The Scripps Research Institute, La Jolla, California.
Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan.
Arthritis Rheumatol. 2015 May;67(8):2097-107. doi: 10.1002/art.39178.
Amyloid deposits are prevalent in osteoarthritic (OA) joints. We undertook this study to define the dominant precursor and to determine whether the deposits affect chondrocyte functions.
Amyloid deposition in human normal and OA knee cartilage was determined by Congo red staining. Transthyretin (TTR) in cartilage and synovial fluid was analyzed by immunohistochemistry and Western blotting. The effects of recombinant amyloidogenic and nonamyloidogenic TTR variants were tested in human chondrocyte cultures.
Normal cartilage from young donors did not contain detectable amyloid deposits, but 7 of 12 aged normal cartilage samples (58%) and 12 of 12 OA cartilage samples (100%) had Congo red staining with green birefringence under polarized light. TTR, which is located predominantly at the cartilage surfaces, was detected in all OA cartilage samples and in a majority of aged normal cartilage samples, but not in normal cartilage samples from young donors. Chondrocytes and synoviocytes did not contain significant amounts of TTR messenger RNA. Synovial fluid TTR levels were similar in normal and OA knees. In cultured chondrocytes, only an amyloidogenic TTR variant induced cell death as well as the expression of proinflammatory cytokines and extracellular matrix-degrading enzymes. The effects of amyloidogenic TTR on gene expression were mediated in part by Toll-like receptor 4, receptor for advanced glycation end products, and p38 MAPK. TTR-induced cytotoxicity was inhibited by resveratrol, a plant polyphenol that stabilizes the native tetrameric structure of TTR.
These findings are the first to suggest that TTR amyloid deposition contributes to cell and extracellular matrix damage in articular cartilage in human OA and that therapies designed to reduce TTR amyloid formation might be useful.
淀粉样沉积物在骨关节炎（OA）关节中很常见。我们进行这项研究是为了确定主要的前体，并确定沉积物是否影响软骨细胞的功能。
通过刚果红染色确定人正常和 OA 膝关节软骨中的淀粉样沉积。通过免疫组织化学和 Western blot 分析软骨和滑液中的转甲状腺素蛋白（TTR）。在人软骨细胞培养物中测试重组淀粉样和非淀粉样 TTR 变体的作用。
年轻供体的正常软骨不含可检测的淀粉样沉积物，但 12 个年轻供体的正常软骨样本中有 7 个（58%）和 12 个 OA 软骨样本（100%）在偏光下用刚果红染色呈绿色双折射。TTR 主要位于软骨表面，在所有 OA 软骨样本和大多数老年正常软骨样本中均有检测到，但在年轻供体的正常软骨样本中未检测到。软骨细胞和滑膜细胞不含有大量的 TTR 信使 RNA。正常和 OA 膝关节的滑膜液 TTR 水平相似。在培养的软骨细胞中，只有淀粉样 TTR 变体诱导细胞死亡以及促炎细胞因子和细胞外基质降解酶的表达。淀粉样 TTR 对基因表达的影响部分是通过 Toll 样受体 4、晚期糖基化终产物受体和 p38 MAPK 介导的。白藜芦醇可抑制 TTR 诱导的细胞毒性，白藜芦醇是一种植物多酚，可稳定 TTR 的天然四聚体结构。
这些发现首次表明 TTR 淀粉样沉积导致人类 OA 关节软骨中的细胞和细胞外基质损伤，并且旨在减少 TTR 淀粉样形成的治疗方法可能是有用的。
