[Effects of recombinant human growth hormone on local expression of insulin-like growth factor-Ⅰ during orthodontic tooth movement].

OBJECTIVE: To explore in vivo the expression of insulin-like growth factor-Ⅰ(IGF-Ⅰ)under stress, and to analyze changes of the local expression related to recombinant human growth hormone(rhGH)treatment.

METHODS: Forty Wistar rats were randomly divided into control and growth hormone groups, 20 in each group. A force of 0.49 N was applied to move the right upper first molars mesially. The growth hormone group and control group received daily subcutaneous injections of rhGH and equivalent volumes of saline, respectively. The rats were sacrificed on days 1, 3, 7 and 14. Micro-CT-reconstructed images were used to survey root resorption, and horizontal sections of the maxillae were prepared for tartrate-resistant acid phosphate(TRAP)and immunohistochemistry staining.

RESULTS: Tooth moved faster in the growth hormone group([0.291±0.017], [0.513±0.111]mm)than in the control group([0.245±0.033], [0.368± 0.052]mm)on days 7 and 14(P<0.05). More osteoclasts on day 3, and fewer osteoclasts on day 7 were observed in the growth hormone group([4.0±0.7], [2.6±0.6]cell/high-power field)than in the control group([2.8±0.6], [3.8±0.8]cell/high-power field)(P<0.05). The number of IGF-Ⅰ positive osteoclasts in the growth hormone group([4.7 ± 0.7]cell/high-power field)was significantly greater than that in the control group([2.7±0.5]cell/high-power field)(P<0.01)on day 3. Compared with the control group([18.6±1.5], [23.3± 3.8]cell/high-power field), IGF-Ⅰ positive PDL cells increased on days 7 and 14 in the growth hormone groups([29.6±3.4], [37.5±6.1]cell/high-power field)(P<0.01).

CONCLUSIONS: rhGH could stimulate IGF-Ⅰ expression in PDL, and accelerate bone remodeling and tooth movement.