Neural and marrow-derived stromal cell sphere transplantation in a rat model of traumatic brain injury

Cell-based therapy for traumatic brain injury

Traumatic brain injury is a major economic burden to hospitals in terms of emergency department visits, hospitalizations, and utilization of intensive care units. Current guidelines for the management of severe traumatic brain injuries are primarily supportive, with an emphasis on surveillance (i.e. intracranial pressure) and preventive measures to reduce morbidity and mortality. There are no direct effective therapies available. Over the last fifteen years, pre-clinical studies in regenerative medicine utilizing cell-based therapy have generated enthusiasm as a possible treatment option for traumatic brain injury. In these studies, stem cells and progenitor cells were shown to migrate into the injured brain and proliferate, exerting protective effects through possible cell replacement, gene and protein transfer, and release of anti-inflammatory and growth factors. In this work, we reviewed the pathophysiological mechanisms of traumatic brain injury, the biological rationale for using stem cells and progenitor cells, and the results of clinical trials using cell-based therapy for traumatic brain injury. Although the benefits of cell-based therapy have been clearly demonstrated in pre-clinical studies, some questions remain regarding the biological mechanisms of repair and safety, dose, route and timing of cell delivery, which ultimately will determine its optimal clinical use.

Exosomes/miRNAs as mediating cell-based therapy of stroke

Cell-based therapy, e.g., multipotent mesenchymal stromal cell (MSC) treatment, shows promise for the treatment of various diseases. The strong paracrine capacity of these cells and not their differentiation capacity, is the principal mechanism of therapeutic action. MSCs robustly release exosomes, membrane vesicles (~30–100 nm) originally derived in endosomes as intraluminal vesicles, which contain various molecular constituents including proteins and RNAs from maternal cells. Contained among these constituents, are small non-coding RNA molecules, microRNAs (miRNAs), which play a key role in mediating biological function due to their prominent role in gene regulation. The release as well as the content of the MSC generated exosomes are modified by environmental conditions. Via exosomes, MSCs transfer their therapeutic factors, especially miRNAs, to recipient cells, and therein alter gene expression and thereby promote therapeutic response. The present review focuses on the paracrine mechanism of MSC exosomes, and the regulation and transfer of exosome content, especially the packaging and transfer of miRNAs which enhance tissue repair and functional recovery. Perspectives on the developing role of MSC mediated transfer of exosomes as a therapeutic approach will also be discussed.

Improvements in biomaterial matrices for neural precursor cell transplantation

Progress is being made in developing neuroprotective strategies for traumatic brain injuries; however, there will never be a therapy that will fully preserve neurons that are injured from moderate to severe head injuries. Therefore, to restore neurological function, regenerative strategies will be required. Given the limited regenerative capacity of the resident neural precursors of the CNS, many investigators have evaluated the regenerative potential of transplanted precursors. Unfortunately, these precursors do not thrive when engrafted without a biomaterial scaffold. In this article we review the types of natural and synthetic materials that are being used in brain tissue engineering applications for traumatic brain injury and stroke. We also analyze modifications of the scaffolds including immobilizing drugs, growth factors and extracellular matrix molecules to improve CNS regeneration and functional recovery. We conclude with a discussion of some of the challenges that remain to be solved towards repairing and regenerating the brain.

Basic fibroblast growth factor increases the transplantation‑mediated therapeutic effect of bone mesenchymal stem cells following traumatic brain injury

Basic fibroblast growth factor (bFGF) has proven useful for neural stem and progenitor cells during the transplantation‑mediated therapeutic effect of bone mesenchymal stem cells (BMSCs). Endogenous bFGF expression levels increase during brain development and gradually diminish with aging. To date, few studies have been conducted on exogenous bFGF promoting BMSC transplantation‑mediated functional recovery in adult rats following traumatic brain injury (TBI). The results of the present study showed that BMSCs in the TBI cortex and dentate gyrus showed differentiation along the glial and neuronal lines, which are possibly enhanced by bFGF. The neuronal differentiation rate was not consistent with neurological functional recovery rate over time. bFGF may promote the transplantation‑mediated therapeutic effect of BMSCs more significantly and rapidly in rats following TBI, with a small proportion of differentiated neurons. In conclusion, exogenous bFGF functions as a booster of the transplantation‑mediated therapeutic effect of BMSCs following TBI.

Protective effects of BDNF overexpression bone marrow stromal cell transplantation in rat models of traumatic brain injury

Bone marrow stromal cells (MSCs) were used as cell therapy for various diseases in recent years. Some reports showed that transplanted MSCs promote functional recovery in animal models of brain trauma. But other studies indicate that tissue replacement by this method may not be the main source of therapeutic benefit. Neurotrophic factors such as brain-derived neurotrophic factor (BDNF) therapeutic potential may contribute to the recovery of function after trauma. Our previous study showed that BDNF-MSCs could promote the survival of neurons in neuronal injured models in vitro. The present study was undertaken to explore the therapeutic effects of MSCs transfected with BDNF in vivo. After intraventricular injection of MSCs-BDNF, BDNF levels were increased significantly in cerebrospinal fluid by ELISA. Further studies showed that treatment of traumatic brain injury with MSCs-BDNF could attenuate neuronal injury as measurement of biological behavior assessment. These studies demonstrate that by increasing the brain concentration of BDNF, intraventricularly transplanted MSCs-BDNF might play an important role in the treatment of traumatic brain injury and might be an optional therapeutic strategy.

