Analysis of allogeneic and syngeneic bone marrow stromal cell graft survival in the spinal cord

Electrical stimulation promotes functional recovery after spinal cord injury by activating endogenous spinal cord-derived neural stem/progenitor cell: an in vitro and in vivo study

BACKGROUND CONTEXT

Electrical stimulation is a noninvasive treatment method that has gained popularity in the treatment of spinal cord injury (SCI). Activation of spinal cord-derived neural stem/progenitor cell (SC-NSPC) proliferation and differentiation in the injured spinal cord may elicit considerable neural regenerative effects.

PURPOSE

This study aimed to explore the effect of electrical stimulation on the neurogenesis of SC-NSPCs.

STUDY DESIGN

This study analyzed the effects of electrical stimulation on neurogenesis in rodent SC-NSPCs in vitro and in vivo and evaluated functional recovery and neural circuitry improvements with electrical stimulation using a rodent SCI model.

METHODS

Rats (20 rats/group) were assigned to sham (Group 1), SCI only (Group 2), SCI + electrode implant without stimulation (Group 3), and SCI + electrode with stimulation (Group 4) groups to count total SC-NSPCs and differentiated neurons and to evaluate morphological changes in differentiated neurons. Furthermore, the Basso, Beattie, and Bresnahan scores were analyzed, and the motor- and somatosensory-evoked potentials in all rats were monitored.

RESULTS

Biphasic electrical currents enhanced SC-NSPC proliferation differentiation and caused qualitative morphological changes in differentiated neurons in vitro. Electrical stimulation promoted SC-NSPC proliferation and neuronal differentiation and improved functional outcomes and neural circuitry in SCI models. Increased Wnt3, Wnt7, and β-catenin protein levels were also observed after electrical stimulation.

CONCLUSIONS

Our study proved the beneficial effects of electrical stimulation on SCI. The Wnt/β-catenin pathway activation may be associated with this relationship between electrical stimulation and neuronal regeneration after SCI.

CLINICAL SIGNIFICANCE

The study confirmed the benefits of electrical stimulation on SCI based on cellular, functional, electrophysiological, and histological evidence. Based on these findings, we expect electrical stimulation to make a positive and significant difference in SCI treatment strategies.

Challenges in Translating Regenerative Therapies for Spinal Cord Injury

Regenerating the injured spinal cord is a substantial challenge with many obstacles that need to be overcome to achieve robust functional benefits. This abundance of hurdles can partly explain the limited success when applying regenerative intervention treatments in animal models and/or people. In this article, we elaborate on a few of these obstacles, starting with the applicability of animal models and how they compare to the clinical setting. We then discuss the requirement for combinatorial interventions and the associated problems in experimental design, including the addition of rehabilitative training. The article expands on differences in lesion sizes and locations between humans and common animal models, and how this difference can determine the success or failure of an intervention. An additional and frequently overlooked problem in the translation of interventions that applies beyond the field of neuroregeneration is the reporting bias and the lack of transparency in reporting findings. New data mandates are tackling this problem and will eventually result in a more balanced view of the field. Finally, we will discuss strategies to negotiate the challenging course of successful translation to facilitate successful translation of regeneration promoting interventions.

Neuroprotection and Axonal Regeneration Induced by Bone Marrow Mesenchymal Stromal Cells Depend on the Type of Transplant

Mesenchymal stromal cell (MSC) therapy to treat neurodegenerative diseases has not been as successful as expected in some preclinical studies. Because preclinical research is so diverse, it is difficult to know whether the therapeutic outcome is due to the cell type, the type of transplant or the model of disease. Our aim here was to analyze the effect of the type of transplant on neuroprotection and axonal regeneration, so we tested MSCs from the same niche in the same model of neurodegeneration in the three transplantation settings: xenogeneic, syngeneic and allogeneic. For this, bone marrow mesenchymal stromal cells (BM-MSCs) isolated from healthy human volunteers or C57/BL6 mice were injected into the vitreous body of C57/BL6 mice (xenograft and syngraft) or BALB/c mice (allograft) right after optic nerve axotomy. As controls, vehicle matched groups were done. Retinal anatomy and function were analyzed in vivo by optical coherence tomography and electroretinogram, respectively. Survival of vision forming (Brn3a⁺) and non-vision forming (melanopsin⁺) retinal ganglion cells (RGCs) was assessed at 3, 5 and 90 days after the lesion. Regenerative axons were visualized by cholera toxin β anterograde transport. Our data show that grafted BM-MSCs did not integrate in the retina but formed a mesh on top of the ganglion cell layer. The xenotransplant caused retinal edema, detachment and folding, and a significant decrease of functionality compared to the murine transplants. RGC survival and axonal regeneration were significantly higher in the syngrafted retinas than in the other two groups or vehicle controls. Melanopsin⁺RGCs, but not Brn3a⁺RGCs, were also neuroprotected by the xenograft. In conclusion, the type of transplant has an impact on the therapeutic effect of BM-MSCs affecting not only neuronal survival but also the host tissue response. Our data indicate that syngrafts may be more beneficial than allografts and, interestingly, that the type of neuron that is rescued also plays a significant role in the successfulness of the cell therapy.

De-osteogenic-differentiated mesenchymal stem cells accelerate fracture healing by mir-92b

Background

Mesenchymal stem cells (MSCs) are promising targets for therapeutic use in regenerative medicine and tissue engineering. In the previous study, we have found that MSCs could be reverted to a primitive stem cell population after in vitro induction of osteogenic and de-osteogenic differentiation (de-osteogenic differentiated MSCs, De-Os-MSCs). De-Os-MSCs showed improved cell survival and osteogenic potential. However, the underlying mechanism and its potential effect on fracture healing has not been explored.

Methods

MSCs were isolated from the rat bone marrow. MicroRNAs were cloned into lentiviral vectors and transduced into MSCs to observe the effects on osteogenesis. The expression levels of marker genes were evaluated by quantitative RT-PCR. Ectopic bone formation model was used to evaluate the bone regeneration ability of mir-92b transduced MSCs in vivo. An open femur fracture model was established, and MSCs or De-Os-MSCs were administrated to the fracture sites. Histological, biomechanical and microCT analysis were used to evaluate the quality of bone.

Results

In the present study, we found that mir-92b was significantly increased in the secretions of De-Os-MSCs. And mir-92b could promote the osteogenic differentiation potential of MSCs by activating pERK and JNK signaling pathways. The ectopic bone formation assay showed that MSCs overexpressing mir-92b formed more bone like tissues in vivo. Most importantly, we found local administration of De-Os-MSCs could accelerate fracture healing using an open femur fracture model in rats. The quality of bone property was much better as shown by microCT and biomechanical testing.

Conclusion

Taken together, our study demonstrated that mir-92b promoted osteogenesis of MSCs, which was partially accounted for the enhanced osteogenic differentiation potential of De-Os-MSCs. And De-Os-MSCs had shown better regenerative capacity in accelerating fracture healing when they were locally given.

The translational potential of this article

De-Os-MSCs could be used to accelerate fracture healing, and reduce the occurrence of delayed unions and non-unions.

Progress in Stem Cell Therapy for Spinal Cord Injury

Background

Spinal cord injury (SCI) is one of the serious neurological diseases that occur in young people with high morbidity and disability. However, there is still a lack of effective treatments for it. Stem cell (SC) treatment of SCI has gradually become a new research hotspot over the past decades. This article is aimed at reviewing the research progress of SC therapy for SCI.

Methods

Review the literature and summarize the effects, strategies, related mechanisms, safety, and clinical application of different SC types and new approaches in combination with SC in SCI treatment.

