IADR Abstract Archives
Effect of Varying Doses of Intermittent PTH on the TMJ
Objectives: Intermittent administration of parathyroid hormone (PTH) is the only FDA-approved agent capable of making new bone to treat osteoporosis. Similar to bone, other mesenchymal connective tissues such as joint cartilage have receptors for PTH; however, the effect of intermittent PTH on cartilaginous tissue is unclear. Similar to osteogenic cells, PTH could expand chondrogenic cell populations, advancing the treatment approaches for temporomandibular joint (TMJ) disorders and condylar growth disturbances. Therefore, the objective of this study was to examine the effect of varying doses of intermittent PTH on the mandibular condylar cartilage of the TMJ.
Methods: Sixty, 6-week-old young, growing C57BL/6 mice were equally divided into four groups: vehicle (saline) and 3 doses of intermittent PTH administration (25, 100 and 200 μg/kg). Following four weeks of daily subcutaneous injections of either the vehicle or PTH, the mandibular condyle and TMJ were dissected from all animals for gene expression and micro-CT analyses, and linear mandibular measurements.
Results: Micro-CT analysis of the subchondral bone showed a significant decrease in percent bone volume (BV/TV) and trabecular thickness (Tb.Th) in the 100 and 200 µg PTH groups compared to the 25 µg group (P<0.05). Mandibular measurements demonstrated a significant decrease in condyle head length in the 100 µg group compared to the 25 µg group (P<0.05). Gene expression analysis showed a 4-fold increase in Sox9 expression and a 3-fold increase in Col10 expression in the 25 µg group compared to the vehicle group. In the 200 µg group, Col2 expression was the lowest and Col10 expression was the highest among all groups.
Conclusions: Intermittent PTH at low dose (25 µg/kg) produces an anabolic response in the TMJ cartilage and subchondral bone whereas a high dose (200 µg/kg) appears to compromise cartilage integrity.
This research was supported by the American Association of Orthodontists Foundation (AAOF).
Methods: Sixty, 6-week-old young, growing C57BL/6 mice were equally divided into four groups: vehicle (saline) and 3 doses of intermittent PTH administration (25, 100 and 200 μg/kg). Following four weeks of daily subcutaneous injections of either the vehicle or PTH, the mandibular condyle and TMJ were dissected from all animals for gene expression and micro-CT analyses, and linear mandibular measurements.
Results: Micro-CT analysis of the subchondral bone showed a significant decrease in percent bone volume (BV/TV) and trabecular thickness (Tb.Th) in the 100 and 200 µg PTH groups compared to the 25 µg group (P<0.05). Mandibular measurements demonstrated a significant decrease in condyle head length in the 100 µg group compared to the 25 µg group (P<0.05). Gene expression analysis showed a 4-fold increase in Sox9 expression and a 3-fold increase in Col10 expression in the 25 µg group compared to the vehicle group. In the 200 µg group, Col2 expression was the lowest and Col10 expression was the highest among all groups.
Conclusions: Intermittent PTH at low dose (25 µg/kg) produces an anabolic response in the TMJ cartilage and subchondral bone whereas a high dose (200 µg/kg) appears to compromise cartilage integrity.
This research was supported by the American Association of Orthodontists Foundation (AAOF).