Role of mesenchyme stem cells in the chondro-osseous graft reconstruction of temporomandibular joint for continuous growth of the mandible and midface

Abstract Introduction This study included 37 children who were treated by reconstruction of the temporomandibular joint (TMJ) by chondro-osseous graft from the iliac crest. The role of granular mesenchyme stem cells of the graft is to simulate normal condyle for continuous growth; it is also involved in repair and remodelling of the condyle, as shown by experimental studies conducted on rabbits and by clinical application. This technique has been used in treatment of ankylosis of the TMJ, hemifacial microsomia and traumatic hypoplasia of the condyle. The total number of cases was 37 children: 26 cases with ankylosis of the TMJ (10 girls and 16 boys), 10 children with hemifacial microsomia or first arch dysplasia syndrome (4 girls and 6 boys) and 1 girl with traumatic hypoplasia of the condyle. Their age was between 4 and 13 years (mean, 8.5 years). Follow-up period was between 3 and 10 years; all cases were treated in the Maxillofacial Unit, Surgical Specialty Hospital, Medical City, Baghdad, Iraq. The aim of this research is to discuss the role of mesenchyme stem cells of the chondroosseous graft reconstruction of the TMJ for continuous growth of the mandible and midface. Materials and methods Animal experiments were performed on six rabbits (age, 3 months); TMJ reconstruction was done after excision of the condyle. Three months later, the animals were killed and post-mortem studies macroscopically showed that the chondro-osseous graft was united, remodelled and healed with the ramus; the head shape was similar to that of the control. Results The graft was fixed by a stainless steel wire of 0.5 mm and did not show any corrosive property, infection or resorbtion of the bone surrounding the wire or changes in the colour of the wire. Microscopically, there were four distinct zones or layers; the first layer, consisting of fibrocartilage layer, was thick due to functional demand of hard masticatory processes; the second proliferative layer showed several layers of active round granular mesenchyme stem cells; the third layer showed hypertrophic chondrocyte conversion into osteocyte and the cartilage arranged in a multidirectional fashion due to environmental changes in masticatory function requirements instead of vertical columnar growth pattern as in iliac crest as a weight bearing bone; and the fourth layer was an os-teoid layer with bone marrow spaces in between. Conclusion This valuable research shows the ability of the chondroosseous graft to be a good substitute of the condyle with regard to both growth and func-tion in children.