Results

A large number of studies have focused on SC therapy for SCI, most of which showed good effects. The common SC types for SCI treatment include mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), neural stem cells (NSCs), induced pluripotent stem cells (iPSCs), and embryonic stem cells (ESCs). The modes of treatment include in vivo and in vitro induction. The pathways of transplantation consist of intravenous, transarterial, nasal, intraperitoneal, intrathecal, and intramedullary injections. Most of the SC treatments for SCI use a number of cells ranging from tens of thousands to millions. Early or late SC administration, application of immunosuppressant or not are still controversies. Potential mechanisms of SC therapy include tissue repair and replacement, neurotrophy, and regeneration and promotion of angiogenesis, antiapoptosis, and anti-inflammatory. Common safety issues include thrombosis and embolism, tumorigenicity and instability, infection, high fever, and even death. Recently, some new approaches, such as the pharmacological activation of endogenous SCs, biomaterials, 3D print, and optogenetics, have been also developed, which greatly improved the application of SC therapy for SCI.

Conclusion

Most studies support the effects of SC therapy on SCI, while a few studies do not. The cell types, mechanisms, and strategies of SC therapy for SCI are very different among studies. In addition, the safety cannot be ignored, and more clinical trials are required. The application of new technology will promote SC therapy of SCI.

Comparison of Mesenchymal Stromal Cells Isolated from Murine Adipose Tissue and Bone Marrow in the Treatment of Spinal Cord Injury

The use of mesenchymal stromal cell (MSC) transplantation to repair the injured spinal cord has shown consistent benefits in preclinical models. However, the low survival rate of grafted MSC is one of the most important problems. In the injured spinal cord, transplanted cells are exposed to hypoxic conditions and exposed to nutritional deficiency caused by poor vascular supply. Also, the transplanted MSCs face cytotoxic stressors that cause cell death. The aim of this study was to compare adipose-derived MSCs (AD-MSCs) and bone marrow-derived MSCs (BM-MSCs) isolated from individual C57BL6/J mice in relation to: (i) cellular characteristics, (ii) tolerance to hypoxia, oxidative stress and serum-free conditions, and (iii) cellular survival rates after transplantation. AD-MSCs and BM-MSCs exhibited a similar cell surface marker profile, but expressed different levels of growth factors and cytokines. To research their relative stress tolerance, both types of stromal cells were incubated at 20.5% O₂ or 1.0% O₂ for 7 days. Results showed that AD-MSCs were more proliferative with greater culture viability under these hypoxic conditions than BM-MSCs. The MSCs were also incubated under H₂O₂-induced oxidative stress and in serum-free culture medium to induce stress. AD-MSCs were better able to tolerate these stress conditions than BM-MSCs; similarly when transplanted into the spinal cord injury region in vivo, AD-MSCs demonstrated a higher survival rate post transplantation Furthermore, this increased AD-MSC survival post transplantation was associated with preservation of axons and enhanced vascularization, as delineated by increases in anti-gamma isotype of protein kinase C and CD31 immunoreactivity, compared with the BM-MSC transplanted group. Hence, our results indicate that AD-MSCs are an attractive alternative to BM-MSCs for the treatment of severe spinal cord injury. However, it should be noted that the motor function was equally improved following moderate spinal cord injury in both groups, but with no significant improvement seen unfortunately following severe spinal cord injury in either group.

Biomaterial-Supported Cell Transplantation Treatments for Spinal Cord Injury: Challenges and Perspectives

Spinal cord injury (SCI), resulting in para- and tetraplegia caused by the partial or complete disruption of descending motor and ascending sensory neurons, represents a complex neurological condition that remains incurable. Following SCI, numerous obstacles comprising of the loss of neural tissue (neurons, astrocytes, and oligodendrocytes), formation of a cavity, inflammation, loss of neuronal circuitry and function must be overcome. Given the multifaceted primary and secondary injury events that occur with SCI treatment options are likely to require combinatorial therapies. While several methods have been explored, only the intersection of two, cell transplantation and biomaterial implantation, will be addressed in detail here. Owing to the constant advance of cell culture technologies, cell-based transplantation has come to the forefront of SCI treatment in order to replace/protect damaged tissue and provide physical as well as trophic support for axonal regrowth. Biomaterial scaffolds provide cells with a protected environment from the surrounding lesion, in addition to bridging extensive damage and providing physical and directional support for axonal regrowth. Moreover, in this combinatorial approach cell transplantation improves scaffold integration and therefore regenerative growth potential. Here, we review the advances in combinatorial therapies of Schwann cells (SCs), astrocytes, olfactory ensheathing cells (OECs), mesenchymal stem cells, as well as neural stem and progenitor cells (NSPCs) with various biomaterial scaffolds.

Transplantation of choroid plexus epithelial cells into contusion-injured spinal cord of rats

Purpose: The effect of the transplantation of choroid plexus epithelial cells (CPECs) on locomotor improvement and tissue repair including axonal extension in spinal cord lesions was examined in rats with spinal cord injury (SCI).

Methods: CPECs were cultured from the choroid plexus of green fluorescent protein (GFP)-transgenic rats, and transplanted directly into the contusion-injured spinal cord lesions of rats of the same strain. Locomotor behaviors were evaluated based on BBB scores every week after transplantation until 4 weeks after transplantation. Histological and immunohistochemical examinations were performed at 2 days, and every week until 5 weeks after transplantation.

Results: Locomotor behaviors evaluated by the BBB score were significantly improved in cell-transplanted rats. Numerous axons grew, with occasional interactions with CPECs, through the astrocyte-devoid areas. These axons exhibited structural characteristics of peripheral nerves. GAP-43-positive axons were found at the border of the lesion 2 days after transplantation. Cavity formation was more reduced in cell-transplanted than control spinal cords. CPECs were found within the spinal cord lesion, and sometimes in association with astrocytes at the border of the lesion until 2 weeks after transplantation.

Conclusion: The transplantation of CPECs enhanced locomotor improvement and tissue recovery, including axonal regeneration, in rats with SCI.

Tissue source determines the differentiation potentials of mesenchymal stem cells: a comparative study of human mesenchymal stem cells from bone marrow and adipose tissue

Background

Mesenchymal stem cells (MSCs) possess intrinsic regeneration capacity as part of the repair process in response to injury, such as fracture or other tissue injury. Bone marrow and adipose tissue are the major sources of MSCs. However, which cell type is more effective and suitable for cell therapy remains to be answered. The intrinsic molecular mechanism supporting the assertion has also been lacking.

Methods

Human bone marrow-derived MSCs (BMSCs) and adipose tissue-derived MSCs (ATSCs) were isolated from bone marrow and adipose tissue obtained after total hip arthroplasty. ATSCs and BMSCs were incubated in standard growth medium. Trilineage differentiation including osteogenesis, adipogenesis, and chondrogenesis was performed by addition of relevant induction mediums. The expression levels of trilineage differentiation marker genes were evaluated by quantitative RT-PCR. The methylation status of CpG sites of Runx2, PPARγ, and Sox9 promoters were checked by bisulfite sequencing. In addition, ectopic bone formation and calvarial bone critical defect models were used to evaluate the bone regeneration ability of ATSCs and BMSCs in vivo.

Results

The results showed that BMSCs possessed stronger osteogenic and lower adipogenic differentiation potentials compared to ATSCs. There was no significant difference in the chondrogenic differentiation potential. The CpG sites of Runx2 promoter in BMSCs were hypomethylated, while in ATSCs they were hypermethylated. The CpG sites of PPARγ promoter in ATSCs were hypomethylated, while in BMSCs they were hypermethylated. The methylation status of Sox9 promoter in BMSCs was only slightly lower than that in ATSCs.

