Gel electrophoretic studies on proteoglycans and collagen of abnormal human growth cartilage: proteoglycan abnormalities in pseudoachondroplasia and in Kniest's disease.

Abstract

The microchemical study of growth cartilage biopsies may improve the classification and the genetic advice of some types of growth disturbances and contribute to the understanding of biochemical defects. Small tibial growth cartilage biopsies were performed during orthopedic surgery in cases with achondroplasia, pseudoachondroplasis (three cases), Kniest's disease (two cases), diastrophic dwarfism (two cases), parastrematic dwarfism, pycnodysos tosis, mucolipidosis type III, Blount's disease, and in three normal growing children. Five human fetal cartilages were also studied. The proteoglycans were extracted with 4 M guanidinium chloride. After dialysis against 8 M urea at pH 7, the proteoglycans were obtained by ion chromatography in urea on DEAE-cellulose and submitted to gel electrophoresis on polyacrylamide-agarose gels. The gel electrophoresis of the proteoglycans of growth cartilage of normal growing children gave two metachromatic bands situated close one to another. The proteoglycans extracted from fetal growth cartilage gave a single band with a slightly slower migration. An abnormal gel electrophoretic pattern was found in pseudoachondroplasia and in Kniest's disease. In pseudoachondroplasia a single wide band was found; in overcharged tubes several thin, more rapid bands appeared in addition to the main band. In Kniest's disease three bands were found. In all of the other syndromes studied two normally or almost normally situated bands were present. Small differences in the width and intensity of the bands observed in several cases were difficult to assess. In all cases except mucolipidosis III and Kniest's disease the collagen was extracted by using limited cleavage and solubilization with pepsin, purified and analyzed by polyacrylamide gel electrophoresis. A type of collagen with a single alpha band was found.