Abstract:

Objective　The studywas to investigate the circadian rhythm of the proliferation index (PI) of the mandibular osteoblast after distraction osteogenesis (DO) by a comparative study to explain the different rhythm characteristics.Methods　 Fourty-eight healthy goats were employed and divided randomly into DO group and control. Fourweeks after the right side mandi- ble of DO group was distracted, animals of the both groups were killed at 0:00, 4:00, 8:00, 12:00, 16:00, 20:00 time point subsequently. Samples of 2 cm×2 cm×0.5 cm bone tissue were excised from distracted zone of DO group and the right mental foramen zone of the control. Primary cell culture method was employed to isolate the osteoblast from bone tissue and a flow cyto- metric analysis was used to detect the PI of osteoblast. The data was analyzed with cosinor rhythmometry method and the different rhythm between the two groups were investigated.Results　The PI in the two groups demonstrated cosinorwaves. The mesor and amplitude in DOgroupwere significant higher comparedwiththe control(P<0·05), buttherewas no significant difference forthe acrophase between the two groups (P>0·05).Conclusion　The PI of osteoblast after DOshowed significant circadian rhythm. It is suggested that DO is helpful to promote osteoblast proliferation and bone regeneration.

Key words: distraction osteogenesis, osteoblast, circadian rhythm, flow cytometry