Motor impairment following ischemic stroke remains a leading cause of disability and reduced quality of life for our veterans and the general population. Physical therapy (PT) has been the mainstay of rehabilitation to restore motor function, but there is a clear need to improve and expand rehabilitation strategies. The use of adjunct medication has been extensively studied as one approach to enhance clinical outcomes. However, no drugs are presently established to be effective in enhancing rehabilitation-aided motor recovery. Studies from our lab and others suggest that certain drugs, such as amphetamine, hold such promise. Unfortunately, negative cardiovascular side effects associated with amphetamine have hindered its clinical application in stroke rehabilitation. Understanding the mechanisms underlying the rehabilitative potential of drugs will aid in the development of more effective, safer therapies. To this end the ability of amphetamine to enhance basic fibroblast growth factor (FGF2) signaling in the brain may be one such mechanism. In this proposal we will test the hypothesis that upregulation of FGF2 in the brain can significantly enhance motor recovery following ischemic stroke by facilitating neurite outgrowth from spared motor pathways through fibroblast growth factor receptor-1 (FGFR1)-related mechanisms.
In aim I we will demonstrate that direct upregulation of FGF2 through intranasal application of plasmid DNA encoding FGF2 enhances motor recovery following permanent middle cerebral artery occlusion (MCAO) in rats. The importance of pairing treatment with physical therapy and the effects of delaying treatment on motor performance will also be assessed. Anterograde and retrograde tract tracing techniques will be used to ascertain the extent to which the unlesioned motor cortex sends new neuronal projections to once-denervated motor regions (i.e. the red nucleus). Biochemical studies will assess changes in transgene and native FGF2 expression and FGFR-related signaling implicated in neurite outgrowth.
In Aim II we will extend our previously published work and determine the role of FGFR1 in mediating amphetamine-enhanced motor recovery and neural plasticity (i.e. neurite outgrowth) following permanent MCAO in rats. Two complementary approaches will be employed. A pharmacological approach will use the tyrosine kinase inhibitor, ponatinib, to globally inhibit FGFR signaling in the brain. A genetic approach will use a recombinant adeno-associated viral construct encoding for shRNA to FGFR1 to more specifically knock down FGFR1 in the unlesioned motor cortex, which we have previously established to be the site of new neuronal efferents.
Aim III will follow the same intervention design as Aim II except the importance of FGFR signaling in mediating enhanced motor improvement and neurite outgrowth induced by plasmid-mediated upregulation of FGF2, as established in Aim I, will be tested. Taken together, the findings of this proposal will provide the framework for future mechanistic and translational studies to optimize rehabilitation paradigms for improved functional recovery following stroke.
Stroke is the leading cause of motor impairment leading to long-term disability and reduced quality of life for our veterans and the general population. Of the estimated 700,000 Americans suffering a stroke each year 40% are left with moderate impairment and up to 30% have severe disabilities. Direct inpatient and outpatient annual costs to the Veterans Health Administration (VHA) are in excess of $300 million with cost of care correlating with level of disability. Physica therapy (PT) remains the primary strategy to improve motor function, but there is a clear need to enhance its efficacy. The development of adjunct therapy to provide neurorestorative benefit is needed. The goals of this project are to demonstrate that fibroblast growth factor therapy is such a strategy and to delineate the mechanisms through which it works. The findings of this project will provide the framework on which to develop more efficacious drug-enhanced rehabilitative therapy for stroke patients. Such therapy will improve the quality of life for our veterans at reduced cost to the VHA.
