Vascular events in placentae and organ allografts

Gene polymorphisms for plasminogen activator inhibitor-1/tissue plasminogen activator and development of allograft coronary artery disease

BACKGROUND

Impaired fibrinolytic activity has been linked to the presence and severity of allograft vasculopathy (Tx CAD). This impairment may be associated with the presence of certain fibrinolytic protein gene polymorphisms.

METHODS AND RESULTS

To investigate the relation between donor-specific fibrinolytic protein genotypes and Tx CAD, we identified donor plasminogen activator inhibitor-1 (PAI-1) HindIII and tissue plasminogen activator (TPA) EcoRI restriction fragment length polymorphisms-based genotypes by Southern blot analysis in 48 recipients of cardiac allografts and correlated these genotypes with the development of CAD. No association was found between donor TPA genotypes and the presence of Tx CAD. Among the 48 patients, 17% were homozygous for the 1/1 PAI-1 genotype, 51% for the 2/2 PAI-1 genotype, and 32% for the 1/2 PAI-1 genotype. The actuarial freedom from any CAD for the recipients with each respective donor PAI-1 genotype at 12 and 24 months was 100% and 100% for the 1/1 PAI-1 genotype, 92% and 92% for the 1/2 PAI-1 genotype, and 75% and 45% for the 2/2 PAI-1 genotype (P=0.03). Recipients with a diseased 2/2 PAI-1 genotyped allograft had longer ischemic times (P=0.02) than those recipients with a Tx CAD-free allograft.

CONCLUSIONS

These data suggest that recipients with a 2/2 PAI-1 genotype are at a significant risk of developing Tx CAD. This genotype may serve as a useful screening tool for predicting the future development of Tx CAD.

Antiphospholipid antibodies or not? The role of beta 2 glycoprotein 1 in autoantibody-mediated pregnancy loss

Antiphospholipid antibodies are a family of autoantibodies including lupus anticoagulant and anticardiolipin antibodies that appear to react with negatively charged phospholipids. These antibodies induce thrombosis and pregnancy complications including recurrent stillbirth, recurrent miscarriage, pre-eclampsia and intra-uterine growth retardation. Recent evidence indicates that antiphospholipid antibodies do not bind directly to phospholipid but rather to phospholipid-binding proteins or to a combination of phospholipid and phospholipid-binding proteins. This opens the possibility that antiphospholipid antibodies may be pathogenic by disrupting the function of phospholipid-binding proteins rather than membrane phospholipid. The antigenic role of one phospholipid-binding protein, beta 2 glycoprotein, has been studied in the greatest detail and is reviewed. Despite being highly conserved and expressed at high levels, the physiological function of beta 2 glycoprotein 1 remains unknown. However, a number of putative roles have been proposed which allow speculation as to the mechanism by which antiphospholipid antibodies may disrupt haemostasis and pregnancy.

Intercellular adhesion molecule-1 (ICAM-1) and HLA-DR antigens are expressed on endovascular cytotrophoblasts in abnormal pregnancies

PROBLEM

We asked if the lack of normal trophoblastic invasion of spiral arteries in the basal plate of abnormal pregnancies was associated with the expression of HLA-DR antigens and intercellular adhesion molecules (ICAM-1) on endovascular cytotrophoblasts.

METHOD

The basal plates of placentae from 15 normal and 55 abnormal pregnancies, including preeclampsia, small-for-gestational age infants, and mothers with history of secondary recurrent spontaneous abortion, were studied immunocytochemically by using monoclonal antibodies to HLA-DR and ICAM-1. Spiral and uteroplacental arteries were identified by using a triple antibody technique with antibodies to cytokeratin, alpha-smooth muscle actin, and von Willebrand factor to detect cytotrophoblasts, arterial smooth muscle cells, and endothelium, respectively.

RESULTS

Placentae with normal placentation showed the presence of uteroplacental arteries that contained endovascular cytotrophoblasts that were negative for HLA-DR and ICAM-1 antigens. Placentae from abnormal pregnancies showed the presence of spiral arteries without trophoblastic invasion and uteroplacental arteries that were surrounded by numerous macrophages and T lymphocytes. Endovascular cytotrophoblasts in uteroplacental arteries of placentae from abnormal pregnancies reacted with antibodies to HLA-DR and ICAM-1 antigens.