Conclusions

The epigenetic memory obtained from either bone marrow or adipose tissue favored MSC differentiation along an osteoblastic or adipocytic lineage. The methylation status of the main transcription factors controlling MSC fate contributes to the differential differentiation capacities of different source-derived MSCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0716-x) contains supplementary material, which is available to authorized users.

Article Commentary: Stem Cell Research in Cell Transplantation: An Analysis of Geopolitical Influence by Publications

One of the fastest growing fields in researching treatments for neurodegenerative and other disorders is the use of stem cells. These cells are naturally occurring and can be obtained from three different stages of an organism's life: embryonic, fetal, and adult. In the US, political doctrine has restricted use of federal funds for stem cells, enhancing research towards an adult source. In order to determine how this legislation may be represented by the stem cell field, a retrospective analysis of stem cell articles published in the journal Cell Transplantation over a 2-year period was performed. Cell Transplantation is considered a translational journal from preclinical to clinical, so it was of interest to determine the publication outcome of stem cell articles 6 years after the US regulations. The distribution of the source of stem cells was found to be biased towards the adult stage, but relatively similar over the embryonic and fetal stages. The fetal stem cell reports were primarily neural in origin, whereas the adult stem cell ones were predominantly mesenchymal and used mainly in neural studies. The majority of stem cell studies published in Cell Transplantation were found to fall under the umbrella of neuroscience research. American scientists published the most articles using stem cells with a bias towards adult stem cells, supporting the effect of the legislation, whereas Europe was the leading continent with a bias towards embryonic and fetal stem cells, where research is “controlled” but not restricted. Japan was also a major player in the use of stem cells. Allogeneic transplants (where donor and recipient are the same species) were the most common transplants recorded, although the transplantation of human-derived stem cells into rodents was the most common specific transplantation performed. This demonstrates that the use of stem cells is an increasingly important field (with a doubling of papers between 2005 and 2006), which is likely to develop into a major therapeutic area over the next few decades and that funding restrictions can affect the type of research being performed.

Innate Allorecognition Results in Rapid Accumulation of Monocyte-Derived Dendritic Cells

Although the mechanisms governing the innate recognition of pathogen-associated molecular patterns have been well defined, how allogeneic cellular stimuli evoke innate responses remains less so. In this article, we report that upon i.v. transfer (to avoid major iatrogenic interference), allogeneic but not syngeneic leukocytes could induce a rapid (after 1 d) accumulation of host monocyte-derived dendritic cells (moDCs) without any increase in conventional DCs. This occurred in various donor-host strain combinations, did not require MHC mismatch, and could be induced by various donor cell types including B cells, T cells, or NK cells. Using RAG(-/-)γc(-/-) and scid γc(-/-)mice with different MHC, we found that the presence of either donor or host lymphoid cells was required. Alloinduced moDC accumulation was significantly reduced when splenocytes from mice deficient in NK cells by genetic ablation were used as donors. A major component of this moDC accumulation appears to be recruitment. Our findings provide new insights into how the innate and adaptive immune system may interact during allogeneic encounters and thus transplant rejection.

Bone Marrow Stromal Cell Intraspinal Transplants Fail to Improve Motor Outcomes in a Severe Model of Spinal Cord Injury

Bone marrow stromal cells (BMSCs) have been reported to exert potential neuroprotective properties in models of neurotrauma, although precise mechanisms underlying their benefits are poorly understood. Despite this lack of knowledge, several clinical trials have been initiated using these cells. To determine whether local mechanisms mediate BMSC neuroprotective actions, we grafted allogeneic BMSCs to sites of severe, compressive spinal cord injury (SCI) in Sprague-Dawley rats. Cells were administered 48 h after the original injury. Additional animals received allogeneic MSCs that were genetically modified to secrete brain-derived neurotrophic factor (BDNF) to further determine whether a locally administered neurotrophic factor provides or extends neuroprotection. When assessed 2 months post-injury in a clinically relevant model of severe SCI, BMSC grafts with or without BDNF secretion failed to improve motor outcomes. Thus, allogeneic grafts of BMSCs do not appear to act through local mechanisms, and future clinical trials that acutely deliver BMSCs to actual sites of injury within days are unlikely to be beneficial. Additional studies should address whether systemic administration of BMSCs alter outcomes from neurotrauma.

Autophagy Plays a Protective Role in Tumor Necrosis Factor-α-Induced Apoptosis of Bone Marrow-Derived Mesenchymal Stem Cells

Bone marrow-derived mesenchymal stem cells (BMSCs) are being broadly investigated for treating numerous inflammatory diseases. However, the low survival rate of BMSCs during the transplantation process has limited their application. Autophagy can maintain cellular homeostasis and protect cells against environmental stresses. Tumor necrosis factor-α (TNF-α) is an important inflammatory cytokine that can induce both autophagy and apoptosis of BMSCs. However, the actual role of autophagy in TNF-α-induced apoptosis of BMSCs remains poorly understood. In the current study, BMSCs were treated with TNF-α/cycloheximide (CHX), and cell death was examined by the Cell Counting Kit-8, Hoechst 33342 staining, and flow cytometric analysis as well as by the level of caspase-3 and caspase-8. Meanwhile, autophagic flux was examined by analyzing the level of microtubule-associated protein light chain 3 B (LC3B)-II and SQSTEM1/p62 and by examining the amount of green fluorescent protein-LC3B by fluorescence microscopy. Then, the cell death and autophagic flux of BMSCs were examined after pretreatment and cotreatment with 3-methyladenine (3-MA, autophagy inhibitor) or rapamycin (Rap, autophagy activator) together with TNF-α/CHX. Moreover, BMSCs pretreated with lentiviruses encoding short hairpin RNA of beclin-1 (BECN1) were treated with TNF-α/CHX, and then cell death and autophagic flux were detected. We showed that BMSCs treated with TNF-α/CHX presented dramatically elevated autophagic flux and cell death. Furthermore, we showed that 3-MA and shBECN1 treatment accelerated TNF-α/CHX-induced apoptosis, but that Rap treatment ameliorated cell death. Our results demonstrate that autophagy protects BMSCs against TNF-α-induced apoptosis. Enhancing the autophagy of BMSCs may elevate cellular survival in an inflammatory microenvironment.

Modern stem cell therapy: approach to disease

Various types of stem cells exist, each with their own advantages and disadvantages. Considering the current available evidence, important preclinical and clinical studies regarding the therapeutic potential of stem cells, stem cell therapy might be the important strategy for tissue repair. The development of stem cell therapy for tissue repair has primarily relied on stem cells, especially mesenchymal stem cells. Multilineage differentiation into all of the described cells are considered as important candidates for a range of diseases like neurological diseases, cardiovascular diseases, gastrointestinal cancer and genetic defects, as well as for acute and chronic wounds healing and pharmaceutical treatment. We review the properties and multipotency of stem cells and their differentiation potential, once cultured under specific growth conditions, for use in cell-based therapies and functional tissue replacement.

Epigenetic memory gained by priming with osteogenic induction medium improves osteogenesis and other properties of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are highly plastic cells that are able to transdifferentiate or dedifferentiate under appropriate conditions. In the present study, we reported here that after in vitro induction of osteogenic differentiation, MSCs could be reverted to a primitive stem cell population (dedifferentiated osteogenic MSCs, De-Os-MSCs) with improved cell survival, colony formation, osteogenic potential, migratory capacity and increased expression of Nanog, Oct4 and Sox2. Most importantly, our results showed great superiority of the De-Os-MSCs over untreated MSCs in ectopic bone formation in vivo. Furthermore, Nanog-knockdown in MSCs could reverse these enhanced properties in De-Os-MSCs in vitro, indicating a central role of Nanog in the transcriptional network. In addition, epigenetic regulations including DNA methylation and histone modifications may play important roles in regulating the de-osteogenic differentiation process. And we found decreased methylation and promoter accrual of activating histone marks, such as H3K4me3 and H4ac on both Nanog and Oct4 gene promoters. Taken together, our study demonstrated that epigenetic memory in De-Os-MSCs gained by priming with osteogenic induction medium favored their differentiation along osteoblastic lineage with improved cell survival and migratory abilities, which may have application potential in enhancing their regenerative capacity in mammals.

