Green laser light irradiation enhances differentiation and matrix mineralization of osteogenic cells

Low level laser therapy (LLLT) in both infrared and visible light is a therapeutic tool ever more proposed in clinical practice in different fields. The effect of near infrared LLLT has been described in a growing number of scientific publications related to bone tissue healing, both in vitro and in vivo. More recently, green visible light using potassium-titanyl-phosphate KTiOPO4 (KTP, 532 nm) laser has been proposed in dermatology, urology, oral and maxillofacial surgery but has never been tested on bone tissue. The aim of the present work was to perform a preliminary in vitro study to analyze the effects of KTP laser, on the osteogenic differentiation of bone marrow stromal cells (BMSCs).

Using a power meter the first step of this study aimed to evaluate the real power emitted by the KTP laser device and the amount of energy absorbed by culture medium and plastic in order to calculate the appropriate irradiation parameters for cultured cells. Primary bone marrow stromal cells prepared from C57BL/6 mice were cultured and induced to differentiate in the osteogenic lineage in the presence or in the absence of KTP LLLT at a fluence of 4 J/cm(2) three times a week. Specific staining of the cells and the extracellular matrix, microscopic analysis as well as quantitative RT-PCR were used to assess cell proliferation and differentiation.

We show here that KTP LLLT enhances the osteogenic differentiation of bone marrow stromal cells and the mineralization of their extracellular matrix.

Our results highlight that this LLLT experimental protocol with green light (KTP, 532 nm) at 4 J/cm(2) has a positive effect on the osteogenic differentiation of murine bone marrow stromal cells. These preliminary results could be used as a basis to further investigate the effect of this KTP laser protocol on bone tissue engineering models in vivo and in vitro.