Mechanobiological Mechanism for Inflammatory Bone Loss

描述（由申请人提供）：我们的长期目标是阐明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，其特征在于高分子量聚乙烯（UHMWPE）磨损颗粒诱导的炎性骨丢失和宿主骨-假体结合的丧失。临床观察结果表明，UHMWPE磨损颗粒、变形应变增加和流体压力增加可能是植入物松动的原因。宿主骨-假体界面的机械不稳定性放大UHMWPE磨损颗粒诱导的TNF-α信号传导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神经磷酸酶和NFATcl，并诱导成骨细胞和巨噬细胞中的TNF-α基因。我们的中心假设是，来自UHMWPE磨损颗粒和机械扰动的会聚信号放大了TNF-α基因表达，增强了破骨细胞生成，并通过共激活钙调神经磷酸酶/NFAT轴促进了成骨细胞表型的丧失。我们将模拟假体周围的有效关节空间的机械扰动基板变形，并通过应用类似于人类步态周期的流体流动模式。具体目的是：1）验证UHMWPE磨损颗粒和机械扰动通过共激活成骨细胞中的钙调磷酸酶/NFATd轴来增强TNF-α的产生，2）验证UHMWPE磨损颗粒和机械扰动通过共激活巨噬细胞中的钙调磷酸酶/NFATc 1/TNF-α轴来增强RANKL支持的破骨细胞生成，和3）确定UHMWPE磨损颗粒和机械扰动对成骨细胞表型损失的组合效应。为了实现这些目标，我们将在存在和不存在临床相关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、钙调神经磷酸酶Ap -/-小鼠和TNF-α受体-/-小鼠的原代小鼠成骨细胞进行一系列功能丧失和获得研究、剂量反应和时程实验。可以预见，拟议研究的结果将导致在存在机械扰动的情况下开发生物材料诱导的炎性骨丢失的基于机制的治疗方法。

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.