Investigating the role of biomechanical forces on the enteric nervous system in Hirschsprung disease

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PROJECT SUMMARY As a pediatric surgeon at Texas Children’s Hospital, the nation’s largest children’s hospital and a central hub for the treatment of Hirschsprung’s disease (HSCR)—a disorder caused by defective enteric nervous system (ENS) development, I strive not only to deliver excellent surgical care, but also to decipher the mechanisms behind disease etiology. In my practice, I remove the abnormal, aganglionic intestine and pull-through “normal” ganglionated intestine but continue to be perplexed by the nearly 50% incidence of postoperative bowel dysfunction. Thus, my goal as an aspiring surgeon-scientist is to investigate the postnatal mechanisms that result in these poor postoperative outcomes. The K08 program is an ideal foundation to develop the technical and scientific skills I need to make translational impact for my patients. The present application lays out a five-year educational and research plan focused on identifying drivers of persistent postoperative dysfunction in the ganglionated HSCR colon microenvironment. Enteric neurons have long been recognized as mechanically sensitive to extrinsic force (axial stretch and radial distention) and intrinsic mechanics (tissue stiffness), both of which are present before and after HSCR surgery. It is not known how these forces affect ENS phenotype and function, which raises the question of whether known mechanosensitive ion channels and/or focal adhesion kinase (FAK) signaling could be pathophysiological mediators of ENS responses to tension. Consistent with our logic, the ion channel Piezo1 and focal adhesion molecule FAK are ubiquitously present in the gastrointestinal tract, but their role in ENS response to biomechanical forces requires further investigation. My data demonstrates that HSCR intestine at baseline has a dysregulated ECM, which leads to changes in tissue stiffness, and that extrinsic force further dysregulates the ECM. Still, it remains unclear how these changes in the ECM microenvironment regulate the ENS. Therefore, we hypothesize that biomechanical forces on the intestine have Piezo1-FAK dependent effects on the ENS and regulate ECM composition in a manner that governs the ENS microenvironment, which ultimately contributes to gut dysfunction in HSCR. I will address this research question in two aims, under the guidance of my mentor, Dr. Keswani, and expert scientific advisory committee. In Aim 1, I will define the role of clinically relevant, extrinsic mechanical forces on the ENS in normal and HSCR intestine. This will allow me to develop new technical expertise in live cell calcium imaging, ex vivo tissue culture, and in vivo tension models to evaluate the signaling of Piezo1-FAK in ENS responses to extrinsic mechanical forces. Aim 2 will focus on testing how biomechanical forces regulate the ECM to alter the ENS microenvironment in HSCR, and whether changes in the ECM are indicative of post-surgical prognosis in HSCR. In this aim, I will work with novel biomechanical and hydrogel models to investigate the interaction between the ENS and ECM, and develop a novel risk prediction model using human HSCR tissue features. Completion of these aims will launch my career as a surgeon-scientist with meaningful impact for the care for my patients.