Implantation of a collagen scaffold seeded with adult rat hippocampal progenitors in a rat model of penetrating brain injury

Penetrating brain injury (PBI) is a complex central nervous system injury in which mechanical damage to brain parenchyma results in hemorrhage, ischemia, broad areas of necrosis, and eventually cavitation. The permanent loss of brain tissue affords the possibility of treatment using a biomaterial scaffold to fill the lesion site and potentially deliver pharmacological or cellular therapeutic agents. The administration of cellular therapy may be of benefit in both mitigating the secondary injury process and promoting regeneration through replacement of certain cell populations. This study investigated the survival and differentiation of adult rat hippocampal neural progenitor cells delivered by a collagen scaffold in a rat model of PBI. The cell-scaffold construct was implanted 1 week after injury and was observed to remain intact with open pores upon analysis 4 weeks later. Implanted neural progenitors were found to have survived within the scaffold, and also to have migrated into the surrounding brain. Differentiated phenotypes included astrocytes, oligodendrocytes, vascular endothelial cells, and possibly macrophages. The demonstrated multipotency of this cell population in vivo in the context of traumatic brain injury has implications for regenerative therapies, but additional stimulation appears necessary to promote neuronal differentiation outside normally neurogenic regions.

Improve the viability of transplanted neural cells with appropriate sized neurospheres coated with mesenchymal stem cells

Consequences of central nervous system (CNS) physical injuries and neurodegenerative diseases are severe because the CNS has limited capacity to replace neurons lost through injuries or diseases. Neural stem cells (NSCs) are the most versatile and promising cell source for the regeneration of injured and diseased CNS. However, cell therapy faces many problems related to cell survival, control of cell fate and proper cell engraftment after transplantation. Cell survival is one of the most challenging technical issues as only a small percentage of implanted cells can survive after transplantation. These cells often die in the first few days after transplantation due to acute inflammation/immune response, trophic factor withdrawal, oxidative stress, excitotoxicity, hypoxia, or anoikis. To use appropriate size of cell aggregates, such as neurospheres, rather than individual cell suspension, may prevent anoikis and improve viability. Cells in aggregates or groups can form a community to provide paracrine signaling or trophic support for neighboring transplanted cells to be able to survive in the community manner. One important parameter in the neurosphere structure is the size or diameter. If the sphere size is too big, the nutrient and oxygen support for the cells in the core of the neurosphere will be limited or insufficient. If the sphere size is too small, the beneficial impact of the multicellular community may be limited. To this end, we hypothesize that the survival of transplanted NSCs may be improved with the transplantation of multicellular neurospheres as compared to the transplantation of individual cells in suspension, and there is an optimal range of the sphere size to get the highest viability for the transplanted neural cells. Another major factor is the immune response to the transplanted neural cells. Even with immunosuppressant used, host immune response can still jeopardize the viability of the transplanted cells. Mesenchymal stem cells (MSCs) have been demonstrated to possess immunosuppressive and neuroprotective properties. We further hypothesize that the viability of transplanted neural cells may be further improved in neurospheres coated with layers of MSCs on the surface of neurospheres by suppressing the host immune response at the transplantation site.

Injection Parameters Affect Cell Viability and Implant Volumes in Automated Cell Delivery for the Brain

The technique of central nervous system cell implantation can affect the outcome of preclinical or clinical studies. Our goal was to evaluate the impact of various injection parameters that may be of consequence during the delivery of solute-suspended cells. These parameters included ( 1 ) the type and concentration of cells used for implantation, ( 2 ) the rate at which cells are injected (flow rate), ( 3 ) the acceleration of the delivery device, ( 4 ) the period of time between cell loading and injection into the CNS (delay), and ( 5 ) the length and gauge of the needle used to deliver the cells. Neural progenitor cells (NPCs) and bone marrow stromal cells (BMSCs) were injected an automated device. These parameters were assessed in relation to their effect on the volume of cells injected and cell viability. Longer and thinner cannulae and higher cell concentrations were detrimental for cell delivery. Devices and techniques that optimize these parameters should be of benefit.

Treatment of TBI with collagen scaffolds and human marrow stromal cells increases the expression of tissue plasminogen activator

This study examines the effects of combination therapy of collagen scaffolds and human marrow stromal cells (hMSCs) on the expression of tissue plasminogen activator (tPA) after traumatic brain injury (TBI) in rats. Adult male Wistar rats (n=48) were injured with controlled cortical impact and treated either with scaffolds suffused with hMSCs (3×10(6)) or hMSCs (3×10(6)) alone transplanted into the lesion cavity 1 week after TBI. A control group was treated with saline. Neurological function was assessed using the Morris Water Maze test (MWM) and modified Neurological Severity Scores (mNSS). The rats were sacrificed 14 days after TBI and brain samples were processed for immunohistochemical analysis and quantitative Western blot and quantitative real-time polymerase chain reaction (qRT-PCR) studies. Enhanced functional improvement was observed on both the mNSS and MWM tests in the scaffold+hMSC-treated group compared to the other two groups. Immunostaining with anti-human mitochondrial antibody (E5204) showed more hMSCs in the injury zone of the scaffold+hMSC group compared to the hMSC-alone group. Triple staining showed that more neurons were tPA-positive in the scaffold+hMSC group compared to the other two groups (p<0.05). Western blot analysis and qRT-PCR showed that scaffold+hMSC and hMSC-alone treatment enhanced the expression of tPA compared to controls (p<0.05), but tPA expression was significantly greater in the scaffold+hMSC group. The induction of tPA by hMSCs after TBI may be one of the mechanisms involved in promoting functional improvement after TBI.

Manual vs automated delivery of cells for transplantation: accuracy, reproducibility, and impact on viability

BACKGROUND

Cellular transplantation holds promise for the management of a variety of neurological disorders. However, there is great variability in cell type, preparation methods, and implantation technique, which are crucial to clinical outcomes.

OBJECTIVE

We compared manual injection with automated injection using a prototype device to determine the possible value of a mechanized delivery system.

METHODS

Neural progenitor cells and bone marrow stromal cells were injected using manual or automated methods. Consistency of injection volumes and cell number and viability were evaluated immediately or 1 day after injection.

