THE EFFECT OF SMALL-BOWEL TRANSPLANTATION ON THE MORPHOLOGY AND PHYSIOLOGY OF INTESTINAL MUSCLE - A COMPARISON OF AUTOGRAFTS VERSUS ALLOGRAFTS IN DOGS

The effects of acute (AR) and chronic rejection (CR) on intestinal smo oth muscle that are responsible for the dysmotility following small bo wel transplantation (SBTX) are incompletely understood. Jejunal and il eal specimens from normal control dogs (n=7), and autotransplanted dog s were examined at 7 days (n=6) and 1 (n=7), 3 (n=6), 6 (n=6), and 12 months (n=6). Allo-transplanted dogs that developed AR (n=8) and CR (n =5) were examined for gross and microscopic morphology (muscle thickne ss, the number and size of myocytes, and inflammatory infiltrate), and for contractile and intracellular electrical function in vitro. Auto- SBTX did not alter morphology at any period, but contractile function was impaired at 7 days (73.6%) compared with normal intestine. Acute r ejection did not influence myocyte number or size, but was associated with a prominent infiltrate of neutrophils and lymphocytes, and severe ly impaired contractile function (20.6%) compared with auto-SBTX contr ols. Acute rejection also significantly inhibited the amplitude of slo w waves and of inhibitory junction potentials. Chronic rejection cause d thickening of muscularis propria by both hyperplasia (175.5%) and hy pertrophy (202.6%) accompanied by moderate inflammatory cell infiltrat e compared with auto-SBTX controls. We conclude that the marked inflam matory infiltrate into the muscularis propria indicates that the graft muscle is injured by both acute and chronic rejection; impaired funct ion of intestinal smooth muscle following SBTX results from both rejec tion and the injury associated with transplantation, and chronic rejec tion following SBTX is associated with both hyperplasia and hypertroph y of the muscularis propria.