Low level laser therapy (830 nm) improves bone repair in osteoporotic rats: Similar outcomes at two different dosages Paulo Sérgio Bossini a, ⁎, Ana Claudia Muniz Rennó b , Daniel Araki Ribeiro b , Renan Fangel a , Alessa Castro Ribeiro a , Manoela de Assis Lahoz a , Nivaldo Antonio Parizotto a a Department of Physiotherapy, Federal University of São Carlos (UFSCar), Rodovia Washington Luís (SP-310), Km 235, São Carlos, SP, Brazil b Department of Bioscience, Federal University of São Paulo (UNIFESP), Avenida Ana Costa, 95, Santos, SP, Brazil abstract article info Article history: Received 20 April 2010 Received in revised form 6 October 2011 Accepted 10 November 2011 Available online 21 November 2011 Section Editor: Andrzej Bartke Keywords: Bone repair Osteoporosis LLLT Ovariectomy Angiogenesis Rat Background and objective: The goal of this study was to investigate the effects of low level laser therapy (LLLT) in osteoporotic rats by means of subjective histopathological analysis, deposition of collagen at the site of fracture, biomechanical properties and immunohistochemistry for COX-2, Cbfa-1 and VEGF. Material and methods: A total of 30 female Wistar rats (12 weeks-old, ±250 g) were submitted to ovariectomy (OVX). Eight weeks after the OVX, a tibial bone defect was created in all animals and they were randomly divided into 3 groups (n = 10): control bone defect group (CG): bone defects without any treatment; laser 60 J/cm 2 group (L60): animals irradiated with LLLT, at 60 J/cm 2 and laser 120 J/cm 2 group (L120): animals irradiated with LLLT, at 120 J/cm 2 . Results: In the laser treated groups, at both fluences, a higher amount of newly formed bone was evidenced as well as granulation tissue compared to control. Picrosirius analysis demonstrated that irradiated animals presented a higher deposition of collagen fibers and a better organization of these fibers when compared to other groups, mainly at 120 J/cm 2 . COX-2, Cbfa-1 or VEGF immunoreactivity was detected in a similar manner either 60 J/cm 2 or 120 J/cm 2 fluences. However, no differences were shown in the biomechanical analysis. Conclusion: Taken together, our results support the notion that LLLT improves bone repair in the tibia of osteo- porotic rats as a result of stimulation of the newly formed bone, fibrovascularization and angiogenesis. © 2011 Elsevier Inc. All rights reserved. 1. Introduction Osteoporosis is a complex disease characterized by a decrease of bone mass, resulting in bone weakness and an increase in susceptibility to fractures (Culhan et al., 1994; Mitchel et al., 1998). This disease is attributed to age, postmenopausal estrogen deficiency and clinical disorders, and it has immense social–economic significance, being recognized as a major public health problem (Culhan et al., 1994). The lower bone mass and bone mineral density due to osteoporosis proba- bly lead to a delay in fracture healing rates and bone repair quality (Hollinger et al., 2008). Many authors suggest that, in osteoporotic peo- ple, there are an impairment of the proliferative activity of osteoblast progenitor cells, gene expression and osteoblast function, a diminished osteoblast response to signaling cues and an imbalance between the coupling of bone formation and resorption (Meyer et al., 2001). Conse- quently, bone healing in osteoporotic individuals may be delayed and new bone quality may be poor (Hollinger et al., 2008). In this context, there is a critical need to develop technologies ca- pable of treating osteoporotic fractures. One promising treatment is the use of the low level laser therapy (LLLT), which seems to induce osteogenesis and stimulate fracture healing (Gauthier et al., 2005). Its action is based on the absorption of the light by tissues, which will generate modifications in the cell metabolism. When the LLLT is applied on tissue, the light is absorbed by photoreceptors located in the cells, called chromophores (Dortbudak, 2000). Once absorbed, the light can modulate cell chemical reactions and stimulate the mito- chondrial respiration, the production of molecular oxygen and ATP synthesis (Karu and Lubart, 2000; Stein et al., 2005). These effects can increase the synthesis of DNA, RNA and cell-cycle regulatory pro- teins, stimulating cell proliferation (Dortbudak, 2000). In vitro studies using osteoblastic cells showed that LLLT is capable of increasing mitochondrial activity (Pires-Oliveira et al., 2008), oste- oblast DNA and RNA synthesis, bone nodule formation (Stein et al., 2005), osteocalcin and osteopontin gene expression and alkaline phosphatase activity (Liu et al., 2007; Rennó et al., 2007). Also, the LLLT has demonstrated to be able to accelerate the process of fracture repair in rabbits and rats, increasing the callus volume and bone min- eral density (BMD) (Liu et al., 2007; Rennó et al., 2007; Ribeiro and Matsumoto, 2008). However, little attention has been given to the effect of LLLT on bone with osteopenia or osteoporosis (Rennó et al., 2006). Particularly, our research group has showed that LLLT exerts a positive effect on osteogenesis in osteopenic rats, increasing femoral Experimental Gerontology 47 (2012) 136–142 ⁎ Corresponding author at: Rodovia Washington Luís (SP-310), Km 235, São Carlos, São Paulo, 13565-905, Brazil. Tel.: + 55 16 3351 8630; fax: 55 16 3361 2081. E-mail address: paulobossini@ig.com.br (P.S. Bossini). 0531-5565/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.exger.2011.11.005 Contents lists available at SciVerse ScienceDirect Experimental Gerontology journal homepage: www.elsevier.com/locate/expgero