Analgesia for neuropathic pain by dorsal root ganglion transplantation of genetically engineered mesenchymal stem cells: initial results

Background

Cell-based therapy may hold promise for treatment of chronic pain. Mesenchymal stem cells (MSCs) are readily available and robust, and their secretion of therapeutic peptides can be enhanced by genetically engineering. We explored the analgesic potential of transplanting bone marrow-derived MSCs that have been transduced with lentivectors. To optimize efficacy and safety, primary sensory neurons were targeted by MSC injection into the dorsal root ganglia (DRGs).

Results

MSCs were transduced using lentivectors to express enhanced green fluorescent protein (EGFP) or to co-express the analgesic peptide glial cell line-derived neurotrophic factor (GDNF) and EGFP by a viral 2A bicistronic transgene cassette. Engineered MSCs were injected into the 4^th lumbar (L4) and L5 DRGs of adult allogeneic rats to evaluate survival in the DRGs. MSCs were detected by immunofluorescence staining up to 2–3 weeks after injection, distributed in the extracellular matrix space without disrupting satellite glial cell apposition to sensory neurons, suggesting well-tolerated integration of engrafted MSCs into DRG tissue. To examine their potential for inhibiting development of neuropathic pain, MSCs were injected into the L4 and L5 DRGs ipsilateral to a spinal nerve ligation injury. Animals injected with GDNF-engineered MSCs showed moderate but significant reduction in mechanical allodynia and hyperalgesia compared to controls implanted with MSCs expressing EGFP alone. We also observed diminished long-term survival of allografted MSCs at 3 weeks, and the development of a highly-proliferating population of MSCs in 12% of DRGs after transplantation.

Conclusions

These data indicate that genetically modified MSCs secreting analgesic peptides could potentially be developed as a novel DRG-targeted cell therapy for treating neuropathic pain. However, further work is needed to address the challenges of MSC survival and excess proliferation, possibly with trials of autologous MSCs, evaluation of clonally selected populations of MSCs, and investigation of regulation of MSC proliferation.

Immunosuppression of allogenic mesenchymal stem cells transplantation after spinal cord injury improves graft survival and beneficial outcomes

Cell therapy for spinal cord injury (SCI) is a promising strategy for clinical application. Mesenchymal stem cells (MSC) have demonstrated beneficial effects following transplantation in animal models of SCI. However, despite the immunoprivilege properties of the MSC, their survival in the injured spinal cord is reduced due to the detrimental milieu in the damaged tissue and immune rejection of the cells. The limited survival of the engrafted cells may determine the therapy success. Therefore, we compared two strategies to increase the presence of the cells in the injured spinal cord in rats: increasing the amount of MSC transplants and using immunosuppressive treatment with FK506 after transplantation. Functional outcomes for locomotion and electrophysiological responses were assessed. The grafted cells survival and the amount of cavity and spared tissue were studied. The findings indicate that immunosuppression improved grafted cells survival. A cell-dose effect was found regarding locomotion recovery and tissue protection independent of immunosuppression. Nevertheless, immunosuppression enhanced the electrophysiological outcomes and allowed filling of the cavity formed after injury by new regenerative tissue and axons. These results indicate that MSC transplantation combined with immunosuppression prolongs the survival of engrafted cells and improves functional and morphological outcomes after SCI.

Localized delivery of brain-derived neurotrophic factor-expressing mesenchymal stem cells enhances functional recovery following cervical spinal cord injury

Neurotrophins, such as brain-derived neurotrophic factor (BDNF), are important in modulating neuroplasticity and promoting recovery after spinal cord injury. Intrathecal delivery of BDNF enhances functional recovery following unilateral spinal cord hemisection (SH) at C2, a well-established model of incomplete cervical spinal cord injury. We hypothesized that localized delivery of BDNF-expressing mesenchymal stem cells (BDNF-MSCs) would promote functional recovery of rhythmic diaphragm activity after SH. In adult rats, bilateral diaphragm electromyographic (EMG) activity was chronically monitored to determine evidence of complete SH at 3 days post-injury, and recovery of rhythmic ipsilateral diaphragm EMG activity over time post-SH. Wild-type, bone marrow-derived MSCs (WT-MSCs) or BDNF-MSCs (2×10(5) cells) were injected intraspinally at C2 at the time of injury. At 14 days post-SH, green fluorescent protein (GFP) immunoreactivity confirmed MSCs presence in the cervical spinal cord. Functional recovery in SH animals injected with WT-MSCs was not different from untreated SH controls (n=10; overall, 20% at 7 days and 30% at 14 days). In contrast, functional recovery was observed in 29% and 100% of SH animals injected with BDNF-MSCs at 7 days and 14 days post-SH, respectively (n=7). In BDNF-MSCs treated SH animals at 14 days, root-mean-squared EMG amplitude was 63±16% of the pre-SH value compared with 12±9% in the control/WT-MSCs group. We conclude that localized delivery of BDNF-expressing MSCs enhances functional recovery of diaphragm muscle activity following cervical spinal cord injury. MSCs can be used to facilitate localized delivery of trophic factors such as BDNF in order to promote neuroplasticity following spinal cord injury.

Bone marrow-derived mesenchymal stem cells expressing the Shh transgene promotes functional recovery after spinal cord injury in rats

Spinal cord injury (SCI) is one of the most disabling diseases. Cell-based gene therapy is becoming a major focus for the treatment of SCI. Bone marrow-derived mesenchymal stem cells (BMSCs) are a promising stem cell type useful for repairing SCI. However, the effects of BMSCs transplants are likely limited because of low transplant survival after SCI. Sonic hedgehog (Shh) is a multifunctional growth factor which can facilitate neuronal and BMSCs survival, promote axonal growth, prevent activation of the astrocyte lineage, and enhance the delivery of neurotrophic factors in BMSCs. However, treatment of SCI with Shh alone also has limited effects on recovery, because the protein is cleared quickly. In this study, we investigated the use of BMSCs overexpressing the Shh transgene (Shh-BMSCs) in the treatment of rats with SCI, which could stably secrete Shh and thereby enhance the effects of BMSCs, in an attempt to combine the advantages of Shh and BMSCs and so to promote functional recovery. After Shh-BMSCs treatment of SCI via the subarachnoid, we detected significantly greater damage recovery compared with that seen in rats treated with phosphate-buffered saline (PBS) and BMSCs. Use of Shh-BMSCs increased the expression and secretion of Shh, basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), improved the behavioral function, enhanced the BMSCs survival, promoted the expression level of neurofilament 200 (NF200), and reduced the expression of glial fibrillary acidic protein (GFAP). Thus, our results indicated that Shh-BMSCs enhanced recovery of neurological function after SCI in rats and could be a potential valuable therapeutic intervention for SCI in humans.

