Title: Comparative assessment of routine H&E and Mason’s Trichrome Stain to Differentiate Normal from Infected Urinary Bladders in the Göttingen Minipig   Authors: Stephanie D. Rivera, MS, HT(ASCP); Anthony Romanello, BS; Ronnie Chamanza, BVSc, MSc, FRC Path, MRCVS, FIATP, Preclinical Sciences & Translational Safety, Johnson & Johnson Innovative Medicine, Spring House, Pa Abstract: The objective of this experiment was to evaluate the difference between normal and infected Göttingen minipig urinary bladder and determine the difficulty of microscopically evaluating infectious urinary bladder. The focus was on the histology of the tissue using routine Hematoxylin and Eosin(H&E) staining and the Masson Trichrome (MT) special stain to demonstrate the morphology of normal and infectious urinary bladder. To improve on the translation between preclinical and clinical studies, the Göttingen minipig model is appropriate to use for research for diseased human bladder treatment because the minipig anatomy and organ system are similar to humans.The procedure was designed to evaluate normal uninfected urinary bladder and bacteria infected (E. coli) urinary bladder by evaluating morphology/cellular changes associated with the resultant inflammatory response in the urinary bladder of the Ellegaard Gottingen Minipig. The H&E-stained urinary bladder tissue section and a Masson Trichrome stained urinary bladder section were used to evaluate control ‘normal’ tissue vs infected tissue cellular differences.Optimal microscopic evaluation requires that the urinary bladders are properly fixed and processed. By using proper fixation and diligent histologic practices, all components of the urinary bladder are captured for proper histologic evaluation.