Survival and differentiation of transplanted neural stem cells derived from human induced pluripotent stem cells in a rat stroke model.

BACKGROUND: Although administration of various stem cells has shown promise in stroke models, neural stem cells (NSCs) derived from human induced pluripotent stem cells (iPSCs) have advantages over other cell types. We studied whether these cells could survive, differentiate, and improve stroke recovery in an ischemic stroke model. METHODS: Human iPSCs were induced in vitro to an early NSC stage. One week after focal cerebral ischemia, 20 rats received cells or vehicle by intracerebral injection. Graft cell fate, infarct volume, and behavioral deficits were assessed. RESULTS: Graft cells were found in 8 of the transplanted rats (80%), with estimated mean graft cell numbers nearly double the amount transplanted 1 month later. Graft cells also expressed markers of NSCs in 5 rats (63%), neurons in all 8 rats (100%), rare astrocytes in 4 rats (50%), and signs of proliferation in 4 rats (50%), but no tumor formation was observed. Stroke volume and behavioral recovery were similar between the groups. CONCLUSIONS: To our knowledge, this is the first report of transplantation of NSCs derived from human iPSCs in a stroke model. Human iPSC-derived NSCs survived in the postischemic rat brain and appeared to differentiate, primarily into neurons. This cell transplantation approach for stroke appears to be feasible, but further optimization is needed.

Injected Versus Oral Cyclosporine for Human Neural Progenitor Grafting in Rats.

BACKGROUND: Neural cell transplantation is a promising therapy for stroke, but rejection of human cells in animal models is an obstacle to furthering this research. Many antirejection strategies have been reported, but few comparison data are available. We asked if human neural cell grafts would have different survival or differentiation with injected or oral cyclosporine regimens. METHODS: Rats received intracerebral grafts of human embryonic stem cell-derived neural progenitors, and 6 rats each were randomized to 4 cyclosporine regimens: 1) daily injections, 2) initial injections followed by oral drug in the drinking water, 3) oral drug only, or 4) no cyclosporine. Histology was performed 14 days after grafting for quantification of markers of human cells, neural cell types, and immune cells. RESULTS: More rats in the injection (6/6) and injection+oral (5/6) groups had surviving graft cells than in the oral (1/6) and control (3/6) groups (p<0.05), with a trend toward a greater number of surviving graft cells as well. All rats with surviving graft cells also had these cells co-label for a neural progenitor marker, and a minority of graft cells co-labeled for a cell division marker and a neuronal marker. Rats with areas of dead graft cell debris were seen in all of the groups. In these areas, cells that labeled for microglial markers also contained the human nuclear marker in their cytoplasm, suggesting phagocytosis of the graft cells. CONCLUSIONS: Human neural cell survival in rat brain tissue differed between cyclosporine regimens, but microglial phagocytosis of graft cells occurred in all the groups. Frequent injection of laboratory animals is undesirable, and a compromise strategy of peritransplant injections followed by drug in the drinking water showed good results in preventing graft cell rejection. Further research is needed to optimize the antirejection approach for this application.

Behavioral outcome measures used for human neural stem cell transplantation in rat stroke models.

Stroke is a leading cause of death and disability, leading to the development of various stroke models to test new treatments, most commonly in the rat. Human stroke trials focus on disability, related primarily to neurological deficits. To better model the clinical application of these treatments, many behavioral tests have been developed using the rat stroke model. We performed a systematic review of all the behavioral outcome measures used in published studies of human neural stem cell transplantation in rat stroke models. The reviewed tests include motor, sensory, cognitive, activity, and combination tests. For each test, we give a brief description, trace the origin of the test, and discuss test performance in the reviewed studies. We conclude that while many behavioral tests are available for this purpose, there does not appear to be consensus on an optimal testing strategy.