Rapid conditional targeted ablation model for hemolytic anemia in the rat.

Effective methods for cell ablation are important tools for examining the anatomical, functional, and behavioral consequences of selective loss of specific cell types in animal models. We have developed an ablation system based on creating genetically modified animals that express human CD59 (hCD59), a membrane receptor, and administering intermedilysin (ILY), a toxin produced by Streptococcus intermedius, which binds specifically to hCD59 to induce cell lysis. As proof-of-concept in the rat, we generated an anemia model, SD-Tg(CD59-HBA1)Bryd, which expresses hCD59 on erythrocytes. Hemolysis is a common complication of inherited or acquired blood disorders, which can result in cardiovascular compromise and death. A rat model that can replicate hemolysis through specific ablation of erythrocytes would allow further study of disease and novel treatments. In vitro, complete lysis of erythrocytes expressing hCD59 was observed at and above 250 pM ILY, while no lysis was observed in wild-type erythrocytes at any ILY concentration (8-1,000 pM). In vivo, ILY intravenous injection (100 ng/g body wt) dramatically reduced the hematocrit within 10 min, with a mean hematocrit reduction of 43% compared with 1.4% in the saline control group. Rats injected with ILY at 500 ng/g intraperitoneally developed gross signs of anemia. Histopathology confirmed anemia and revealed hepatic necrosis, with microthrombi present. These studies validate the hCD59-ILY cell ablation technology in the rat and provide the scientific community with a new rapid conditional targeted ablation model for hemolytic anemia and hemolysis-associated sequelae.

Differential susceptibility to colorectal cancer due to naturally occurring gut microbiota.

Recent studies investigating the human microbiome have identified particular bacterial species that correlate with the presence of colorectal cancer. To evaluate the role of qualitatively different but naturally occurring gut microbiota and the relationship with colorectal cancer development, genetically identical embryos from the Polyposis in Rat Colon (Pirc) rat model of colorectal cancer were transferred into recipients of three different genetic backgrounds (F344/NHsd, LEW/SsNHsd, and Crl:SD). Tumor development in the pups was tracked longitudinally via colonoscopy, and end-stage tumor burden was determined. To confirm vertical transmission and identify associations between the gut microbiota and disease phenotype, the fecal microbiota was characterized in recipient dams 24 hours pre-partum, and in Pirc rat offspring prior to and during disease progression. Our data show that the gut microbiota varies between rat strains, with LEW/SsNHsd having a greater relative abundance of the bacteria Prevotella copri. The mature gut microbiota of pups resembled the profile of their dams, indicating that the dam is the primary determinant of the developing microbiota. Both male and female F344-Pirc rats harboring the Lewis microbiota had decreased tumor burden relative to genetically identical rats harboring F344 or SD microbiota. Significant negative correlations were detected between tumor burden and the relative abundance of specific taxa from samples taken at weaning and shortly thereafter, prior to observable adenoma development. Notably, this naturally occurring variation in the gut microbiota is associated with a significant difference in severity of colorectal cancer, and the abundance of certain taxa is associated with decreased tumor burden.