Quantitative Analysis and Localization of mRNA Transcripts of Type I Collagen, Osteocalcin, MMP 2, MMP 8, and MMP 13 During Bone Healing in a Rat Calvarial Experimental Defect Model

Abstract

The study examined the expression of matrix metalloproteinases (MMPs), type I collagen and osteocalcin during bone healing in a rat calvarial experimental defect model. Twelve-week-old male Wistar rats were used. A full-thickness standardized trephine defect was made in the parietal bone, with the rat under anesthesia. RNA was extracted from tissue that filled the original bone defect on days 1 and 3 and in weeks 1, 2, 3, 5, 8, 10, 12, 18, and 24 and processed for quantitative analysis of expression of type I collagen, osteocalcin and matrix metalloproteinases (MMPs) 2, 8, and 13 by using real-time polymerase chain reaction. Alternatively, the rats were fixed by perfusion through the aorta and resected calvaria were processed for in situ hybridization for these molecules. The expression of type I collagen, osteocalcin and MMPs 2 and 13 increased toward week 2 and decreased thereafter, whereas the expression of MMP 8 was the highest on day 1. The mRNA transcripts of type I collagen and osteocalcin were localized in osteoblasts and osteocytes, some of which expressed MMPs 2, 8, and 13. Osteoblasts and osteocytes may play a role in the remodeling of extracellular matrices with MMPs during healing of a defect in bone.

Calcification during bone healing in a standardised rat calvarial defect assessed by micro‐CTandSEM‐EDX

“…MMPs may be involved in calcification in bone development (Sasano et al , ). Our previous study showed that osteoblasts and osteocytes express MMPs 2, 8 and 13 as well as bone matrix proteins such as type I collagen and osteocalcin during bone healing in rat calvarial defects (Itagaki et al , ). Osteoblasts and osteocytes may degrade organic components by using MMPs and play a role in the remodelling of extracellular matrices during healing of bone, contributing to a decrease in organic components, as described above.…”

Long bone fracture repair in mice harboring GFP reporters for cells within the osteoblastic lineage

“…39 Once the early osteoblast in-growth phase is completed, the entire cartilagenous zone is filled with osteoclasts and the intensity of the Col3.6 blue activity diminishes. The advancement of the Col3.6 blue cells presumably is dependent on the MMP13 that are highly expressed in early osteoblastic cells, 40 while the removal phase of the mineralized cartilage is dependent on the activity of the osteoclasts. The removal is critical for the final resolution of the fracture, as studies using agents that block osteoclast activity have a persistent unresorbed mineralized callus.…”

Remodeling of extracellular matrices initiates and advances calcification during development and healing of bones and teeth

“…We investigated MMPs during bone healing using a rat calvarial experimental model. The study examined the expression of MMPs, type I collagen and osteocalcin [26]. A full-thickness standardized trephine defect was made in the parietal bone of 12-week-old rats (Fig.…”