Current concept in neural regeneration research: NSCs isolation, characterization and transplantation in various neurodegenerative diseases and stroke: A review

Since last few years, an impressive amount of data has been generated regarding the basic in vitro and in vivo biology of neural stem cells (NSCs) and there is much far hope for the success in cell replacement therapies for several human neurodegenerative diseases and stroke. The discovery of adult neurogenesis (the endogenous production of new neurons) in the mammalian brain more than 40 years ago has resulted in a wealth of knowledge about stem cells biology in neuroscience research. Various studies have done in search of a suitable source for NSCs which could be used in animal models to understand the basic and transplantation biology before treating to human. The difficulties in isolating pure population of NSCs limit the study of neural stem behavior and factors that regulate them. Several studies on human fetal brain and spinal cord derived NSCs in animal models have shown some interesting results for cell replacement therapies in many neurodegenerative diseases and stroke models. Also the methods and conditions used for in vitro culture of these cells provide an important base for their applicability and specificity in a definite target of the disease. Various important developments and modifications have been made in stem cells research which is needed to be more specified and enrolment in clinical studies using advanced approaches. This review explains about the current perspectives and suitable sources for NSCs isolation, characterization, in vitro proliferation and their use in cell replacement therapies for the treatment of various neurodegenerative diseases and strokes.

The effect of a polyurethane-based reverse thermal gel on bone marrow stromal cell transplant survival and spinal cord repair

Cell therapy for nervous tissue repair is limited by low transplant survival. We investigated the effects of a polyurethane-based reverse thermal gel, poly(ethylene glycol)-poly(serinol hexamethylene urethane) (ESHU) on bone marrow stromal cell (BMSC) transplant survival and repair using a rat model of spinal cord contusion. Transplantation of BMSCs in ESHU at three days post-contusion resulted in a 3.5-fold increase in BMSC survival at one week post-injury and a 66% increase in spared nervous tissue volume at four weeks post-injury. These improvements were accompanied by enhanced hindlimb motor and sensorimotor recovery. In vitro, we found that ESHU protected BMSCs from hydrogen peroxide-mediated death, resulting in a four-fold increase in BMSC survival with two-fold fewer BMSCs expressing the apoptosis marker, caspase 3 and the DNA oxidation marker, 8-oxo-deoxyguanosine. We argue that ESHU protected BMSCs transplanted is a spinal cord contusion from death thereby augmenting their effects on neuroprotection leading to improved behavioral restoration. The data show that the repair effects of intraneural BMSC transplants depend on the degree of their survival and may have a widespread impact on cell-based regenerative medicine.

Gene expression changes in the injured spinal cord following transplantation of mesenchymal stem cells or olfactory ensheathing cells

Transplantation of bone marrow derived mesenchymal stromal cells (MSC) or olfactory ensheathing cells (OEC) have demonstrated beneficial effects after spinal cord injury (SCI), providing tissue protection and improving the functional recovery. However, the changes induced by these cells after their transplantation into the injured spinal cord remain largely unknown. We analyzed the changes in the spinal cord transcriptome after a contusion injury and MSC or OEC transplantation. The cells were injected immediately or 7 days after the injury. The mRNA of the spinal cord injured segment was extracted and analyzed by microarray at 2 and 7 days after cell grafting. The gene profiles were analyzed by clustering and functional enrichment analysis based on the Gene Ontology database. We found that both MSC and OEC transplanted acutely after injury induce an early up-regulation of genes related to tissue protection and regeneration. In contrast, cells transplanted at 7 days after injury down-regulate genes related to tissue regeneration. The most important change after MSC or OEC transplant was a marked increase in expression of genes associated with foreign body response and adaptive immune response. These data suggest a regulatory effect of MSC and OEC transplantation after SCI regarding tissue repair processes, but a fast rejection response to the grafted cells. Our results provide an initial step to determine the mechanisms of action and to optimize cell therapy for SCI.

Autologous biological pacing function with adrenergic-responsiveness in porcine of complete heart block

AIMS

To assess the efficacy of autologous biological pacing function by autograft of gene-transferred mesenchymal stem cells in a porcine model of complete heart block.

METHODS AND RESULTS

Fourteen healthy young male pigs were randomized into active group (n=8) and control group (n=6). Porcine MSCs were transfected with Ad.HCN4 or Ad.Null. The pacemaker function of transfected MSCs was studied by whole-cell patch clamp. The CHB model of porcine was created with transthoracic ablation technique and the transfected MSCs were autografted into the free wall of right ventricle. The pacing function was studied by ECG and ambulatory Holter recording weekly. The adrenergic responsiveness was evaluated by the variation of heart rate after isoprenaline infusion or food provision following an overnight fasting. HCN4-MSCs expressed a robust time-dependent inward current (If) and the current density of If was 4.3±0.6 pA/pF at -105 mV. In week 2 after autograft, the heart rate of active group became significantly higher than control (53±5 bpm vs. 38±4 bpm, P<0.05) and the percent of pacing beats in active group was higher than control (69±10% vs. 28±8%, P<0.05). By infusion of isoprenaline, the heart rate was increased significantly in both groups. However, there was a significant increase of heart rate when presenting food for active group (P<0.05) while not in control.

CONCLUSIONS

Our findings demonstrated that autografted HCN4-MSCs could increase the heart rate by providing an adrenergic-responsive biological pacing function, indicating a promising approach without immunological or ethical issues for the treatment of complete heart block.

Primary bone marrow mesenchymal stromal cells rescue the axonal phenotype of Twitcher mice

Krabbe's disease (KD) is a demyelinating disorder caused by the deficiency of lysosomal galactocerebrosidase (GALC), affecting both the central (CNS) and the peripheral nervous system (PNS). A current therapy, hematopoietic stem cell transplantation (HSCT), is ineffective at correcting the PNS pathology. We have previously shown that systemic delivery of immortalized bone marrow-derived murine mesenchymal stromal cells (BM-MSCs) diminishes the neuropathology of transplanted Twitcher mice, a murine model of KD. In this study, to move one step closer to clinical application, the effectiveness of a systematic delivery of primary BM-MSCs to promote recovery of the Twitcher PNS was assessed. Primary BM-MSCs grafted to the Twitcher sciatic nerve led to increased GALC activity that was not correlated to decreased psychosine (the toxic GALC substrate) accumulation. Nevertheless, BM-MSC transplantation rescued the axonal phenotype of Twitcher mice in the sciatic nerve, with an increased density of both myelinated and unmyelinated axons in transplanted animals. Whereas no increase in myelination was observed, upon transplantation an increased proliferation of Schwann cell precursors occurred. Supporting these findings, in vitro, BM-MSCs promoted neurite outgrowth of Twitcher sensory neurons and proliferation of Twitcher Schwann cells. Moreover, BM-MSCs expressed nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) and promoted increased BDNF synthesis by neighboring Schwann cells. Besides their action in neurons and glia, BM-MSCs led to macrophage activation in Twitcher sciatic nerves. In summary, primary BM-MSCs diminish the neuropathology of Twitcher sciatic nerves by coordinately affecting neurons, glia, and macrophages.

