The pathogenic mechanisms of inflammatory bowel disease (IBD) including Crohn's disease (CD) and ulcerative colitis (UC) have yet to be elucidated despite numerous studies in gastroenterology and mucosal immunology. Dextran sulfate sodium (DSS)-induced murine colitis represents an experimental model for human IBD (Jurjus AR, Khoury NN, Reimund JM: Animal models of inflammatory bowel disease. J Pharmacol Toxicol Methods 50:81-92, 2004). The administration of DSS dissolved in water to mice or rats caused hematochezia, body weight loss, shortening of the intestine, mucosal ulcers, and infiltration of neutrophils. Acute colitis, which occurred during the administration of DSS, and chronic colitis, which occurred a little time after the administration of DSS, was seen in this model. Acute colitis was considered to be induced by innate immunity but not acquired immunity because it also occurred in severe combined immunodeficiency (SCID) mice. However, chronic colitis was considered to be caused by lymphocytes that are activated by the cytokines secreted from the activated macrophages (Okayasu I, Hatakeyama S, Yamada M, Ohkusa T, Inagaki Y, Nakaya R: A novel method in the induction of reliable experimental acute and chronic ulcerative colitis in mice. Gastroenterology 98:694-702, 1990).
To induce colitis we treat the mice with 3.0 % dextran sulfate sodium (DSS, m.w. 36,000-50,000, MP Biomedicals) in acidified water, as described by Ohkawara T et al., 2005 [Ohkawara T, Takeda H, Kato K, Miyashita K, Kato M, Iwanaga T, Asaka M: Polaprezinc (N-(3-aminopropionyl)-L-histidinato zinc) ameliorates dextran sulfate sodium-induced colitis in mice. Scand J Gastroenterology 40; 1321-11327, 2005]. Mice are examined daily and mean DSS/water consumption and body weight are recorded. Diarrhea score is also assessed daily by using a 0-to-4 scale: 0 - normal, 1 - slightly loose feces, 2 - loose feces, 3- semi-liquid stool, and 4 - liquid stool. Fecal blood is tested by using a Hemocult kit (ColoScreen pack, Helena Labs). The presence of blood results in a color change from white to blue that is proportional to the amount of blood present in the sample. Mice are receiving DSS during 5 days and the treatment stops. Mice are sacrificed at various time points: at day 5, 12, 19 and 26, to monitor the progression of the colitis. At those time points mice are anesthetized with ketamine (100mg/kg i.p.) and xylazine (10 mg/kg i.p.), perfused with 10 mL of PBS through the left ventricle and used for histology or myeloperoxidase assay. For histology, the entire colon is removed and opened along the mesenteric border. Then, the tissue is removed, fixed in 4% of paraformaldehyde, embedded in paraffin, sectioned, and stained with hematoxylin and eosin in a standard fashion. The histological score (of each cecum, proximal, transversal and distal colon) calculates as the sum of 4 parameters as follows: A) the amount of inflammation, 0 to 3 (0, none; 1, slight; 2, moderate; 3, severe); B) regeneration, 0 to 4 (0, complete regeneration or normal tissue; 1, almost complete regeneration; 2, regeneration with crypt depletion; 3, surface epithelium not intact; 4, no tissue repair); C) crypt damage, 0 to 4 (0, none; 1, basal 1/3 damaged; 2, basal 2/3 damaged; 3, only surface epithelium intact; 4, entire crypt and epithelium lost); D) Percent involvement (1 for 1-25%, 2 for 26-50%, 3 for 51-75%, and 4 for 76-100%. Each section is then scored for features listed under A, B, and C separately and multiply with percent involvement score.
Finally, overall average histological score could be calculated as well (Dieleman LA, Palmen MJHJ, Akol H, Bloemena A, Pena AS, Meuwissen SGM, Van Rees EP: Chronic experimental colitis induced by dextran sulphate sodium (DSS) is characterized by Th1 and Th2 cytokines. Clin Exper Immunol 114:385-391, 1998).
More details: Jerkic M, Peter M, Ardelean D, Fine M, Konerding MA, Letarte M. DSS leads to chronic colitis and pathological angiogenesis