Third Department of Internal Medicine, Faculty of Medicine, University of Toyama, Toyama, Japan.
Cell Transplant. 2012;21(2-3):453-64. doi: 10.3727/096368911X605367.
Effective mobilization of hematopoietic stem cells (HSCs) in injured organs has not been established. Matrix metalloproteinase-9 (MMP-9) is known to release HSCs from bone marrow (BM) into the peripheral blood, but its role in the recruitment of HSCs to injured organs is unclear. In this study we tried to clarify the role of the host MMP-9 in trafficking of HSCs toward the injured liver, especially the relation of MMP-9 with the chemokine receptor 4 (CXCR4)-chemokine ligand 12 (CXCL12) axis, and to examine whether MMP-9 deficiency affects BM cell trafficking to the injured liver in mice. In vitro, we investigated the effect of MMP-9 on migration activity and CXCR4 expression on lineage-negative (Lin(-)) BM cells. In vivo, we induced acute and chronic liver injury in MMP-9 knockout (KO) and control mice by inoculation of carbon tetrachloride, followed by transplantation of Lin(-) BM cells obtained from enhanced green fluorescent protein (EGFP)-transgenic mice, and counted the BM cells mobilized in the injured liver. In a migration assay, active MMP-9, but not proMMP-9, increased the number of migrated Lin(-) BM cells, which was inhibited by tissue inhibitor of metalloproteinase-1 or a MMP inhibitor. This chemoattractant function by MMP-9 was synergistic when cotreated with CXCL12. CXCR4 expression on Lin(-) BM cells was dose- and time-dependently increased by active MMP-9. At the same time, treatment with MMP-9 enhanced CXCL12 expression, and CXCL12 reciprocally increased MMP-9 expression in BM cells. In in vivo studies, many EGFP(+) cells were seen in control recipient mice. In contrast, few EGFP(+) cells were observed in MMP-9 KO mice. BM cells tended to differentiate into desmin(+) cells. In conclusion, MMP-9 contributes to the mobilization of BM cells in the injured liver by upregulating the expression of CXCR4 on Lin(-) BM cells and attracting BM cells along its gradient of CXCL12. Therefore, host MMP-9 plays an important role in BM cell migration in the injured liver.
尚未确立在受伤器官中有效动员造血干细胞 (HSCs) 的方法。已知基质金属蛋白酶-9 (MMP-9) 可将 HSCs 从骨髓 (BM) 释放到外周血中，但它在募集 HSCs 到受伤器官中的作用尚不清楚。在这项研究中，我们试图阐明宿主 MMP-9 在 HSCs 向受伤肝脏迁移中的作用，特别是 MMP-9 与趋化因子受体 4 (CXCR4)-趋化因子配体 12 (CXCL12) 轴的关系，并研究 MMP-9 缺乏是否会影响骨髓细胞向受伤肝脏的迁移在小鼠中。在体外，我们研究了 MMP-9 对谱系阴性 (Lin(-)) BM 细胞迁移活性和 CXCR4 表达的影响。在体内，我们通过接种四氯化碳在 MMP-9 敲除 (KO) 和对照小鼠中诱导急性和慢性肝损伤，然后移植来自增强型绿色荧光蛋白 (EGFP)-转基因小鼠的 Lin(-) BM 细胞，并计算动员到受伤肝脏中的 BM 细胞数。在迁移实验中，活性 MMP-9（而非前 MMP-9）增加了迁移的 Lin(-) BM 细胞数量，而组织金属蛋白酶抑制剂-1 或 MMP 抑制剂可抑制这种趋化作用。这种由 MMP-9 引起的趋化作用与 CXCL12 共同作用时具有协同作用。活性 MMP-9 剂量依赖性和时间依赖性地上调 Lin(-) BM 细胞上的 CXCR4 表达。同时，MMP-9 处理增强了 CXCL12 的表达，而 CXCL12 反过来又增加了 BM 细胞中的 MMP-9 表达。在体内研究中，在对照受体小鼠中观察到许多 EGFP(+) 细胞。相比之下，在 MMP-9 KO 小鼠中观察到的 EGFP(+) 细胞很少。BM 细胞倾向于分化为结蛋白(+) 细胞。总之，MMP-9 通过上调 Lin(-) BM 细胞上的 CXCR4 表达并吸引 BM 细胞沿着其 CXCL12 梯度来促进 BM 细胞在受伤肝脏中的动员。因此，宿主 MMP-9 在 BM 细胞向受伤肝脏的迁移中发挥重要作用。
