Low-level laser therapy for osteonecrotic lesions: effects on osteoblasts treated with zoledronic acid

Clinical studies have shown that low-level laser therapy (LLLT) can improve local tissue healing of bisphosphonate-induced osteonecrosis of the jaw. However, the effects of laser irradiation on bisphosphonate-treated osteoblasts have not been completely elucidated.

Human osteoblasts were cultured in plain culture medium (DMEM). After 48 h, plain DMEM was replaced by DMEM with no fetal bovine serum, for a 24-h incubation followed by addition of zoledronic acid (5 μM) for additional 48 h. Cells were subjected to LLLT (InGaAsP; 780 ± 3 nm; 0.025 W) at 0.5, 1.5, 3, 5, and 7 J/cm(2), three times every 24 h. Cell viability, total protein production, alkaline phosphatase activity (ALP), mineral nodule formation, gene expression of collagen type I and ALP, and cell morphology were evaluated.

LLLT at 0.5 J/cm(2) increased cell viability of cultured osteoblasts. ALP activity and gene expression, in addition to mineral nodule formation and Col-I gene expression, were not increased by LLLT. LLLT applied to ZA-treated cells increased Col-I expression at 0.5, 1.5, and 3 J/cm(2) but did not improve any other cell activity assessed.

LLLT showed limited effects on bisphosphonate-treated osteoblasts.