Retinoic acid receptor beta mediates all-trans retinoic acid facilitation of mesenchymal stem cells neuronal differentiation

All-trans retinoic acid plays an important role in nervous system development. However, the effects of all-trans retinoic acid on the neuronal differentiation of mesenchymal stem cells and the mechanisms through which this differentiation takes place are still poorly understood. Here, we investigated the biological effects of all-trans retinoic acid on the neuronal differentiation of mesenchymal stem cells and the signaling pathways that mediated these effects. We found that the neuronal differentiation efficiency of mesenchymal stem cells following all-trans retinoic acid pre-induction was greater and the axonal length was longer than was observed with mesenchymal stem cells that were not pre-induced. mRNA and protein levels of the neural-markers Nestin, NSE, MAP-2, Tau and Tuj1 were stronger in neural-like cells derived from all-trans retinoic acid-pretreated mesenchymal stem cells than in those not pre-induction. Interestingly, the neuronal excitability of differentiated neural-like cells exhibited the same patterns between these two groups. Clear expression of retinoic acid receptor alpha and gamma in mesenchymal stem cells was observed, while retinoic acid receptor beta was barely detected. However, retinoic acid receptor beta expression in mesenchymal stem cells after neuronal induction increased dramatically, in contrast with retinoic acid receptor alpha and gamma expression, and retinoic acid receptor beta expression in mesenchymal stem cells receiving all-trans retinoic acid pre-induction was even stronger. Next, retinoic acid receptor alpha, beta and gamma were over-expressed by recombinant adenovirus infection prior to neuronal induction. Retinoic acid receptor alpha and gamma over-expression did not impact the neuronal differentiation of mesenchymal stem cells. However, retinoic acid receptor beta over-expression promoted neuronal differentiation to a similar level as observed following all-trans retinoic acid pre-induction. The neuronal differentiation promoting effects of all-trans retinoic acid on mesenchymal stem cells could be inhibited by siRNA silencing of retinoic acid receptor beta and by LE135, an inhibitor of retinoic acid receptor beta. Taken together, these results suggest that all-trans retinoic acid pre-induction facilitates the neuronal differentiation of mesenchymal stem cells. These facilitation effects are achieved by activating the retinoic acid receptor beta signaling pathway.

Multimodal in vivo imaging reveals limited allograft survival, intrapulmonary cell trapping and minimal evidence for ischemia-directed BMSC homing

Background

Despite positive reports on the efficacy of stem cell therapy for the treatment of cardiovascular disease, the nature of stem cell homing to ischemic tissues remains elusive.

Results

We used a mouse model of peripheral tissue ischemia to study the survival and homing capacity of dual reporter gene (eGFP/Luciferase) expressing bone marrow-derived stromal cells (BMSC). Cell homing and survival were studied in the presence and absence of ciclosporin A (CsA) immunosuppression using bioluminescence imaging (BLI) together with confocal endomicroscopy. Different injection strategies were applied: central venous (CV), intra-arterial (IA) and intramuscular (IM). BLI and confocal endomicroscopy evidenced complete rejection of the IM injected allogeneic BMSC transplant within 5 to 10 days. Immunosuppression with CsA could only marginally prolong graft survival. IM injected BMSC did not migrate to the site of the arterial ligation. CV injection of BMSC resulted in massive pulmonary infarction, leading to respiratory failure and death. Intrapulmonary cell trapping was evidenced by confocal endomicroscopy, BLI and fluorescence microscopy. IA injection of BMSC proved to be a feasible and safe strategy to bypass the lung circulation. During the follow-up period, neither BLI nor confocal endomicroscopy revealed any convincing ischemia-directed homing of BMSC.

Conclusions

BLI and confocal endomicroscopy are complementary imaging techniques for studying the in vivo biology of dual reporter gene-expressing BMSC. Allogeneic BMSC survival is limited in an immunocompetent host and cannot be preserved by CsA immunosuppression alone. We did not find substantial evidence for ischemia-directed BMSC homing and caution against CV injection of BMSC, which can lead to massive pulmonary infarction.

Comparison of mesenchymal stem cells derived from fat, bone marrow, Wharton's jelly, and umbilical cord blood for treating spinal cord injuries in dogs

Previous animal studies have shown that transplantation of mesenchymal stem cells (MSCs) into spinal cord lesions enhances axonal regeneration and promotes functional recovery. We isolated the MSCs derived from fat, bone marrow, Wharton's jelly and umbilical cord blood (UCB) positive for MSC markers and negative for hematopoietic cell markers. Their effects on the regeneration of injured canine spinal cords were compared. Spinal cord injury was induced by balloon catheter compression. Dogs with injured spinal cords were treated with only matrigel or matrigel mixed with each type of MSCs. Olby and modified Tarlov scores, immunohistochemistry, ELISA and Western blot analysis were used to evaluate the therapeutic effects. The different MSC groups showed significant improvements in locomotion at 8 weeks after transplantation (P<0.05). This recovery was accompanied by increased numbers of surviving neuron and neurofilament-positive fibers in the lesion site. Compared to the control, the lesion sizes were smaller, and fewer microglia and reactive astrocytes were found in the spinal cord epicenter of all MSC groups. Although there were no significant differences in functional recovery among the MSCs groups, UCB-derived MSCs (UCSCs) induced more nerve regeneration and anti-inflammation activity (P<0.05). Transplanted MSCs survived for 8 weeks and reduced IL-6 and COX-2 levels, which may have promoted neuronal regeneration in the spinal cord. Our data suggest that transplantation of MSCs promotes functional recovery after SCI. Furthermore, application of UCSCs led to more nerve regeneration, neuroprotection and less inflammation compared to other MSCs.

Fate of transplanted bone marrow derived mesenchymal stem cells following spinal cord injury in rats by transplantation routes

This research was performed to investigate the differences of the transplanted cells' survival and differentiation, and its efficacy according to the delivery routes following spinal cord injury. Allogenic mesenchymal stem cells (MSCs) were transplanted intravenously (IV group) or intralesionally (IL group) at post-injury 1 day in rats. Behavioral improvement, engraftment and differentiation of the transplanted cells and the expression of neurotrophic factors of the transplanted groups were analyzed and compared with those of the control group. At 6 weeks post-injury, the mean BBB motor scales in the control, IV and IL groups were 6.5 ± 1.8, 11.1 ± 2.1, and 8.5 ± 2.8, respectively. Regardless of the delivery route, the MSCs transplantation following spinal cord injuries presented better behavioral improvement. The differentiations of the engrafted cells were different according to the delivery routes. The engrafted cells predominantly differentiated into astrocytes in the IV group and on the other hand, engrafted cells of the IL group demonstrated relatively even neural and glial differentiation. The expressions of neuronal growth factor were significantly higher in the IL group (mean relative optical density, 2.4 ± 0.15) than those in the control (2.16 ± 0.04) or IV group (1.7 ± 0.23). Transplantation of MSCs in the early stage of spinal cord injury gives a significant clinical improvement. However, the fate of the transplanted MSCs and expression of neuronal growth factors are different along the transplantation route.

Stem cells for central nervous system repair and rehabilitation

The central nervous system (CNS) has limited capacity for self-repair. Current treatments are often incapable of reversing the debilitating effects of CNS diseases that result in permanent and/or progressive physical and cognitive impairments. One promising repair strategy is transplantation of stem cells, which can potentially replace lost neurons and/or glia or promote repair through secretion of trophic factors. Various types of stem cells exist, each with their own advantages and disadvantages. Although no consensus exists regarding the optimal cell type to use, moderate functional improvements have been shown in animal models of CNS diseases using different types of stem cells. However, the precise mechanism of action behind their beneficial effects remains unknown. In addition, many barriers to clinical use still need to be resolved before transplantation of stem cells can be used as effective biologics. These barriers include--depending on the stem cell type--possible tumor formation, difficulty with harvest, limited in vivo differentiation and integration, and ethical issues regarding use.

Characterization of adherent umbilical cord blood stromal cells regarding passage, cell number, and nano-biomarking utilization

Adherent umbilical cord blood stromal cells (AUCBSCs) are multipotent cells with differentiation capacities. Therefore, these cells have been investigated for their potential in cell-based therapies. Quantum Dots (QDs) are an alternative to organic dyes and fluorescent proteins because of their long-term photostability. In this study we determined the effects of the cell passage on AUCBSCs morphology, phenotype, and differentiation potential. QDs labeled AUCBSCs in the fourth cell passage were differentiated in the three mesodermal lineages and were evaluated using cytochemical methods and transmission electron microscopy (TEM). Gene and protein expression of the AUCBSCs immunophenotypic markers were also evaluated in the labeled cells by real-time quantitative PCR and flow cytometry. In this study we were able to define the best cellular passage to work with AUCBSCs and we also demonstrated that the use of fluorescent QDs can be an efficient nano-biotechnological tool in differentiation studies because labeled cells do not have their characteristics compromised.

