Effects of insulin-like growth factor-I on nasopremaxillary growth under different masticatory loadings in growing mice

It is well accepted that reduced masticatory function induced by a diet wit h soft physical consistency causes alterations in the craniofacial morpholo gy in growing animals. It is assumed that these alterations are associated with reduced proliferative activity of osteoblasts on the bone surface, ind icating a significant role for mechanical stimuli mediated by various local growth factors including insulin-like growth factor-I (IGF-I). Here, the e ffects of IGF-I on the linear growth of nasal and premaxillary bones subjec ted to different masticatory loadings were examined. The length of the nasa l bone and the width of the premaxilla were measured. These dimensions were significantly greater in mice fed a solid diet than in mice fed a granulat ed diet. In animals treated with IGF-I, the nasal bone length and premaxill ary width increased significantly in a subgroup receiving a solid diet, but these changes were not found in a similar group fed a granulated diet. No statistically significant differences in these dimensions were found betwee n solid-diet mice injected with saline and granulated-diet group injected w ith IGF-I. It is concluded that IGF-I induces nasal and premaxillary growth , and that its effect is enhanced or accelerated by increased mechanical ma sticatory loading. (C) 2000 Elsevier Science Ltd. All rights reserved.