Introduction: Ulcerative colitis (UC) affects over 500,000 individuals in the United States and current therapies are directed only at symptomatic remission. Definitive treatment for UC (colectomy) is invasive, associated with high morbidity, and diminishes quality of life. Effective treatment of UC requires mucosal repair, which can be achieved subsequent to inflammation reduction and restoration of epithelial barrier function. Extracellular matrix hydrogels (ECMH) can induce an in-vitro shift in macrophage phenotype towards an anti-inflammatory cytokine profile but it is unknown whether this phenotype shift will occur in-vivo and, if so, whether the response would be robust enough to restore epithelial barrier function for effective UC treatment. The objective of the present study was to determine the efficacy of ECMH for restoration of colonic mucosa in-vitro and in a rat model of UC.
Materials and Methods: The effect of ECMH on the paracellular permeability and transepithelial electrical resistance (TEER) was assessed in-vitro with monolayers of colonic epithelial cells. The adherence strength of two forms ECMH to rat and pig colonic mucosa was tested in-vitro (Fig 1A). The efficacy of ECMH treament was evaluated in a rat model of UC; specifically, by administering 5% dextran sodium sulfate (DSS) in drinking water for 7d.
Retention time of the ECMH following enema delivery was evaluated qualitatively using FITC Protein Labeling Kit and quantitatively with 14C radiolabeled ECMH. The presence and location of FITC-ECMH was imaged in explanted tissue. The concentration of 14C-ECMH was measured in homogenized tissue by accelerator mass spectroscopy (AMS).
Colitis was induced and rats were divided into groups based on treatment (ECMH, vehicle, no enema) and length of survival (7d or 14d post-DSS, n=14/group/time point). Outcomes included clinical response, barrier function (measured by serum concentration of enterically administered TRITC-dextran 4h prior to sacrifice), colon length, gross and histologic scores, and ex-vivo secreted cytokine profile.
Results and Discussion: ECMH is adhesive to both healthy rat and pig colon with tensile strength that varied based on ECMH source and colon species (Fig 1B). The ability for ECMH to stick to diseased colon was tested in colitic rats. When ECMH was integrally radiolabeled with 14C and delivered via rectal enema, AMS showed that approximately 50% of the total of 40mg of ECMH was retained following 2h and 10% of the initial ECMH volume was retained for 24h post-enema (Fig 1C). Similarly, FITC-ECMH delivery and visualization in explanted colons of colitic rats showed ECMH remained in the colon for up to 24h (Fig 1D). ECMH is not only mucoadhesive but also imparts biologic change in colonic epithelial cells. In-vitro, treating damaged epithelial cells with ECMH resulted in expedited restoration of barrier function with increased electrical resistance (Fig 2A) and decreased paracellular permeability (Fig 2B). More importantly, daily ECMH enema treatment for 7d resulted in increased barrier function in colitic rats (Fig 2C) and, in turn, resulted in lower clinical disease activity (Fig 2D) and grossly improved healing of explanted tissues (Fig 2E).
Conclusion: The present study showed that ECMH is mucoadhesive and remains adherent to the colon for >24 hours and results in markedly diminished clinical signs of UC. Results of the present study suggest that ECMH enemas are a potential therapy for UC.
This material is based upon work supported by the National Science Foundation Graduate Research Fellowship grant number DGE-1247842
References:
[1] Lichtenstein et al. Importance of Mucosal Healing in Ulcerative Colitis. Inflamm Bowel Dis 2010;16:338–346
[2] Gaudio et al. Dextran Sulfate Sodium (DSS) in Rats. Digestive Diseases and Sciences, 1999.