Relevance of ADAMTS13 to liver transplantation and surgery

A disintegrin-like and metalloproteinase with thrombospondin type-1 motifs 13 (ADAMTS13) specifically cleaves unusually-large von Willebrand factor (VWF) multimers under high shear stress, and down-regulates VWF function to form platelet thrombi. Deficiency of plasma ADAMTS13 activity induces a life-threatening systemic disease, termed thrombotic microangiopathy (TMA) including thrombotic thrombocytopenic purpura (TTP). Children with advanced biliary cirrhosis due to congenital biliary atresia sometimes showed pathological features of TMA, with a concomitant decrease of plasma ADAMTS13 activity. Disappearance of their clinical findings of TTP after successful liver transplantation suggested that the liver is a major organ producing plasma ADAMTS13. In situ hybridization analysis showed that ADAMTS13 was produced by hepatic stellate cells. Subsequently, it was found that ADADTS13 was not merely responsible to development of TMA and TTP, but also related to some kinds of liver dysfunction after liver transplantation. Ischemia-reperfusion injury and acute rejection in liver transplant recipients were often associated with marked decrease of ADAMTS13 and concomitant formation of unusually large VWF multimers without findings of TMA/TTP. The similar phenomenon was observed also in patients who underwent hepatectomy for liver tumors. Imbalance between ADAMTS13 and VWF in the hepatic sinusoid might cause liver damage due to microcirculatory disturbance. It can be called as “local TTP like mechanism” which plays a crucial role in liver dysfunction after liver transplantation and surgery.

Clinicopathological analysis for recurrence of stage Ib gastric cancer (according to the second English edition of the Japanese classification of gastric carcinoma)

BACKGROUND

The prognosis for patients with stage Ib (second English edition of the Japanese classification of gastric carcinoma) gastric cancer is promising, with an expected 5-year survival of 90%. Despite this relatively high survival rate, the outcome for patients who experience recurrence is poor. To date, however, prognostic and recurrence factors for stage Ib gastric cancer are poorly understood, and appropriate adjuvant chemotherapy protocols have not been developed.

METHODS

We retrospectively analyzed data from 86 stage Ib gastric cancer patients who underwent curative gastrectomy to determine the rates and predictive factors of recurrence.

RESULTS

Eleven patients showed recurrence, with a 12.8% 5-year cumulative recurrence rate. Nearly all of these patients were initially histologically diagnosed with poorly differentiated adenocarcinoma. Based on univariate analyses, recurrence was associated with gender and histological type. Multivariate analyses revealed that the only independent risk factor for recurrence was histologically undifferentiated-type adenocarcinoma. The 5-year survival rate of patients with undifferentiated-type adenocarcinoma was 84%. The predominant recurrence pattern was peritoneal dissemination, and was typically observed 1-3 years post-resection.

CONCLUSION

This retrospective study identified undifferentiated-type adenocarcinoma as the only risk factor for recurrence in stage Ib gastric cancer patients. Although randomized controlled studies are necessary, stage Ib gastric cancer patients with this identified recurrence risk factor would be candidates for adjuvant chemotherapy.

ADAMTS13 activity decreases after hepatectomy, reflecting a postoperative liver dysfunction

BACKGROUND/AIMS

The precise mechanism and prophylactic strategy of deteriorated hepatic function after liver surgery have not been fully understood. The substrate of ADAMTS13, unusually large von Willebrand factor multimers, is produced in vascular endothelial cells at liver injury, leading to platelet aggregation. The decrease of plasma ADAMTS13 activity may involve not only the formation of platelet thrombi in the liver, but also subsequent progression of liver dysfunction through a microcirculatory disturbance. This study evaluated changes of plasma ADAMTS13 activity and its clinical relevance in patients with hepatectomy.

METHODOLOGY

Plasma ADAMTS13 activity and its related parameters were sequentially determined after hepatectomy in 70 patients.

RESULTS

ADAMTS13 activity significantly decreased preoperative 67.0 +/- 30.6 to 48.1 +/- 24.6% after hepatectomy (p < 0.0001). Pringle's maneuver for longer than 45 minutes (p = 0.0007) and major hepatectomy (p = 0.0002) were significantly associated with the decrease of ADAMTS13 activity to less than 40%. The decreased ADAMTS13 activity reflected postoperative thrombocytopenia (p = 0.0028) and hyperbilirubinemia (p < 0.05).

CONCLUSIONS

Plasma ADAMTS13 activity significantly decreased after hepatectomy due to ischemic injury together with liver mass reduction, reflecting a postoperative liver dysfunction. Monitoring of ADAMTS13 activity may be useful to prevent further development of the liver failure after hepatectomy.

Plasma ADAMTS13 activity may predict early adverse events in living donor liver transplantation: observations in 3 cases

A disintegrin-like and metalloproteinase with thrombospondin type-1 motifs 13 (ADAMTS13) is a metalloproteinase that specifically cleaves the multimeric von Willebrand factor (VWF). Deficiency of ADAMTS13 increases the unusually large VWF multimers (UL-VWFM), which leads to platelet clumping and/or thrombus formation, resulting in microcirculatory disturbance. We serially determined the activity of plasma ADAMTS13, together with VWF antigen (VWF:Ag) and UL-VWFM, in association with the development of early graft dysfunction in 3 liver transplant recipients and 4 patients with major hepatectomy as controls. In case 1, ADAMTS13 activity decreased markedly from 108% to less than 3% with concomitant thrombocytopenia on posttransplantation day 7, when acute rejection occurred. Simultaneously, UL-VWFM were detected. During the second episode of rejection, VWF:Ag increased to 368% with the appearance of UL-VWFM, while ADAMTS13 activity was as low as 18%, indicating an imbalance between a large amount of UL-VWFM and low activity of ADAMTS13. Administration of fresh frozen plasma (FFP) together with treatment for acute rejection resulted in an improvement of ADAMTS13 activity and disappearance of the UL-VWFM. In case 2, ADAMTS13 activity promptly decreased to 9% with thrombocytopenia on day 1, when ischemia-reperfusion injury occurred. Subsequently, the ADAMTS13 activity increased steadily without appearance of UL-VWFM, and the patient recovered uneventfully. ADAMTS13 activity decreased to 15% immediately after transplantation in case 3 as well. In contrast, ADAMTS13 activity never decreased below 20% in 4 patients with major hepatectomy as controls. In conclusion, these results indicate that the kinetics of ADAMTS13 and UL-VWFM could be good indicators of adverse events after liver transplantation. Our findings not only suggest a novel mechanism for thrombocytopenia, but also provide a useful tool for diagnosis of graft dysfunction in the early stage after transplantation.

Effects of clopidogrel on platelet activation and coagulation of non-anticoagulated rat blood under high shear stress

Clopidogrel is a new thienopyridine derivative similar to ticlopidine, which inhibits adenosine diphosphate-induced platelet aggregation. The in vitro effects of clopidogrel on shear-induced platelet activation and coagulation were assessed after oral administration to rats, by subjecting non-anticoagulated blood to haemostatometry. Clopidogrel significantly inhibited shear-induced platelet activation and coagulation 2 h after administration at doses of 7.5 and 15 mg/kg. Both ticlopidine (200 mg/kg) and aspirin (200 mg/kg) inhibited shear-induced platelet activation, but not coagulation. The peak inhibition of plaetelet activation by clopidogrel occurred 2 h after oral administration, but significant inhibition persisted even after 24 h. These results suggest that clopidogrel could be a more potent antithrombotic agent than ticlopidine or aspirin, and also that ADP plays an important role in shear-induced platelet activation.