An in vitro model for abnormal skeletal development in the lysosomal storage diseases

Lysosomal storage diseases such as GM1-gangliosidosis are associated with skeletal abnormalities. Radiological and histological studies, both in human and corresponding animal models, indicate retarded bone formation. Since cartilage maturation leads to bone formation, we developed an in vitro system to study and compare the biological features of cartilage from dogs affected with GM1-gangliosidosis with age-matched controls. Costochondral chondrocytes were grown in monolayer and in agarose culture. Both affected and control cells dedifferentiated in monolayer; however, in agarose culture they re-expressed the chondrocytic phenotype. Cells from affected dogs were enlarged and contained numerous large vacuoles when compared with control cells. This morphology was similar to that seen in vivo. In addition, the affected cells appeared to have a reduction in mitosis and alcian blue staining proteoglycans. Cultures from affected animals contained fewer cells positive for alkaline phosphatase activity. Both affected and control cells expressed collagen types I and II and were positive for the lectin Ricinus communis agglutinin-I. However, the staining of the control culture for type II collagen was more prominent than in the affected cells. These findings suggest that culture of chondrocytes in agarose may be a useful method for studying the biology of cartilage which leads to skeletal abnormalities in lysosomal storage diseases.