Establishment of a novel dwarf rat strain: cartilage calcification insufficient (CCI) rats

The molecular mechanism research of cartilage calcification induced by osteoarthritis

To explore the molecular mechanism of cartilage calcification induced by osteoarthritis (OA) based on distal-less homeobox gene 5 – alkaline phosphatase – integrin-binding sialoprotein – ecto-nucleotide pyrophosphatase 1 (DLX5-ALPL-IBSP-ENPP1) signal axis. Twenty-four rabbits were selected to build models of cartilage calcification induced by OA and randomly divided into 3 groups. The first group was the normal group whose rabbits were injected into 0.9% saline (0.3 mL), and the second group was model group. The third group was model group whose rabbits were injected into DLX5 antibody by caudal vein. Alizarin red calcium staining was used to analyze calcium deposition of cartilage matrix. Immunohistochemical staining was used to analyze the relative expression levels of proteins DLX5 and ENPP1, and western blot was used to analyze the DLX5, ALPL, IBSP, and ENPP1 expression. Calcium salt precipitation was the most serious, and the calcification area increased in the model group. Although calcified nodules appeared in the anti-DLX5 group, they were relatively few. Immunohistochemical staining analysis showed that the protein DLX5 located in the nucleus and the protein ENPP1 located in the extracellular matrix. Western blot analysis showed that the expressions of proteins DLX5, ALPL, IBSP, and ENPP1 were the highest in OA Model group than that of NC group, followed by anti-DLX5 group. The proteins DLX5, ALPL, IBSP, and ENPP1 can promote cartilage calcification induced by OA based on DLX5-ALPL-IBSP-ENPP1 signal axis.

Immunohistochemical and ultrastructural evaluation of matrix components in mandibular condylar cartilage in comparison with growth plate cartilage in cartilage calcification insufficient rats

Matrix components of growth plate cartilage and mandibular condylar cartilage were immunohistochemically analyzed in cartilage calcification insufficient (CCI) rats, a model for dwarf rats. Reduction in total tibial length, elongation of growth plate, and appearance of noncartilaginous regions in the growth plate were observed in CCI rats. Immunoreactivity for type I collagen and hyaluronic acid (HA) staining were observed in the noncartilaginous region. However, weak immunoreactivity was observed for aggrecan, collagen types II and X, and decorin in this region. Transmission electron microscopy indicated that the noncartilaginous region showed a loose network of thin collagen fibrils, indicating that HA is predominantly involved in capturing space of the noncartilaginous region in the growth plate. Meanwhile, the mandibular condylar cartilage in CCI rats also showed elongation of the cartilaginous region and had a noncartilaginous region, predominantly comprising thick collagen fibrils. The structural difference between the two types of cartilages in CCI rats may be due to the presence of the fibrous cell zone and the fibrocartilaginous nature of the normal condylar cartilage. Additionally, the reduction in mandibular length was relatively less than the reduction in tibial length. The outline of the condylar process showed only slight abnormality. These results suggest that the condylar cartilage compensated its growth by supplying the characteristic noncartilaginous region effectively and may adapt to severe structural changes observed in CCI rats.

The aggrecanopathies; an evolving phenotypic spectrum of human genetic skeletal diseases

The large chondroitin sulphated proteoglycan aggrecan (ACAN) is the most abundant non-collagenous protein in cartilage and is essential for its structure and function. Mutations in ACAN result in a broad phenotypic spectrum of non-lethal skeletal dysplasias including spondyloepimetaphyseal dysplasia, spondyloepiphyseal dysplasia, familial osteochondritis dissecans and various undefined short stature syndromes associated with accelerated bone maturation. However, very little is currently known about the disease pathways that underlie these aggrecanopathies, although they are likely to be a combination of haploinsufficiency and dominant-negative (neomorphic) mechanisms. This review discusses the known human and animal aggrecanopathies in the context of clinical presentation and potential disease mechanisms.