Growth factors and cytokines upregulate gelatinase expression in bone marrow CD34(+) cells and their transmigration through reconstituted basement membrane

The mechanism(s) underlying the release of stem/progenitor cells from bone marrow into the circulation is poorly understood. We hypothesized that matr ix metalloproteinases (MMPs), especially gelatinases, which are believed to participate in the proteolysis of basement membranes and in the migration of leukocytes, may facilitate this process. First, we investigated whether CD34(+) stem/progenitor cells express gelatinases A (MMP-2) and/or B (MMP-9 ) and whether growth factors and cytokines (granulocyte colony-stimulating factor [G-CSF], granulocyte-macrophage colony-stimulating factor [GM-CSF], stem cell factor [SCF], macrophage colony-stimulating factor [M-CSF], inter leukin-3 [IL-3], IL-6, IL-8, and tumor necrosis factor-alpha [TNF-alpha]) a re able to modulate their expression. Next, we examined the transmigration of these stem/progenitor cells through reconstituted basement membrane (Mat rigel) and its modulation by growth factors and cytokines. CD34(+) cells we re obtained from steady-state bone marrow and peripheral blood (from leukap heresis products collected either in steady-state hematopoiesis or after mo bilization with G-CSF plus chemotherapy or G-CSF alone). We found that peri pheral blood CD34(+) cells, regardless of whether they were mobilized or no t, strongly expressed both gelatinases (MMP-5 and MMP-9) in contrast to ste ady-state bone marrow CD34(+) cells, which did not. However, all the growth factors and cytokines tested could induce MMP-2 and MMP-9 secretion by the latter cells. Moreover, the stimulatory effects of G-CSF and SCF on both M MP-5 and MMP-9 secretion were found to be significantly higher in CD34(+) c ells isolated from bone marrow than in those from peripheral blood. In addi tion TNF-alpha, GM-CSF, and IL-6 increased the secretion of a partially act ive form of MMP-2. Basal transmigration of bone marrow CD34(+) cells throug h Matrigel was lower than that of peripheral blood CD34(+) cells (P < .0001 ), but growth factors and cytokines increased it by 50% to 150%. Positive c orrelations were established between expression of gelatinases and CD34(+) cell migration (r > .9). The stimulatory effect of G-CSF was significantly greater on the migration of CD34(+) cells from bone marrow than on those fr om peripheral blood (P = .004). Moreover, CD34(+) cell migration was reduce d to approximately 50% by antibodies to MMP-2 and MMP-9, tissue inhibitors of metalloproteinases (rhTIMP-1 and -2), and o-phenanthroline. TNF-alpha-in duced gelatinase secretion and migration of CD34(+) cells and of clonogenic progenitors (colony-forming unit-granulocyte-macrophage [CFU-GM], burst-fo rming unit-erythroid [BFU-E], colony-forming unit granulocyte, erythroid, m onocyte, megakaryocyte [CFU-GEMM], and colony-forming unit-megakaryocyte [C FU-MK]) were dose-dependent. Therefore, this study demonstrated that CD34() cells that are circulating in peripheral blood express both MMP-5 and MMP -9 and transmigrate through Matrigel. In contrast, CD34(+) cells from stead y-state bone marrow acquire similar properties after exposure to growth fac tors and cytokines, which upregulate expression of gelatinases and transmig ration of these cells when they enter the bloodstream. Hence, we suggest th at growth factors and cytokines induce release of stem/progenitor cells fro m bone marrow into peripheral blood during mobilization, as well as during steady-state hematopoiesis, by signaling through gelatinase pathways. (C) 1 999 by The American Society of Hematology.