A new vascularized mandible heterotopic transplant model for studies on the growth of condylar cartilage.

PURPOSE We developed a vascularized mandibular heterotopic transplant (VMHT) model to allow the observation of condylar cartilage growth in the absence of external and dynamic factors, such as mastication. MATERIALS AND METHODS In VMHT, we performed a transplantation between 2 age-matched inbred rats (male Lewis rats aged 6 weeks). The hemimandibular tissue, with the common carotid artery and external jugular vein as vascular pedicle, was harvested from the donor rat and transplanted to the neck of the recipient rat with the use of vascular anastomosis under an operating microscope. To evaluate the stability of VMHT, we investigated both the weight change of the recipient rats and the blood circulatory conditions of the grafts via the radioactive microsphere method, laser Doppler blood flowmeter, and angiography. RESULTS Although the body weight of the recipient rats decreased immediately after transplantation, these values subsequently increased, indicating a good nutritional environment in the recipient rat. Also, the VMHT graft tissue and the mandibular condyle had favorable blood circulation, equivalent to normal conditions. CONCLUSIONS In VMHT, transplantation between the 2 age-matched inbred rats using anastomosis of the similar blood vessels enables us to minimize the influences of genetic factors, hemodynamics, hormones, and other external factors. Our investigation indicated that the transplant possessed favorable growth conditions, equivalent to the environment of the endogenous mandibular condyle. Thus, we are able to maintain conditions similar to the normal environment of the mandibular condyle. This model will be very useful in future investigations of the influences of external and functional factors on chondrogenesis and enchondral ossification of the mandibular condyle.