RESULTS

When cells were delivered as a series of 3 manual injections from the same syringe, the variation in fluid volume was greater than for single manual injections. Automated delivery of a series of 3 injections resulted in a lower variability in the amount of delivery than manual injection for both cell lines (1.2%-2.6% coefficient of variability for automated delivery vs 4.3%-24.0% for manual delivery). The amount delivered from injection 1 to injection 3 increased significantly with manual injections, whereas the amount injected did not vary over the 3 injections for the automated unit. Cell viability 1 day after injection was typically 30% to 40% of the value immediately after injection for the bone marrow stromal cells and 30% to 70% for the neural progenitor cells. There were no significant differences in viability attributed to the method of injection.

CONCLUSION

The automated delivery device led to enhanced consistency of volumetric cell delivery but did not improve cell viability in the methods tested. Automated techniques could be useful in standardizing reproducible procedures for cell transplantation and improve both preclinical and clinical research.

The treatment of TBI with human marrow stromal cells impregnated into collagen scaffold: functional outcome and gene expression profile

We have previously demonstrated that human marrow stromal cells (hMSCs) embedded in collagen I scaffolds significantly enhance the restorative therapeutic effect of hMSCs after traumatic brain injury (TBI). In this study, we test the hypothesis that the collagen scaffold alters gene expression in hMSCs and that hMSCs impregnated into scaffolds increase the astrocytic expression of vascular endothelial growth factor (VEGF) in the injured brain. Following TBI induced by controlled cortical impact injury, scaffold with hMSCs (3.0×10(6)), hMSCs-only and saline were implanted into the lesion cavity one week after brain injury (n=8/each group). Morris water maze and modified neurological severity scores were performed to evaluate the spatial learning and sensorimotor functions, respectively. Lesion volume and expression of VEGF were measured one week after different treatments. In vitro, total RNA from hMSCs was extracted one week after culture with or without collagen I scaffold for evaluation of gene microarrays. Furthermore, an RT-PCR study on a select subgroup of genes was performed to identify the changes of expression between the culturing hMSCs with collagen scaffolds and hMSCs only. The treatment of TBI with collagen scaffold impregnated with hMSCs significantly decreases the functional deficits from TBI within 7days after treatment, and significantly enhances the VEGF expression of astrocytes in the injured brain compared to the hMSCs-only group. In vitro data indicate that collagen scaffolds stimulate hMSCs to express multiple factors which may contribute to hMSC survival, tissue repair and functional recovery after TBI.

Combining erythropoeitin and bone marrow stromal cell therapy after stroke

Both Erythropoietin (EPO) and bone marrow stromal cells (BMSCs) have been shown to improve outcome after stroke. EPO may improve outcome after stroke through its actions on blood progenitor cells, angiogenesis, or direct action in the CNS. BMSCs may improve outcome after stroke by regeneration, altering plasticity of viable cells, or prevention of cell death. Sorting out these potential modes of actions for EPO and BMSCs has been difficult using in vivo models of stroke. This study investigated neuroprotection afforded by EPO, BMSCs and the combination of these modalities in mouse hippocampal slice cultures after oxygen glucose deprivation (OGD). Significant neuroprotection was observed following post-injury treatment of slice cultures with BMSCs and neuroprotection was augmented by treating BMSCs with EPO. EPO alone did not protect neurons from OGD when given after injury, but was effective when given prior to OGD. The failure of EPO to protect when given after injury did not appear to result from its inability to activate EPO signaling pathways involving phosphorylation of Akt. This study supports the implication that BMSCs may rescue dying neurons after ischemia by providing trophic support. The data also show that EPO’s actions as a neuroprotective agent following stroke may be mediated by its actions on BMSCs.

Structure and biocompatibility of an injectable bone regeneration composite

With the development of minimally invasive techniques, injectable materials have become one of the major hotspots in the biomaterial field. We have developed an injectable bone regeneration composite (IBRC) using calcium alginate hydrogel as matrix to carry nano-hydroxyapatite/collagen particles. In this work, we evaluated the homogeneity of IBRC by dry/wet weight ratio test. The results showed that the structural homogeneity was determined by controlling the molar ratios of trisodium phosphate to calcium sulfate rather than alginate concentration in the studied ranges. Pore sizes of wet IBRC samples were characterized by thermoporometry. The pore properties of dried IBRC were tested by mercury porosimetry. Average pore size and porosity of dried IBRC declined with increasing alginate concentration. In contrast, surprisingly, pore size of wet homogeneous IBRC increased with increasing alginate concentration. Meanwhile, the swelling ratio did not increase with varying alginate concentration, but the swelling degree increased with increasing alginate concentration. In vitro cell culture showed that IBRC had no obvious cytotoxic effect on the rat bone mesenchymal stem cells. The morphology and viability of cells were also related to MR value. IBRC had good histocompatibility with a mild short-term inflammatory response in rat dorsum muscle. In addition, the excellent ability of IBRC to promote bone healing was confirmed by 5-mm-diameter cranial defects using histological analysis and bone mineral density measurement.

Cellular transplantation for the nervous system: impact of time after preparation on cell viability and survival

OBJECT

Cell transplantation has shown promise for the treatment of various neurological disorders, but the factors that influence cell survival and integration following transplantation are poorly understood. In fact, little is known regarding how simple but potentially critical variables, including the method of cellular preparation and administration, might affect transplant success. The goal of the present study was to determine the impact of time between tissue preparation and implantation on cellular viability. Time can vary with cell preparation, delivery to the operating room, and surgical technique. This study was also designed to evaluate the sensitivity of various methods of assessing implant viability.

METHODS

Cell lines of neural progenitor cells and bone marrow stromal cells were generated from healthy adult mice. On the day of experimentation, the cells were collected, suspended in a balanced salt solution, and sequentially assessed for viability for up to 3.5 hours based on their appearance under phase-contrast microscopy, their ability to retain a fluorescent dye, and their attachment to a cultivation surface for 24 hours.

