Effect of macrophage colony-stimulating factor on osteoclast differentiation and the relevant morphologic modification in the mandibular condyle of osteopetrotic (op/op) mice

Abstract

Osteopetrotic (op/op) mice have a prominent deficiency of osteoclasts caused by the absence of functional macrophage colony-stimulating factor (M-CSF). In the present study, we examined bone formation of the mandibular condyle after consecutive injections of M-CSF using 5 days-old mutant mice. In the M-CSF injected op/op mice, bone resorption on the inner surface of the mandibular ramus was noted at 10 days after birth, normally five days after the start of M-CSF injections, while there was no signs for bone resorption in untreated op/op mice of the some age. This activity increased with the progress in bone marrow cavity formation on postnatal day 15 and there after. In untreated op/op mice the condylar heads were still composed of cartilage tissue at even 25 days after birth. The op/op mice treated by M-CSF may provide us with new knowledge not only about the role of M-CSF in osteoclast differentiation in the mandible but also about the correlations in bone remodeling and morphology of the mandibular condyle and ramus.