Most patients with cystic fibrosis (CF) experience a range of gastrointestinal (GI) complications. Meconium ileus is present in about 10% of CF newborns. Later in life, the loss or dysfunction of the CF transmembrane conductance regulator (CFTR) channel activity causes impairment in intestinal fluid secretion and homeostasis, contributing to the development of constipation, distal intestinal obstruction, and other GI diseases. In addition to CF patients, chronic constipation affects approximately 2-27% of general population worldwide; it is one of the most common GI issues in geriatric population. In this proposal, we will address these two health issues. Based on our previous findings and preliminary data, we hypothesize that (i) the impairment in intestinal fluid secretion and homeostasis plays a critical role in the pathogenic process of chronic constipation in CF patients and in geriatric population. (ii) CFTR-MRP4 complexes and the associated secretory mechanisms are impaired in these two populations. And (iii) the CFTR-MRP4 complexes can be targeted to restore the impaired secretion and alleviate/cure chronic constipation. Three specific aims were designed to test our hypothesis: (1) test the regulatory role of CFTR-MRP4 macromolecular complexes in compartmentalized cAMP/cGMP signaling and in the CFTR-mediated fluid secretion using intestinal stem cells (ISCs) cultures from CF patients with chronic constipation. (2) test the effects of the current FDA-approved highly effective CFTR modulator therapies (e.g., Kalydeco® and Trikafta®) and MRP4 inhibitors on intestinal fluid secretion in enteroids from CF patients with chronic constipation, and study if these two types of modulators have additive or synergistic effect. And (3) test if the CFTR-dependent fluid secretion in aged mouse gut is impaired which contributes to chronic constipation and investigate the underlying molecular mechanism. Our proposal incorporates both conceptual and technical innovations that will not only advance our understanding of disease pathogenesis of chronic constipation in CF patients and in large ageing populations, but also help identify possible therapeutic targets for interventions. We will use patient-derived and clinically relevant samples and adopt a personalized medicine platform: a Bench to Bedside and Back approach, which warrant a high potential to translate our bench-side findings to clinical disease management.