RESULTS

When viability was measured based on the ability of cells to retain a fluorescent dye, there was a decrease in viability of 10-15% each hour. Based on the ability of the cells to attach to a culture surface and grow for 24 hours, viability decreased more rapidly at approximately 20% per hour. In addition, only about one-third of the cells judged viable based on phase-contrast microscopy or acute dye retention were found to be viable based on plating, and only 10% of the cells initially judged as viable were still capable of survival after 3 hours in suspension.

CONCLUSIONS

The authors' results indicate that that there can be significant losses in viability between preparation and implantation and that more sophisticated methods of evaluation, such as the ability of cells to attach to a substrate and grow, may be required to detect decreases in viability. The time between preparation and implantation will be an important factor in clinical trial design.

Unrestricted somatic stem cells from human umbilical cord blood grow in serum-free medium as spheres

Background

Human umbilical cord blood-derived unrestricted somatic stem cells (USSCs), which are capable of multilineage differentiation, are currently under investigation for a number of therapeutic applications. A major obstacle to their clinical use is the fact that in vitro expansion is still dependent upon fetal calf serum, which could be a source of pathogens. In this study, we investigate the capacity of three different stem cell culture media to support USSCs in serum-free conditions; HEScGRO™, PSM and USSC growth medium^ACF. Our findings demonstrate that USSCs do not grow in HEScGRO™ or PSM, but we were able to isolate, proliferate and maintain multipotency of three USSC lines in USSC growth medium^ACF.

Results

For the first one to three passages, cells grown in USSC growth medium^ACF proliferate and maintain their morphology, but with continued passaging the cells form spherical cell aggregates. Upon dissociation of spheres, cells continue to grow in suspension and form new spheres. Dissociated cells can also revert to monolayer growth when cultured on extracellular matrix support (fibronectin or gelatin), or in medium containing fetal calf serum. Analysis of markers associated with pluripotency (Oct4 and Sox2) and differentiation (FoxA2, Brachyury, Goosecoid, Nestin, Pax6, Gata6 and Cytokeratin 8) confirms that cells in the spheres maintain their gene expression profile. The cells in the spheres also retain the ability to differentiate in vitro to form cells representative of the three germline layers after five passages.

Conclusions

These data suggest that USSC growth medium^ACF maintains USSCs in an undifferentiated state and supports growth in suspension. This is the first demonstration that USSCs can grow in a serum- and animal component-free medium and that USSCs can form spheres.

Neurotrophic actions of bone marrow stromal cells on primary culture of dorsal root ganglion tissues and neurons

Application of adult bone marrow stromal cells (BMSCs) provides therapeutic benefits to the treatment of neurological insults. The aim of this study was to explore the potential of nonhematopoietic BMSCs to produce soluble factors and stimulate signaling pathways in neurons that mediate trophic effects. A combination of enzyme-linked immunosorbent assay and two-dimensional gel electrophoresis coupled with mass spectrometry showed that the BMSCs released into the culture medium an array of soluble factors such as nerve growth factor, brain-derived neurotrophic factor, basic fibroblast growth factor, and ciliary neurotrophic factor, which have been shown to exhibit potent neurotrophic effects on neural cells. Immunochemistry, cell viability assay, and quantitative real-time RT-PCR collectively showed that neurite outgrowth and neurogenesis in cultured rat dorsal root ganglion (DRG) explants and neurons were enhanced after they were cocultured with rat BMSCs. Western blot analysis revealed that BMSC-conditioned medium activated phosphorylation of mitogen-activated protein kinase/extracellular signal-regulated protein kinase and/or phosphoinositide 3-kinase/serine/threonine kinase (PI3K/Akt) in primary culture of rat DRG neurons, which suggested that BMSCs trigger endogenous survival signaling pathways in neurons through their secreted soluble factors. Our data help to elucidate the mechanisms by which BMSCs function as a cell therapy agent in peripheral nerve regeneration.

Treatment of traumatic brain injury in mice with bone marrow stromal cell-impregnated collagen scaffolds

OBJECT

This study was designed to investigate new ways of delivering human marrow stromal cells (hMSCs) to the injured brain by impregnating them into collagen scaffolds in a mouse model of traumatic brain injury (TBI).

METHODS

Eight C57BL/6 J mice were injured with controlled cortical impact and received transplantation into the lesion cavity of 0.3 x 10(6) hMSCs impregnated into 3D porous collagen scaffolds. Additional experimental groups of 8 mice each received scaffolds implanted alone into the lesion cavity, hMSCs administered alone intracerebrally or intravenously, or saline injected into the lesion core. All treatments were performed 7 days after TBI. Spatial learning was measured using a modified Morris water maze test, and brain tissue samples were processed for histopathological analysis.

RESULTS

The results showed that hMSC-impregnated scaffolds were more effective than hMSCs administered alone (either intravenously or intracerebrally) in improving spatial learning, reducing lesion volume, and increasing vascular density after TBI.

CONCLUSIONS

Collagen scaffolds populated with hMSCs may be a new way to reconstruct injured brain tissue and improve neurological function after TBI.

Brain cortex regeneration affected by scaffold architectures

Object

The aim of this study was to compare designed scaffolds with a random-pored sponge scaffold to determine what role scaffold architecture plays in a cortical injury model.

