Expression Patterns of Matrix Metalloproteinases and Vascular Endothelial Growth Factor During Epiphyseal Ossification

Abstract

ABSTRACT:In situ hybridization studies allowed for the localization of three MMPs and the angiogenic factor VEGF during secondary ossification. MMPs were widely expressed during ossification of the secondary center, whereas expression of VEGF was restricted to later stages. Introduction:The spatiotemporal expression patterns of the matrix metalloproteinases gelatinase-B (MMP-9), collagenase-3 (MMP-13), and membrane-type 1 metalloproteinase (MMP-14) and the angiogenic peptide vascular endothelial growth factor (VEGF) were studied during development of the proximal epiphysis of the rat tibia. Materials and Methods: Cell expression was analyzed by in situ hybridization. Studies on osteoclastic activity, matrix mineralization, cell proliferation, and vascular progression were also performed. Results: MMP-9, MMP-13, and MMP-14 were expressed in discrete perichondrial cells that gave way to sites of intrachondral canal formation. High expression levels for the three MMPs were found at the blind ends of advancing intrachondral canals and at the expanding borders of the marrow space. Signals for MMP-9 and MMP-13 were in close proximity but did not overlap, whereas MMP-14 was expressed in both MMP-9 + and MMP-13 + cells. VEGF was not expressed during formation of intrachondral vascular canals but was observed in hypertrophic chondrocytes during formation of the bone marrow cavity. Conclusions: Expression of MMPs and VEGF are constant events during development of the secondary ossification center. We propose that MMPs are involved in targeting proteolytic activity during epiphyseal development. VEGF is not expressed during early formation of vascular canals, but it may have a role in the formation of the bone marrow cavity.

Epidermal Growth Factor Receptor (EGFR) Signaling Regulates Epiphyseal Cartilage Development through β-Catenin-dependent and -independent Pathways

“…Their SOCs were eventually formed through an alternative mechanism bypassing the cartilage canal step. All these MMPs were found to be expressed abundantly at the blind ends of canals and at the expanding borders of the marrow space in the epiphyseal region during SOC development (34). Our studies demonstrate that EGFR signaling in chondrocytes supports cell autonomous action for these MMPs, particularly those synthesized by hypertrophic chondrocytes adjacent to the marrow space.…”

Developmental Mechanisms in Articular Cartilage Degradation in Osteoarthritis

“…Alkaline phosphatase shows the most pronounced expression also in hypertrophic chondrocytes [64, 65]. This phenotypic modification in growth plate chondrocytes is associated with dramatic alteration in regulatory gene expression, namely, upregulation of growth factors such as TGF β 1 and -3 [35, 50], BMP-2, -4, -6, and -7 [39, 40, 66–68], connective tissue growth factor (CTGF) [69], vascular endothelial growth factor (VEGF) [59, 70], and Indian hedgehog (Ihh) [35, 71, 72]. Inflammation-related cytokine IL-1 expression also has been observed only in the hypertrophic chondrocytes [73].…”

Bone development in the femoral epiphysis of mice: The role of cartilage canals and the fate of resting chondrocytes

“…Here, it is concluded that the macrophages enable the advancement of the canals within the chondroepiphysis and this process is coupled with programmed cell death of several chondrocytes. This early step of excavation is induced by the expression of several matrix metalloproteinases (MMPs) that cleave components of the hyaline cartilage matrix Lee et al, 2001;Á lvarez et al, 2005a;Melton et al, 2006) and this is illustrated by a weakly toluidine blue stained layer immediately in front of the canal tips. Expression of MMPs is a key event during early canal formation (Á lvarez et al, 2005a) and mice, deficient in MMPs, show both severely impaired vascularization and delayed ossification of chondroepiphysis (Holmbeck et al, 1999;Zhou et al, 2000).…”