Targeting WNT/CaMKII in Osteoarthritis

腕骨是覆盖骨骼末端的组织，允许关节无摩擦地运动。骨关节炎是一种常见的关节炎，它的主要症状是疼痛和关节炎。骨关节炎与心血管疾病一起是全球残疾的主要原因;它影响超过50%的65岁以上的人口，因此是影响老年人健康的主要因素之一。这是一种致残性疾病，在1999-2000年期间，英国经济损失了3600万个工作日，损失了近32亿英镑的生产（NICE 2012 OA指南草案）。我们没有任何治疗方法可以阻止骨关节炎的进展，唯一的补救措施是止痛药和关节置换。关节软骨的破坏是由一种叫做WNTs的分子所驱动的，而WNTs是关节软骨破坏的一种分子机制。因此，从理论上讲，阻断WNT应该阻止骨关节炎中的软骨破坏。然而，不幸的是，WNTs也介导软骨的重要和基本功能，如细胞增殖，因此这种非选择性阻断WNTs也导致软骨破裂。阻断WNTs的破坏作用同时保留有益作用的机会来自于我们发现一种称为CaMKII的分子介导WNTs的破坏作用，而不是有益作用。此外，我们还发现，与正常软骨相比，骨关节炎中的CaMKII被强烈激活。最后，已知阻断小鼠中的CaMKII导致疼痛感知的减少。因此，阻断CaMKII可能是一种同时减少软骨破坏和减少骨关节炎致残症状的极好策略。在本申请中，我们希望了解CaMKII激活在骨关节炎中的功能，并探索CaMKII阻断是否可以减少小鼠实验性骨关节炎模型中的软骨破坏以及疼痛。虽然我们知道WNT/CaMKII激活会导致软骨中的有害作用，但我们忽略了CaMKII如何工作以及CaMKII阻断的“大局”。在第一组实验中，我们将确定软骨中WNT激活的所有基因，以及哪些基因依赖于CaMKII。从这个分析中，我们将确定可能的，也许是意想不到的，在第二组实验中，我们将观察在患有骨关节炎的小鼠中阻断CaMKII是否会改善其关节的完整性以及疼痛症状。这些研究将导致对WNT信号传导作用的理解。这将使我们能够靶向CaMKII以防止骨关节炎中的软骨退化。这不能用非特异性WNT抑制来完成，因为WNT信号也介导积极作用，但靶向CaMKII是可行的，CaMKII特异性介导破坏性作用。最后，CaMKII以两种不同的形式存在于软骨中。我们将探讨哪种CaMKII亚型在软骨破坏中最重要。这一部分对于设计或选择仅阻断导致软骨破坏的CaMKII变体的新药至关重要。这些研究可以为WNT信号传导如何工作提供新的见解，可能对骨关节炎的治疗产生重要影响，并使制药行业受益，因为已经有几种CaMKII抑制剂可用于临床前和临床研究。最后，CaMKII和WNT信号传导在癌症、阿尔茨海默病和心血管疾病中也起着重要作用（并且是潜在的靶点），并且该领域的知识肯定也将有益于生物医学研究的这些其他领域。

Cartilage is the tissue that covers the ends of the bones and that allows the frictionless motion of the joint. Cartilage loss leads to pain, impairment of the joint, and is called Osteoarthritis. Osteoarthritis is, together with cardiovascular disease, the main cause of disability worldwide; it affects over 50% of the population over the age of 65 and therefore is one of the major factors affecting wellbeing in the elderly. It is a disabling disease, costing the UK economy of 36 million working days in 1999-2000 costing the economy nearly 3.2 billion in lost production (NICE 2012 OA guidance draft). We do not have any treatment that stops progression of osteoarthritis and the only remedies are pain killers and joint replacement. There is a great need for drugs that can stop the degradation of articular cartilage as well as control the pain.One of the molecular mechanisms known to mediate cartilage breakdown is driven by molecules called WNTs. Therefore, theoretically, blocking WNTs should halt cartilage breakdown in Osteoarthritis. Unfortunately, however, WNTs also mediate important and essential functions for cartilage such as cell proliferation, and therefore such non-selective blockade of WNTs has also resulted in cartilage breakdown.The opportunity to block the damaging effects of WNTs while preserving the beneficial ones comes from our discovery that a molecule called CaMKII mediates the damaging effects of WNTs, but not the beneficial ones. In addition, we have discovered that CaMKII is strongly activated in osteoarthritis compared with normal cartilage. Finally, it is known that blocking CaMKII in mice results in reduction of pain perception. Therefore blocking CaMKII could represent a terrific strategy to simultaneously reduce cartilage breakdown and reduce the disabling symptoms of osteoarthritis. In this application we want to understand the function of CaMKII activation in osteoarthritis, and explore if CaMKII blockade can reduce cartilage breakdown as well as pain in an experimental osteoarthritis model in mice. Although we know that WNT/CaMKII activation leads to deleterious effects in cartilage, we ignore how CaMKII works, and the "big picture" of CaMKII blockade. In a first set of experiments we will identify all the genes activated by WNTs in cartilage and which ones are dependent on CaMKII. From this analysis we will identify possible, perhaps unexpected, consequences of CaMKII blockade and gain insight into the molecular mechanisms of how CaMKII drives cartilage breakdown.In a second set of experiments we will see whether blocking CaMKII pharmacologically in mice with osteoarthritis will improve the integrity of their joints as well as the symptoms in terms of pain.These studies will lead to the understanding of the role of WNT signalling in cartilage integrity and will allow us to target CaMKII to prevent cartilage degradation in osteoarthritis. This could not be done with non-specific WNT inhibition because the WNT signal also mediates positive effects, but could be feasible targeting CaMKII, which specifically mediates the damaging ones. Finally, CaMKII is present in cartilage in two different forms. We will explore which sub-type of CaMKII is most important in cartilage breakdown. This part will be crucial for the design or selection of new drugs that block only the variant of CaMKII that causes cartilage breakdown.These studies could give new insight into how WNT signalling works, may have important consequences in the therapy of osteoarthritis, and benefit the pharmaceutical industry, since several CaMKII inhibitors are already available and could be tested in pre-clinical and clinical studies. Finally, CaMKII and WNT signalling also play important roles (and are potential targets) in cancer, Alzheimer's disease, and cardiovascular diseases, and knowledge in this field will certainly benefit also these other fields of biomedical research.