Methods

Cylindrical scaffolds (3 × 3 mm) were made of a poly-(ε-caprolactone) polymer with 2 different molds from a 3D printer and had either: 1) unidirectional channels and microgrooves oriented longitudinally within the cylinder or 2) orthogonally intersecting channels and axial microgrooves within the cylinder. Additional randomized porosity was imparted using a salt-leaching method. A control scaffold without channels or microgrooves but containing random pores was also made. Scaffolds were implanted for 1, 4, and 8 weeks in a cylindrical defect created 3 mm posterior to the bregma in rat cortex. Control animals had tissue removed but received no implant. Brains were coronally cryosectioned and sections were stained. Antibodies for nestin, glial fibrillary acidic protein (GFAP), and TUJ1 were used to identify neural progenitors, activated astrocytes, and neuronal axons. Tissue ingrowth (H & E), astrocytic infiltration (GFAP), parenchymal inflammation (GFAP), and defect width (H & E) were quantified from images.

Results

Defect widths grew and parenchymal inflammation decreased over time with no statistical difference between groups. Total tissue ingrowth and astrocytic infiltration increased over time and was greatest in the orthogonal design group. Specific cell ingrowth, which was aligned with microgrooves interiorly in the orthogonal group and exteriorly in the longitudinal channel group, was qualitatively assessed from nestin and TUJ1 labeling.

Conclusions

Scaffold architecture can benefit brain tissue regeneration by integrating the following design principles: 1) large (100s of micrometers) pores or channels oriented toward the parenchyma for increased astrocytic infiltration; 2) microgrooves oriented in the desired direction of cellular migration and neuronal alignment; and 3) fully interconnecting channels for cellular migration and tissue integration.

Cell therapies for traumatic brain injury

Preliminary discoveries of the efficacy of cell therapy are currently being translated to clinical trials. Whereas a significant amount of work has been focused on cell therapy applications for a wide array of diseases, including cardiac disease, bone disease, hepatic disease, and cancer, there continues to be extraordinary anticipation that stem cells will advance the current therapeutic regimen for acute neurological disease. Traumatic brain injury is a devastating event for which current therapies are limited. In this report the authors discuss the current status of using adult stem cells to treat traumatic brain injury, including the basic cell types and potential mechanisms of action, preclinical data, and the initiation of clinical trials.

Protection of dopamine neurons by bone marrow stromal cells

Transplantation of bone marrow stromal cells (BMSC) has recently been demonstrated to provide neuroprotection in animal models of brain injuries such as ischemia and trauma. The present study was undertaken to explore whether BMSC can promote the survival of dopamine (DA) neurons in neuronal insult models in vitro. We also examined whether BMSC can increase the survival rate of embryonic DA neurons grafted into the striatum of a rat model of Parkinson's disease (PD). Treatment with conditioned media derived from BMSC cultures was found to significantly prevent the death of DA neurons in in vitro cell injury models such as serum deprivation and exposure to the neurotoxin 6-OHDA. In a transplantation study, we also found that the survival of grafted DA cells was significantly enhanced by treating donor cells with the conditioned media at the steps of both cell dissociation and implantation. The results suggest that BMSC may secrete diffusible factors able to protect DA neurons against neuronal injuries. Indeed, BMSC expressed mRNA encoding brain-derived neurotrophic factor, fibroblast growth factor-2 and glial cell line-derived neurotrophic factor, all of which have previously been shown to exhibit potent neurotrophic effects on DA cells. Enzyme-linked immunosorbent assay revealed that the cells release these growth factors into culture media. The present data indicate that BMSC may be a potential donor source of cell-based regenerative therapy for PD where the progressive loss of the midbrain DA neurons takes place.

Collagen scaffolds populated with human marrow stromal cells reduce lesion volume and improve functional outcome after traumatic brain injury

OBJECTIVE

Traumatic brain injury (TBI) causes extensive loss of cerebral parenchyma; however, no strategy for reconstruction has been clinically effective. Our group and others have used human marrow stromal cells (hMSCs) to treat rats subjected to TBI and found no significant changes in the lesion volume, although functional outcome was improved significantly. To identify new ways of delivering hMSCs into the injured brain and to maximize the therapeutic benefits of hMSC treatment, we investigated the use of collagen scaffolds implanted with hMSCs as a cell delivery system for treatment of TBI.

METHODS

Collagen scaffolds populated with 3 x 10(6) hMSCs were transplanted into the lesion cavity of the injured cortex 4 days after TBI, and the rats were euthanized 35 days after TBI. We measured sensorimotor function and spatial learning using an array of function tests, and the brain tissue was processed for histopathology analysis.

CONCLUSION

The data show that scaffolds populated by hMSCs improve spatial learning and sensorimotor function, reduce the lesion volume, and foster the migration of hMSCs into the lesion boundary zone after TBI in rats. hMSC-populated scaffolds may be a new way to reconstruct the injured brain and improve neurological function after TBI.

Apoptotic cell death and regeneration in the newborn retina after irradiation prior to bone marrow transplantation

PURPOSE

We studied the contribution made by circulating bone marrow (BM)-derived cells to the newborn and mature retinas of BM-transplanted mice.

METHODS

Newborn and adult C57BL/6J mice were administered a lethal dose of total-body irradiation, after which pathologic changes to the retinas were periodically assessed. In addition, mice received BM cells from 8-week-old green fluorescent protein (GFP) transgenic mice, and the subsequent differentiation of GFP+ cells was studied.

RESULTS

Within 5 hr after irradiation of newborn mice, retinal cells began to die due to apoptosis. By contrast, irradiation of adult mice elicited no histologic changes in the retina. BM cells generally did not differentiate in adult mice, but numerous GFP+ BM cells were integrated into the retinal tissue of newborn mice, where they expressed various cell type-specific markers. Finally, examination of whole retina mounts showed that GFP+ cells also contributed to retinal vascularization.

CONCLUSIONS

Our findings underscore the importance of careful evaluation of the biological effects of irradiation in models making use of BM transplantation.