Factors Affecting Residence Time of Mesenchymal Stromal Cells (MSC) Injected into the Myocardium

The therapeutic mechanism of mesenchymal stromal/stem cells (MSC) for the treatment of acute myocardial infarction is not well understood. Our goal was to get insights into this mechanism by analyzing the survival kinetics of allogeneic and syngeneic cell transplants under different tissue conditions. Two MSC cell banks, stably and equally expressing the luciferase reporter construct, were developed for these studies and injected directly to the myocardium of Lewis rat recipients under syngeneic or allogeneic transplantation conditions. Cell survival was monitored by real-time fashion for up to 2 weeks, using optical imaging device (IVIS, Xenogen Corp.). We found that both syngeneic and allogeneic grafts reduced significantly in size during the first week of transplantation, either in the normal or in the late infarcted heart (5 days after MI) and allotransplants became always smaller than syngeneic grafts during this period. Low dose of cyclosporine A treatment had a benefit on both allo- and syngeneic graft sizes, suggesting that multiple mechanisms play a role in early graft reduction. The MSC characteristic factors IL-6, IL-8, MCP-1, and VEGF were well above the control level in the heart tissue at 4 days after cell injection, suggesting that the peak therapeutic effect of MSC can be expected during the first week of the administration. Although allogeneic cells induced immunoglobulin production, their biological effects (cell survival, factor productions) are very similar to the syngeneic transplants and therefore they could deliver the same therapeutic effect as the syngeneic cells. Finally, freshly infarcted tissue (30 min) supported better the survival of MSC than late postischemic tissue (5 days) but only “off the shelf” allogeneic cell transplants fits with this treatment strategy.

Bone marrow stromal cell transplantation for treatment of sub-acute spinal cord injury in the rat

Bone marrow stromal cells (BMSCs) have been studied as effective transplants for the treatment of spinal cord injury (SCI). Our previous study showed that BMSCs infused into the cerebrospinal fluid (CSF) exhibited distinct effects on the recovery of acute SCI. The present study examined the effects of BMSCs in sub-acute SCI (2weeks post-injury) by transplanting them directly into the lesion. The spinal cord was crush-injured at the Th8-9 level in rats, and 2weeks later, cultured BMSCs (5x10(5)) derived from GFP-transgenic rats of the same strain were transplanted into the lesion. Tissue repair and nerve regeneration were examined by immunohistochemistry and electron microscopy. GFP-labeled BMSCs survived as cell assemblies in the spinal cord for 1-2weeks after transplantation. The dorsal side of BMSC assemblies in the spinal cord usually showed an expanded GFAP-negative, astrocyte-devoid area, in which extracellular matrices including collagen fibrils were deposited. Numerous regenerating axons associated with Schwann cells grew out through such astrocyte-devoid extracellular matrices. Ascending (CGRP-containing) and descending (5HT- and TH-containing) axons were included in these regenerating axons. Regenerated axons were myelinated by Schwann cells beyond 2weeks post-transplantation. Cavity formation was reduced in the cell transplantation group. Locomotory behavior assessed by the BBB scale improved to 9.8 points in the cell transplantation group, while it was to 5.5-5.7 in the control. BMSC transplantation into lesions of advanced SCI has markedly beneficial effects on tissue repair and axonal outgrowth, leading to improved locomotion in rats.

Noninvasive quantification and optimization of acute cell retention by in vivo positron emission tomography after intramyocardial cardiac-derived stem cell delivery

OBJECTIVES

The aim of this study was to quantify acute myocardial retention of cardiac-derived stem cells (CDCs) and evaluate different delivery methods with positron emission tomography (PET).

BACKGROUND

Success of stem cell transplantation for cardiac regeneration is partially limited by low retention/engraftment of the delivered cells. A clinically applicable method for accurate quantification of cell retention would enable optimization of cell delivery.

METHODS

The CDCs were derived from syngeneic, male Wistar Kyoto (WK) rats labeled with [(18)F]-fluoro-deoxy-glucose ((18)FDG) and injected intramyocardially into the ischemic region of female WK rats after permanent left coronary artery ligation. The effects of fibrin glue (FG), bradycardia (adenosine), and cardiac arrest were examined. Imaging with (18)FDG PET was performed for quantification of cell retention. Quantitative polymerase chain reaction (PCR) for the male-specific SRY gene was performed to validate the PET results.

RESULTS

Myocardial retention of cells suspended in phosphate-buffered saline 1 h after delivery was 17.6 +/- 11.5% by PCR and 17.8 +/- 7.3% by PET. When CDCs were injected immediately after induction of cardiac arrest, retention was increased to 75.6 +/- 18.6%. Adenosine slowed the ventricular rate and doubled CDC retention (35.4 +/- 5.3%). A similar increase in CDC retention was observed after epicardial application of FG at the injection site (37.5 +/- 8.2%). The PCR revealed a significant increase in 3-week cell engraftment in the FG animals (22.1 +/- 18.6% and 5.3 +/- 3.1%, for FG and phosphate-buffered saline, respectively).

CONCLUSIONS

In vivo PET permits accurate measurement of CDC retention early after intramyocardial delivery. Sealing injection sites with FG or lowering ventricular rate by adenosine might be clinically translatable methods for improving stem cell engraftment in a beating heart.

Analysis of host-mediated repair mechanisms after human CNS-stem cell transplantation for spinal cord injury: correlation of engraftment with recovery

BACKGROUND

Human central nervous system-stem cells grown as neurospheres (hCNS-SCns) self-renew, are multipotent, and have potential therapeutic applications following trauma to the spinal cord. We have previously shown locomotor recovery in immunodeficient mice that received a moderate contusion spinal cord injury (SCI) and hCNS-SCns transplantation 9 days post-injury (dpi). Engrafted hCNS-SCns exhibited terminal differentiation to myelinating oligodendrocytes and synapse-forming neurons. Further, selective ablation of human cells using Diphtheria toxin (DT) abolished locomotor recovery in this paradigm, suggesting integration of human cells within the mouse host as a possible mechanism for the locomotor improvement. However, the hypothesis that hCNS-SCns could alter the host microenvironment as an additional or alternative mechanism of recovery remained unexplored; we tested that hypothesis in the present study.

METHODS AND FINDINGS

Stereological quantification of human cells using a human-specific cytoplasmic marker demonstrated successful cell engraftment, survival, migration and limited proliferation in all hCNS-SCns transplanted animals. DT administration at 16 weeks post-transplant ablated 80.5% of hCNS-SCns. Stereological quantification for lesion volume, tissue sparing, descending serotonergic host fiber sprouting, chondroitin sulfate proteoglycan deposition, glial scarring, and angiogenesis demonstrated no evidence of host modification within the mouse spinal cord as a result of hCNS-SCns transplantation. Biochemical analyses supplemented stereological data supporting the absence of neural stem-cell mediated host repair. However, linear regression analysis of the number of engrafted hCNS-SCns vs. the number of errors on a horizontal ladder beam task revealed a strong correlation between these variables (r = -0.78, p<0.05), suggesting that survival and engraftment were directly related to a quantitative measure of recovery.

CONCLUSIONS

Altogether, the data suggest that the locomotor improvements associated with hCNS-SCns transplantation were not due to modifications within the host microenvironment, supporting the hypothesis that human cell integration within the host circuitry mediates functional recovery following a 9 day delayed transplant.

