137: Histochemical, ultrastructural and microchemical studies on growth cartilage in chondrodysplasias

Abstract

Histochemical, ultrastructural and microchemical studies were performed on small growth cartilage biopsies from 21 chondrodys-plastics and 4 children with normal growth. The biopsies were carried out during orthopaedic surgery with the informed consent of the parents. The cartilage was separated from bone by microdissection of freeze-dried sections. Proteoglycans and collagen were extracted, purified and subjected to gel electrophoresis. CNBr collagen peptides were also analyzed in several cases. In Kniest disease the chondrocytes contain metachromatic inclusions. The ultra-structural study discloses large dilatations of the rough endoplasmic reticulum with a fibrillo-granular content. The gel electrophoresis of proteoglycans shows an abnormal supplementary band. In pseudo-achondroplasia the chondrocytes contain large vacuoles bound by rough endoplasmic reticulum with alternately electron-dense and lucent layers. The inclusions are positive for proteins and for tryptophan and resistant to collagenase. The gel electrophoretic pattern of proteoglycans is abnormal. In pycnodysostosis single smooth membrane bound inclusions with granular and lamellar structure are present in chondrocytes. The histochemical studies suggest a phospholipid content. The ultrastructural study of polyepiphyseal dysplasia discloses two distinct forms. In diastrophic dwarfism many cells of the basal zone are degenerated and the capsules have an abnormal organization. The data strongly suggest that the pathophysiology of certain chondrodysplasias is related to proteoglycan and lipid troubles of chondrocytes.