Plasticity and remodeling of brain

The injured brain can be stimulated to amplify its intrinsic restorative processes to improve neurological function. Thus, after stroke, both cell and pharmacological neurorestorative treatments, amplify the induction of brain neurogenesis and angiogenesis, and thereby reduce neurological deficits. In this manuscript, we describe the use of bone marrow mesenchymal cells (MSCs) and erythropoietin (EPO) as examples of cell-based and pharmacological neurorestorative treatments, respectively, for both stroke and a mouse model of experimental autoimmune encephalomyelitis (EAE). We demonstrate that these therapies significantly improve neurological function with treatment initiated after the onset of injury and concomitantly promote brain plasticity. The application of MRI to monitor changes in the injured brain associated with reduction of neurological deficit is also described.

Basic fibroblast growth factor promotes bone marrow stromal cell transplantation-mediated neural regeneration in traumatic brain injury

The current study was designed to evaluate the effects of basic fibroblast growth factor (bFGF) on human BMSC (hBMSC) transplantation-mediated neural regeneration in traumatic brain injury (TBI). Fibrin gel was used as a delivery vehicle to release bFGF locally in the TBI sites in a controlled manner. To test this hypothesis, hBMSCs suspended in fibrin gel containing bFGF were transplanted to rat TBI sites. Transplantation of hBMSCs suspended in fibrin gel without bFGF served as a control. hBMSC transplantation and bFGF treatment showed enhanced neural tissue regeneration than that of the control. The infarction volume and apoptotic activity of the transplanted hBMSCs were significantly decreased, and functional outcomes were significantly improved in the hBMSC transplantation and bFGF treatment group than in the control group. This study demonstrates that bFGF significantly enhances histological and functional recovery when used in hBMSC transplantation therapy in TBI.

Embryonic stem cells produce neurotrophins in response to cerebral tissue extract: Cell line-dependent differences

In the present study, we compare the capacity of two different embryonic stem (ES) cell lines to secrete neurotrophins in response to cerebral tissue extract derived from healthy or injured rat brains. The intrinsic capacity of the embryonic cell lines BAC7 (feeder cell-dependent cultivation) to release brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3) exceeded the release of these factors by CGR8 cells (feeder cell-free growth) by factors of 10 and 4, respectively. Nerve growth factor (NGF) was secreted only by BAC7 cells. Conditioning of cell lines with cerebral tissue extract derived from healthy or fluid percussion-injured rat brains resulted in a significant time-dependent increase in BDNF release in both cell lines. The increase in BDNF release by BAC7 cells was more pronounced when cells were incubated with brain extract derived from injured brain. However, differences in neurotrophin release associated with the origin of brain extract were at no time statistically significant. Neutrophin-3 and NGF release was inhibited when cell lines were exposed to cerebral tissue extract. The magnitude of the response to cerebral tissue extract was dependent on the intrinsic capacity of the cell lines to release neurotrophins. Our results clearly demonstrate significant variations in the intrinsic capability of different stem cell lines to produce neurotrophic factors. Furthermore, a significant modulation of neurotrophic factor release was observed following conditioning of cell lines with tissue extract derived from rat brains. A significant modulation of neurotrophin release dependent on the source of cerebral tissue extract used was not observed.

Human marrow stromal cell treatment provides long-lasting benefit after traumatic brain injury in rats

OBJECTIVE

This study was designed to investigate the effects of human bone marrow stromal cell (hMSC) administration in rats for 3 months after traumatic brain injury (TBI).

METHODS

Adult male Wistar rats (n = 60) were injured with controlled cortical impact and divided into four groups. The three treatment groups (n = 10 each) were injected with 2 x 10, 4 x 10, and 8 x 10 hMSCs, respectively, intravenously, whereas the control group (n = 30) received phosphate-buffered saline. All injections were performed 1 day after injury into the tail veins of rats. Neurological functional evaluation of animals was performed before and after injury by use of Neurological Severity Scores. Animals were sacrificed 3 months after TBI, and brain sections were stained by immunohistochemistry.

RESULTS

Statistically significant improvement in functional outcome was observed in all three treatment groups compared with control values (P < 0.05). This benefit was visible 14 days after TBI and persisted until 3 months (end of trial). There was no difference in functional outcome among the three treatment groups. Histological analysis showed that hMSCs were present in the lesion boundary zone at 3 months with all three doses tested.

CONCLUSION

hMSCs injected in rats after TBI survive until 3 months and provide long-lasting functional benefit. Functional improvement may be attributed to stimulation of endogenous neurorestorative functions such as neurogenesis and synaptogenesis.

Human Mesenchymal Stem Cells Express Neural Genes, Suggesting a Neural Predisposition

Because of their unique attributes of plasticity and accessibility, bone marrow-derived mesenchymal stem cells (MSCs) may find use for therapy of neurodegenerative disorders. Our previous studies of adult human MSCs demonstrated that these cells express an extensive assortment of neural genes at a low but clearly detectable level. Here, we report expression of 12 neural genes, 8 genes related to the neuro-dopaminergic system, and 11 transcription factors with neural significance by human MSCs. Our results suggest that, as opposed to cells that do not express neural genes, human MSCs are predisposed to differentiate to neuronal and glial lineages, given the proper conditions. Our findings add a new dimension in which to view adult stem cell plasticity, and may explain the relative ease with which MSCs, transplanted into the central nervous system (CNS) differentiate to a variety of functional neural cell types. Our results further promote the possibility that adult human MSCs are promising candidates for cell-based therapy of neurodegenerative diseases.

Long-term recovery after bone marrow stromal cell treatment of traumatic brain injury in rats

OBJECT

This study was designed to follow the effects of bone marrow stromal cell (BMSC) administration in rats after traumatic brain injury (TBI) for a 3-month period.

