Combination Treatment of Ischemic Stroke with Perlecan DV and Neural Stem Cells

Stroke, the third leading cause of death, leads to long-term disability in the United States. Stem cell therapy offers great promise in treating stroke. Extensive injury from stroke results from ischemia-reperfusion (IR), which damages the blood-brain barrier (BBB), the vessel network separating the brain from the circulatory system. IR causes biphasic openings in the BBB, the first occurring within several hours of insult and the second at 24-74 hours after stroke. The latter are generally irreversible and, thus, the most damaging. Clinically, stem cell therapy is currently aiming for stroke rehabilitation by delivering cells during the recovery (not subacute) phase. Our long-term goal is to limit early-stage BBB injuries, an outcome that would protect against the second phase of stroke damage. We base this proposal on our extensive and novel preliminary and pilot data derived from a stroke mouse model showing that human neural stem cells (hNSCs) transplanted into the brain 24h post-IR improves neurological function and reduces BBB damage. Besides compromising the BBB, stroke causes loss of cerebral parenchyma and its associated cells and promotes inflammation. Presently, tissue plasminogen activator (tPA) is the sole FDA-approved antithrombotic treatment available for stroke. While tPA’s thrombolytic role within the vasculature is beneficial, tPA’s harmful effects (non-thrombolytic role) within brain parenchyma have been reported. Further, tPA has a narrow time window (5h) can exacerbate BBB damage and increase hemorrhagic complications. Our preliminary data in a stroke mouse model suggest that hNSCs transplanted at early IR ameliorates BBB damage and improves stroke outcome. Further, we found that a protein fragment of the brain extracellular matrix (ECM) component perlecan, termed domain V (DV), is neuroprotective and most of DV’s therapeutic benefit is derived from its 25-kDa LG3 subdomain. Since aging is a strong risk factor for stroke, we will use both young adult and aged mice to test the effect of delayed tPA-induced IR injury. Most preclinical stroke studies employ young-adult animals instead of aged animals, in whom neurobehavioral deficits are found to be worse. In this study, we will test the hypothesis that NSCs ameliorate pathophysiology and neurological outcomes in delayed tPA-treated (6h) mice. Further, ameliorating BBB damage before tPA using a neuroprotectant (e.g., LG3) will improve the brain environment for NSC survival and allow for greater tPA efficacy. We will employ a filament MCAO/reperfusion (IR injury) mouse model that mimics ischemic stroke injuries seen in patients. Aim 1 will determine the effects of early NSC treatment on delayed tPA-treated acute stroke injury in young adult and aged mice. Aim 2 will test if early sub-acute human NSC transplantation improves long-term stroke recovery following tPA-induced (6h) stroke pathophysiology. This study is significant because it will generate new preclinical data that demonstrate the optimal strategy for NSC treatment for acute ischemic stroke. The study will use innovative methods by employing and combining adjuvant pharmacological treatment (neuroprotectant) with NSCs, to improve stroke outcome in mice suffering from a relatively severe form of ischemic-reperfusion damage (delayed tPA administration, 6 hours post-MCAO), currently a tPA-excluded condition. Knowledge that hNSC transplant could antagonize delayed tPA-induced BBB damage and hemorrhage in ischemic mouse brains could have a far-reaching clinical impact for a large population of patients excluded from current tPA therapy due to its narrow time window or patients currently not eligible for tPA treatment.