Targeting WNT/CaMKII in Osteoarthritis

软骨是覆盖在骨头末端的组织，它使关节无摩擦运动。软骨损失导致疼痛，损害关节，这被称为骨关节炎。骨关节炎与心血管疾病一起，是全世界致残的主要原因；它影响了超过50%的65岁以上人口，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，它使英国经济损失了3600万个工作日，使经济损失了近32亿美元的生产（NICE 2012 OA指导草案）。我们没有任何治疗方法可以阻止骨关节炎的发展，唯一的补救措施是止痛药和关节置换。我们非常需要能够阻止关节软骨退化和控制疼痛的药物。已知介导软骨破裂的分子机制之一是由称为WNTs的分子驱动的。因此，从理论上讲，阻断wnt可以阻止骨关节炎的软骨破坏。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也会导致软骨破坏。我们发现一种叫做CaMKII的分子可以介导WNTs的破坏性作用，但不能介导WNTs的有益作用，从而有机会在保留有益作用的同时阻断WNTs的破坏性作用。此外，我们发现与正常软骨相比，CaMKII在骨关节炎中被强烈激活。最后，已知阻断小鼠的CaMKII会导致疼痛感知的减少。因此，阻断CaMKII可能是同时减少软骨破裂和减少骨关节炎致残症状的绝佳策略。在这个应用中，我们想要了解CaMKII激活在骨关节炎中的功能，并探索CaMKII阻断是否可以减少实验性骨关节炎模型小鼠的软骨破坏和疼痛。虽然我们知道WNT/CaMKII激活会对软骨产生有害影响，但我们忽略了CaMKII是如何工作的，以及CaMKII阻断的“大局”。在第一组实验中，我们将确定软骨中所有由wnt激活的基因，以及哪些基因依赖于CaMKII。从这一分析中，我们将确定可能的，也许是意想不到的，CaMKII阻断的后果，并深入了解CaMKII如何驱动软骨破坏的分子机制。在第二组实验中，我们将看到在患有骨关节炎的小鼠中，从药理学上阻断CaMKII是否会改善关节的完整性以及疼痛症状。这些研究将使我们了解WNT信号在软骨完整性中的作用，并使我们能够靶向CaMKII来防止骨关节炎中的软骨退化。非特异性WNT抑制无法做到这一点，因为WNT信号也介导积极作用，但针对CaMKII可能是可行的，因为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。我们将探讨哪种亚型CaMKII在软骨破裂中最重要。这部分对于设计或选择仅阻断导致软骨破裂的CaMKII变体的新药至关重要。这些研究可以对WNT信号传导如何起作用提供新的见解，可能对骨关节炎的治疗产生重要影响，并使制药行业受益，因为几种CaMKII抑制剂已经可用，并且可以在临床前和临床研究中进行测试。最后，CaMKII和WNT信号在癌症、阿尔茨海默病和心血管疾病中也发挥着重要作用（并且是潜在的靶点），在这一领域的知识肯定也会使这些其他生物医学研究领域受益。

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.