Implantation site and lesion topology determine efficacy of a human neural stem cell line in a rat model of chronic stroke.

Stroke remains one of the most promising targets for cell therapy. Thorough preclinical efficacy testing of human neural stem cell (hNSC) lines in a rat model of stroke (transient middle cerebral artery occlusion) is, however, required for translation into a clinical setting. Magnetic resonance imaging (MRI) here confirmed stroke damage and allowed the targeted injection of 450,000 hNSCs (CTX0E03) into peri-infarct tissue, rather than the lesion cyst. Intraparenchymal cell implants improved sensorimotor dysfunctions (bilateral asymmetry test) and motor deficits (footfault test and rotameter). Importantly, analyses based on lesion topology (striatal vs. striatal + cortical damage) revealed a more significant improvement in animals with a stroke confined to the striatum. However, no improvement in learning and memory (water maze) was evident. An intracerebroventricular injection of cells did not result in any improvement. MRI-based lesion, striatal and cortical volumes were unchanged in treated animals compared to those with stroke that received an intraparenchymal injection of suspension vehicle. Grafted cells only survived after intraparenchymal injection with a striatal + cortical topology resulting in better graft survival (16,026 cells) than in animals with smaller striatal lesions (2,374 cells). Almost 20% of cells differentiated into glial fibrillary acidic protein+ astrocytes, but <2% turned into FOX3+ neurons. These results indicate that CTX0E03 implants robustly recover behavioral dysfunction over a 3-month time frame and that this effect is specific to their site of implantation. Lesion topology is potentially an important factor in the recovery, with a stroke confined to the striatum showing a better outcome compared to a larger area of damage.

Effects of implantation site of stem cell grafts on behavioral recovery from stroke damage.

BACKGROUND AND PURPOSE: Findings that MHP36 stem cells grafted into intact parenchyma contralateral to the lesion induced by middle cerebral artery occlusion promoted recovery from stroke deficits led us to investigate whether implantation site of stem cells affects the functional efficacy of MHP36 grafts. METHODS: MHP36 cells (200 000/8 microL) were implanted in the left (n=8) or right (n=9) parenchyma or infused into the right ventricle (intraventricular; n=7) 2 to 3 weeks after stroke induced by 60 minutes of intraluminal right middle cerebral artery occlusion. Additionally, intact (n=11) and stroke (n=7) control groups were tested for 14 weeks in bilateral asymmetry, rotation bias, and spatial learning tasks before histological investigation of cell distribution and differentiation. RESULTS: Rats with left and right parenchymal grafts showed reduced bilateral asymmetry but no improvement in spatial learning. Conversely, spatial learning improved in rats with intraventricular grafts, but marked asymmetry persisted. No grafted group showed reduced amphetamine-induced rotation bias or reduced lesion volume relative to stroke controls. In all grafted groups, cells occupied both sides of the brain. A third of cells grafted in the striatum crossed the midline to occupy homologous regions in intact and lesioned hemispheres and differentiated into site-appropriate phenotypes. CONCLUSIONS: After stroke, both the intact and lesioned hemispheres attract grafted stem cells, suggesting repair processes that utilize cells both for local repair and to augment plastic changes in contralateral motor pathways. However, differential effects of parenchymal and intraventricular grafts suggest that different mechanisms are implicated in recovery from cognitive and sensorimotor deficits induced by stroke.

Effects of implantation site of dead stem cells in rats with stroke damage.

Searching for valid control grafts, we assessed the performance of rats subjected to middle cerebral artery occlusion (MCAO) and grafted with freeze-thawed dead stem cells into sites previously used for active grafts (ipsilateral and contralateral striatum and ventricle) on bilateral asymmetry and water maze tests. We expected to find that sham grafted groups had impairments equivalent to those of MCAO-only controls, relative to intact controls. This proved to be the case for contralateral and intraventricular grafts, and for asymmetry in rats with ipsilateral grafts. However, spatial learning was substantially impaired and lesion volume was increased by 55% with ipsilateral dead cell grafts. Exacerbation of stroke effects indicates potential hazards in the use of dead cells for sham grafts.

In vivo and in vitro characterization of the angiogenic effect of CTX0E03 human neural stem cells.

