Hematopoietic Progenitor Cell Mobilization by Granulocyte Colony-Stimulating Factor and Erythropoietin in the Absence of Matrix Metalloproteinase-9

Abstract

The use of mobilized hematopoietic progenitor cells (HPC) has largely replaced the use of bone marrow HPC for autologous and allogeneic transplantation; however, the mechanisms of HPC mobilization remain unclear. A better understanding of these mechanisms, may allow the development of improved (potentially more rapid and/or higher yield) HPC mobilization strategies, especially for patients who mobilize poorly using current mobilization protocols. Clinically, granulocyte colony-stimulating factor (G-CSF) is widely used to induce HPC mobilization, and evidence suggests that metalloproteinase enzymes released by activated granulocytes play an important role in the G-CSF-induced HPC mobilization. These enzymes may act to disrupt putative cell-cell and/or cell-extracellular matrix interactions within the hematopoietic microenvironment thereby releasing HPC into the blood. Matrix metalloproteinase-9 (MMP-9) appears to be important for G-CSF-induced mobilization. Using an MMP-9 knock-out (KO) mouse model, we investigated the role of MMP-9 in G-CSF and erythropoietin (EPO)-based HPC mobilization at clinically relevant cytokine doses. There were few hematologic or hematopoietic differences between the wild-type and MMP-9KO mice during steady-state hematopoiesis. When treated subcutaneously with EPO (500 U/kg per day) and G-CSF (15 microg/kg per day) for 5 days and assayed on day 6, similarly increased extramedullary hematopoiesis and numbers of HPC in the spleen and blood were observed for both the wild-type and MMP-9KO mice. These data demonstrate that MMP-9 is not required for EPO + G-CSF mobilization and that alternative mobilization mechanisms must be active at clinically relevant cytokine concentrations.

Sequential morphological characteristics of murine fetal liver hematopoietic microenvironment in Swiss Webster mice

“…These results reveal that both MMP-1 and MMP-9 contribute to the beginning of erythropoiesis, but the mechanisms involved are still unknown. Robinson et al (2005) have shown that MMP-9 is not required for erythropoietin and granulocyte colony-stimulating factor (G-CSF) mobilization. On the other hand, Heissig et al (2002) have confirmed that MMP-9 promotes the release of the cell-soluble Kit ligand (SkitL) by bone marrow, a ligand that favors the homing of endothelial and hematopoietic cells from quiescent to proliferative niches.…”

Mechanisms of G-CSF-mediated hematopoietic stem and progenitor mobilization

“…25,26 In addition, mice deficient in the protease matrix metalloproteinase 9 (MMP-9), which is thought to mediate kitL cleavage, mobilize normally in most strains of mice. [27][28][29][30] VCAM-1/VLA-4 axis Together with its major ligand very late antigen 4 (VLA-4, also known as a4b1 integrin), vascular cell adhesion molecule 1 (VCAM-1) has a major role in anchoring HSPCs to bone marrow stromal cells 31 and regulating HSPC trafficking between the marrow and peripheral sites. 32 VLA-4 on HSPCs tethers them to VCAM-1-expressing cells, such as sinusoid endothelium and stromal reticular cells 33 and also fibronectin 34 in the extracellular matrix.…”

“…12,59 However, the role that proteases have in mobilization was thrown into question when it was shown that MMP-9-deficient mice mobilize normally in response to IL-8, 27 and other groups were unable to reproduce the mobilization defect previously seen in these mice using G-CSF. [27][28][29][30] Moreover, mice lacking combinations of neutrophil elastase, cathepsin G, or MMP-9 mobilize normally even in the presence of a broad-spectrum metalloproteinase inhibitor. 27 Collectively, these data suggest that while not absolutely required, neutrophil proteases may augment G-CSF-induced HSPC mobilization in the appropriate genetic background.…”

AMD3100 synergizes with G-CSF to mobilize repopulating stem cells in Fanconi anemia knockout mice

“…However, in preliminary studies, we have found that the responsiveness of myeloid progenitors to a number of cytokines and chemokines (including stem cell factor, G-CSF and stromal cell-derived factor-1) have failed to discern such a phenotype (unpublished data, 2007). Alternatively, it has recently been shown that hematopoietic progenitor and stem cell mobilization is dependent on a complex model involving both protease dependent and independent mechanisms [41][42][43][44]. Given our observations in these studies and the fidelity with which the murine models recapitulate the human mobilization defects, the FA murine models may be useful in future studies to discern the basic mechanisms underlying this clinical phenotype.…”