Selective peripheral neuromodulation through organ-specific AAV-mediated gene transfer

Peripheral neuromodulation has been pursued to control conditions such as chronic pain and dysfunctions of pelvic organs. The expansion of such therapies is challenged by incomplete understanding of peripheral neural circuits, which comprise complex networks of peripheral ganglia and nerves that innervate multiple organs and carry axons of afferent as well as efferent peripheral neurons. Methods for manipulation of neural activity through genetically engineered receptors and channels such as channelrhodopsins and DREADDs (Designer Receptor Exclusively Activated by Designed Drug) create an opportunity for the development of tools for targeted neuromodulation through viral vector-mediated cell-specific gene transfer. The use of cell-specific promoters and combinatorial vector systems for targeted expression of optogenetic or pharmacogenetic transgenes presents a potential solution to the neuroanatomical challenges of peripheral neuromodulation. The long-term objective of this research program is to develop strategies for peripheral neuromodulation through cell-specific delivery of neuromodulatory transgenes to peripheral ganglia using adeno-associated viral (AAV) vectors. Based on our work on the biodistribution of AAV vectors, the objective of this application is to provide proof-of-concept fo site-specific targeting of transgene expression to afferent and efferent systems. We will address the central hypothesis that cell-specific targeting of a neuromodulatory transgene to peripheral neurons by AAV vectors enables organ-specific functional interventions. To address the Specific Aims of the project, we will develop AAV vectors for cell-specific targeting of DREADD, validate neuroanatomically their restricted biodistribution, and demonstrate the neuromodulatory function of the transgenes using behavioral, in vitro and in vivo neurophysiological, and in vivo imaging analyses. Aim 1: Test the feasibility of a strategy for organ-specific neuromodulation of afferent systems through AAV-mediated gene transfer. We will test the hypothesis that combinatorial AAV vector targeting of colon-innervating sensory neurons, using a Cre- dependent vector that carries the gene for the inhibitory DREADD (hM4Di) and an AAV-Cre vector, will enable organ-specific control of afferent activity. Aim 2: Test the feasibility of a strategy for organ-specific neuromodulation of efferent autonomic systems through AAV-mediated gene transfer. We will test the hypothesis that cell-specific AAV vector targeting to parasympathetic bladder post-ganglionic neurons, using a vector that carries the gene for the excitatory DREADD (hM3Dq) under the control of the cholineacetyl transferase (ChaT) promoter, will promote bladder emptying in a rodent model of spinal cord injury. The proposed strategies and vector tools will enable functional dissection of peripheral neural circuits, applicable to multiple organs and across species and animal models. These approaches can be extended to optogenetic neuromodulation, to integration with closed-loop platforms, and potentially to development of next generation neuromodulation therapies as the clinical translation of AAV-mediated gene transfer advances.