CTX0E03 is a human neural stem cell line previously reported to reduce sensory motor deficits in a middle cerebral artery occlusion (MCAo) model of stroke. The objective of this study was to investigate if CTX0E03 treatment promotes angiogenesis. As stroke leads to damage of the vasculature in the brain, angiogenesis may contribute to the functional recovery. To test this hypothesis, the angiogenic activity of CTX0E03 was assessed both in vitro and in vivo. In vitro, CTX0E03 expression of trophic and proangiogenic factors was determined by real-time RT-PCR, Western blot, and ELISA, and its angiogenic activity was investigated in well-established angiogenesis assays. In vivo, angiogenesis was investigated in naive mice and MCAo rat brain and was evaluated by immunohistochemistry (IHC) using Von Willebrand factor (VWF), a marker of blood vessel formation, and BrdU/CD31 double labeling in naive mice only. In vitro results showed that CTX0E03-conditioned medium and coculture significantly increased total tubule formation compared with controls (p=0.002 and p=0.0008, respectively). Furthermore, CTX0E03 cells were found to be in direct association with the tubules by ICC. In vivo CTX0E03-treated brains demonstrated a significant increase in areas occupied by VWF-positive microvessels compared with vehicle-treated naive mice (two-way ANOVA, Interaction p<0.05, Treatment p<0.0001, Time p<0.0) and MCAo rat (p=0.001 unpaired t test, Welch's correction). CTX0E03-treated naive mouse brains showed an increase in BrdU/CD31 colabeling. In conclusion, in vitro CTX0E03 cells express proangiogenic factors and may promote angiogenesis by both release of paracrine factors and direct physical interaction. Furthermore, in vivo CTX0E03-treated rodent brains exhibited a significant increase in microvessels at the site of implantation compared with vehicle-injected groups. Taken together these data suggest that CTX0E03 cell therapy may provide significant benefit to stroke patients through upregulation of angiogenesis in the ischemic brain.

Human neural progenitor cell engraftment increases neurogenesis and microglial recruitment in the brain of rats with stroke.

MAIN OBJECTIVES: Stem cell transplantation is to date one of the most promising therapies for chronic ischemic stroke. The human conditionally immortalised neural stem cell line, CTX0E03, has demonstrable efficacy in a rodent model of stroke and is currently in clinical trials. Nonetheless, the mechanisms by which it promotes brain repair are not fully characterised. This study investigated the cellular events occurring after CTX0E03 transplantation in the brains of rats that underwent ischemic stroke. METHODS: We focused on the endogenous proliferative activity of the host brain in response to cell transplantation and determined the identity of the proliferating cells using markers for young neurons (doublecortin, Dcx) and microglia (CD11b). So as to determine the chronology of events occurring post-transplantation, we analysed the engrafted brains one week and four weeks post-transplantation. RESULTS: We observed a significantly greater endogenous proliferation in the striatum of ischemic brains receiving a CTX0E03 graft compared to vehicle-treated ischemic brains. A significant proportion of these proliferative cells were found to be Dcx+ striatal neuroblasts. Further, we describe an enhanced immune response after CTX0E03 engraftment, as shown by a significant increase of proliferating CD11b+ microglial cells. CONCLUSIONS: Our study demonstrates that few Dcx+ neuroblasts are proliferative in normal conditions, and that this population of proliferative neuroblasts is increased in response to stroke. We further show that CTX0E03 transplantation after stroke leads to the maintenance of this proliferative activity. Interestingly, the preservation of neuronal proliferative activity upon CTX0E03 transplantation is preceded and accompanied by a high rate of proliferating microglia. Our study suggests that microglia might mediate in part the effect of CTX0E03 transplantation on neuronal proliferation in ischemic stroke conditions.

Implantation of c-mycER TAM immortalized human mesencephalic-derived clonal cell lines ameliorates behavior dysfunction in a rat model of Parkinson's disease.

Human neural stem cells offer the hope that a cell therapy treatment for Parkinson's disease (PD) could be made widely available. In this study, we describe two clonal human neural cell lines, derived from two different 10-week-old fetal mesencephalic tissues and immortalized with the c-mycER(TAM) transgene. Under the growth control of 4-hydroxytamoxifen, both cell lines display stable long-term growth in culture with a normal karyotype. In vitro, these nestin-positive cells are able to differentiate into tyrosine hydroxylase (TH)-positive neurons and are multipotential. Implantation of the undifferentiated cells into the 6-OHDA substantia nigral lesioned rat model displayed sustained improvements in a number of behavioral tests compared with noncell-implanted, vehicle-injected controls over the course of 6 months. Histological analysis of the brains showed survival of the implanted cells but no evidence of differentiation into TH-positive neurons. An average increase of approximately 26% in host TH immunoreactivity in the lesioned dorsal striatum was observed in the cell-treated groups compared to controls, with no difference in loss of TH cell bodies in the lesioned substantia nigra. Further analysis of the cell lines identified a number of expressed trophic factors, providing a plausible explanation for the effects observed in vivo. The exact mechanisms by which the implanted human neural cell lines provide behavioral improvements in the PD model are not completely understood; however, these findings provide evidence that cell therapy can be a potent treatment for PD acting through a mechanism independent of dopaminergic neuronal cell replacement.