ALBERT

Description: Damage of endothelial cells (EC) is known to be involved in pathogenesis of microangiopathy, hepatic veno-occlusive disease, sepsis, capillary leak syndrome, and acute or chronic graft-versus-host disease (GvHD) as major causes of morbidity and mortality in patients after hematopoietic stem-cell transplantation (HSCT). We recently demonstrated in 39 patients undergoing allogeneic stem cell transplantation that numbers of circulating EC (CEC) increased significantly after conditioning regimens and that patients treated with reduced intensity conditioning (RIC) showed significantly lower cell numbers (Woywodt et al., Blood, 2004 May 1;103(9):3603-5). Here we report on the measurement of plasma levels of von Willebrand factor (vWF), thrombomodulin (TM), PAI-I and TAFI in the course of HSCT. Measurement of vWF, TM, PAI-I and TAFI was performed in the 39 patients (20 male, 19 female; n = 21: HLA-matched unrelated donor; n = 18: related donors). Blood samples were collected before starting conditioning regimen (day −7), the day before transplantation (day −1) and at day +7, +14 and +21 after transplantation. 28 patients received a conventional regimen with cyclophosphamide (120 mg/kg) and either total body irradiation with 12 Gy (n = 14) or busulfan (16 mg/kg, n = 14). 11 patients undergoing stem-cell transplantation were treated with reduced intensity conditioning with fludarabine (150 mg/m²) and busulfan (8 mg/kg body) or melphalan (120 mg/m²). Median baseline vWF was elevated (262%, range 68–612, normal range: 50–150). Median baseline PAI-I (11.3 U/l; range 1.8–34.4; normal range: 〈 20) and median baseline TAFI (90%; range 46–126; normal range: 70–120) were within normal limits. TM level was lower than normal values (median 3.95 ng/ml; range 2.69–9.36; normal range: 6.6–10.6). Levels of vWF increased after conditioning regimen and remained elevated until day +21 (day −1: median 262; day+7: 268; day +14: 327; day +21: 374; p 〈 0.01). Median TM remained low at all time points (day −1: median 4.26; day +7: 3.86; day +14: 3.97; day +21: 4.52). Levels of TAFI remained unchanged (day −1: median 82; day +7: median 91, day +14: median 88; day +21: median 89). There were also no differences in levels of PAI-I before or after conditioning regimen or after transplantation (day −1: median 11.4, day +7: median 10.8, day + 14: median 14, day + 21: median 11.8). There was no significant difference in vWF in patients undergoing reduced intensity conditioning compared to patients treated with conventional regimens. Interestingly, there was no correlation between the endothelial markers as vWF and TM and numbers of CEC. Our data indicate that significant alterations of the hemostatic system occur in patients undergoing HSCT. Further studies are warranted to define the clinical role of both, hemostatic alterations and CEC in the course of HSCT.

Description: Circulating endothelial cells (CECs) have been detected in a variety of vascular disorders, but their interactions with healthy endothelium remain unknown. The aim of this study was to evaluate the response of human endothelial cells (ECs) to apoptotic or necrotic ECs in an in vitro model and to delineate pathogenetic pathways. Here we show that incubation of the human microvascular endothelial cell line (HMEC-1) with apoptotic ECs resulted in increased expression of chemokines and enhanced binding of leukocytes to HMEC-1 cells, whereas exposure of HMEC-1 cells to necrotic ECs caused no changes in leukocyte-binding affinity. Both apoptotic and necrotic cells were bound and engulfed by HMEC-1 cells and primary human umbilical vein endothelial cells (HUVECs). We therefore suggest that exposures to apoptotic and necrotic ECs induce different patterns of chemokine synthesis and leukocyte adhesion in healthy ECs. These data indicate that CECs are not only markers of vascular damage but may induce proinflammatory signals in the endothelium.

Description: Damage to endothelial cells is the common feature of vascular disorders associated with hematopoietic stem cell transplantation (HSCT). Elevated numbers of circulating endothelial cells reflect the extent of endothelial damage in a variety of disorders but their use in HSCT has not been investigated so far. We studied 39 patients undergoing allogeneic HSCT with different conditioning regimens and 22 healthy controls. Circulating endothelial cells were enumerated with immunomagnetic isolation during the course of HSCT. After conditioning, cell numbers were significantly elevated (median 44 cells/mL) compared with baseline (median 16 cells/mL) and controls (median 8 cells/mL). Patients who received radiation had an earlier peak when compared with patients who received chemotherapy. Patients who received reduced-intensity conditioning had significantly lower cell numbers (median 24 cells/mL) than those who received standard conditioning. These observations provide a novel marker to investigate microvascular endothelial damage and the effects of different conditioning regimens in patients undergoing HSCT. (Blood. 2004;103:3603-3605)