Immunolocalization of MMP 2, 9 and 13 in prednisolone induced osteoporosis in mice
Bao Sun1*, Jing Sun1*, Xiuchun Han1, Hongrui Liu1, Juan Li1, Juan Du1, Wei Feng1, Bo Liu1, Jian Cui1, Jie Guo1, Norio Amizuka2 and Minqi Li1
1Department of Bone Metabolism, School of Stomatology Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Jinan, China and 2Department of Developmental Biology of Hard Tissue, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan
*We regard these authors equally contributed to this article
Offprint requests to: Minqi Li, DDS, PhD, Department of Bone Metabolism, School of Stomatology, Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Wenhua West Road 44-1, Jinan 250012, China. e-mail: liminqi@sdu.edu.cn
Summary. Long-term use of glucocorticoids (GC) causes rapid bone loss and increases the risk of osteoporotic fractures. Matrix metalloproteinase (MMPs), the most prominent kind of proteases implicated in the proteolytic degradation of the extracellular matrix (ECM), have been reported to be involved in pathological process of GC induced osteoporosis. However, the underlining mechanisms are still unclear. The aim of this study was to investigate the spatial expression and the potential function of MMP 2, 9 and 13 in osteoporosis induced by prednisolone in the tibiae of mice. In this experiment, mice were given prednisolone (15 mg/kg body weight) in PBS intragastrically every other day, or only PBS as control. Two weeks later, mice were fixed with transcardial perfusion of 4 % paraformaldehyde in 0.1 M phosphate buffer (pH 7.4), and tibiae were extracted for histochemical analysis. Compared with control group, the number of TRAP-positive osteoclasts and the immunoreactivity of MMP 2, 9 and 13 were significantly increased in the trabecular bone of mice administered with prednisolone, leading to the decrease of trabecular bone volume. On the other hand, lighter eosin staining areas containing numerous empty lacunae of osteocytes and crevices were seen in the narrowing cortical bone. Furthermore, intense immunoreaction of MMP 2 and MMP 13 were found in the enlarged lacunae and the crevices, respectively. Taken together, we concluded that prednisolone administration induced the increase of MMP 2, 9 and 13 expressions, while MMP 2 and MMP 13 played essential roles in the osteocytic osteolysis and the early impaired areas in the cortical bone. Therefore, MMPs might be new potential therapeutic targets for prevention and treatment of glucocorticoid induced osteoporosis, especially osteocytic osteolysis. Histol Histopathol 31, 647-656 (2016)
Key words: Prednisolone, MMPs, Osteoclast, Osteocytic osteolysis, Osteoporosis
DOI: 10.14670/HH-11-702