Mechanobiological Mechanism for Inflammatory Bone Loss

描述（由申请人提供）：我们的长期目标是阐明导致假体周围骨丢失的机械生物学机制。髋关节置换术的长期临床成功受到假体松动的限制，假体松动的特征是超高分子量聚乙烯（UHMWPE）磨损颗粒引起的炎症性骨丢失和宿主骨-假体整合的丧失。临床观察表明，超高分子量聚乙烯磨损颗粒、变形应变增加和流体压力增加可能是导致种植体松动的原因。宿主骨-假体界面的机械不稳定性放大超高分子量聚乙烯磨损颗粒诱导的TNF-a信号的机械生物学机制同样未知。我们的初步数据表明，临床相关的UHMWPE磨损颗粒、变形应变和流体剪切应力激活钙调磷酸酶和NFATcl，诱导成骨细胞和巨噬细胞中TNF-a基因的表达。我们的中心假设是，来自UHMWPE磨损颗粒的汇聚信号和机械扰动通过共同激活钙调神经磷酸酶/NFAT轴，放大了TNF-a基因的表达，增强了破骨细胞的发生，并促进了成骨细胞表型的丧失。我们将通过基板变形和应用类似于人类步态周期的流体流动模式来模拟有效关节空间中的假体周围机械扰动。具体目的是：1)验证UHMWPE磨损颗粒和机械扰动通过共同激活成骨细胞中的钙调磷酸酶/NFATd轴来放大TNF-a的产生；2)验证UHMWPE磨损颗粒和机械扰动通过共同激活巨噬细胞中的钙调磷酸酶/NFATc1/TNF-a轴来增强rankl支持的破骨细胞生成；3)确定UHMWPE磨损颗粒和机械扰动对成骨细胞表型丧失的组合作用。为了实现这些目标，我们将在存在和不存在临床相关的UHMWPE磨损颗粒、变形应变和流体剪切应力的情况下，使用药理学抑制剂、NFATcl siRNA和来源于正常小鼠的原代小鼠成骨细胞、钙调磷酸酶Ap -/-小鼠和TNF-a受体-/-小鼠进行一系列功能丧失和功能获得的研究、剂量反应和时间过程实验。据设想，该研究的结果将导致在机械扰动存在的情况下，基于机制的生物材料诱导的炎症性骨质流失治疗的发展。

DESCRIPTION (provided by applicant): Our long-range goal is to elucidate a mechanobiological mechanism responsible for periprosthetic bone loss. The long-term clinical success of hip arthoplasties is limited by prosthesis loosening which is characterized by ultrahigh molecular weight polyethylene (UHMWPE) wear particle-induced inflammatory bone loss and loss of host bone-prosthesis integration. Clinical observations have implicated UHMWPE wear particles, increased deformational strains and increased fluid pressure as possible causes for the implant loosening. The mechanobiological mechanism by which mechanical instability at the host bone-prosthesis interface amplifies UHMWPE wear particle-induced TNF-a signaling is likewise unknown. Our preliminary data indicate that clinically relevant UHMWPE wear particles, deformational strains and fluid shear stress activate calcineurin and NFATcl and induce the TNF-a gene in osteoblasts and macrophages. Our central hypothesis is that converging signals from UHMWPE wear particles and mechanical perturbation amplify TNF-a gene expression, augment osteoclastogenesis and promote the loss of osteoblastic phenotypes by co-activating the calcineurin/NFAT axis. We will simulate the periprosthetic mechanical perturbation in effective joint space by substrate deformation and by applying fluid flow patterns resembling a human gait cycle. Specific Aims are 1) To verify that UHMWPE wear particles and mechanical perturbation amplify TNF- a production by co-activating the calcineurin/NFATd axis in osteoblasts, 2) To verify that UHMWPE wear particles and mechanical perturbation enhance RANKL-supported osteoclastogenesis by co-activating the calcineurin/NFATc1/TNF-a axis in macrophages, and 3) To determine the combinatorial effect of UHMWPE wear particles and mechanical perturbation on loss of osteoblastic phenotypes. In order to accomplish these aims, we will conduct a series of loss- and gain-of-function studies, dose response and time course experiments using pharmacological inhibitors, NFATcl siRNA and primary mouse osteoblasts derived from normal mice, calcineurin Ap -/- mice and TNF-a receptor -/- mice in the presence and absence of clinically relevant UHMWPE wear particles, deformational strains and fluid shear stress. It is envisioned that resrults from the proposed study will lead to the development of mechanism-based treatments for biomaterial- induced inflammatory bone loss in the presence of mechanical perturbations.