Calcified Tissue International

, Volume 50, Issue 4, pp 327–335

The extracellular matrix of cartilage in the growth plate before and during calcification: Changes in composition and degradation of type II collagen

  • Mauro Alini
  • Yasumoto Matsui
  • George R. Dodge
  • A. Robin Poole
Laboratory Investigations

DOI: 10.1007/BF00301630

Cite this article as:
Alini, M., Matsui, Y., Dodge, G.R. et al. Calcif Tissue Int (1992) 50: 327. doi:10.1007/BF00301630

Summary

Calcification occurs in the extracellular matrix of the hypertrophic zone of the growth plate when the extra-cellular matrix volume is reduced to a minimum and alkaline phosphatase content is maximal. The present study shows that significant quantitative and qualitative changes occur in the composition and structure of macromolecules in the extracellular matrix before and during calcification in the proximal tibial growth plate of the bovine fetus. These were detected in part by using microchemical and microimmuno-chemical analyses of sequential transverse frozen sections at chemical analyses of sequential transverse frozen sections at defined sites throughout the growth plate. Concentrations of matrix molecules in the extracellular matrix have not previously been determined biochemically. They were measured per unit matrix volume by using combined immunochemical/chemical-histomorphometric analyses. The concentrations within the extracellular matrix of the C-propeptide of type II collagen, aggregating proteoglycan (aggrecan), and hyaluronic acid all progressively increased in the maturing and hypertrophic zones, being maximal (or near maximal) at the time of initiation of mineralization. These results for proteoglycan are contrary to some earlier reports of a loss of proteoglycan prior to mineralization which measured the tissue content of proteoglycan rather than that present in the extracellular matrix, the volume of which is progressively reduced as the growth plate matures. The C-propeptide data provides a quantitative confirmation of previous immunohistochemical studies. Total collagen concentration (measured as hydroxyproline) in the extracellular matrix initially increased through the proliferating and maturing zones but then rapidly decreased in the hypertrophic zone. Immunohistochemical studies revealed that this is associated with the unwinding of the triple helix of type II collagen (previously shown to result from cleavage) which starts in pericellular sites in the zone of maturation (when type X collagen is first synthesized) and then extends throughout the hypertrophic zone. The significance of these matrix changes in the development and mineralization of the growth plate is discussed.

Key words

Growth plateCollageProteoglycansCalcification

Copyright information

© Springer-Verlag New York Inc. 1992

Authors and Affiliations

  • Mauro Alini
    • 1
    • 2
  • Yasumoto Matsui
    • 1
    • 2
  • George R. Dodge
    • 1
    • 2
  • A. Robin Poole
    • 1
    • 2
  1. 1.Joint Diseases LaboratoryShriners Hospital for Crippled ChildrenMontrealCanada
  2. 2.Division of Surgical Research, Department of SurgeryMcGill UniversityMontrealCanada
  3. 3.Department of Orthopaedic Surgery, School of MedicineNagoya UniversityNagoyaJapan
  4. 4.Department of Pathology and Cell BiologyJefferson Medical CollegePhiladelphiaUSA
  5. 5.Joint Diseases LaboratoryShriners HospitalMontrealCanada