Novel evidence that crosstalk between the complement, coagulation and fibrinolysis proteolytic cascades is involved in mobilization of hematopoietic stem/progenitor cells (HSPCs)

Abstract

The role of blood proteinases in the mobilization of hematopoietic stem/progenitor cells (HSPCs) is still not well understood. As previously reported, activation of the complement cascade (ComC) and cleavage of C5 by C5 convertase are enabling events in the release of C5a that plays a crucial role in the egress of HSPCs from bone marrow (BM) into peripheral blood (PB) and explains why C5-deficient mice are poor mobilizers. Here we provide evidence that during granulocyte colony-stimulating factor- and AMD3100-induced mobilization, not only the ComC but also two other evolutionarily ancient proteolytic enzyme cascades, the coagulation cascade (CoaC) and the fibrynolytic cascade (FibC), become activated. Activation of all three cascades was measured by generation of C5a, decrease in prothrombin time and activated partial thromboplastin time as well as an increase in the concentrations of plasmin/antiplasmin and thrombin/antithrombin. More importantly, the CoaC and FibC, by generating thrombin and plasmin, respectively, provide C5 convertase activity, explaining why mobilization of HSPCs in C3-deficient mice, which do not generate ComC-generated C5a convertase, is not impaired. Our observations shed more light on how the CoaC and FibC modulate stem cell mobilization and may lead to the development of more efficient mobilization strategies in poor mobilizers. Furthermore, as it is known that all these cascades are activated in all the situations in which HSPCs are mobilized from BM into PB (for example, infections, tissue/organ damage or strenuous exercise) and show a circadian rhythm of activation, they must be involved in both stress-induced and circadian changes in HSPC trafficking in PB.

Extracellular molecules in hematopoietic stem cell mobilisation

“…Exogenous immunoglobulins can enhance mobilization and this is associated with the activation of C3 and to a lesser extent C5, but an essential role for immunoglobulins has not yet been shown [111]. It has recently been reported that there is crosstalk between the complement cascade and the fibrinolysis and coagulation cascades to further enhance HSPC mobilization [117]. The activation of these cascades would be consistent with the drop in platelet counts seen during G-CSF-induced mobilization [41].…”

Hematopoietic Stem/Progenitor Cells Express Several Functional Sex Hormone Receptors—Novel Evidence for a Potential Developmental Link Between Hematopoiesis and Primordial Germ Cells

“…Blood was collected on days 0, 3, 7, 14, 21, and 28, and white blood cell (WBC), platelet, red blood cells (RBC), and hematocrit were measured on a Hemavet instrument (HV950FS; Drew Scientific Group) as described [21]. Experiments were performed twice (each time, n = 5).…”

“…Samples were run within 2 h of collection on a Hemavet 950 hematology analyzer (Drew Scientific, Inc.) as described [21].…”

Mutation Drivers of Immunological Responses to Cancer

“…A potential connection between thrombin and the immune response against cancer may come from the role of thrombin in the complement cascade, whose role in anticancer immunity is beginning to be recognized (35-37). Thrombin is known to cleave C3 and C5 into their corresponding subunits, activating the complement pathway (38, 39). …”