Intracellular trafficking of Bisphosphonates in bone mesenchymal Stem Cells

描述（申请人提供）：含氮双膦酸盐（n-BP）有效控制骨转换失调、肿瘤转移的溶骨病变，具有抗肿瘤活性。不幸的是，颌骨骨坏死（ONJ）是n-BP治疗的主要并发症。下颌特异性n-BP相关骨坏死的原因尚不清楚，这使得设计靶向治疗具有挑战性。n- bp通过阻断甲羟戊酸信号通路中的法尼酯焦磷酸（FPP）合成酶作用于破骨细胞和癌细胞；其结果是小GTPase信号蛋白的戊酰化缺失和细胞存活和分化的失调。我们已经证明，与中胚层来源的髂骨（ICMSCs）和长骨（LBMSCs）相比，来自神经嵴来源的上颌骨/下颌骨（OFMSCs）的口面骨髓间质细胞或骨间充质干细胞（BMSCs）具有高增殖能力，其增殖倍数长。因此，它们可能很容易屈服于n-BP，类似于快速增殖的癌细胞。我们的初步研究表明，OFMSCs确实比ICMSCs对n-BP更敏感，这是基于n-BP摄取增强，从细胞质中消除缓慢，存活率降低和成骨分化减少。我们假设OFMSCs对n-BP的敏感性在一定程度上有助于ONJ的启动，该启动基于位点依赖性n-BP摄取、细胞内加工、甲羟戊酸途径中FPP合成酶的抑制以及随之而来的小GTPase信号蛋白的戊酰化缺失。在目的1中，我们将确定n-BP在OFMSCs中的摄取和细胞内运输如何调节生存，目的2将在小动物模型中探索基于骨髓间充质干细胞的治疗来预防ONJ。其目标是制定ONJ的预防措施。

DESCRIPTION (provided by applicant): Nitrogen-containing bisphosphonates (n-BP) effectively control dysregulated bone turnover, osteolytic lesions of cancer metastasis and have anti-tumor activities. Unfortunately, osteonecrosis of the jaw (ONJ) is a major complication of n-BP therapy. Reasons for jaw-specific location of n-BP related osteonecrosis are unclear making it challenging to design targeted therapies. n-BPs act on osteoclasts and cancer cells by blocking the farnesyl pyrophosphate (FPP) synthase in the mevalonate signaling pathway; the outcome is loss of prenylation of small GTPase signaling proteins and dysregulation of cell survival and differentiation. We have shown that orofacial bone marrow stromal cells or bone mesenchymal stem cells (BMSCs) from neural crest-derived maxilla/mandible (OFMSCs) are highly proliferative with long population doublings relative to those of mesoderm-derived iliac bone (ICMSCs) and long bones (LBMSCs). Therefore, they may readily succumb to n-BP similar to rapidly proliferative cancer cells. Our preliminary studies showed that OFMSCs are indeed more sensitive to n-BP than ICMSCs based on enhanced n-BP uptake, slow elimination from the cytosol, decreased survival and decreased osteogenic differentiation. We hypothesize that sensitivity of OFMSCs to n-BP contributes in part to initiation of ONJ based on site-dependent n-BP uptake, intracellular processing, inhibition of FPP synthase in the mevalonate pathway and consequent loss of prenylation of small GTPase signaling proteins. In aim 1 we will determine how uptake and intracellular trafficking of n-BP in OFMSCs modulates survival and aim 2 will explore BMSC-based therapy to prevent ONJ in a small animal model. The goal is to formulate preventive measures for ONJ. PUBLIC HEALTH RELEVANCE: Bisphosphonate is an effective therapy for bone complications associated with cancer metastasis but a major complication is jaw bone necrosis. We want to understand how jaw bone stem cells readily succumb to effects of bisphosphonate so the complication of jaw necrosis can be prevented.