Cellular immune response to intrastriatally implanted allogeneic bone marrow stromal cells in a rat model of Parkinson's disease

BACKGROUND

Marrow stromal cells (MSC), the non-hematopoietic precursor cells in bone marrow, are being investigated for therapeutic potential in CNS disorders. Although in vitro studies have suggested that MSC may be immunologically inert, their immunogenicity following transplantation into allogeneic recipients is unclear. The primary objective of this study was to investigate the cellular immune response to MSC injected into the striatum of allogeneic recipients (6-hydroxydopamine [6-OHDA]-hemilesioned rats, an animal model of Parkinson's disease [PD]), and the secondary objective was to determine the ability of these cells to prevent nigrostriatal dopamine depletion and associated motor deficits in these animals.

METHODS

5-Bromo-2-deoxyuridine (BrdU) - labeled MSC from two allogeneic sources (Wistar and ACI rats) were implanted into the striatum of adult Wistar rats at the same time as 6-OHDA was administered into the substantia nigra. Behavioral tests were administered one to two weeks before and 16-20 days after 6-OHDA lesioning and MSC transplantation. Immunocytochemical staining for T helper and T cytotoxic lymphocytes, microglia/macrophages, and major histocompatibility class I and II antigens was performed on post-transplantation days 22-24. MSC were detected with an anti-BrdU antibody.

RESULTS

Tissue injury due to the transplantation procedure produced a localized cellular immune response. Unexpectedly, both sources of allogeneic MSC generated robust cellular immune responses in the host striatum; the extent of this response was similar in the two allograft systems. Despite these immune responses, BrdU+ cells (presumptive MSC) remained in the striatum of all animals that received MSC. The numbers of remaining MSC tended to be increased (p = 0.055) in rats receiving Wistar MSC versus those receiving ACI MSC. MSC administration did not prevent behavioral deficits or dopamine depletion in the 6-OHDA-lesioned animals.

CONCLUSION

MSC, when implanted into the striatum of allogeneic animals, provoke a marked immune response which is not sufficient to clear these cells by 22-24 days post-transplantation. In the experimental paradigm in this study, MSC did not prevent nigrostriatal dopamine depletion and its associated behavioral deficits. Additional studies are indicated to clarify the effects of this immune response on MSC survival and function before initiating trials with these cells in patients with PD or other neurodegenerative disorders.

Allogeneic stromal cell implantation in brain tissue leads to robust microglial activation

Although adult and embryonic stem cell-based therapy for central nervous system (CNS) injury is being developed worldwide, less attention is given to the immunological aspects of allogeneic cell implantation in the CNS. The latter is of major importance because, from a practical point of view, future stem cell-based therapy for CNS injury will likely be performed using well-characterised allogeneic stem cell populations. In this study, we aimed to further describe the immunological mechanism leading to rejection of allogeneic bone marrow-derived stromal cells (BM-SC) after implantation in murine CNS. For this, we first investigated the impact of autologous and allogeneic BM-SC on microglia activation in vitro. Although the results indicate that both autologous and allogeneic BM-SC do not activate microglia themselves in vitro, they also do not inhibit activation of microglia after exogenous stimuli in vitro. Next, we investigated the impact of allogeneic BM-SC on microglia activation in vivo. In contrast to the in vitro observations, microglia become highly activated in vivo after implantation of allogeneic BM-SC in the CNS of immune-competent mice. Moreover, our results suggest that microglia, rather than T-cells, are the major contributors to allograft rejection in the CNS.

Adult spinal cord stem/progenitor cells transplanted as neurospheres preferentially differentiate into oligodendrocytes in the adult rat spinal cord

Neural stem/progenitor cells (NSPCs) capable of generating new neurons and glia reside in the adult mammalian spinal cord. Transplantation of NSPCs has therapeutic potential for spinal cord injury, although there is limited information on the ability of these cells to survive and differentiate in vivo. Neurospheres cultured from the periventricular region of the adult spinal cord contain NSPCs that are self-renewing and multipotent. We examined the survival, proliferation, migration, and differentiation of adult spinal cord NSPCs generated from green fluorescent protein (GFP) transgenic rats and transplanted into the intact spinal cord. The grafted GFP-expressing cells survived for at least 6 weeks in vivo and migrated from the injection site along the rostro-caudal axis of the spinal cord. Transplanted cells transiently proliferated following transplantation and approximately 17% of the GFP-positive cells were apoptotic at 1 day. Also, better survival was seen with NSPCs transplanted as neurospheres in comparison to NSPCs transplanted as dissociated cells. By 1 week posttransplantation, grafted cells primarily expressed an oligodendrocytic phenotype and only 2% differentiated into astrocytes. Approximately 75% versus 38% of the grafted cells differentiated into oligodendrocytes after transplantation into spinal white versus gray matter, respectively. This is the first report to examine the time course of cell survival, proliferation, apoptosis, and phenotypic differentiation of transplanted NSPSs in the spinal cord. This is also the first report to examine the differences between transplanted NSPCs grafted as neurospheres or dissociated cells, and to compare the differentiation potential after transplantation into spinal cord white versus gray matter.

Immunological properties of umbilical cord blood-derived mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) are promising candidates for developing cell therapies for intractable diseases. To assess the feasibility of transplantation with human umbilical cord blood (hUCB)-derived MSCs, we analyzed the ability of these cells to function as alloantigen-presenting cells (APC) in vitro. hUCB-MSCs were strongly positive for MSC-related antigens and stained positively for human leukocyte antigen (HLA)-AB and negatively for HLA-DR. When treated with interferon (IFN)-gamma, the expression of HLA-AB and HLA-DR, but not the co-stimulatory molecules CD80 and CD86, was increased. hUCB-MSCs did not provoke allogeneic PBMC (peripheral blood mononuclear cell) proliferation, even when their HLA-molecule expression was up-regulated by IFN-gamma pretreatment. When added to a mixed lymphocyte reaction (MLR), hUCB-MSCs actively suppressed the allogeneic proliferation of the responder lymphocytes. This suppressive effect was mediated by soluble factors. We conclude that hUCB-MSCs can suppress the allogeneic response of lymphocytes and may thus be useful in allogeneic cell therapies.

Efficient intracytoplasmic labeling of human umbilical cord blood mesenchymal stromal cells with ferumoxides

Mesenchymal stromal cells (MSCs) are multipotent cells found in several adult tissues; they have the capacity to differentiate into mesodermal, ectodermal, and endodermal tissues in vitro. There have been several reports that MSCs have therapeutic effects in a variety of diseases. Therefore, using a cell labeling technique, monitoring their temporal and spatial migration in vivo, would be useful in the clinical setting. Magnetic resonance imaging (MRI)--tracking of superparamagnetic iron oxide (SPIO)-labeled cells--is a noninvasive technique for determining the location and migration of transplanted cells. In the present study, we evaluated the influence and toxicity of SPIO (ferumoxides) labeling on multiple differentiated MSCs. To evaluate the influence and toxicity of ferumoxides labeling on differentiation of MSCs, a variety of concentrations of ferumoxides were used for labeling MSCs. We found that the cytoplasm of adherent cells was effectively labeled at low concentrations of ferumoxides. Compared with unlabeled controls, the ferumoxides-labeled MSCs exhibited a similar proliferation rate and apoptotic progression. The labeled MSCs differentiated into osteoblasts and adipocytes in an identical fashion as the unlabeled cells. However, chondrogenesis and neurogenesis were inhibited at high concentrations of ferumoxides. Our results suggest the effective concentration for ferumoxides use in tracking MSCs.