Enteric glial cells (EGCs) regulate intestinal homeostasis and may be involved in purinergic signaling and motility, but their precise role is not understood, especially in humans. In the inflamed state, they convert to a `more reactive phenotype', releasing inflammatory mediators that could contribute to pathophysiology. PROBLEM: The role of human EGCs (hEGCs) in the physiology and pathophysiology of the GI tract is not known, and addressing this critical gap in knowledge is important in determining how hEGCs modulate GI functions in health and disease. Our preliminary data support the concept that purinergic signals in hEGCs regulate cellular communication, synaptic physiology, motor behavior, and inflammatory signals. Significance of these translational studies is underscored by significant species differences in glial responses, mechanisms and a 7 fold higher glial to neuron ratio in human ENS (versus mouse). Groundbreaking ? mechanistic, translational studies are proposed on `mechanosensitivity', `modulation of motility' and postoperative ileus. It became necessary to develop and apply sophisticated new technologies to study i.e. mechanical stimulation (pressure, shear stress, radial stretch) of hEGCs, currents, Vm, Ca2+waves, monitor ATP release using a `sniffer cell', spaciotemporal imaging of motility, and gene expression (i.e. RiboTag mouse & a 107-custom gene readout of `reactive glia'). Studies on surgical trauma/intestinal manipulation, IL1? or conditioned media from hEGCs provide precise ways to study `reactive glia' in human gut. OVERALL HYPOTHESIS: ?Human EGCs are critical regulators of mechanosensitivity, cell-to-cell communication, synaptic physiology, neuromuscular transmission and motility in the human intestinal tract and inflammation disrupts their normal activity. Purinergic signaling plays a pivotal role in `function and dysfunction'. EGCs exert inhibitory modulation of neural network activity. EGCs may exert differential (opposing) effects in the two muscle layers by acting in the ENS to modulate ascending and descending phases of the peristaltic reflex and coordinate or synchronize motility. Glial activation disrupts motility in postoperative ileus. Studies are supported by a dream team of investigators with a record of collaboration, a superb environment, strong preliminary data (Figs 1-16), 2 new publications in `Inflammatory Bowel Diseases' in 2016 and one revised publication to `GLIA' on the `basic hEGC model'. Our overall hypothesis is tested in 4 original Aims.
AIM 1 : To investigate mechanotransduction pathways of ATP release in hEGCs.
AIM 2 : To evaluate mechanosensory transduction and glial communication in the ENS of intact neural plexus networks in human intestine.
AIM 3 : To determine the role of hEGCs in the modulation of motility.
AIM 4 : To determine the impact of inflammation in postoperative ileus on reactive glia and motility and use human tissue to the extent it is possible. IMPACT: Translational studies will fill a critical gap in knowledge of glia in the `little brain' of the human gut in health and disease, with implications for motility disorders, gut inflammation and therapeutics.
Health care costs for postoperative ileus and motility disorders is high into the billions of dollars107,109 and treatments remain inadequate. Purinergic receptors are potential therapeutic targets in these diseases and some drugs are in clinical trials for inflammatory diseases and shown to have efficacy. Development of more effective treatment strategies is severely hampered by our poor understanding of human gut neurobiology. Enteric glial cells (EGCs) are abundant in the gut and they may play a role in the neurophysiology and pathophysiology of the gut. They regulate intestinal homeostasis and few animal studies suggest a role in motility and purinergic signaling, but their precise role is not understood, especially in humans. The role of human EGCs in the physiology and pathophysiology of the gastrointestinal tract is not known, and addressing this critical gap in knowledge is important in determining how these cells regulate gastrointestinal functions in health and disease (POI and motility disorders). This also has important implications for identifying potential new targets for therapy including receptors, channels and purinergic drugs.
