An immunohistochemical study of cartilage during distraction osteogenesis in rabbits

Abstract

Ossification during distraction osteogenesis is generally classified into two types: intramembranous and endochondral. The development of intramembranous or endochondral bone formation is influenced by different conditions. It is unknown whether the cartilage in the distraction gap is transformed into the new bone or not. The purpose of our experimental work was to investigate the morphological features of the ossification that occurs during the transition of cartilage to bone in mandibular distraction osteogenesis using the rabbit model. The cortical osteotomy were performed, and the custom-made devices were applied. Immediately after surgery, the devices were lengthened 0.25 mm every 12 hours for 10 days. After the lengthening was completed, 4 rabbits were sacrificed and then same number at 5- and 10-day. Histological staining techniques together with immunohistochemistry were performed. Apoptotic cells were identified by means of an in situ detection assay for nuclear DNA fragmentation using a modified TUNEL procedure. The cartilage in the distraction gap ossifies in the following two patterns: endochondral ossification and trans-chondroid bone formation. Apoptotic cells were discerned in the hypertrophic chondrocytes. The apoptosis is implicated to play a role in the process of the transition of the cartilage to bone in mandibular distraction osteogenesis.