Effect of low level Ga-Al-As laser irradiation on osteogenic regulation of human osteoblastic cell line - CRL 1427

A thesis submitted to the College of Dental Medicine of Nova Southeastern University of the degree of Master of Science in Dentistry. Introduction: One of the challenges in orthodontics is obtaining desired tooth movement. A recent development in orthodontics offers patients more comfort by minimizing pain, and shortening the treatment time. Low level laser therapy (LLLT) emerged as a technology that may accelerate the velocity of tooth movement and shorten the orthodontic treatment period. LLLT (630-1000nm) has been shown to modulate various biological processes including wound healing and bone remodeling. Bone remodeling is one of the biological processes that ensue during tooth movement. Bone remodeling is a continuous process characterized by bone deposition at sites of tension and bone resorption on the pressure sites. At cellular level bone remodeling is regulated by receptor activator of NF-κB (RANK) and receptor activator of NF-κB ligand (RANKL) and Osteoprotegrin (OPG). RANK and RANKL promotes osteoclastic differentiation and promotes bone resorption. OPG is a soluble decoy receptor that competes with RANK for binding to RANKL and inhibits the osteoclastic activity. The goal of the research is to understand the regulatory effects of LLLT on bone metabolism at the cellular level. Furthermore, the purpose of this study is to evaluate the critical parameters of low level lasers on the early stage of ostegenic regulation of human osteoblast cells. In this study, CRL-1427 cells derived from human osteosarcoma which have an osteoblast phenotype were used as cell model. Methods: Human osteoblast cells CRL1427(ATCC, Manassas, VA) were cultured in minimum essential medium supplemented with 10% fetal bovine serum and 1% antibiotics and incubated in at 37°C with 5% CO2. The monolayer of cells after reaching 70-80% confluency were irradiated with a single dose of Galium Aluminum Arsenide (Ga-Al-As) laser, with a wave length of 830nm and output power of 85mW with 0.6, 1.5, 1.8 Joules/cm2 energy exposure regimes. The mRNA expressions of Alkaline phosphatase (ALP), Osteoprotegerin (OPG), RANKL and RANK were compared after seven days by quantitative real time PCR. Results: We observed that treatment of CRL 1427 cells with LLLT (1.5, 1.8 Joules/cm2) irradiation significantly increased the expression of ALP, OPG, RANKL and RANK mRNAs compared to the control group (P≤0.05). There was no significant difference between the control group and mRNA expression of ALP, OPG, RANK, or RANKL at 0.6J/cm2of irradiation. Conclusion: LLLT irradiation can directly influence the expression of genes associated with bone metabolism and potentially represents a mechanism that facilitates rapid bone remodeling