1 cell transferred rats, the high levels of pro-inflammatory cells (Th1 cells and M1 macrophages) and cytokines (IFN-γ, TNF-α, -β, IL-1β) were detected in the injured spinal cord; however, the anti-inflammatory cells (Th2 cells, regulatory T cells, and M2 macrophages) and cytokines (IL-4, -10, and -13) were found in MBP-Th2 cell transferred animals. MBP-Th2 cell transfer resulted in decreased lesion volume, increased myelination of axons, and preservation of neurons. This was accompanied by significant locomotor improvement. These results indicate that MBP-Th2 adoptive transfer has beneficial effects on the injured spinal cord, in which the increased number of Th2 cells may alter the local microenvironment from one primarily populated by Th1 and M1 cells to another dominated by Th2, Treg, and M2 cells and is conducive for SCI repair.

Engineering Stem Cells for Biomedical Applications

Stem cells are characterized by a number of useful properties, including their ability to migrate, differentiate, and secrete a variety of therapeutic molecules such as immunomodulatory factors. As such, numerous pre-clinical and clinical studies have utilized stem cell-based therapies and demonstrated their tremendous potential for the treatment of various human diseases and disorders. Recently, efforts have focused on engineering stem cells in order to further enhance their innate abilities as well as to confer them with new functionalities, which can then be used in various biomedical applications. These engineered stem cells can take on a number of forms. For instance, engineered stem cells encompass the genetic modification of stem cells as well as the use of stem cells for gene delivery, nanoparticle loading and delivery, and even small molecule drug delivery. The present Review gives an in-depth account of the current status of engineered stem cells, including potential cell sources, the most common methods used to engineer stem cells, and the utilization of engineered stem cells in various biomedical applications, with a particular focus on tissue regeneration, the treatment of immunodeficiency diseases, and cancer.

Hypothyroxinemia induced by maternal mild iodine deficiency impairs hippocampal myelinated growth in lactational rats

Hypothyroxinemia induced by maternal mild iodine deficiency causes neurological deficits and impairments of brain function in offspring. Hypothyroxinemia is prevalent in developing and developed countries alike. However, the mechanism underlying these deficits remains less well known. Given that the myelin plays an important role in learning and memory function, we hypothesize that hippocampal myelinated growth may be impaired in rat offspring exposed to hypothyroxinemia induced by maternal mild iodine deficiency. To test this hypothesis, the female Wistar rats were used and four experimental groups were prepared: (1) control; (2) maternal mild iodine deficiency diet inducing hypothyroxinemia; (3) hypothyroidism induced by maternal severe iodine deficiency diet; (4) hypothyroidism induced by maternal methimazole water. The rats were fed the diet from 3 months before pregnancy to the end of lactation. Our results showed that the physiological changes occuring in the hippocampal myelin were altered in the mild iodine deficiency group as indicated by the results of immunofluorescence of myelin basic proteins on postnatal day 14 and postnatal day 21. Moreover, hypothyroxinemia reduced the expressions of oligodendrocyte lineage transcription factor 2 and myelin-related proteins in the treatments on postnatal day 14 and postnatal day 21. Our data suggested that hypothyroxinemia induced by maternal mild iodine deficiency may impair myelinated growth of the offspring.

Adoptive transfer of M2 macrophages promotes locomotor recovery in adult rats after spinal cord injury

