Bone loss prevention in ovariectomized rats using stable amorphous calcium carbonate

Authors

Galit Shaltiel, Elad Bar-David, Oren E. Meiron, Eitan Waltman, Assaf Shechter, Eliahu D. Aflalo, David Stepensky, Amir Berman, Berdine R. Martin, Connie M. Weaver, Amir Sagi

Abstract

In assessing the relationship between calcium supplementation and maintaining bone mass or reducing the risk of fracture, the effectiveness of calcium supplementation has never been decisive. Freshwater crayfish rely on amorphous calcium carbonate (ACC), an instable polymorph of calcium carbonate, as the main mineral in the exoskeleton and in the temporary storage organ, the gastrolith. Inspired by the crayfish model, we have previously shown an increase in calcium bioavailability in rats administered with synthetic stable ACC vs. crystalline calcium carbonate (CCC). The current study compared the effects of amorphous calcium derived from either gastrolith or synthetic ACC with those of crystalline calcium, found in commercial CCC or calciumcitrate supplements, in a bone loss prevention model. Rats were subjected to either sham or ovariectomy (OVX) operation (n~20/ group) followed by administration of food pellets supplemented with 0.5% calcium from either source over 12 weeks. Micro-computed tomography (μCT) and histomorphometric analyses revealed bone loss prevention by both gastrolith and ACC treatments, manifested by an increase in morphometric bone parameters, compared to both CCC- and calcium citrate-treated groups. Both gastrolith and ACC treatments resulted in bone formation in the tibia cancellous bone, indicated by dynamic histomorphometry parameters, compared to either the CCC or calcium citrate treatments. Levels of urine deoxypyridinoline (DPD), suggested an anti-resorptive effect of ACC, which was also the only treatment that led to a significant increase in vertebral mechanical strength, as supported by μCT analysis of topology and orientation parameters of the vertebral trabeculae. To our knowledge, such levels of bone loss prevention by calcium supplements have never been reported. These findings thus suggest the potential of both natural (crayfish gastrolith) and, to a greater extent, synthetic ACC sources for the prevention of metabolic bone disorders and possibly of osteoporotic processes.

Link to Article

http://dx.doi.org/10.4236/health.2013.57A2003

Comparable Effects of Alendronate and Strontium Ranelate on Femur in Ovariectomized Rats

Authors

BaiLing Chen, YiQiang Li, XiaoXi Yang, DengHui Xie

Abstract

This study compared the effects of alendronate (ALN) and strontium ranelate (SR) on bone mineral density (BMD), bone histomorphometry, and biomechanics in ovariectomized (OVX) rats. We randomly assigned 48 3-month-old female Sprague–Dawley rats to four groups: sham, OVX, ALN, and SR. Rats in the OVX, ALN, and SR groups received bilateral OVX. Rats in the ALN and SR groups were orally administrated ALN (7 mg/kg/week) and SR (500 mg/kg/day). Rats in the sham and OVX groups were treated with saline. All treatments continued for 12 weeks. Femoral BMD examination, distal femoral bone histomorphometry analysis, and biomechanical tests at the femoral diaphysis and metaphysis were performed to evaluate the effects of treatments in OVX rats. Results showed that both ALN and SR significantly increased femoral BMD (total femur, diaphyseal BMD, and distal metaphyseal BMD), distal femoral bone histomorphometric parameters (BV/TV, Tb.N, and Tb.Th), and femoral biomechanical parameters (maximum load, failure load, stiffness) compared with the OVX group (P < 0.05). No differences were found between ALN and SR in increasing femoral BMD, distal femoral bone histomorphometric parameters (BV/TV, Tb.N, and Tb.Th), and femoral diaphysis biomechanical parameters (maximum load, failure load, stiffness) (P > 0.05). The SR group was inferior to the ALN group in femoral metaphysis biomechanical parameters (P < 0.05). In conclusion, ALN (7 mg/kg/week) and SR (500 mg/kg/day) have similar effects by increasing BMD, distal femoral bone histomorphometric parameters, and femoral metaphysis biomechanical properties. Although ALN has greater effects than SR on distal femoral metaphysis biomechanical properties, in general, ALN and SR have comparable effects on the femur in OVX rats.

