Effects of ultrasound and 1,25-dihydroxyvitamin D-3 on growth factor secretion in co-cultures of osteoblasts and endothelial cells

It has been shown that low-intensity pulsed ultrasound (US) accelerates fra cture healing in animal models and in clinical studies, However, the mechan ism by which US accelerates fracture healing remains unclear. Systemic fact ors and several growth factors, such as platelet-derived growth factor (PDG F), are thought to be involved in the process of fracture healing, In the p resent study, we examined the effects of US and 1,25-dihydroxyvitamin D-3 [ 1,25-(OH)(2)D-3] on growth factor secretion in a co-culture system of human osteoblastic cells (SaOS-2) and endothelial cells (HUVEC), US was applied to cultured cells for 20 min daily for four consecutive days. US treatment increased the PDGF-AB level in the conditioned media. 1,25-(OH)(2)D-3 (1 x 10(-8) M) also enhanced PDGF-AB secretion. The secretion of PDGF-AB was syn ergistically increased by the combination of US and 1,25-(OH)(2)D-3. These results suggest that the stimulation of growth factor secretion from cells by US and 1,25-(OH)(2)D-3 treatment may be involved in the acceleration of fracture healing, (C) 2000 World Federation for Ultrasound in Medicine & Bi ology.