Classically activated pro-inflammatory (M1) and alternatively activated anti-inflammatory (M2) macrophages populate the local microenvironment after spinal cord injury (SCI). The former type is neurotoxic while the latter has positive effects on neuroregeneration and is less toxic. In addition, while the M1 macrophage response is rapidly induced and sustained, M2 induction is transient. A promising strategy for the repair of SCI is to increase the fraction of M2 cells and prolong their residence time. This study investigated the effect of M2 macrophages induced from bone marrow-derived macrophages on the local microenvironment and their possible role in neuroprotection after SCI. M2 macrophages produced anti-inflammatory cytokines such as interleukin (IL)-10 and transforming growth factor β and infiltrated into the injured spinal cord, stimulated M2 and helper T (Th)2 cells, and produced high levels of IL-10 and -13 at the site of injury. M2 cell transfer decreased spinal cord lesion volume and resulted in increased myelination of axons and preservation of neurons. This was accompanied by significant locomotor improvement as revealed by Basso, Beattie and Bresnahan locomotor rating scale, grid walk and footprint analyses. These results indicate that M2 adoptive transfer has beneficial effects for the injured spinal cord, in which the increased number of M2 macrophages causes a shift in the immunological response from Th1- to Th2-dominated through the production of anti-inflammatory cytokines, which in turn induces the polarization of local microglia and/or macrophages to the M2 subtype, and creates a local microenvironment that is conducive to the rescue of residual myelin and neurons and preservation of neuronal function.

The Olig family affects central nervous system development and disease

Neural cell differentiation and maturation is a critical step during central nervous system development. The oligodendrocyte transcription family (Olig family) is known to be an important factor in regulating neural cell differentiation. Because of this, the Olig family also affects acute and chronic central nervous system diseases, including brain injury, multiple sclerosis, and even gliomas. Improved understanding about the functions of the Olig family in central nervous system development and disease will greatly aid novel breakthroughs in central nervous system diseases. This review investigates the role of the Olig family in central nervous system development and related diseases.

Olig2 overexpression accelerates the differentiation of mouse embryonic stem cells into oligodendrocyte progenitor cells in vitro

Oligodendrocyte progenitor cells (OPCs) transplantation is receiving considerable attention in the field of regenerative medicine therapy for demyelinating diseases. Although embryonic stem cells (ESCs) have been successfully induced to differentiate into OPCs with cytokines cocktails in vitro, the regulatory roles of many key transcription factors in this process are not clear. Here, we introduced oligodendrocyte lineage transcription factor 2 (Olig2), a basic helix-loop-helix transcription factor, into mouse embryonic stem cells (mESCs) to investigate its effects on the differentiation of mESCs into OPCs. The results showed that Olig2 overexpression alone did not affect pluripotency of mESCs, but in the stimulation of differentiating cocktails, Olig2 accelerated mESCs to differentiate into OPCs, shortening the induction time span from normal 21 days to 11 days. Further study demonstrated the Olig2-mESCs derived OPCs were able to differentiate into C-type natriuretic peptid (CNP) and Myelin Basic Protein (MBP) positive mature oligodendrocytes (OLs) in vitro, suggesting these induced OPCs might be favorable for myelin regeneration in vivo.

Lymphocytes and autoimmunity after spinal cord injury

Over the past 15 years an immense amount of data has accumulated regarding the infiltration and activation of lymphocytes in the traumatized spinal cord. Although the impact of the intraspinal accumulation of lymphocytes is still unclear, modulation of the adaptive immune response via active and passive vaccination is being evaluated for its preclinical efficacy in improving the outcome for spinal-injured individuals. The complexity of the interaction between the nervous and the immune systems is highlighted in the contradictions that appear in response to these modulations. Current evidence regarding augmentation and inhibition of the adaptive immune response to spinal cord injury is reviewed with an aim toward reconciling conflicting data and providing consensus issues that may be exploited in future therapies. Opportunities such an approach may provide are highlighted as well as the obstacles that must be overcome before such approaches can be translated into clinical trials.

Graft of a tissue-engineered neural scaffold serves as a promising strategy to restore myelination after rat spinal cord transection

