Intra-articular injection of parathyroid hormone in the temporomandibular joint as a novel therapy for mandibular asymmetry

Osteoblasts of calvaria induce higher numbers of osteoclasts than osteoblasts from long bone

Several studies have demonstrated the existence of functional differences between osteoclasts harbored in different bones. The mechanisms involved in the occurrence of such a heterogeneity are not yet understood. Since cells of the osteoblast lineage play a critical role in osteoclastogenesis, osteoclast heterogeneity may be due to osteoblasts that differ at the different bone sites. In the present study we evaluated possible differences in the capacity of calvaria and long bone osteoblasts to induce osteoclastogenesis. Osteoblasts were isolated from calvaria and long bone of mice and co-cultured with osteoclast precursors obtained from bone marrow of both types of bone, spleen and peripheral blood. Irrespective of the source of the precursors, a significantly higher number of TRACP-positive multinucleated cells were formed with calvaria osteoblasts. The expression of osteoclastogenesis related genes was analyzed by qPCR. OPG was significantly higher expressed by long bone osteoblasts. The RANKL/OPG ratio and TNF-α gene expression were significantly higher in calvaria osteoblast cultures. OPG added to the culture system inhibited osteoclastogenesis in both groups. Blocking TNF-α had no effect on osteoclastogenesis. Calvaria and long bone osteoblasts were pre-stimulated with VitD3 for 5days. Subsequently, osteoclast precursors were added to these cultures. After a co-culture of 6days, it was shown that VitD3 pre-stimulation of long bone osteoblasts strongly improved their capacity to induce osteoclast formation. This coincided with an increased ratio of RANKL/OPG. Taken together, the data demonstrated differences in the capacity of calvaria and long bone osteoblasts to induce osteoclastogenesis. This appeared to be due to differences in the expression of RANKL and OPG. VitD3 pre-stimulation improved the ability of long bone osteoblasts to induce osteoclast formation. Our findings demonstrate bone-site specific differences in osteoblast-mediated formation of osteoclasts. The data may suggest that the heterogeneity of osteoclasts is partially due to the way the osteoblasts induce their formation.

Three-dimensional longitudinal changes in craniofacial growth in untreated hemifacial microsomia patients with cone-beam computed tomography

INTRODUCTION

The purpose of this study was to evaluate the concept that the affected and contralateral sides do not grow at the same rate in patients with hemifacial microsomia. Changes in the cranial base, maxilla, mandible, and occlusal plane were evaluated on 3-dimensional images from cone-beam computed tomography data in untreated patients.

METHODS

Six patients were classified as having mandibular Pruzansky/Kaban type I, IIA, or IIB hemifacial microsomia. Cone-beam computed tomography (MercuRay; Hitachi, Tokyo, Japan) scans were taken before orthodontic treatment during both growth and postpuberty periods.

RESULTS

The cranial base as defined by the position of the mastoid process was in a different position between the affected and contralateral control sides. The nasomaxillary length or height was shorter on the affected side for all 6 patients with hemifacial microsomia regardless of its severity, and it grew less than on the contralateral control side in 5 of the 6 patients. The occlusal plane angle became more inclined in 4 of the 6 patients. The mandibular ramus was shorter on the affected side in all patients and grew less on the affected side in 5 of the 6 patients. The mandibular body grew slower, the same, or faster than on the control side.

CONCLUSIONS

The cranial base, position of the condyle, lengths of the condyle and ramus, and positions of the gonial angle and condyle can vary between the affected and contralateral control sides of patients with hemifacial microsomia, with the ramus and nasomaxillary length usually growing slower than they grow on the control side. These results suggest that many factors affect the growth rate of the craniofacial region and, specifically, the mandible in patients with hemifacial microsomia.

Effects of intermittent versus continuous parathyroid hormone administration on condylar chondrocyte proliferation and differentiation

Endochondral ossification is a complex process involving chondrogenesis and osteogenesis regulated by many hormones and growth factors. Parathyroid hormone (PTH), one of the key hormones regulating bone metabolism, promotes osteoblast differentiation and osteogenesis by intermittent administration, whereas continuous PTH administration inhibits bone formation. However, the effects of PTH on chondrocyte proliferation and differentiation are still unclear. In this study, intermittent PTH administration presented enhanced effects on condylar chondrocyte differentiation and bone formation, as demonstrated by increased mineral nodule formation and alkaline phosphatase (ALP) activity, up-regulated runt-related transcription factor 2 (RUNX2), ALP, collagen type X (COL10a1), collagen type I (COL1a1), osteocalcin (OCN), bone sialoprotein (BSP), bone morphogenetic protein 2 (BMP2) and osterix (OSX) mRNA and/or protein expression. On the contrary, continuous PTH administration promoted condylar chondrocyte proliferation and suppressed its differentiation, as demonstrated by up-regulated collagen type II (COL2a1) mRNA expression, reduced mineral nodule formation and down-regulated expression of the mRNAs and/or proteins mentioned above. Our data suggest that PTH can regulate condylar chondrocyte proliferation and differentiation, depending on the type of PTH administration. These results provide new insight into the effects of PTH on condylar chondrocytes and new evidence for using local PTH administration to cure mandibular asymmetry.