Article: Matheny JB, Slyfield CR, Tkachenko EV, Lin I, Ehlert KM, Tomlinson RE, Wilson DL, Hernandez CJ; (2013) Anti-resorptive Agents Reduce the Size of Resorption Cavities: A three-dimensional dynamic bone histomorphometry study. Bone, 57 (1): 277-283
Abstract: Alterations in resorption cavities and bone remodeling events during anti-resorptive treatment are believed to contribute to reductions in fracture risk. Here, we examine changes in the size of individual remodeling events associated with treatment with a selective estrogen receptor modulator (raloxifene) or a bisphosphonate (risedronate). Adult female rats (6 months of age) were submitted to ovariectomy (n = 17) or sham surgery (SHAM, n = 5). One month after surgery, the ovariectomized animals were separated into three groups: untreated (OVX, n = 5), raloxifene treated (OVX + Ral, n = 6) and risedronate treated (OVX + Ris, n = 6). At 10 months of age, the lumbar vertebrae were submitted to three-dimensional dynamic bone histomorphometry to examine the size (depth, breadth and volume) of individual resorption cavities and formation events. Maximum resorption cavity depth did not differ between the SHAM (23.66 +/- 1.87 mu m, mean +/- SD) and OVX (22.88 +/- 3.69 mum) groups but was smaller in the OVX + Ral (14.96 +/- 2.30 mu m) and OVX+ Ris (14.94 +/- 2.70 mu m) groups (p < 0.01). Anti-resorptive treatment was associated with reductions in the surface area of resorption cavities and the volume occupied by each resorption cavity (p < 0.01 each). The surface area and volume of individual formation events (double-labeled events) in the OVX + Ris group were reduced as compared to other groups (p < 0.02). Raloxifene treated animals showed similar amounts of bone remodeling (ES/BS and dLS/BS) compared to sham-operated controls but smaller cavity size (depth, breadth and volume). The current study shows that anti-resorptive agents influence the size of resorption cavities and individual remodeling events and that the effect of anti-resorptives on individual remodeling events may not always be directly related to the degree of suppression of bone remodeling.
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