Traumatic brain injury (TBI) often causes cognitive deficits which are thought to arise from hippocampal structural damage. Apolipoprotein E (APOE, gene; APOE, protein) has been shown to support effective repair and remodeling after neuronal injury, which suggests potential uses of APOE in the treatment of TBI.The thesis is devoted to the testing of hypothesis that gene therapy by means of cationic liposome-mediated APOE2 and APO3 gene transfer could facilitate structural and functional recovery after experimental TBI.To determine the structural and functional changes associated with severe diffuse TBI, adult and old male Wistar rats were subjected to weight drop impact acceleration injury (Marmarou A. et al., 1994) and sacrificed at days 5 and 10 after trauma. The mixture of DOTAP liposomes and 25 µg of recombinant plasmid pCMV-APOE2 or pCMV-APOE3 cDNA was infused intraventicularly immediately after TBI using ALZET osmotic pump. The entire brain frontal sections and hippocampal CA1 regions in particular were analyzed by light and electron microscopy, immunocytochemical and confocal analysis using markers selective for neurons (NeuN) and astrocytes (GFAP), and TUNEL staining for determining cell death. Neurofunctional outcomes were assessed using the motor function scale, Morris water maze and open field test.Significant changes in the morphofunctional state of hippocampus, as well as in the neurological and cognitive functions were confirmed. It was proved that gene therapy, specifically cationic-liposome mediated APOE2 or APOE3 gene transfer to the CNS cells by plasmid vector significantly prevented the evolution of secondary hippocampal injury, decreased a TBI-induced death of neurons and improved qualitative composition of neuronal population, normalized neuron-glial relations, decreased gliosis and microglial activation, axonal damage, myelin destruction and lipofuscin accumulation, all these having age-related peculiarities. After gene therapy, a lower intensity of the processes of apoptosis in the animal brain and a decrease of its rate in old animals were observed.It was shown that prevention of secondary brain injury evolution after TBI by means of gene therapy is accompanied by the improvement of motor skills, spatial memory, learning, searching behavior and emotionality.We came to conclusion that cationic liposome-mediated APOE2 and APO3 gene transfer may have therapeutic potential for the treatment of secondary brain injury and cognitive dysfunction following TBI.The principles of further designing of therapeutic agents for TBI, as well as in clinics, on the basis of APOE molecule or its functionally relevant domains were elaborated.
