An experimental study on the growth of condylar cartilage, using a new vascularized mandible heterotopic transplant model

Abstract

Purpose: To clarify the influence of external and dynamic factors on the growth of mandibular condyle, we developed vascularized mandible heterotopic transplant (VMHT) model. In this report, we discuss histologic changes in the mandibular condylar cartilage in the absence of external factors, using VMHT models. Materials and Methods: Thirty VMHT model using male Lewis rats aged 6 weeks were produced. Six VMHT rats were randomly selected for death at 1, 2, 4, 7, and 14 days after transplantation. We histologically investigated the mandibular condyles of the grafts and controls, the left mandibles of recipient rats. Results: In the transplanted mandibular condyle of VMHT models, the cell arrangement became increasingly irregular with the passage of time, with a concomitant, irregular thickening or thinning of the cartilage layer. There was heterotopic fibrous ossification, extending horizontally under the proliferative cell layer in these regions of thin cartilage. After these events, cartilage cells had disappeared almost completely by 14 days after transplantation. Conclusions: This study indicated that external and dynamic factors are not necessary for the differentiation and proliferation of the condylar cartilage cells. Instead, these factors affect the maintenance of the orderly growth of the cartilage cells and may serve a critical role in the differentiation of undifferentiated mesenchymal cells into chrondroblasts. © 2003 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 61:239-245, 2003