24 The Open Bone Journal, 2010, 2, 24-31 1876-5254/10 2010 Bentham Open Open Access Fourier-Transform Raman Spectroscopy Study of the Ovariectomized Rat Model of Osteoporosis Renato Aparecido de Souza *,1,2 , Diego Pereira Jerônimo 2 , Hélio Andrade Gouvêa 2 , Murilo Xavier 1,2 , Marco Túlio de Souza 3 , Humberto Miranda 2 , Maira Gaspar Tosato 4 , Airton Abrahão Martin 4 and Wellington Ribeiro 2 1 Department of Physical Therapy, Vales do Jequitinhonha e Mucuri Federal University, UFVJM, Rua da Glória, 187, 39100-000, Diamantina, Minas Gerais, Brazil 2 Laboratory of Physiology and Pharmacodynamics, Institute of Research and Development, IP&D, Vale do Paraiba University, UNIVAP, Av. Shishima Hifumi, 2911, 12244-000, São José dos Campos, São Paulo, Brazil 3 Faculty of Medicine, Vale do Sapucaí University, UNIVAS, Av. Pref. Tuany Toledo, 470, 37500-000, Pouso Alegre, Minas Gerais, Brazil 4 Laboratory of Biomedical Vibrational Spectroscopy, Institute of Research and Development, IP&D, Vale do Paraiba University, UNIVAP, Av. Shishima Hifumi, 2911, 12244-000, São José dos Campos, São Paulo, Brazil Abstract: The ovariectomized rat model of osteoporosis was studied using FT-Raman spectroscopy on the surface of site- specific bones. Twelve, 3 month old female Wistar rats (230 ± 10 g) were divided into two groups (n = 6 per group), one group was: ovariectomized (OVX) and the other sham-operated (SHAM). The rats were sacrificed to collect samples twelve weeks after the surgical operation. The right femur and tibia as well as the third lumbar vertebra were harvested and subjected to FT-Raman analysis on the following bones sites: femoral neck (FN), femoral mid-shaft (FS), proximal tibial metaphysis (PTM), tibial mid-shaft (TS), and lumbar vertebral body (LVB). Analysis of individual Raman peaks showed site-dependent variations in the bone: the ovariectomy induced lower mineral content (959 cm -1 ) in trabecular bone sites (FN, PTM and LVB) and higher matrix content (1265 and 1665 cm -1 ) in cortical bone sites (FS and TS). In addition, a lower mineral to matrix ratio and a higher carbonate/phosphate were observed in the OVX group, which indicated a change in bone chemical content and some degree of remodeling specially in the trabecular bone sites. These data support the hypothesis that FT-Raman spectroscopy can be used to evaluate the bone alterations induced by this experimental model. Keywords: Vibrational spectroscopy, bone, osteoporosis, ovariectomy, rats. INTRODUCTION Osteoporosis is a disabling skeletal disorder characterized by progressive bone mass loss and microarchitecture deterioration of bone tissue which predisposes patients to increased bone fracture risk [1]. Osteoporosis is the most common metabolic bone disorder worldwide and, therefore, is considered as a serious public health concern [2]. More than 200 million people worldwide are currently estimated to suffer from this disease. According to the World Health Organization criteria, 1/3 of the white women older than 65 have osteoporosis and osteoporotic fractures will occur in about 50% of women older than 75 years [3]. In Brazil, one in every five Brazilian women > 50 years of age has already had some kind of osteoporotic fracture [4]. Osteoporosis associated with ovarian hormone deficiency following menopause is by far the most common cause of age-related bone loss [1-3]. Experimental animal models *Address correspondence to this author at the Laboratory of Physiology and Pharmacodynamics, Institute of Research and Development, IP&D, Vale do Paraiba University, UNIVAP, Av. Shishima Hifumi, 2911, 12244-000, São José dos Campos, São Paulo, Brazil, Fax: +55-12-3947-1149; E-mail: tatosouza2004@yahoo.com.br have provided knowledge about aetiology, pathophysiology, and diagnosis, as well as about preventive and therapeutical techniques, regarding postmenopausal osteoporosis (PMO) [5,6]. The ovariectomized (OVX) rat is a well-established model of PMO and the site-specific development of osteo- porosis in this model is one of the most reliable biological responses in skeletal research [7]. The OVX rat model is considered an appropriate model for studying female post- menopausal osteoporosis because of the many similarities in their pathophysiological mechanisms. OVX exhibit dec- reased bone mineral density (BMD), poor trabecular micro- architecture and bone strength, and increased bone turnover rate (resorption exceeding formation) [5-8]. Thus, ovariec- tomy in rats has been widely used as a model of PMO and has been validated as a clinically relevant model of this condition in humans. The choice of methods to evaluate bone quality, which is defined as an adequate and functional chemical, structural, and metabolic interaction of its mineral and matrix phases [9], is as important as the choice of the animal model. There has been extensive studies about the bones of OVX rats including the use of peripheral computerized tomography (pQCT), high-resolution microcomputed tomography