THE INSULIN-LIKE GROWTH FACTOR AXIS IN OSTEOARTHRITIS

描述（由申请人提供）：胰岛素样生长因子（IGF）是关节软骨中基质稳态的关键调节因子，并且已经提出骨关节炎（OA）期间代谢失调是由于IGF不敏感性。IGF结合蛋白（IGFBPs）可以促进或抑制IGF活性，也可以独立于IGF发挥作用。申请人的初步研究表明，IGFBP-3在OA期间增加，如在未培养的OA软骨提取物中直接评估的。工作假说认为IGFBP-2定位于细胞膜上，起维持基质稳态的作用。软骨中的IGFBP-3含量在OA期间增加2-3倍，但IGFBP-2不增加。IGFBP-3可以与软骨细胞上其自身特异性的高亲和力蛋白结合，也可以与丰富的细胞外锚定位点结合。后者包括纤连蛋白（FN）基质中的位点，其中锚定的IGFBP-3起隔离IGF的作用。IGFBP-3的总体作用是限制IGF作用和软骨修复。具体目标是：（1）在人软骨中OA进展期间IGFBP-3、IGFBP-2、IGF-I和II以及IGF受体（IGF-IR）的定位（免疫组织化学研究），并在适当情况下，可能共同定位的IGF与BP-3和FN（通过免疫电子显微镜）;检查体外IGFBP-3和IGF的选定相互作用;并检测分离的软骨细胞中是否存在高亲和力IGFBP-3结合蛋白（推定受体）;（2）IGF轴各组分水平和合成的变化（IGFBP，IGFs，IGFIR），以及推定的IGFBP-3锚，纤连蛋白，在OA过程中;和（3）IGFBP的功能，如通过它们对基质合成和细胞分裂的影响所评估的。在OA期间，通过培养人软骨切片并通过添加IGF和各种IGF类似物来检查IGFBP的作用，来确定驻留IGFBP的总体功能，所述IGF和各种IGF类似物已经突变以选择性地失去其结合IGFBP的能力，或仅失去其结合IGF受体的能力。此外，反义寡脱氧核苷酸将用于阻断IGFBP-3，以及在软骨基质透化后阻断抗体。长期目标是设计合理的方案，将IGF轴向修复模式转移，以确定人类OA管理的治疗候选者。

DESCRIPTION (provided by applicant): The Insulin-like growth factors (IGFs) are key regulators of matrix homeostasis in articular cartilage, and it has been proposed that dysregulation of metabolism during osteoarthritis (OA) is due to IGF insensitivity. The IGF binding proteins (IGFBPs) can either promote or inhibit IGF activity or may act independently of IGFs. Preliminary studies by the applicant indicate that IGFBP-3 is increased during OA, as assessed directly in extracts of uncultured OA cartilage. The working hypothesis states that IGFBP-2 is Iocated on the cell membrane and acts to maintain matrix homeostasis. IGFBP-3 content in cartilage, but not IGFBP-2, increases 2-3 fold during OA. IGFBP-3 can bind to its own specific, high affinity proteins on the chondrocyte and can also bind to abundant extracellular anchoring sites. The latter include sites in the fibronectin (FN) matrix, where anchored IGFBP-3 acts to sequester IGFs. The overall effect of IGFBP-3 is to restrict IGF action and repair of cartilage. The Specific Aims are: (1) the localization of IGFBP-3, IGFBP-2, IGF-I and II and the IGF receptor (IGF-IR) during OA progression in human cartilage (immunohistochemical studies) and, as appropriate, the possible co-localization of IGF with BP-3 and FN (by immunoelectron microscopy); to examine selected interactions of IGFBP-3 and IGF in vitro; and to test isolated chondrocytes for the presence of high affinity IGFBP-3 association proteins (putative receptors); (2) changes in the levels and synthesis of the components of the IGF axis (IGFBPs, IGFs, IGFIR), as well as in the putative IGFBP-3 anchor, fibronectin, during OA; and (3) the function of the IGFBPs, as assessed by their effects on matrix synthesis and cell division. The overall function of resident IGFBPs will be determined during OA by culturing human cartilage slices and examining the role of IGFBPs by addition of IGFs and various IGF analogs that have been mutated to selectively lose their capacity to bind IGFBPs, or to lose only their ability to bind to the IGF receptor. In addition, antisense oligodeoxynucleotides will be used to block IGFBP-3, as well as blocking antibodies following permeabilization of the cartilage matrix. The long-term goal is to design plausible protocols to shift the IGF axis towards a repair mode so as to define therapeutic candidates for human OA management.