METHODS

Forty adult female Wistar rats were injured by a controlled cortical impact and, 1 week later, were injected intravenously with one of three different doses of BMSCs (2 x 10(6), 4 x 10(6), or 8 x 10(6) cells per animal) obtained in male rats. Control rats received phosphate-buffered saline (PBS). Neurological function in these rats was studied using a neurological severity scale (NSS). The rats were killed 3 months after injury, and immunohistochemical stains were applied to brain samples to study the distribution of the BMSCs. Additional brain samples were analyzed by quantitative enzyme-linked immunosorbent assays to measure the expression of the growth factors brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF). Three months after injury, BMSCs were present in the injured brain and their number was significantly greater in animals that received 4 x 10(6) or 8 x 10(6) BMSCs than in animals that received 2 x 10(6) BMSCs. The cells were primarily distributed around the lesion boundary zone. Functional outcome was significantly better in rats that received 4 x 10(6) or 8 x 10(6) BMSCs, compared with control animals, although no improvement was seen in animals that received 2 x 10(6) BMSCs. All doses of BMSCs significantly increased the expression of BDNF but not that of NGF; however, this increase was significantly larger in animals that received 4 x 10(6) or 8 x 10(6) BMSCs than in controls or animals that received 2 x 10(6) BMSCs.

CONCLUSIONS

In summary, when injected in rats after TBI, BMSCs are present in the brain 3 months later and significantly improve functional outcome.

Effect of atorvastatin on spatial memory, neuronal survival, and vascular density in female rats after traumatic brain injury

Object. Atorvastatin administered after traumatic brain injury (TBI) induced by controlled cortical impact promotes functional improvement in male rats. Note, however, that parallel studies have not been performed in female rats. Therefore, the authors tested the effect of atorvastatin on TBI in female rats.

Methods. Atorvastatin (1 mg/kg/day) was orally administered for 7 consecutive days in female Wistar rats starting 1 day after TBI; control animals received saline. Modified neurological severity scores, the corner turn test, and the Morris water maze test were used to evaluate functional response to treatment. Rats were killed on Day 15 post-TBI, and brain tissue samples were processed for immunohistochemical staining. Atorvastatin administration after brain injury significantly promoted the restoration of spatial memory but did not reduce sensorimotor functional deficits. Treatment of TBI with atorvastatin increased neuronal survival in the CA3 region and the lesion boundary zone and prevented the loss of neuronal processes of damaged neurons in the hippocampal CA3 region but not in the lesion boundary zone on Day 15 after TBI. The protective effect of atorvastatin on the injured neurons perhaps is mediated by increasing the density of vessels in the lesion boundary zone and the hippocampus after TBI.

Conclusions. These data indicate that atorvastatin is beneficial in the treatment of TBI in female rats, although the effect may differ between sexes.

Endogenous stem cell proliferation after central nervous system injury: alternative therapeutic options

The continuous regeneration of glial cells arising from endogenous stem cell populations in the central nervous system (CNS) occurs throughout life in mammals. In the ongoing research to apply stem cell therapy to neurological diseases, the capacity to harness the multipotential ability of endogenous stem cell populations has become apparent. Such cell populations proliferate in response to a variety of injury states in the CNS, but in the absence of a supportive microenvironment they contribute little to any significant behavioral recovery. In the authors' laboratory and elsewhere, recent research on the regenerative potential of these stem cells in disease states such as spinal cord injury has demonstrated that the cells' proliferative potential may be greatly upregulated in response to appropriate growth signals and exogenously applied trophic factors. Further understanding of the potential of such multipotent cells and the mechanisms responsible for creating a favorable microenvironment for them may lead to additional therapeutic alternatives in the setting of neurological diseases. These therapies would require no exogenous stem cell sources and thus would avoid the ethical and moral considerations regarding their use. In this review the authors provide a brief overview of the enhancement of endogenous stem cell proliferation following neurological insult.

Generation of bone marrow-derived neural cells in serum-free monolayer culture

Bone marrow-derived cells (BMCs) are reported to trans-differentiate into neural lineages, and are expected to offer a valuable resource for treating severe diseases of the central nervous system. BMCs that show neural differentiation may differ morphologically from typical marrow stromal cells. The present study aimed to obtain efficient generation of cells with neural features from bone marrow. Serum-free culture was applied to BMCs to prevent the growth of differentiated cells. Using basic fibroblast growth factor and extracellular matrix, rodent BMCs capable of proliferation and neural differentiation expanded in monolayer form. Cultured cells were small, round or spindle-shaped, and expressed nestin. Under neural differentiation conditions, cells developed long, thin cellular processes with branches, and expressed neuronal and glial phenotypes. Intracerebrally transplanted BMCs survived and migrated into the subcortex of syngenic animals.

Neural progenitor cell transplants promote long-term functional recovery after traumatic brain injury

Studies demonstrating the versatility of neural progenitor cells (NPCs) have recently rekindled interest in neurotransplantation methods aimed at treating traumatic brain injury (TBI). However, few studies have evaluated the safety and functional efficacy of transplanted NPCs beyond a few months. The purpose of this study was to assess the long-term survival, migration, differentiation and functional significance of NPCs transplanted into a mouse model of TBI out to 1 year post-transplant. NPCs were derived from E14.5 mouse brains containing a transgene-expressing green fluorescent protein (GFP) and cultured as neurospheres in FGF2-containing medium. Neurospheres were injected into the ipsilateral striatum of adult C57BL/6 mice 1 week following unilateral cortical impact injury. Behavioral testing revealed significant improvements in motor abilities in NPC-treated mice as early as 1 week, and the recovery was sustained out to 1 year post-transplant. In addition, mice receiving NPC transplants showed significant improvement in spatial learning abilities at 3 months and 1 year, whereas an intermediate treatment effect on this behavioral parameter was detected at 1 month. At 14 months post-transplant, GFP(+) NPCs were observed throughout the injured hippocampus and adjacent cortical regions of transplanted brains. Immunohistochemical analysis revealed that the majority of transplanted cells co-labeled for NG2, an oligodendrocyte progenitor cell marker, but not for neuronal, astrocytic or microglial markers. In conclusion, transplanted NPCs survive in the host brain up to 14 months, migrate to the site of injury, enhance motor and cognitive recovery, and may play a role in trophic support following TBI.

