Gene therapy

Alzheimer's disease (AD) is projected to triple by 2050, highlighting the urgent need for disease-modifying treatment strategies. Our gene therapy approach tackles three critical challenges: a) delivering drugs effectively to the brain and brain bioavailability of those delivered drugs, b) intervening early in the disease process to prevent progression into nonreversible stages, and c) managing the behavioral and psychological symptoms of dementia (BPSD) that significantly impact patients and caregivers. Our non-invasive ocular delivery system effectively delivered therapies to CNS as indicated by the localization of those transcribed genes and translated protein products in different brain regions, including the hippocampus, cortex, dorsal lateral geniculate nucleus, red nucleus, and pontine nucleus This approach could overcome the limitations of traditional drug delivery methods for neurological diseases. In a 3xTg AD mouse model of AD, we evaluated the efficacy of Choline Acetyltransferase (ChAT) gene therapy on early disease progression. A single treatment improved impaired memory functions such as cognitive flexibility, memory extinction and working memory, reduced amyloid beta oligomers and phosphorylated tau protein levels, and enhanced mitochondrial dynamics through the regulation of fusion, fission and mitophagy. Additionally, ChAT gene therapy modulated apoptosis, inflammation and the activity of microglia and astrocytes in parts through the activation of AKT. These findings suggest ChAT gene therapy's potential to slow or prevent AD
progression if administered early in the disease course.

Ischemic stroke is defined as a blockage or reduced flow of blood to select areas of brain tissue due to either plaque formation or buildup of blood clots in the small blood vessels. A characteristic of sickle cell anemic patients is the potential for them to experience a similar type of blockage due to the sticky nature of the sickled red blood cells as well as defective oxygen delivery to the brain. Because of this similarity, sickle cell anemia may represent a good animal research model for therapeutic intervention based on stroke models. In recent studies, Granulocyte-Colony Stimulating Factor (GCSF), has been shown to exhibit a robust range of neuroprotective properties against neurological disorders including ischemic stroke through preservation of the endoplasmic reticulum (ER) by modulating various ER stress pathways. Through cognitive deficit analysis in the form of behavioral and locomotor experiments in addition to in situ biomarker analysis by way of western blotting and immunohistochemistry, we found that G-CSF gene therapy exhibited neurogenic and neuroprotective effects in ischemic mouse models and could possibly serve as a good therapy for other diseases that share similar pathology to stroke.

The kynurenine pathway plays a critical role in regulating immunological homeostasis in the brain. Evidence supporting the hypothesis that kynurenine pathway dysfunction may exacerbate progression of neurodegenerative diseases like Parkinson’s is growing. First, we investigate the effects of Interferon-γ, Lipopolysaccharide, and Interleukin-4 on several key kynurenine pathway metabolites using high performance liquid chromatography. We found that Interferon-γ had significant effects on the extracellular concentration of kynurenine metabolites in astrocytes, microglia, and macrophage. GCSF gene therapy is previously demonstrated to exert neuroprotective effects on models of Parkinson’s and Alzheimer’s disease. Seven days after receiving GCSF gene therapy, A53T Parkinson’s mice were found to have increased levels of GCSF and tyrosine hydroxylase positive neurons. A concurrent increase in expression of the kynurenine pathway enzyme kynurenine aminotransferase 2 was observed. GCSF gene therapy may exhibit neuroprotective effects in a Parkinson’s disease mouse model by restoring this key kynurenine pathway enzyme.