Link to Article

http://dx.doi.org/10.1007/s00223-013-9765-z

Recombinant human bone morphogenetic protein-2 stimulates bone formation during interfrontal suture expansion in rabbits

Authors

Sean Shih-Yao Liu, Haisong Xu, Jun Sun, Elias Kontogiorgos, Patrick R. Whittington, Kenner G. Misner, Hee-Moon Kyung, Peter H. Buschang, Lynne A. Opperman

Abstract

Introduction: Suture expansion stimulates bone growth to correct craniofacial deficiencies but has a high potential of treatment relapse. The objective of this study was to investigate whether there is a dose-dependent relationship between the recombinant human bone morphogenetic protein-2 (rhBMP-2) and bone formation during suture expansion. Methods: Fifty 6-week-old male New Zealand white rabbits were randomly assigned to 5 groups to receive 0 (control), 0.01, 0.025, 0.1, or 0.4 mg/mL of rhBMP-2 delivered by absorbable collagen sponge placed over the interfrontal suture. The suture was expanded for 33 days by 200 g of constant force via a spring anchored with 2 miniscrew implants. Distance of suture expansion, suture volume, and cross-sectional area after expansion were measured using radiographs with bone markers and microcomputed tomography. Suture widths and mineralization appositional rates were calculated based on the widths between bone labels under an epifluorescent microscope. Software (Multilevel Win 2.0; University of Bristol, Bristol, United Kingdom) was used to model distance of suture expansion over time as polynomials to compare group differences. Wilcoxon signed rank tests were performed to compare the suture volume and cross-sectional area, mineral apposition rate, and suture width between groups. The significance level was set at P = 0.05. Results: Whereas the sutures were expanded in all groups, sutures were expanded by significantly greater amounts in the control and the 0.01 mg/mL groups without fusing the sutures than in the 0.025, 0.1, and 0.4 mg/mL groups with fusing sutures. Compared with the controls, the 0.01 mg/mL group showed significantly lower suture volumes, cross-sectional areas, and suture widths after expansion. The mineral apposition rate was significantly higher in the 0.01 mg/mL group than in the controls from days 10 to 30. Conclusions: The 0.01 mg/mL dose of rhBMP-2 delivered by absorbable collagen sponge can stimulate bone formation at the bony edges of the suture during suture expansion; however, higher concentrations cause suture fusion. With an appropriate concentration, rhBMP-2 might facilitate suture expansion for clinical uses.

Link to Article

http://dx.doi.org/10.1016/j.ajodo.2013.03.017

Connexin 43 deficiency desensitizes bone to the effects of mechanical unloading through modulation of both arms of bone remodeling

Authors

Shane A. Lloyd, Alayna E. Loiselle, Yue Zhang, Henry J. Donahue

Abstract

Connexin 43 (Cx43) is a gap junction protein that plays an integral role in the skeletal response to mechanical loading and unloading. In a previous study, we demonstrated preservation of trabecular bone mass and cortical bone formation rate in mice with an osteoblast/osteocyte-selective deficiency of Cx43 (cKO) following mechanical unloading via hindlimb suspension (HLS). In the present study, we sought to define the potential mechanisms underlying this response. Following three weeks of HLS, mRNA levels of Sost were significantly greater in wild-type (WT)-Suspended mice vs. WT-Control, while there was no difference between cKO control and cKO-Suspended. Unloading-induced decreases in P1NP, a serum marker of bone formation, were also attenuated in cKO-Suspended. The proportion of sclerostin-positive osteocytes was significantly lower in cKO-Control vs. WT-Control (− 72%, p < 0.05), a difference accounted for by the presence of numerous empty lacunae in the cortical bone of cKO vs. WT. Abundant TUNEL staining was present throughout the cortical bone of the tibia and femur, suggesting an apoptotic process. There was no difference in empty lacunae in the trabecular bone of the tibia or femur. Trabecular and cortical osteoclast indices were lower in cKO-Suspended vs. WT-Suspended; however, mRNA levels of the gene encoding RANKL increased similarly in both genotypes. Connexin 43 deficient mice experience attenuated sclerostin-mediated suppression of cortical bone formation and lower cortical osteoclast activity during unloading. Preservation of trabecular bone mass and attenuated osteoclast activity during unloading, despite an apparent lack of effect on osteocyte viability at this site, suggests that an additional mechanism independent of osteocyte apoptosis may also be important. These findings indicate that Cx43 is able to modulate both arms of bone remodeling during unloading.