Remyelination remains a challenging issue in spinal cord injury (SCI). In the present study, we cocultured Schwann cells (SCs) and neural stem cells (NSCs) with overexpression of neurotrophin-3 (NT-3) and its high affinity receptor tyrosine kinase receptor type 3 (TrkC), respectively, in a gelatin sponge (GS) scaffold. This was aimed to generate a tissue-engineered neural scaffold and to investigate whether it could enhance myelination after a complete T10 spinal cord transection in adult rats. Indeed, many NT-3 overexpressing SCs (NT-3-SCs) in the GS scaffold assumed the formation of myelin. More strikingly, a higher incidence of NSCs overexpressing TrkC differentiating toward myelinating cells was induced by NT-3-SCs. By transmission electron microscopy, the myelin sheath showed distinct multilayered lamellae formed by the seeded cells. Eighth week after the scaffold was transplanted, some myelin basic protein (MBP)-positive processes were observed within the transplantation area. Remarkably, certain segments of myelin derived from NSC-derived myelinating cells and NT-3-SCs were found to ensheath axons. In conclusion, we show here that transplantation of the GS scaffold promotes exogenous NSC-derived myelinating cells and SCs to form myelins in the injury/transplantation area of spinal cord. These findings thus provide a neurohistological basis for the future application or transplantation using GS neural scaffold to repair SCI.

Sonic hedgehog promotes generation and maintenance of human forebrain Olig2 progenitors

Function of oligodendrocytes (OLs), myelin forming cells in the CNS, is disrupted in demyelinating diseases such as periventricular leukomalacia or multiple sclerosis. It is, thus, important to better understand factors that can affect generation or differentiation of human OLs. In rodents, Sonic hedgehog (Shh) is influencing expression of Olig2, a helix-loop-helix transcription factor required for development of OLs. In humans, Olig2 is present in cortical progenitors at midgestation, however the role of Shh in the specification of human OLs, including Olig2 positive (Olig2⁺) progenitors, is not fully understood. Here we studied in vitro effects of Shh signaling on proliferation and specification of human cortical Olig2⁺ progenitors at midgestation. First, we established that the spatial pattern of Olig2 expression in the human developing CNS, described on cryosections, was preserved in mixed and enriched radial glia cell (RGC) cultures. Next, we demonstrated that in vitro treatment with Shh induced an increase in the number of Olig2⁺ progenitors. Shh treatment increased the density of early oligodendrocyte progenitors (OPCs) at the expense of RGC, while the number of late OPCs, did not change. However, inhibition of endogenous Shh with cyclopamine did not reduce the density of Olig2⁺ cells, implying the presence of an additional Shh-independent mechanism for OLs generation in vitro. These results suggest that the primary role of Shh signaling in the human dorsal oligodendrogenesis is the expansion and specification of multipotent radial glia progenitors into Olig2⁺ early OPCs. These results obtained in vitro are relevant to understand primary myelination during CNS development, as well as remyelination in demyelinating diseases.

Stage-specific deletion of Olig2 conveys opposing functions on differentiation and maturation of oligodendrocytes

The temporal and spatial patterning involved in the specification, differentiation, and myelination by oligodendroglia is coordinated in part by the activation and repression of various transcriptional programs. Olig2 is a basic helix-loop-helix transcription factor necessary for oligodendroglial development and expressed continuously throughout the lineage. Despite evidence for the critical role of Olig2 in oligodendroglial specification and differentiation, the function for Olig2 during later stages of oligodendroglial development, namely, the transition into mature oligodendrocytes (OLs) and the formation of the myelin sheath, remains unclear. To address the possibility for a stage-specific role, we deleted Olig2 in oligodendrocyte precursor cells (OPCs) under the control of the CNPase-promoter or in immature OLs under the inducible proteolipid protein promoter. As expected, ablation of Olig2 in OPCs significantly inhibits differentiation, resulting in hypomyelination. However, deletion of the Olig2 gene in immature OLs significantly enhances the maturation process and accelerates the kinetics of myelination/remyelination. Underlying the stage-specific roles for Olig2 is the compensatory expression and function of Olig1, a transcription factor that promotes OL maturation and (re)myelination. Olig1 expression is significantly reduced upon Olig2 deletion in OPCs but is dramatically increased by nearly threefold when deleted in immature OLs. By enforcing expression of Olig1 into OPCs in a null Olig2 background, we demonstrate that overexpression of Olig1 is sufficient to rescue the differentiation phenotype and partially compensates for the Olig2 deletion in vitro. Our results suggest a stage-specific regulatory role for Olig2, mediated by Olig1 that conveys opposing functions on the differentiation and maturation of oligodendrocytes.