Both proliferative diabetic retinopathy and exudative age-related macular degeneration are major causes of blindness which are caused by growth of defective, leaky and tortuous blood vessels in the retina. Hypoxia is implicated in triggering both of these diseases and results in induction of HIF-1alpha transcription factor in addition to the angiogenic factor VEGF. Müller cells are the major glial cell in the retina and they contribute to neovascularization in hypoxic regions of the retina through eliciting secretion of growth factors, cytokines and angiogenic factors. As Müller cells span the breadth of the retina they can secrete angiostatic factors as well as neuroprotective trophic factors, the Müller cell is a valuable cell type for targeting by potential new gene therapies. The current investigation tests the hypoxia responsiveness of an AAV vector containing a hybrid hypoxia response element together with a GFAP promoter, and this vector encodes the angiostatic protein decorin, a well characterized multi-receptor tyrosine kinase inhibitor. Decorin may have advantages over other key angiostatic factors such as endostatin or angiostatin by virtue of its multiple anti-angiogenic signaling modalities. We employed Q-RT-PCR to evaluate the cell specificity and hypoxia responsiveness of an AAV-Vector termed AAV-REG-Decorin containing a hybrid HRE and GFAP promoter driving expression of the decorin transgene. The vector also contains a silencer element between the HRE and the GFAP domains to enable low basal expression in normoxia as well as high level inducibility in hypoxia. AAV-REGDecorin was found to elicit high level expression of decorin mRNA in hypoxia with greater than 9 – fold induction of the transgene in hypoxic conditions in astrocytes by comparison to normoxic astrocytes. AAV-REG-Decorin showed low levels of transgene expression by comparison to the positive control vector AAV-CMV -decorin containing the ubiquitously active CMV-promoter. The expression levels of decorin mRNA from AAV-REG-Decorin and from AAV-GFAP-Decorin were low in the PC12 neuronal cell model and in the ARPE19 line of retinal pigment epithelial cells with respect to those of AAV-CMV-decorin and no induction of Decorin mRNA was found with AAV-REGDecorin in these two control cell lines. Our novel gene therapy vector will serve as a platform for testing efficacy in rodent disease models (OIR and laser induced choroidal neovascularization) for assessment of the benefits of tightly regulated antiangiogenic gene therapy eliciting decorin transgene expression, both in terms of timing and the cellular source of production, during the progression of the retinal pathophysiology.

Diabetic retinopathy is an ischemic retinal neovascular disease causing vision loss among adults. The studies presented involve the design and testing of a gene therapy vector to inhibit retinal revascularization, similar to that found in diabetic retinopathy. Gene therapy has proven to be an effective method to introduce therapeutic proteins to treat retinal diseases. Targeting a specific cell type and expression of therapeutic proteins according to the tissue microenvironment should have an advantage over traditional gene therapy by avoiding unwanted transgene expression. Hypoxia plays a significant role in the pathophysiology of many retinal ischemic diseases. Retinal Mèuller cells provide structural and functional support to retinal neurons, as well as playing a significant role in retinal neovascularization. Targeting Mèuller cells may be an effective strategy to prevent retinal neovascularization under pathological conditions. ... The hypoxia regulated, glial specific vector successfully reduced the abnormal neovascularization in the periphery by 93% and reduced the central vasobliterated area by 90%. A substantial amount of exogenous endostatin was produced in the retinas of P17 OIR mice. A significant increase in human endostatin protein and reduced vascular endothelial growth factor (VEGF) were identified by Western blot and ELISA, respectively. These findings suggest hypoxia-regulated, glial cell-specific scAAV mediated gene expression may be useful to prevent blindness found in devastating retinal diseases involving neovascularization.

Human mesenchymal stem cells (MSCs) are being evaluated for the treatment of a broad array of diseases due to their ability to secrete a variety of therapeutically beneficial paracrine-acting factors. For example, MSC conditioned media (MSC-CM) has been shown to inhibit hypoxia-induced apoptosis in human aortic endothelial cells (HAECs) via activation of the P13-AKT pathway. However, the factors secreted by MSCs responsible for this effect have yet to be identified. Recent studies have shown that the glycoprotein Follistatin-like 1 (FSTL1) activates the P13-AKT pathway by binding to the receptor disco-interacting protein (DIP2A) expressed on the surface of cells. Based on our data indicating that MSCs constitutively secrete high quantities of FSTL1, we hypothesize that this protein principally mediates the anti-apoptopic effect of MSC-CM on HAECs. Loss-of-function studies employing siRNA-mediated knockdown of the protein and neutralizing antibodies will be used to assess the role of FSTL1 in growth and survival of HAECs following exposure to hypoxic stress.