Characterization of a novel T cell activating protein in arthritis

描述(申请人提供)：我们发现了一种新的蛋白质，卵泡抑素样蛋白-1(FSTL-1)，在关节炎小鼠和人类的关节中高度表达，特别是在滑膜血管血管和侵蚀骨的交界处。通过中和FSTL-1对疾病的抑制，证实了FSTL-1在关节炎进展中的关键作用。我们的研究表明，FSTL-1是T细胞的共刺激因子。我们将通过对T细胞活化的详细研究，确定FSTL-1及其在炎症性关节炎小鼠疾病模型中的作用。第一个目的是确定FSTL-1在正常关节中的作用。我们的研究表明，FSTL-1在成年小鼠关节中的水平很低。FSTL-1在成骨细胞中是由关键的骨调节因子-2诱导的，FSTL-1是一种关节炎进展因子，但FSTL-1在正常骨和关节生理中的作用尚不清楚。我们将确定在胚胎发育和出生后发育期间关节内负责产生FSTL-1的细胞。我们将使用一种新的FSTL-1亚型(基因敲除)小鼠来表征FSTL-1的作用，方法是评估FSTL-1低表达对出生和发育到成年的关节结构、骨形成和结构、骨密度和强度以及软骨完整性的影响。第二个目的是确定FSTL-1在关节炎中的作用。FSTL-1是由IL-12诱导的，在关节炎关节中FSTL-1升高，发挥促炎作用。这些发现表明，骨骼不仅是关节炎的目标，而且在关节破坏中起着积极的作用。我们将描述骨在关节炎进展中的作用，重点是FSTL-1作为介体。FSTL-1将通过基因转移过度表达，使用FSTL-1亚型小鼠进行低表达，并在关节炎期间的不同时间使用抗FSTL-1单抗进行中和。我们将比较不同的FSTL-1表达对炎性脉络膜、软骨和骨的形成和侵蚀的影响，动态组织形态计量学的骨形成率，显微计算机断层扫描矿化的变化，破骨细胞活性和基质细胞的变化，以及FSTL-1诱导的促炎细胞因子的表达。第三个目的是确定FSTL-1如何激活T细胞并诱导干扰素-3的分泌。FSTL-1通过增强干扰素-3信号通路促进炎症反应。炎症反应依赖于T细胞，因为T细胞耗尽消除了FSTL-1诱导的爪部炎症。此外，FSTL-1可延长T细胞活化分子CD25的表达。为了确定FSTL-1的T细胞激活特性，我们将确定FSTL-1诱导的T细胞激活表型，FSTL-1是否通过诱导抗凋亡分子来稳定TCR介导的信号转导，FSTL-1是直接还是间接刺激T细胞，FSTL-1的受体，FSTL-1活性所必需的蛋白质结构，以及FSTL-1是否具有额外的炎症作用。FSTL的特征--促进对关节炎的了解，并可能提供新的治疗选择。公共卫生相关性：研究将确定一种新的关节炎进展介质FSTL-1在关节炎和关节发展中的作用。FSTL-1的特征将促进对关节炎的了解，并可能提供新的治疗选择。

DESCRIPTION (provided by applicant): We have discovered that a novel protein, follistatin-like-1 (FSTL-1), is highly expressed in the joints of mice and humans with arthritis, especially at the interface of synovial pannus and eroding bone. A key role for FSTL- 1 in arthritis progression was confirmed by suppression of disease by FSTL-1 neutralization. Our studies indicate that FSTL-1 is a co-stimulator of T cells. We will characterize FSTL-1 and its contribution to inflammatory arthritis in mouse models of disease, with detailed study of T cell activation. The first Aim is to determine the role of FSTL-1 in the normal joint. Our studies demonstrate that FSTL-1 is produced at low levels in the adult mouse joint. FSTL-1 is induced in osteoblasts by TGF-2, a key bone regulatory factor, and FSTL-1 is an arthritis progression factor, but the role of FSTL-1 in normal bone and joint physiology is not characterized. We will determine the cells responsible for FSTL-1 production within the joint during embryogenesis and post-natal development. We will characterize the role of FSTL-1 using a new FSTL-1 hypomorphic (knockdown) mouse by assessing the effect of FSTL-1 under-expression on joint structure at birth and during development to adulthood, bone formation and architecture, bone density and strength, and cartilage integrity. The second Aim is to determine the contribution of FSTL-1 to arthritis. FSTL-1 is induced by IL-12 and FSTL-1 is increased in arthritic joints, where it plays a pro-inflammatory role. These findings suggest that bone is not solely a target of arthritis, but plays an active role in joint destruction. We will characterize the contribution of bone to arthritis progression, focusing on FSTL-1 as a mediator. FSTL-1 will be over-expressed by gene transfer, under-expressed using the FSTL-1 hypomorphic mouse, and neutralized at various times during arthritis using anti-FSTL-1 monoclonal antibody. We will compare the effects of varying FSTL-1 expression on the inflammatory pannus, cartilage and bone formation and erosion, bone formation rate by dynamic histomorphometry, changes in mineralization by micro computer tomography, changes in osteoclastic activity and matrix cells, and expression of pro-inflammatory cytokines induced in response to FSTL-1. The third Aim is to determine how FSTL-1 activates T cells and induces IFN-3 secretion. FSTL-1 promotes inflammation by enhancing IFN-3 signaling. The inflammatory response is dependent on T cells, as T cell depletion abolishes FSTL-1-induced paw inflammation. Furthermore, FSTL-1 prolongs expression of the T cell activation molecule, CD25. To characterize the T cell activating properties of FSTL-1, we will determine the T cell activation phenotype induced by FSTL-1, whether FSTL-1 stabilizes TCR mediated signaling by inducing anti-apoptotic molecules, whether FSTL-1 stimulates T cells directly or indirectly, the receptor for FSTL-1, the protein structure necessary for FSTL-1 activity, and whether FSTL-1 has additional actions on inflammation. Characterization of FSTL- advance understanding of arthritis and may provide new treatment options. PUBLIC HEALTH RELEVANCE: studies will characterize the role in arthritis and joint development of a novel mediator of arthritis progression, FSTL-1. Characterization of FSTL-1 will advance understanding of arthritis and may provide new treatment options.