Comprehensive Structural and Functional Mapping of Mammalian Colonic Nervous System

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ABSTRACT The colon is the site of a multitude of disorders which are leading causes of morbidity and mortality and of significant financial burden. The colonic intrinsic (enteric) and extrinsic innervation play crucial role in regulating the secreto-motor, endocrine, immune functions and pain sensation. There has been increasing understanding of the neurochemical and electrophysiological properties, cell physiology, and functional roles of colonic enteric neurons and their interaction with the parasympathetic, sympathetic and sensory systems during the past decades. However, these data are derived largely from small animal studies and relevant knowledge in large animals and humans is lagging, which has hampered the development of effective therapies. Recent advances in cutting edge approaches including 3-D mapping, innovative viral tracing tools, and neuroimaging provide a means to obtain detailed information on neural circuits and related functions in large animals and human tissues, which has never been achieved before. The overall objective of the proposal is to provide a comprehensive and detailed structural and functional mapping of the intrinsic and extrinsic innervation of various regions of the colon in humans and the pig, as a relevant large animal model based on its structural and physiological similarities to humans. Mice will be utilized for studies involving transgenic, optogenetics and viral tracing approaches. This objective will be achieved by a concerted effort of world expert investigators who developed state-of-the art neuroanatomical, molecular, electrophysiological and functional approaches. Preliminary data obtained by the consortium team showed the feasibility to use CLARITY, high resolution confocal microscopy, viral tracing and optogenetics to provide detailed mapping of extrinsic nerve fibers, enteric circuitries and the expertise to probe human colonic enteric neurons electrophysiologically by fast and high resolution neuroimaging. In addition, the design of new microelectrode array and fiber optic technology has allowed quantifying motor patterns in response to nerve stimulation at a resolution level not attained before. The combined effort and multidisciplinary approaches will fill the gaps in current knowledge on colonic intrinsic and extrinsic neuronal circuits and cell-cell communication, especially in human tissues and pig, a large animal model ideally suited for translational applicability to patients. These findings will set the foundation for understanding neurocircuitry in this organ and will be critical for potential electroceutical interventions to treat colonic disorders.