Characterization of a novel T cell activating protein in arthritis

描述（由申请人提供）：我们发现一种新的蛋白，卵泡他汀样蛋白-1 (FSTL-1)，在患有关节炎的小鼠和人类关节中高表达，特别是在滑膜和侵蚀骨的界面。FSTL-1在关节炎进展中的关键作用通过FSTL-1中和抑制疾病得到证实。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来表征FSTL-1及其在小鼠疾病模型中的炎症性关节炎中的作用。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在成年小鼠关节中产生的水平很低。FSTL-1在成骨细胞中由关键骨调节因子TGF-2诱导，FSTL-1是关节炎进展因子，但FSTL-1在正常骨和关节生理中的作用尚未明确。我们将确定在胚胎发生和出生后发育期间关节内负责FSTL-1产生的细胞。我们将利用一只新的FSTL-1亚形态（敲低）小鼠，通过评估FSTL-1低表达对出生和发育至成年期间关节结构、骨形成和结构、骨密度和强度以及软骨完整性的影响，来表征FSTL-1的作用。第二个目的是确定FSTL-1在关节炎中的作用。FSTL-1受IL-12诱导，在关节炎关节中FSTL-1升高，起促炎作用。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。我们将描述骨对关节炎进展的贡献，重点关注FSTL-1作为中介。FSTL-1将通过基因转移过度表达，通过FSTL-1亚型小鼠低表达，并在关节炎期间的不同时间使用抗FSTL-1单克隆抗体中和。我们将比较不同FSTL-1表达对炎性肿块、软骨和骨形成和侵蚀的影响，动态组织形态学测量的骨形成率，显微计算机断层扫描的矿化变化，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IFN-3分泌。FSTL-1通过增强IFN-3信号传导促进炎症。炎症反应依赖于T细胞，因为T细胞耗竭会消除fstl -1诱导的爪子炎症。此外，FSTL-1延长T细胞活化分子CD25的表达。为了表征FSTL-1的T细胞活化特性，我们将确定FSTL-1诱导的T细胞活化表型，FSTL-1是否通过诱导抗凋亡分子来稳定TCR介导的信号，FSTL-1是否直接或间接刺激T细胞，FSTL-1的受体，FSTL-1活性所需的蛋白质结构，以及FSTL-1是否对炎症有额外的作用。FSTL的特征有助于加深对关节炎的认识，并可能提供新的治疗选择。公共卫生相关性：研究将描述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。表征FSTL-1将促进对关节炎的认识，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.