Marrow Stromal Cell Transplantation after Traumatic Brain Injury Promotes Cellular Proliferation within the Brain

OBJECTIVE

This study was designed to investigate the effects of intracerebral as well as intravenous administration of bone marrow stromal cells (MSCs) on endogenous cellular proliferation after traumatic brain injury (TBI).

METHODS

Two experimental groups of Wistar rats were studied. One group received MSCs intracerebrally, and the other group received MSCs intravenously after injury by controlled cortical impact. MSCs were harvested from the bone marrow of male Wistar rats. For the intracerebral study, 24 male rats were divided into three groups (eight rats per group): rats injected with MSCs (1 x 10(6)) intracerebrally 1 day after TBI; 2) rats injected with phosphate-buffered saline intracerebrally 1 day after TBI; and 3) sham group not subjected to injury and not administered treatment. For the intravenous study, 10 female Wistar rats were injected 1 day after TBI with either MSCs (2 x 10(6)) (n = 5) or phosphate-buffered saline (n = 5) via the tail vein. Neurological function of the rats was evaluated with modified neurological severity scores and rotarod motor test. All rats were injected with bromodeoxyuridine intraperitoneally, to label the newly generating cells. Rats were killed 15 days after TBI, and coronal brain sections were stained immunohistochemically with diaminobenzidine to identify newly generating bromodeoxyuridine-positive cells. To study the differentiation of newly generating cells into neurons, sections were also double-stained for neuronal markers (Tuj1, doublecortin, NeuN) with fluorescein isothiocyanate.

RESULTS

The data demonstrate that newly generating cells were mainly present in the subventricular zone, hippocampal formation, and boundary zone of contusion of both treated and control animals. Intracerebral MSC treatment significantly increased the progenitor cell proliferation in the subventricular zone and boundary zone compared with the controls, whereas intravenous MSC treatment enhanced this endogenous proliferation in subventricular zone, hippocampus, and boundary zone. In both groups, some of the new cells revealed positive staining for neuronal markers. A statistically significant functional improvement was observed in both the intracerebrally as well as intravenously treated groups.

CONCLUSION

Intracerebral and intravenous MSC administration promotes endogenous cellular proliferation after TBI in rats. This may contribute to the functional improvement observed in these rats.

A Review and Rationale for the Use of Cellular Transplantation as a Therapeutic Strategy for Traumatic Brain Injury

Experimental research during the past decade has greatly increased our understanding of the pathophysiology of traumatic brain injury (TBI) and allowed us to develop neuroprotective pharmacological therapies. Encouraging results of experimental pharmacological interventions, however, have not been translated into successful clinical trials, to date. Traumatic brain injury is now believed to be a progressive degenerative disease characterized by cell loss. The limited capacity for self-repair of the brain suggests that functional recovery following TBI is likely to require cellular transplantation of exogenous cells to replace those lost to trauma. Recent advances in central nervous system transplantation techniques involve technical and experimental refinements and the analysis of the feasibility and efficacy of transplantation of a range of stem cells, progenitor cells and postmitotic cells. Cellular transplantation has begun to be evaluated in several models of experimental TBI, with promising results. The following is a compendium of these new and exciting studies, including a critical discussion of the rationale and caveats associated with cellular transplantation techniques in experimental TBI research. Further refinements in future research are likely to improve results from transplantation-based treatments for TBI.

Interactions between human adipose stromal cells and mouse neural stem cells in vitro

Transplantation of adult mesenchymal stem cells (MSCs) into adult rat brain has been known to reduce functional deficits associated with stroke and traumatic brain injury. However, in injured brains, there is no evidence that transplanted MSCs replace lost host brain tissue. In this study, we determined in vitro interaction between human adipose tissue stromal cells (hATSCs), a kind of MSC, and neural stem cells (NSCs). hATSCs were isolated and proliferated from human adipose tissues, and NSCs from the subventricular zone of postnatal mice. When NSCs were cultured on mitomycin-treated hATSC monolayers, their proliferation was decreased, but neuronal differentiation was significantly induced. The percentage of neurons significantly increased in 7 days in cultures of NSCs on hATSCs feeder as compared to NSCs cultured on laminin-coated dishes. When the duration of the cultures was extended to 14 days, hATSCs supported the survival of neurons derived from NSCs. To determine the role of soluble factors from hATSCs, NSCs were cultured with hATSCs conditioned medium or co-cultured with permeable filter on which hATSCs were grown. Although proliferation of NSCs significantly decreased and glial differentiation increased under these experimental conditions, their neuronal differentiation was not affected, indicating that direct physical contact between hATSCs and NSCs is required for induction of neuronal differentiation. These data indicate that hATSCs may provide supportive roles on endogenous neural stem cells, when they are transplanted into damaged brain.

Biologic Transplantation and Neurotrophin-Induced Neuroplasticity After Traumatic Brain Injury

OBJECTIVE

In this review, we analyze progress in the treatment of traumatic brain injury with neurotrophins, growth factors and cell and tissue neurotransplantation. The primary objective of these therapies is to reduce neurologic deficits associated with the trauma by inducing neuroplasticity. These therapies are restorative and not necessarily neuroprotective.

MAIN OUTCOME MEASURES

An extensive literature on administration of neurotrophics factors and cell and tissue cerebral transplantation is reviewed. The effects of these therapeutic approaches on brain biochemical, molecular, cellular, and tissue responses are summarized.

CONCLUSION

The cumulative data indicate that cell therapy shows substantial promise in the treatment of neural injury.