Enhancement of osteogenesis post-splenectomy does not attenuate bone loss in ovariectomized rats

The roles of different immune cell populations and cytokines in bone metabolism have been extensively investigated. However, the influence of whole immune organ removal on osteopathology remains unknown. In the current study, we investigated the effects of splenectomy on bone metabolism and microarchitecture in rats with or without concurrent ovariectomy. Ovariectomized (OVX) rats were used as osteoporosis model. Sixty 12-week-old female rats were randomized into 4 groups (n = 15): sham, splenectomized (SP), ovariectomized, as well as ovariectomized and splenectomized (OVX + SP). Bone microarchitecture was assessed by micro CT analysis at 4 week and 12 week post-operation, respectively. Bone pathology and metabolism were evaluated via immunohistochemical staining. The serum levels of alkaline phosphatase (ALP), tumor necrosis factor-alpha (TNF-α), tartrate-resistant acid phosphatase 5b (Tracp5b), and C-terminal telopeptide (CTx) were analyzed at 4 and 12 weeks post-operation. Removal of the spleen led to alterations in the homeostasis of bone metabolism and increased bone formation in rats. In this study, our findings indicate that the spleen is involved in skeletal metabolism. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1356–1363, 2015.