CONCLUSION

Placentae from normal pregnancies show uteroplacental arteries that contain endovascular cytotrophoblasts that do not react with antibodies to ICAM-1 and HLA-DR antigens, and placentae from abnormal pregnancies with uteroplacental arteries that are associated with arteries that do not show physiological changes contain endovascular cytotrophoblasts that react with antibodies to ICAM-1 an HLA-DR antigens. Normal uteroplacental arteries were found to be not surrounded by round cell infiltrates, but uteroplacental arteries associated with arteries that lack physiological changes were surrounded by round cell infiltrates, indicating that round cell infiltrates and endovascular cytotrophoblasts which react with antibodies to ICAM-1 and HLA-DR antigens are associated with abnormal pregnancies. These findings suggest that the cellular infiltrates are associated with endovascular cytotrophoblasts that react with ICAM-1 and HLA-DR antigens.

Tissue plasminogen activator, plasminogen activator inhibitor-1, and fibrin as indexes of clinical course in cardiac allograft recipients. An immunocytochemical study

BACKGROUND

Tissue-type plasminogen activator (TPA) is the principal activator of plasminogen. Since hemostasis in the microcirculation of allografts is a well-recognized complication of transplantation, we asked (1) whether the distribution and amount of cellular TPA in biopsies of transplanted human hearts are associated with fibrin deposits in and around the microcirculation, (2) whether such changes involve the physiological inhibitors of TPA and plasmin, and (3) whether the presence of these activators and inhibitors of fibrinolysis in tissue is correlated with clinical outcome.

METHODS AND RESULTS

We immunocytochemically quantified the presence of fibrin, plasmin, TPA, and the TPA inhibitor PAI-1 in 938 biopsies from 68 consecutive cardiac allografts over a 54-month period. The localization, distribution, and quantification of TPA in arteriolar smooth muscle cells revealed that 35 of the 68 allografts maintained vascular TPA reactivity consistent with time-zero biopsies of autologous donor hearts: this was designated as the normal TPA group. In contrast, 33 of the 68 allografts significantly lost vascular TPA reactivity compared with time-zero biopsies of autologous donor hearts: this was designated as the depleted TPA group. Analysis of sequential biopsies from both groups during 54 months revealed that the mean cumulative quantitative TPA value for the normal TPA group was 1.0 +/- 0.01, whereas the depleted TPA group value was 1.9 +/- 0.02 (P = .0001), and the mean cumulative quantitative fibrin value for the normal TPA group was 1.0 +/- 0.01, whereas the depleted TPA group value was 1.5 +/- 0.05 (P = .0001). Biopsies of allografts in the depleted TPA group contained endothelial reactivity for TPA-PAI-1 complexes, whereas biopsies from the normal TPA group did not. Plasmin-associated molecules were rarely identified in biopsies of the normal TPA group but were present in the depleted TPA group, and the fibrin-to-plasmin ratio in the normal TPA group always was less than the fibrin-to-plasmin ratio in biopsies from the depleted TPA group. Analysis of demographic and risk factors revealed no significant differences between patients in the normal and depleted TPA groups, but none of the 35 patients in the normal TPA group died or were retransplanted, and 13 of the 33 patients in the depleted TPA group died or required retransplantation (P = .0001).

CONCLUSIONS

Time-zero hearts (n = 68) and 34 of 38 stable allografts contained immunocytochemically detectable TPA only in vascular smooth muscle cells. Twenty-nine of 30 patients with normal TPA in their time-zero biopsies who subsequently developed a poor clinical outcome were found to have depleted TPA in biopsies evaluated during their first postoperative month and remained depleted throughout the study. Of 33 patients with depleted TPA, 39% died or required retransplantation. Depleted arteriolar TPA associated significantly with vascular and interstitial deposits of fibrin, plasmin, and endothelial TPA-PAI-1 complexes. These findings indicate that hemostatic and fibrinolytic pathways are activated in falling allografts, and they reveal evidence of depleted TPA before clinical or histopathological signs of failure. Patients with such allografts were found to be at high risk of death independently of other widely used clinical/laboratory parameters of prediction.