The aim of this study was to identify changes in cartilage intermediate layer protein/nucleotide pyrophosphohydrolase (CILP/NTPPH) expression in articular cartilage during aging. Adult (3‐4 years old) and young (7‐10 days old) porcine articular hyaline cartilage and fibrocartilage were studied by Northern blot analysis, in situ hybridization, and immunohistochemistry using a complementary DNA (cDNA) probe encoding porcine CILP/NTPPH and antibody to a synthetic peptide corresponding to a CILP/NTPPH sequence. Northern blot analysis of chondrocytes showed lower expression of CILP/NTPPH messenger RNA (mRNA) in young cartilage than in adult cartilage. In adult cartilage, extracellular matrix from the surface to the middeep zone was immunoreactive for CILP/NTPPH, especially in the pericellular matrix surrounding the middeep zone chondrocytes. In young cartilage, chondrocytes were moderately immunoreactive for CILP/NTPPH throughout all zones except the calcified zone. The matrix of young cartilage was negative except in the superficial zone. In young cartilage, CILP/NTPPH mRNA expression was undetectable. In adult cartilage, chondrocytes showed strong mRNA expression for CILP/NTPPH throughout middeep zones. Protein and mRNA signals were not detectable below the tidemark. CILP/NTPPH secretion into matrix around chondrocytes increases with aging. In this extracellular site it may generate inorganic pyrophosphate and contribute to age‐related calcium pyrophosphate dihydrate crystal deposition disease.
本研究旨在识别在衰老过程中关节软骨中软骨中间层蛋白/核苷酸
焦磷酸酶(CILP/N
TPPH)表达的变化。通过Northern印迹分析、原位杂交和免疫组织
化学,使用编码猪CILP/N
TPPH的互补DNA(cDNA)探针和对应CILP/N
TPPH序列的合成肽
抗体,研究了成年(3-4岁)和幼年(7-10天)猪关节透明软骨和纤维软骨。Northern印迹分析显示,幼年软骨细胞中CILP/N
TPPH信使RNA(mRNA)的表达低于成年软骨。在成年软骨中,从表面到中深层区的细胞外基质对CILP/N
TPPH呈免疫反应性,特别是在围绕中深层区软骨细胞的细胞周基质中。在幼年软骨中,除
钙化区外,所有区的软骨细胞对CILP/N
TPPH呈现中度免疫反应性。幼年软骨的基质除表层区外均为阴性。在幼年软骨中,CILP/N
TPPH mRNA表达无法检测到。在成年软骨中,软骨细胞在中深层区表现出强烈的CILP/N
TPPH mRNA表达。蛋白和mRNA信号在潮线下方无法检测到。CILP/N
TPPH向软骨细胞周围的基质分泌随着衰老而增加。在这个细胞外部位,它可能产生无机
焦磷酸盐,并有助于与年龄相关的二
水合
钙焦磷酸盐晶体沉着病。