Aigner T, Dietz U, Stöss H, von der Mark K
Max-Planck-Society, Clinical Research Units for Rheumatology, University of Erlangen-Nürnberg, Germany.
Lab Invest. 1995 Aug;73(2):236-43.
Osteophytes are neoplastic cartilaginous and osseous protrusions growing at the margins of osteoarthritic joints. Their formation involves complex patterns of cellular proliferation, differentiation, as well as matrix synthesis and turnover that are poorly understood.
Here we report on an experimental approach using in situ hybridization and immunohistology to elucidate pathways of chrondrocyte differentiation in human osteophytes. Ab and cDNA probes for collagen types were used as specific parameters for chondrocyte phenotypes.
In early precartilaginous mesenchymal tissue, cytoplasmic mRNA for alpha 1(I) and alpha 1(III) collagen genes (Col1A1 and Col3A1) were found by in situ hybridization, correlating with the distribution of type I and III collagen as revealed by Ab staining. Strong expression of type II collagen both at mRNA and protein levels was the hallmark of chondrogenic differentiation in the cartilaginous zone of osteophytes. Type II collagen expression increased in all cartilaginous and fibrocartilaginous areas with growth and maturation of osteophytes. The signal intensity obtained after in situ hybridization with a COL2A1 probe was high and corresponded to that obtained in fetal cartilage, whereas normal adult articular cartilage usually did not show measurable type II collagen expression. In fibrocartilaginous areas, the most abundant, but heterogeneous tissue type seen in osteophytes, type II and III collagen mRNA expression overlapped considerably. Type III collagen was scattered, both pericellularly and interterritorially, over the whole osteophyte, excluding bone and chondrocytic cells of the deep zone. The strongest type I collagen expression was seen in bone and in the superficial fibrous layer. In areas of endochondral ossification, large chondrocytes were found expressing type X collagen, a specific marker for hypertrophic chondrocytes.
These results show that discrete stages of cartilage differentiation can be precisely followed in osteophytes using collagen type-specific cDNA probes and Ab as markers. In addition, a fibrocartilaginous chondrocyte phenotype was identified that expresses type II and III, but not type I collagen.
骨赘是在骨关节炎关节边缘生长的肿瘤性软骨和骨性突起。它们的形成涉及细胞增殖、分化以及基质合成和周转的复杂模式，目前对此了解甚少。
在此我们报告一种使用原位杂交和免疫组织学的实验方法，以阐明人类骨赘中软骨细胞分化的途径。用于胶原蛋白类型的抗体和cDNA探针被用作软骨细胞表型的特定参数。
在早期软骨前间充质组织中，通过原位杂交发现α1（I）和α1（III）胶原基因（Col1A1和Col3A1）的细胞质mRNA，这与抗体染色显示的I型和III型胶原的分布相关。II型胶原在mRNA和蛋白质水平的强表达是骨赘软骨区软骨形成分化的标志。随着骨赘的生长和成熟，II型胶原表达在所有软骨和纤维软骨区域增加。用COL2A1探针进行原位杂交后获得的信号强度很高，与胎儿软骨中获得的信号强度相当，而正常成人关节软骨通常不显示可测量的II型胶原表达。在纤维软骨区域，这是骨赘中最丰富但异质性的组织类型，II型和III型胶原mRNA表达有相当大的重叠。III型胶原在整个骨赘中呈散在分布，在细胞周围和区域间，不包括深部区域的骨和软骨细胞。I型胶原表达最强的区域见于骨和浅表纤维层。在软骨内骨化区域，发现大的软骨细胞表达X型胶原，这是肥大软骨细胞的特异性标志物。
这些结果表明，使用特定类型胶原的cDNA探针和抗体作为标志物，可以在骨赘中精确追踪软骨分化的离散阶段。此外，还鉴定出一种表达II型和III型但不表达I型胶原的纤维软骨细胞表型。
