Migration of bone marrow stem cells in ischaemic brain

Comparison of administration routes for adipose-derived stem cells in the treatment of middle cerebral artery occlusion in rats

Given that adult adipose tissue is an abundant, accessible and safe source of stem cells, the use of adipose-derived stem cells (ADSCs) provides a promising approach in ischemic stroke. The delivery route, however, for transplantation of ADSCs in clinical application remains controversial regarding the time window, cell type, safety issues, 'first pass' effect and therapeutic effect. To determine the optimal administration route in transplantation of ADSCs, we compared the therapeutic effect of the three mainly used administration routes of ADSCs in a middle cerebral artery occlusion (MCAO) rat model. Cells isolated from the adipose tissue of adult rodents were differentiated and characterized in vitro, and further transplanted in vivo by intravenous, intra-arterial or intra-ventricular delivery. The infarct volume, expression of neurotrophic factors and the neurobehavioral improvements were evaluated after the equal dose of BrdU labeled ADSCs transplantation. Our results indicated that the equal dose of ADSCs delivered intravenously were effective in improving the neurological outcome and reducing the infarct volume after ischemic brain injury in long term duration in contrast to intra-arterial and intra-ventricular delivery. At 1-7 days after transplantation, the increased expression levels of BDNF, VEGF, bFGF, Bcl-2, IL-10 and decreased levels of caspase-3 and TNF-α in the intra-ventricular and intra-arterial groups were significant in contrast to the intravenous group. There was no significant difference among the three groups after 7 days. Our findings suggest that compared with the intra-ventricular delivery, intravascular injection allows higher dose injection with fewer invasions and appears to be optimal in application with regard to therapeutic efficacy, safety and feasibility.

Transplantation of mesenchymal stem cells to the brain by topical application in an experimental traumatic brain injury model

Mesenchymal stem cells (MSCs) have been shown in various animal models to be capable of neurorepair and neuroprotection. To carry out a therapeutic function, MSCs must be delivered to the target organ. MSCs are administered to patients via systemic infusion, which has many drawbacks, including a low engraftment rate and the migration of MSCs to non-target organs. However, other approaches such as direct intracerebral injection of MSCs might cause cerebral bleeding. In this study, a traumatic brain injury (TBI) was induced over the right parietal cerebral cortex in Sprague Dawley rats, and green fluorescent protein (GFP)-expressing MSCs (GFP-MSCs), together with a thin layer of fibrin, were applied to the external surface of the contralateral side 2 days later. Within 5 days of topical application, the GFP-MSCs had migrated from the site of application on the cortical surface, through the white matter, and had emerged at the cortical surface of the TBI site on the contralateral cerebral hemisphere, apparently following axons along the corpus callosum. In sham-injured control animals, the topically applied GFP-MSCs proliferated superficially on the cortex at the site of application, and no GFP-MSCs were found at the contralateral cortical surface. In all instances, GFP-MSCs were not detected in other organs of either the test or the control animals. Our study demonstrated that MSCs topically applied to the brain surface can migrate to a TBI site.

Umbilical cord-derived mesenchymal stem cells with forced expression of hepatocyte growth factor enhance remyelination and functional recovery in a rat intracerebral hemorrhage model

BACKGROUND

Spontaneous intracerebral hemorrhage (ICH) carries a high mortality rate, with survivors commonly left with permanent neurological deficits. Mesenchymal stem cell (MSC) transplantation promotes functional recovery in experimental ICH, and treatment with hepatocyte growth factor (HGF) is beneficial in ischemic stroke.

OBJECTIVE

We hypothesize that transplantation of MSCs with previous transduction of HGF has an additive effect in promoting neurological recovery through myelin and axonal regeneration.

METHODS

HGF transduction to human umbilical cord-derived MSCs using lentiviral plasmid pWPI-HGF-GFP was prepared. One week after a collagenase-induced ICH, 80 male Sprague-Dawley rats were divided into 3 groups for stereotactic injection of phosphate-buffered saline (group I), MSC transplant (group II), and HGF-transduced MSC transplant (group III), respectively, into the left ventricle. The animals were assessed weekly for 5 weeks using the Rotarod motor function test, at which time they were killed for Luxol fast blue myelin staining and appropriate immunohistochemistry and Western blotting.

