Mechanism of signal transduction that regulates osteoclast differentiation and its abnormalities in bone distructive diseases

1. 克隆RANKL诱导的破骨细胞祖细胞人白血病细胞株HL60的早期基因，在TPA和1,25 -维生素d诱导分化后表达RANK。RANKL处理由此诱导的HL60细胞可进一步上调RANK。同时，我们通过抑制PCR方法，用RANKL刺激破骨细胞祖细胞（包括原代小鼠脾细胞和小鼠破骨细胞前细胞系C7） 1至4小时，鉴定了几个RANKL靶基因。这些基因包括组织蛋白酶和未表征的转录因子。阐明诱导这些靶基因的RANKL信号通路将有助于鉴定调控破骨细胞分化的主控基因。多发性骨髓瘤（MM）细胞诱导破骨细胞的机制我们证实了巨噬细胞炎症蛋白(MIP)-1 α和β是由MM细胞大量产生的。这些趋化因子不仅通过其共同受体CCR5诱导基质细胞表达RANKL，而且还以自分泌/旁分泌的方式激活MM细胞上的vla4，从而增强细胞与在其表面表达VCAM-1的基质细胞的相互作用。我们还发现MIP-1增强MM细胞与破骨细胞的结合。成骨细胞的存在以依赖于直接细胞间相互作用的方式增强了MM细胞的增殖和存活。这些影响似乎涉及基质蛋白，如破骨细胞大量产生的骨桥蛋白，以及白细胞介素-6，一种已知的MM细胞生长因子。综上所述，这些结果表明骨髓环境中复杂的细胞相互作用，其中MIP-1可能发挥核心作用，不仅导致破骨细胞的有效活化，而且还增强MM的增殖和存活，从而导致恶性循环，导致严重的骨破坏。

1. Cloning of RANKL-induced early genes in osteoclast progenitorsHuman leukemia cell line, HL60, expressed RANK upon differentiation induced by TPA and 1, 25-vitamin D. RANKL treatment of thus induced HL60 cells led to further up-regulation of RANK.Meanwhile, we have identified several RANKL target genes with suppression PCR methods by stimulating osteoclast progenitors including primary mouse spleen cells and a mouse preosteoclast cell line, C7, with RANKL for one to four hours. Among such genes are cathepsins and uncharacterized transcription factors. Elucidation of RANKL signaling pathways that induce these target genes would lead to identification of master genes that regulates osteoclast differentiation.2. Mechanism of osteoclast induction by multiple myeloma (MM) cellsWe demonstrated macrophage inflammatory protein (MIP)-1 alpha and beta are abundantly produced by MM cells. These chemokines not only induced RANKL expression by stromal cells via their common receptor CCR5, but also acts in an autocrine/paracrine fashion to activate VLA-4 on MM cells, thereby enhancing cellular interactions with stromal cells which express VCAM-1 on their surface. We also found that MIP-1 enhances binding of MM cells to osteoclasts. Proliferation and survival of MM cells was enhanced by the presence of osteclasts in a manner dependent on direct cell-cell interactions. These effects appeared to involve matrix proteins such as osteopontin abundantly produced by osteoclasts as well as interleukin-6, a known growth factor for MM cells.Taken together, these results suggested that complex cellular interactions in the bone marrow milieu, in which MIP-1 may play a central role, leads to not only efficient activation of osteoclasts but also enhancement of MM proliferation and survival, thereby causing a vicious cycle that leads to profound bone destruction.