Thrombolysis vs. bleeding from hemostatic sites by a prourokinase mutant compared with tissue plasminogen activator.

BACKGROUND: A single site mutant (M5) of prourokinase (proUK) was developed to make proUK less vulnerable to spontaneous activation in plasma. This was a problem that seriously compromised proUK in clinical trials, as it precluded proUK-mediated fibrinolysis at therapeutic concentrations. METHODS AND RESULTS: After completing dose-finding studies, 12 anesthetized dogs with femoral artery thrombosis were given either M5 (2.0 mg kg(-1)) or tissue plasminogen activator (t-PA) (1.4 mg kg(-1)) by i.v. infusion over 60 min (20% administered as a bolus). Two pairs of standardized injuries were inflicted at which hemostasis was completed prior to drug administration. Blood loss was quantified by measuring the hemoglobin in blood absorbed from these sites. Thrombolysis was evaluated at 90 min and was comparably effective by both activators. Rethrombosis developed in one t-PA dog. The principal difference found was that blood loss was 10-fold higher with t-PA (mean approximately 40 mL) than with M5 (mean approximately 4 mL) (P = 0.026) and occurred at more multiple sites (mean 2.7 vs. 1.2). This effect was postulated to be related to differences in the mechanism of plasminogen activation by t-PA and M5 in which the latter is promoted by degraded rather than intact (hemostatic) fibrin. In addition, two-chain M5 was efficiently inactivated by plasma C1 inactivator, an exceptional property which helped contain its non-specific proteolytic effect. CONCLUSIONS: Intravascular thrombolysis by M5 was accompanied by significantly less bleeding from hemostatic sites than by t-PA. This was attributed to the proUK paradigm of fibrinolysis being retained at therapeutic concentrations by the mutation.

Porcine small intestinal submucosa as a dural substitute.

BACKGROUND: The continuing search for the ideal dural substitute is currently directed toward collagen preparations. Xenogeneic porcine small intestinal submucosa (SIS), a naturally occurring extracellular matrix rich in collagen, has been successfully used as a soft tissue graft in several body organ systems, including preliminary studies as a dural substitute in the rat. METHODS: Eight dogs underwent temporoparietal craniotomy and dural resection with replacement by SIS. Five dogs had contralateral procedures without SIS grafting. Three dogs had contralateral SIS grafts placed 2 months after the initial procedure. Histologic assessment was obtained at 7, 30, 60, 90, and 120 days. Cerebrospinal fluid (CSF) cytological examination and routine serum chemistry preceded sacrifice. RESULTS: Histologic evaluation showed initial graft infiltration by mononuclear round cells, spindle-shaped cells within an eosinophilic staining extracellular matrix, and neovascularity. Complete resorption of the graft was evident by 60 days. This pattern is consistent with the previously described incorporation and remodeling of the SIS graft at other sites. CSF cytology and routine serum chemistry at the time of sacrifice were normal. Response to repeat grafting was identical to that of initial exposure. There was no clinical or histologic evidence of sensitization or graft rejection. No evidence of adverse effect on the underlying cerebral cortex was observed. CONCLUSIONS: Porcine small intestinal submucosa demonstrates a favorable biologic response as a dural substitute in the canine model. It is a promising biomaterial for dural replacement.

Resorbable bioscaffold for esophageal repair in a dog model.

PURPOSE: Porcine-derived, xenogeneic extracellular matrix (ECM) derived from either the small intestinal submucosa (SIS) or urinary bladder submucosa (UBS) was used as a tissue scaffold for esophageal repair in a dog model. METHODS: Patch defects measuring approximately 5 cm in length and encompassing 40% to 50% of the circumference of the esophagus or complete circumferential segmental defects measuring 5 cm in length were created by surgical resection in healthy adult female dogs. The defects were repaired with ECM scaffolds derived from either SIS or UBS. The animals were kept alive for periods ranging from 4 days to 15 months. RESULTS: The xenogeneic scaffolds used for repair of the patch defects were resorbed completely within 30 to 60 days and showed replacement by skeletal muscle, which was oriented appropriately and contiguous with adjacent normal esophageal skeletal muscle, organized collagenous connective tissue, and a complete and intact squamous epithelium. No signs of clinical esophageal dysfunction were seen in any of the animals with the patch defect repair. The xenogeneic scaffolds configured into tubes for repair of the segmental defects all showed stricture within 45 days of surgery. CONCLUSION: These ECMs show promise as a treatment option for esophageal repair, but stricture remains problematic for complete tube grafts.