Bladder reconstruction with amniochorion
Creators: name: Ettinger, Susan Lorraine
Publisher: name: University of British Columbia
Year: 2010

description: Bladder reconstruction has been used since 1851 to surgically enlarge small capacity bladders but various materials grafted onto the bladder remnant, have proved inadequate because of leaky anastomoses, fibrous contracture and encrustation or stone formation. Such inadequacies have continued to prompt investigators to seek alternatives. In the present studies, supratrigonal cystectomies were performed in rabbits and then bladder reconstructions were attempted using one, two or four layers of human amniochorion. Control rabbits underwent supratrigonal cystectomy then closure either with or without the detached bladder remnant. It was hypothesized that amniochorion because of its tensile strength and slow rate of degradation may function as a scaffold for regenerating bladder tissue while maintaining bladder size and function. The abilities of amniochorion: a) to restore bladder size arid function was assessed by measuring bladder capacities before and after surgery; and b) to serve as a temporary scaffold was assessed by the immunologic response and graft degradation, and by the extent of bladder wall regeneration. Bladder capacities were significantly reduced when measured post-operatively, at 4 weeks or less, in both control and experimental groups and this may have been caused by surgical trauma, inflammation and irritation. However, bladder capacities measured from 5 to 17 weeks postoperatively appeared to increase with time, which may have been the result of decreased inflammation and increased quantitities of smooth muscle within regenerating bladder wall. Human amniochorion provoked an immune response when grafted into the rabbit bladder as cytotoxic antihuman antibodies were detected in rabbit sera in a complement-dependent cytotoxicity (CDC) assay using human lymphocytes. Platelet-absorbed sera in some cases produced a negative CDC response reflecting elimination of HLA antibodies and in other cases produced a positive response perhaps indicating the presence of antibodies to a lymphocyte/trophoblast crossreacting antigen. Platelet-absorbed sera in an indirect immunofluorescent assay, using amniochorion, produced positive fluorescence suggesting the presence of antibodies to amniochorion-associated antigens. Absorption with amniochorion, however, removed this reactivity which suggests that some of the antibodies were specific for amniochorion. Amniochorion-absorbed sera produced a positive CDC assay indicating the presence of antibodies cytotoxic to human lymphocytes (perhaps due to HLA antigens). Further evidence of an immune reaction, was the immediate assemblage of inflammatory cells (lymphocytes, polymorphonuclear cells, mast cells and macrophages) and their persistence for several weeks. Remnants of amniochorion could be identified after 9 weeks. Stone formation, probably due to necrotic debris, occurred in 44% of rabbits with single-layered and 87-90% with multi-layered grafts. Histological studies showed that granulation tissue bridged the defect during the first 3-4 weeks, and that urothelium, apparent at 5 weeks, attained normal thickness after 9-16 weeks. Few smooth muscle cells extended into the defect area as early as 5 weeks but after 11-17 weeks were numerous and organized into bundles. However, collagen usually comprised the greatest proportion of tissue in the regenerated wall. This study showed that human amniochorion, while maintaining continence and bladder function, acted as a temporary scaffold for connective tissue overgrowth and urothelial and smooth muscle regeneration. Despite an intense chronic inflammatory response and abundant collagen, a result of ischaemic necrosis and rejection, complete contracture did not occur possibly because of adequate smooth muscle regeneration. Studies using amniochorion as an allograft are required to determine if fibrous contracture occurs after several months and whether or not stone formation can be avoided with diuretic therapy. Amniochorion may become an alternative material to the less than adequate bowel graft currently used.