Reduced growth hormone receptor immunoreactivity in osteoclasts adjacent to the erupting molar in the incisor-absent (osteopetrotic) rat.
First molars fail to erupt in the incisor-absent (ia/ia) rat because of a defect in osteoclast function. Growth factors that regulate local bone metabolism include growth hormone (GH), insulin-like growth factor-I (IGF-I), epidermal growth factor (EGF) and interleukin-1 alpha (IL-1alpha). Since osteoclast function may be affected by these factors, the aim of this study was to determine the distribution of GH receptor (GHr), IGF-I, EGF and IL-1alpha, in osteoclasts located occlusal to the erupting first molar, in the 'eruption pathway', in normal and ia/ia rats. Sagittal sections of the first molar and adjacent bone from 3- and 9-d-old animals were examined. Osteoclasts were identified using tartrate-resistant acid phosphatase (TRAP). The TRAP-positive osteoclast cell numbers were higher in ia/ia animals at 3 and 9 days-of-age. In the ia/ia group, fewer osteoclasts were GHr- and IGF-I-positive at 3 d of age, and at 9 d of age fewer osteoclasts were GHr-positive. In the ia/ia rat, defective osteoclast function failed to resorb bone to provide an eruption pathway for the lower first molar. The expression of GHr, and to some degree IGF-I, by these osteoclasts was reduced, which may be related to their ability to differentiate and function.
Symons
Anne L
AL
School of Dentistry, The University of Queensland, Brisbane, Australia. a.symons@uq.edu.au
D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D007180:Incisor / Q000473:pathology; D007527:Isoenzymes / Q000378:metabolism; D008334:Mandible / Q000502:physiology; D008963:Molar / Q000254:growth & development / Q000473:pathology*; D010010:Osteoclasts / Q000378:metabolism*; D010022:Osteopetrosis / Q000503:physiopathology*; D051381:Rats; D011922:Rats, Mutant Strains; D011986:Receptors, Somatotropin / Q000378:metabolism*; D000071681:Tartrate-Resistant Acid Phosphatase; D014018:Tissue Distribution; D014078:Tooth Eruption / Q000502:physiology*; D014083:Tooth Germ / Q000503:physiopathology
D007527:Isoenzymes; D011986:Receptors, Somatotropin; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase