Effects of Intermittent Irradiation with Low-Level LED Light on Osteoblast-Like Cells Derived from Rat Bone Marrow

Recently, low level laser therapy (LLLT) has been reported to promote wound healing of fractures, tooth extraction sockets and bone-dental implants osseointegration. In this study, we investigated the effects of LLLT on cell proliferation, differentiation and calcification of rat bone marrow-derived osteoblast-like cells using blue LED light irradiation at a wavelength of 455 nm. The irradiation conditions were as follows; LED with a wavelength of 455 nm, 510 mW output power (measured value in the irradiated field: 100 mW/cm2), distance: 20.8 mm, and irradiation for 14 seconds every 1.5 hours at an energy of 5.6 joules/cm2 (up to 4.5 hours). The experimental groups were divided into 4 groups; control group, LED light-irradiation group, FGF-containing media group and LED light-irradiation and FGF-containing media group (n=3). The cell proliferative ability was determined using Cell Counting Kit-8 immediately after the first LED irradiation, after 1.5, 3.0, 4.5 and 12 hours by ELISA. Lab assay ALP was used to search for cell differentiation potential, and ALP activity levels in the samples were determined after 3 and 7 days. And the ALP staining was also performed after 7 days, and the ALP staining positive was determined by analyzing the percentage of stained area in each well. For the search of cellular calcification activity, Alizarin Red staining was used to determine its positivity rate by analyzing the stained area fraction of each well after 14 and 28 days. In all the searched results, both the cell proliferation and differentiation abilities were highest in the LED group. And the calcification ability was significantly higher in the LED, FGF and LED•FGF groups than that in the control group. The results of this study suggested that LLLT with blue LED light irradiation was useful for bone tissue regeneration.