The Formation of the Epiphyseal Bone Plate Occurs via Combined Endochondral and Intramembranous-Like Ossification.

Ángela Fernández-Iglesias,Fernando Santos,Rocío Fuente,Laura Alonso-Durán,José Manuel López,Helena Gil-Peña

doi:10.3390/ijms22020900

Abstract

The formation of the epiphyseal bone plate, the flat bony structure that provides strength and firmness to the growth plate cartilage, was studied in the present study by using light, confocal, and scanning electron microscopy. Results obtained evidenced that this bone tissue is generated by the replacement of the lower portion of the epiphyseal cartilage. However, this process differs considerably from the usual bone tissue formation through endochondral ossification. Osteoblasts deposit bone matrix on remnants of mineralized cartilage matrix that serve as a scaffold, but also on non-mineralized cartilage surfaces and as well as within the perivascular space. These processes occur simultaneously at sites located close to each other, so that, a core of the sheet of bone is established very quickly. Subsequently, thickening and reshaping occurs by appositional growth to generate a dense parallel-fibered bone structurally intermediate between woven and lamellar bone. All these processes occur in close relationship with a cartilage but most of the bone tissue is generated in a manner that may be considered as intramembranous-like. Overall, the findings here reported provide for the first time an accurate description of the tissues and events involved in the formation of the epiphyseal bone plate and gives insight into the complex cellular events underlying bone formation at different sites on the skeleton.

Highlights

The epiphyseal bone plate is a flat bony structure located between the epiphysis and the metaphysis of the long bones [1]
Despite its relatively homogeneous appearance, three zones without clearly defined borders could be recognized in the cartilage: (1) An outer cap of flatter chondrocytes located at the epiphyseal end; (2) an extensive intermediate zone with oval chondrocytes oriented randomly; and (3) a deep zone with chondrocytes aligned in columns
Zones 1 and 3 corresponded to the prospective articular and metaphyseal growth plate cartilages, respectively, whereas zone 2 corresponded to the epiphyseal cartilage that guides bone tissue expansion to establish the secondary ossification center

Summary

Introduction

The epiphyseal bone plate is a flat bony structure located between the epiphysis and the metaphysis of the long bones [1]. The mode of ossification substantially changes when the front nears the region facing the resting cartilage of the growth plate At this location, cartilage is directly transformed into compact bone tissue to generate a flat plate with several layers of densely packed bony lamellae oriented transverse to the long axis of the bone [2]. It is oriented perpendicular to the long axis of the bone, an unusual orientation since most bone structures are oriented such that they are stronger in the direction in which they support load [4] It develops very quickly, so that transformation of cartilage into bone occurs faster than anywhere else in the bone [5]. It is formed in the region immediately adjacent to the resting cartilage of the growth plate and this close spatial proximity suggests that the latter could exert a great deal of influence on its development [6]

Methods

Results

Conclusion