1. Neural stem cell (NSC) transplantation and subsequent treatment with a variant of activated protein C (3K3A-APC) improved engraftment success and motor skills in a mouse model of post-ischemic stroke.
2. 3K3A-APC repaired stroke-damaged regions by facilitating the structural and functional integration of NSC-derived and host neurons.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Despite of the prevalence of neurological disorders and stroke, existing therapies are limited in their ability to enhance functional regeneration of damaged or diseased brain tissue. In this work, treatment with a recombinant protein of APC to complement NSC transplantation led to improved NSC survival, overall sensory and motor functions, and NSC integration after ischemic stroke.
To model ischemic stroke, mice were injured by permanent distal middle cerebral artery occlusion (dMCAO) one week before NSC transplantation and initiation of a 3K3A-APC treatment regimen. As compared to mice that received the vehicle control treatment, those that received 3K3A-APC maintained a greater number of NSCs in the brain. 3K3A-APC treatment not only prevented loss of implanted NSCs but also supported their proliferation for up to one month post-transplantation. Mice that received a full course of 3K3A-APC treatment also performed significantly better than control mice in tests that evaluated their balance and sensorimotor coordination. Assessment of brain histological samples after the treatment period indicated that 3K3A-APC enhanced the ability for engrafted NSCs to differentiate into neuron-like cells. 3K3A-APC also improved the number of contacts between the implanted NSCs and host neurons, and enhanced the activation of neurons in response to mechanical stimulation of the contralateral forelimb.
This work provides strong evidence to support a new therapeutic approach for improving functional restoration of injured brain tissue after ischemic stroke. Because both NSC transplantations and treatment with 3K3A-APC are being evaluated in clinical trials for neurological disorders like stroke and Amyotrophic Lateral Sclerosis, progression to human clinical trials of the combination treatment proposed in this work is promising.
In-Depth [animal study]: To model ischemic stroke, eight-week-old male C57BL/6J mice were injured with dMCAOs one week before NSC transplantation (1e5 cells/mouse) and initiation of 3K3A-APC treatment (0.2mg/kg intravenously). After the initial 3K3A-APC dose, treatment was administered every other day for an additional three doses. Throughout the treatment and testing period, mice were administered daily injections of the immunosuppressant cyclosporine.
One week after transplantation and treatment initiation, the presence of the engrafted NSCs carrying a luciferase tag was measured through bioluminescence imaging. Over a 4-week period, bioluminescence in 3K3A-APC mice (n=5) increased almost 2-fold whereas control mice exhibited a decline of nearly 70%. During this period, mice were also tested for their sensorimotor coordination through the rotarod test and adhesive-removal test. In the rotarod test, 3K3A-APC mice were able to remain walking on the rotating rod for significantly more time than those that received the vehicle treatment (p<0.05). Likewise, mice treated with 3K3A-APC were able to more quickly remove adhesive tape from their forepaws (p<0.05).
Four weeks after transplantation, the brains of mice were collected for histology. In 3K3A-APC mice, a greater number of engrafted NSCs were found to have differentiated into neuron-like cells positive for TUJ1 (p<0.01). Additionally, in mice that received 3K3A-APC, implanted NSCs generated better integration into the host nervous system, as measured by a 9-fold increase in the number of contacts between engrafted and host neurons. Finally, functional activity of the engrafted NSCs was measured through increasing fluorescence expression driven by changes in calcium flux. In mice treated with 3K3A-APC, more implanted NSCs responded to mechanical stimulation (6-fold increase) and with greater activation intensity (p<0.01).
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