British Journal of Oral and Maxillofacial Surgery 43 (2005) 383–391 Healing of fractures in osteoporotic rat mandible shown by the expression of bone morphogenetic protein-2 and tumour necrosis factor- A.A. Shahidul Islam, L. Rasubala, H. Yoshikawa, Y. Shiratsuchi, M. Ohishi ∗ Department of Oral and Maxillofacial Oncology, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan Accepted 4 October 2004 Available online 21 February 2005 Abstract We studied the healing process of mandibular closed fractures in osteoporotic rats using specific antibodies to bone morphogenetic protein-2 (BMP-2) and tumour necrosis factor- (TNF-). We confirmed the osteoporosis in rats after oophorectomy by micro-CT, and then caused unilateral closed fractures in the mandible and monitored the healing process after 7, 14, 21, and 28 days. Data were compared simultaneously with those from a group of rats that had a sham operation. During healing of the fracture in the osteoporotic group there was a prolonged phase of endochondral ossification, with an increased number of osteoclasts (p < 0.01). Expressions of BMP-2 and TNF were more pronounced in the osteoporotic group and there was an increase in the number of osteoblasts and TNF + cells compared with the normal control (p < 0.01). BMP-2 was related to the differentiation of osteoblasts and the higher values of TNF were correlated with the up-regulation of osteoclasts during the prolonged phase of bone turnover. We conclude that the healing of fractures in osteoporotic bone is delayed about a week compared with controls. In the healing of fractures in osteoporotic bone, there were more osteoblasts and osteoclasts but there was a predominance of osteoclasts probably induced by TNF. The prolonged phase of bone turnover with osteoclast predominance in the osteoporotic group is suggestive of the cause of delay in the healing of the fracture. © 2005 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Keywords: TNF-; BMP-2; Osteoporosis; Fracture healing Introduction Fractures are common complications of osteoporosis in older people, but there have been few studies of the healing process of fractures in osteoporotic bones and most of these have been on long bones, such as tibia and femur, and have concentrated on the biomechanical properties of the phases of healing. 1–5 The healing of a fracture involves a complex series of cellular events and these may be further complicated by osteoporosis. Namkung-Matthai et al. reported that osteoporosis influenced the early period of healing of fractures, 3 whereas Kubo et al. suggested that osteoporosis influenced the late period of healing. 4 Although it is well known that some cytokines and ∗ Corresponding author. Tel.: +81 92 642 6447; fax: +81 92 642 6386. E-mail address: m-ohishi@dent.kyushu-u.ac.jp (M. Ohishi). growth factors affect osteoporosis, 6–8 their role in the heal- ing of osteoporotic fractures has not been fully defined. Few reports are available regarding the expression of growth fac- tors or cytokines, but animal studies have indicated that old age and oophorectomy impair both the formation of callus and the final mechanical strength. 2 Bone morphogenetic proteins (BMPs) are the most potent osteoinductive growth factors. They are capable of initiat- ing the development of osteoblasts and the formation of bone during embryonic life and during the healing of fractures. 8–14 We have shown previously that BMP-2 participates in all stages of healing of fractures by causing the proliferation and differentiation of osteoprogenitor cells. 11,12 TNF- is one of the most powerful stimulants of bone absorption and may contribute to osteoporosis by modulating the differen- tiation and function of osteoclasts. 6–8,15–17 Recent evidence 0266-4356/$ – see front matter © 2005 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.bjoms.2004.10.018