Effects of Ultrasound on the Proliferation and Differentiation of Cementoblast Lineage Cells

Abstract

The purpose of this study was to investigate the effects of low-intensity pulsed ultrasound (LIPUS) stimulation on the proliferation and differentiation of cementoblast lineage cells. An immortalized human periodontal ligament cell line (HPL) showing immature cementoblastic differentiation was used. Cultured HPL cells were subjected to LIPUS exposure (frequency = 1 MHz; pulsed 1:4; intensity = 30 mW/cm(2)) or sham exposure for 15 minutes per day. Expression levels of alkaline phosphatase (ALP), type I collagen (Col-I), runt-related gene 2 (Runx2), bone sialoprotein (BSP), osteocalcin (OCN), and osteopontin (OPN) mRNA were analyzed with real-time polymerase chain reaction analysis. Furthermore, ALP activity, collagen synthesis, and protein level of Runx2 were examined after 6 days of LIPUS exposure. mRNA and protein levels of ALP, Col-I, and Runx2 were significantly increased by LIPUS exposure compared to controls, whereas BSP, OCN, and OPN mRNA expression could not be detected in HPL cells, irrespective of LIPUS exposure. LIPUS enhanced ALP activity, collagen synthesis, and Runx2 expression of HPL cells, which provides important insight into the promotion of early cementoblastic differentiation of immature cementoblasts.