Morphological evaluation of cartilage development in the distal femoral epiphysis of human fetuses

Abstract

Introduction: The epiphysis cartilage in the knee joint has been widely studied in recent decades due to the joint complexity and its clinical importance. However, there is little information about morphological and ultrastructural aspects of normal cartilage development of the knee joint, particularly in human fetuses of different age, which could contribute to a better understanding of diseases and malformations during development. Materials and Methods: This research was performed with 20 human fetuses covering the age range 16 to 31 weeks of intrauterine life, which were divided into 4 groups (n = 5). Morphometric analysis of the distal femoral epiphysis cartilage were realized for the parameters: chondrocytes area, percent density of chondrocyte and extracellular matrix (ECM), as well as qualitative analysis of the distribution, organization and characterization of collagen fibers making use of Picrosirius staining under analysis with polarized light. Results: It was verified that the chondrocytes area and density of ECM increased with advancing age, while the density of chondrocytes decreased. Also in the epiphyseal region, immature cartilage of younger fetuses, initially with characteristics of a proliferation zone starts to present, in older age fetuses, characteristics of a maturation zone, with larger chondrocytes and more distant from each other. In the epiphysis surface the organization and orientation of the collagen ibers changed in different groups, from an irregular orientation in the younger fetuses group, to a pantograph organization in the most developed fetuses group. Conclusion: During fetal development, the maturation of cartilage combines increasing ECM percent density and changes in the collagen fibers organization and orientation, contributing to the required cartilage properties for each stage of its development.