G-CSF Enhances Cellular Fibrinolysis

Effects of rhG-CSF Plus Dexamethasone on Hemostatic Parameters in Healthy Granulocyte Donors: Role of u-PA and Nitric Oxide

Granulocyte colony-stimulating factor (G-CSF) is widely used to reduce the risk of infection resulting from neutropenias and to mobilize and collect CD34+ hematopoetic progenitor cells (HPCs) for autologous and allogenic transplantation. The safety of recombinant human G-CSF (rhG-CSF) administration in healthy donors has been investigated in several studies. However, there are limited cumulative data about the effects of rhG-CSF on hemostasis. Hemostatic parameters, including urokinase-type plasminogen activator antigen (u-PA:Ag) and nitric oxide in 17 healthy granulocyte apheresis donors who donated for neutropenic patients were evaluated. rhG-CSF (single dose, 10 μg/kg subcutaneously) and dexamethasone (8 mg, single dose oral) were given to donors 12 hours before granulocyte apheresis. Two blood samples were drawn at time 0 (T0) before rhG-CSF and dexamethasone administration and at time 1 (T1), immediately before the apheresis. A statistically significant rise in coagulant factor VIII (FVIII) and von Willebrand factor (vWF), and slightly rise in u-PA:Ag were observed after G-CSF plus dexamethasone administration. In addition, there were positive correlations between vWF-D-dimer and FVIII-D-dimer. A significant decrease in mean total nitric oxide (NOx), nitrite, and nitrate levels was also found after G-CSF plus dexamethasone administration. Moreover, there was a strong negative correlation between nitrite and D-dimer levels ( r = −0.611; P = .009). Even if partially compensated with u-PA and protein C, increased FVIII and vWF activity, and decreased nitric oxide levels may still partially contribute to progress of thrombosis risk in rhG-CSF plus dexamethasone administered healthy granulocyte donors. Large numbers of healthy donors exposed to G-CSF plus dexamethasone will be needed to evaluate the risk of thrombosis in this population.

A novel role of complement in mobilization: immunodeficient mice are poor granulocyte-colony stimulating factor mobilizers because they lack complement-activating immunoglobulins

Complement (C) and innate immunity emerge as important and underappreciated modulators of mobilization of hematopoietic stem/progenitor cells (HSPC). We reported that (a) C becomes activated in bone marrow (BM) during granulocyte-colony-stimulating factor (G-CSF)-induced mobilization by the classic immunoglobulin (Ig)-dependent pathway and that (b) C3 cleavage fragments increase the responsiveness of HSPC to a stromal derived factor-1 gradient. Since patients suffering from severe combined immunodeficiency (SCID) mobilize poorly, we hypothesized that this could be directly linked to the lack of C activating Ig in these patients. In the current study to better elucidate the role of C activation in HSPC mobilization, we mobilized mice that lack Ig (RAG2, SCID, and Jh) by G-CSF or zymosan, compounds that activate C by the classic Ig-dependent and the alternative Ig-independent pathways, respectively. In addition, we evaluated mobilization in C5-deficient animals. Mobilization was evaluated by measuring the number of colony-forming unit-granulocyte macrophage and leukocytes circulating in peripheral blood. We found that (a) G-CSF- but not zymosan-induced mobilization was severely reduced in RAG2, SCID, and Jh mice; (b) impaired G-CSF-induced mobilization was restored after infusion of purified wild-type Ig; and (c) mobilization was severely reduced in C5-deficient mice. These data provide strong evidence that the C system plays a pivotal role in mobilization of HSPC and that egress of HSPC from BM occurs as part of an immune response. Disclosure of potential conflicts of interest is found at the end of this article.