Interrelationship between plasminogen activator activity and tissue repair of the bladder (author's transl).

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In the present study the interrelationship between fibrinolytic activity and tissue repair of the urinary bladder or bladder urine after burn injury made on the guinea pig bladder epithelium was studied by the histochemical fibrin slide technique. It is well known that the fibrinolytic activity present in tissue and tissue extract is caused by an activating agent (plasminogen activator).Fibrinolytic activity in the normal bladder wall of guinea pig was observed in relation to some blood vessels in the submucosa or muscular coat. There was also a wide-spread diffuse lysis along the transitional epithelial lining and related with the desquamated epithelial cells lying freely in the bladder cavity.On injury to normal bladder epithelium the following was observed: A burn injury transiently increased fibrinolytic activity in the thin layer of connective tissue contacting basal membrane (tunica propria) which was adjacent to the injured area. This activity diminished after the 7th day, and the fibrinolytic activity appeared in many hyperplastic blood vessels in the lower part of the lamina propria from the 16th day and gradually decreased on the 30th day after burn injury. Strong proteinase activity observed in some sections occurred in the burned part with necrotic mass extruded into the bladder cavity. It seemed that the proteinase activity could be caused by plasmin formed to activate plasminogen in the necrotic mass by urine containing urokinase. The fibrinolytic activity in the bladder urine increased during the early stage after injury and the activity gradulally decreased with the bladder epithelial healing.It was found that the thin layer immediately under the epithelium (tunica propria) consists of a vascularized connective tissue which contains reactive capillaries, angioblasts and capillary buds. These reactive cells contain the plasminogen activator. However, such a region is fibrinolytically quiesent under the normal condition. After injury of the bladder epithlium an intense fibrinolytic activity appeared along the tunica propria.It is considered possible that the intense fibrinolytic activity along the tunica propria must be playing an important role there, such as an origin of the new cells and as resolution of fibrin deposits occurring in early stage of tissue repair.It has been well known, based on clinical experience, by urologists for many years that the bladder possess remarkable powers of reconstraction even after electro- or partial resection. Our experimental study indicates that the intense fibrinolytic activity along the tunica propria could contribute a defense to production of extensive fibrosis, following the healing process after the bladder epithelium injury.