Link to Article

http://dx.doi.org/10.1016/j.bone.2013.07.022

Neonatal iron deficiency causes abnormal phosphate metabolism by elevating FGF23 in normal and ADHR mice

Authors

Erica L. Clinkenbeard PhD, Emily G. Farrow PhD, Lelia J. Summers, Taryn A. Cass, Jessica L. Roberts, Christine A. Bayt, Tim Lahm MD, Marjorie Albrecht, Matthew R. Allen PhD, Munro Peacock MD, Kenneth E. White PhD

Abstract

FGF23 gain of function mutations can lead to autosomal dominant hypophosphatemic rickets (ADHR) disease onset at birth, or delayed onset following puberty or pregnancy. We previously demonstrated that the combination of iron deficiency and a knock-in R176Q FGF23 mutation in mature mice induced FGF23 expression and hypophosphatemia that paralleled the late onset ADHR phenotype. As anemia in pregnancy and in premature infants is common, the goal of this study was to test whether iron deficiency alters phosphate handling in neonatal life. Wild type (WT) and ADHR female breeder mice were provided control or iron-deficient diets during pregnancy and nursing. Iron-deficient breeders were also made iron replete. Iron deficient WT and ADHR pups were hypophosphatemic, with ADHR pups having significantly lower serum phosphate (P < 0.01) and widened growth plates. Both genotypes increased bone FGF23 mRNA (>50 fold; P < 0.01). WT and ADHR pups receiving low iron had elevated intact serum FGF23 with ADHR mice affected to a greater degree (P < 0.01). Iron deficient mice also showed increased Cyp24a1 and reduced Cyp27b1, and low serum 1,25(OH)2 vitamin D. Iron repletion normalized most abnormalities. Because iron deficiency can induce tissue hypoxia, oxygen deprivation was tested as a regulator of FGF23, and was shown to stimulate FGF23 mRNA in vitro and serum C-terminal FGF23 in normal rats in vivo. These studies demonstrate that FGF23 is modulated by iron status in young WT and ADHR mice and that hypoxia independently controls FGF23 expression in situations of normal iron. Therefore, disturbed iron and oxygen metabolism in neonatal life may have important effects on skeletal function and structure through FGF23 activity on phosphate regulation.

Link to Article

http://dx.doi.org/10.1002/jbmr.2049

Distraction Osteogenesis Following Low-Dose Hyperfractionated Irradiation in the Rat Mandible

Authors

Sagar S. Deshpande, BS, Laura A. Monson, MD, Christi M. Cavaliere, MD, Alexander L. Ayzengart, MD, Steven R. Buchman, MD

Abstract

Purpose: The investigators hypothesized that low-dose hyperfractionated radiation would impair mandibular distraction osteogenesis (DO) in a murine mandibular model. Materials and Methods: Male Sprague-Dawley rats underwent fractionated radiation (30 Gy) of the left mandible. After a 2-week recovery period, an external frame distractor was applied and gradual distraction of the mandible was performed. Tissue was harvested after a 28-day consolidation period. Gross, radiologic, and histologic evaluations were undertaken. Control animals underwent surgery for an identical time frame without preoperative radiation. Results: Animals subjected to preoperative radiation (n = 10) showed suboptimal bone formation, including bone atrophy, incomplete bridging of the distraction gap, and gross bony defects or nonunion, compared with controls (n = 10). Although physical lengthening was achieved, irradiation consistently led to a detrimental effect on the normal process of DO. Conclusion: This set of experiments establishes a valuable rodent model to evaluate the effects of radiation on DO and may help to formulate strategies to optimize DO before it is widely applied in oncologic reconstruction.

Link to Article

http://dx.doi.org/10.1016/j.joms.2013.02.011