Bone Marrow Microenvironments for Hematopoiesis

1)破骨细胞生成对骨髓形成的分析：破骨细胞是造血细胞，参与骨吸收和重塑。NF-κB受体活化因子配体（RANKL）和巨噬细胞集落刺激因子（M-CSF）对破骨细胞的发育至关重要。Toll样受体（TLR）家族与RANK共享一些下游信号传导，然而，从未报道过在没有RANKL的情况下通过TLR的信号传导诱导破骨细胞生成。我们发现，在M-CSF和LPS（一种TLR 4配体）存在的情况下，在培养物中不添加RANKL的情况下，蛋白酪氨酸磷酸酶SHP-1缺陷的me^v/me^v骨髓细胞可产生大量成熟破骨细胞。破骨细胞前体存在于BM细胞的Kit阳性细胞富集部分中。尽管me^v/me^v骨髓细胞需要与野生型细胞相当浓度的RANKL或TNF-α来启动破骨细胞生成，但me^v/me^v骨髓细胞中多核破骨细胞的数量与野生型细胞相比， ...更多信息 在存在M-CSF的情况下，等效剂量的RANKL或TNF-α显著增加了骨髓培养物。这些结果表明SHP-1功能的缺陷不仅通过RANKL/RANK加速生理性破骨细胞的发育，而且通过LPS获得了破骨细胞生成的异常途径。2）无血胚胎干（ES）细胞系的造血诱导：转录因子Tal-1对于造血发育的特化是必需的。缺乏Tall的小鼠不能产生任何造血前体。使用我们与基质细胞的共培养系统，我们证明了四环素控制下的转录因子PU.1在Tall空ES细胞中的强制表达挽救了表达巨噬细胞限制性标记物的破骨细胞和巨噬细胞样吞噬细胞的发育。未产生其他造血谱系细胞。它们的发生依赖于M-CSF和RANKL。这些结果表明，PU.1的表达是破骨细胞生成的关键事件，Tal-1可能位于PU.1的上游，在破骨细胞生成的调节层次。少

1)Analysis of osteoclastogenesis for bone marrow formation :Osteoclasts are hematopoietic cells, which participate in bone resorption and remodeling. Receptor activator of NF-κB ligand(RANKL) and macrophage colony-stimulating factor(M-CSF) are critical for development of osteoclasts. The Toll-like receptor(TLR) family shares some of the downstream signaling with RANK, however, the signaling via TLRs has never been reported to induce osteoclastogenesis without RANKL. We showed that significant numbers of mature osteoclasts were generated from protein tyrosine phosphatase SHP-1-defective me^v/me^v bone marrow cells in the presence of M-CSF and LPS, a TLR4 ligand without addition of RANKL in culture. The osteoclast precursors were present in the Kit-positive cell enriched fraction of BM cells. Although me^v/me^v bone marrow cells required a comparable concentration of RANKL or TNF-α as wild-type cells for the initiation of osteoclastogenesis, numbers of multinucleated osteoclasts in me^v/ … More me^v bone marrow cultures were significantly increased by the equivalent dose of RANKL or TNF-α in the presence of M-CSF. These results indicate that a defect of SHP-1 function not only accelerates physiological osteoclast development by RANKL/RANK, but also acquires an aberrant pathway for osteoclastogenesis by LPS.2)Induction of hematopoiesis from blood-less embryonic stem (ES) cell line :Transcription factor Tal-1 is essential for the specification of hematopoietic development. Mice lacking Tall fail to generate any hematopoietic precursors. Using our co-culture system with stromal cells, we demonstrate that enforced expression of the transcription factor PU.1 under tetracycline control in Tall-null ES cells rescues the development of osteoclasts and macrophage-like phagocytes expressing a macrophage restricted marker. Other hematopoietic lineage cells were not generated. Their development was dependent on M-CSF and RANKL. These results suggest that the expression of PU.1 is a critical event for osteoclastogenesis and that Tal-1 may lie upstream of PU.1 in a regulatory hierarchy during osteoclastogenesis. Less