Whole Blood Tissue Factor Procoagulant Activity Remains Detectable during Severe Aplasia following Bone Marrow and Peripheral Blood Stem Cell Transplantation

Abstract

SummaryUsing a novel whole blood assay, we recently demonstrated that tissue factor procoagulant activity (TF PCA) is present in normal individuals. Preliminary experiments suggested that this activity is localized in the mononuclear cell fraction. Postulating that whole blood TF PCA would therefore be undetectable when monocytes and neutrophils are absent from peripheral blood, we assayed TF PCA during the peri-transplant period in 15 consecutive patients undergoing allogeneic (n = 12) or autologous (n = 3) bone marrow transplantation (BMT) or peripheral blood stem cell transplantation (PBSCT). Baseline (pre-transplant) mean TF PCA was higher in patients compared to normal controls (P <0.005). Unexpectedly, although TF PCA during the period of profound aplasia was significantly reduced compared to baseline (p <0.05), fully 55% of the initial activity remained detectable. During the engraftment phase, TF PCA returned to pre-transplant levels, with a linear correlation between monocyte counts and TF PCA (r = 0.63). In contrast to normal whole blood, incubation of aplastic samples with E. Coli lipopolysaccharide ex vivo failed to induce TF PCA. Throughout the period of study – but especially during the aplastic phase – the absolute number of circulating endothelial cells (CECs) that were TF antigen-positive was increased compared to normals (P <0.001). However, removal of these cells from whole blood samples failed to significantly diminish total TF PCA indicating that CECs alone could not account for the detectable TF PCA during aplasia. We conclude that neither circulating mature myelo-monocytic cells nor endothelial cells can account for all the functionally intact TF in peripheral blood. Further studies are needed to identify the other source(s) of TF PCA.

Intravascular tissue factor initiates coagulation via circulating microvesicles and platelets

“…The presence of functionally active TF in circulating microvesicles and platelets could explain why substantial blood-based TF activity is retained after the selective depletion of leukocytes from blood (23). Microvesicles are shedded by various blood cells in response to activation, maturation, mechanical stress, and other stimuli.…”

“…In the plasma compartment, TF is present under physiological conditions and its concentration is increased in patients with unstable angina and myocardial infarction (7)(8)(9). The presence of TF in neutrophils and/or unstimulated monocytes has been a matter of debate (10)(11)(12). Prolonged activation of the monocytes with lipopolysaccharide (LPS) induces the expression of TF as a result of the transcriptional activation of the TF gene (13).…”

Andrographolide inhibits NF-κB activation and attenuates neointimal hyperplasia in arterial restenosis

“…The purity of monocytes was routinely >95% and viability was greater than >96%, measured through trypan blue exclusion. Human umbilical endothelial cells (HUVECs) and murine pulmonary vein endothelial cells (PVECs) were cultured as previously described [8,12,13].…”

Administration of granulocyte-colony-stimulating factor for allogeneic hematopoietic cell collection may induce the tissue factor-dependent pathway in healthy donors

“…29 However, it was reported that a considerable amount of remaining TF:PCA originating neither from myelomonocytes nor circulating endothelial cells was detected during the peritransplant period. 30 The rise of endogenous rhG-CSF levels during the aplasia period of stem cell transplantation has been previously shown, but the effect of endogenous rhG-CSF levels on TF:PCA remains to be elucidated. 31 We observed a significant increase in cytofluorimetric surface TF expression after G-CSF on both CD33 þ dim (mature myeloid cells) and bright cells (monocytes and myeloid progenitor cells) without a major change in TF:Ag on CD14 þ cells (monocytes).…”

“…19 However, one study observing the effect of rhG-CSF on patients undergoing allogeneic stem cell transplantation showed a significant decrease in ATIII levels at the fifth day vs the transplant day. 20 Another study Induction of TF-dependent pathway by rhG-CSF P Topcuoglu et al of cancer patients showed that administration of rhG-CSF at different dosages (1,3,10,30 and 60 mg/kg/day, i.v.) for 14 days did not affect ATIII levels.…”