RESULTS

Animals receiving transplanted HGF-transduced MSCs (group III) exhibited significantly better motor function recovery than animals treated with MSCs alone (group II), which in turn performed better than the phosphate-buffered saline controls at 2 weeks after transplantation. Luxol fast blue staining of myelin displayed significantly less demyelination and significantly higher reactivity in myelin basic protein and growth-associated protein-43 in immunohistochemistry and Western blotting and significantly reduced myelin-associated glycoprotein activity in group III animals.

CONCLUSION

Animals transplanted with HGF-transduced MSCs 1 week after experimental ICH were shown to achieve a better neurological recovery. This improved neurological recovery from ICH is attributed to nerve fiber remyelination and axonal regeneration.

Modulation of the major histocompatibility complex by neural stem cell-derived neurotrophic factors used for regenerative therapy in a rat model of stroke

Background

The relationship between functional improvements in ischemic rats given a neural stem cell (NSC) transplant and the modulation of the class I major histocompatibility complex (MHC) mediated by NSC-derived neurotrophins was investigated.

Methods

The levels of gene expression of nerve growth factor (NGF), brain-derived neurotropic factor (BDNF) and neurotrophin-3 (NT-3) were assayed from cultures of cortical NSC from Sprague-Dawley rat E16 embryos. The levels of translated NGF in spent culture media from NSC cultures and the cerebral spinal fluid (CSF) of rats with and without NGF injection or NSC transplant were also measured.

Results

We found a significant increase of NGF, BDNF and NT-3 transcripts and NGF proteins in both the NSC cultures and the CSF of the rats. The immunochemical staining for MHC in brain sections and the enzyme-linked immunosorbent assay of CSF were carried out in sham-operated rats and rats with surgically induced focal cerebral ischemia. These groups were further divided into animals that did and did not receive NGF administration or NSC transplant into the cisterna magna. Our results show an up-regulation of class I MHC in the ischemic rats with NGF and NSC administration. The extent of caspase-III immunoreactivity was comparable among three arms in the ischemic rats.

Conclusion

Readouts of somatosensory evoked potential and the trap channel test illustrated improvements in the neurological function of ischemic rats treated with NGF administration and NSC transplant.

Microglia and neuroprotection: from in vitro studies to therapeutic applications

Microglia are the main immune cells in the brain, playing a role in both physiological and pathological conditions. Microglial involvement in neurodegenerative diseases is well-established, being microglial activation and neuroinflammation common features of these neuropathologies. Microglial activation has been considered harmful for neurons, but inflammatory state is not only associated with neurotoxic consequences, but also with neuroprotective effects, such as phagocytosis of dead neurons and clearance of debris. This brought to the idea of protective autoimmunity in the brain and to devise immunomodulatory therapies, aimed to specifically increase neuroprotective aspects of microglia. During the last years, several data supported the intrinsic neuroprotective function of microglia through the release of neuroprotective molecules. These data led to change the traditional view of microglia in neurodegenerative diseases: from the idea that these cells play an detrimental role for neurons due to a gain of their inflammatory function, to the proposal of a loss of microglial neuroprotective function as a causing factor in neuropathologies. This "microglial dysfunction hypothesis" points at the importance of understanding the mechanisms of microglial-mediated neuroprotection to develop new therapies for neurodegenerative diseases. In vitro models are very important to clarify the basic mechanisms of microglial-mediated neuroprotection, mainly for the identification of potentially effective neuroprotective molecules, and to design new approaches in a gene therapy set-up. Microglia could act as both a target and a vehicle for CNS gene delivery of neuroprotective factors, endogenously produced by microglia in physiological conditions, thus strengthening the microglial neuroprotective phenotype, even in a pathological situation.