The injury response of aged tendons in the absence of biglycan and decorin

Authors

Andrew A. Dunkman, Mark R. Buckleya, Michael J. Mienaltowski, Sheila M. Adams, Stephen J. Thomas, Akash Kumar, David P. Beason, Renato V. Iozzo, David E. Birk, Louis J. Soslowsky

Abstract

Recent studies have demonstrated that the small leucine-rich proteoglycans (SLRPs) biglycan and decorin impact tendon development, aging and healing in mature mice. However, despite the increased risk of tendon injury in the elderly, the role of SLRPs in tendon repair has not been investigated in aged animals. Therefore, our objective was to elucidate the influences of bigylcan and decorin on tendon healing in aged mice to relate our findings to previous work in mature mice. Since the processes of aging and healing are known to interact, our hypothesis was that aging mediates the role of biglycan and decorin on tendon healing. Patellar tendons from wild-type, biglycan-null and decorin-null mice were injured at 270 days using an established model. At 3 and 6 weeks post-surgery, structural, mechanical and biochemical analyses were performed and compared to uninjured controls. Early stage healing was inferior in biglycan-null and decorin-null mice as compared to wild type. However, tendons of all genotypes failed to exhibit improved mechanical properties between 3 and 6 weeks post-injury. In contrast, in a previous investigation of tendon healing in mature (i.e., 120 day-old) mice, only biglycan-null mice were deficient in early stage healing while decorin-null mice were deficient in late-stage healing. These results confirm that the impact of SLRPs on tendon healing is mediated by age and could inform future age-specific therapies for enhancing tendon healing.

Link to Article

http://dx.doi.org/10.1016/j.matbio.2013.10.008

Effects of unfractionated heparin on renal osteodystrophy and vascular calcification in chronic kidney disease rats

Authors

Yan Meng, Hao Zhang, Yingbin Li, Qingnan Li, Li Zuo

Abstract

Unfractionated heparin (UFH) is the most widely used anticoagulant in hemodialysis for chronic kidney disease (CKD) patients. Many studies have verified that UFH can induce bone loss in subjects with normal bone, but few have focused on its effect on renal osteodystrophy. We therefore investigated this issue in adenine-induced CKD rats. As CKD also impairs mineral metabolism systemically, we also studied the impacts of UFH on serum markers of CKD–mineral and bone disorder (CKD–MBD) and vascular calcification. We administered low and high doses of UFH (1 U/g and 2 U/g body weight, respectively) to CKD rats and compared them with CKD controls. At sacrifice, the serum markers of CKD–MBD did not significantly differ among the two UFH CKD groups and the CKD control group. The mean bone mineral densities (BMDs) of the total femur and a region of interest (ROI) constituted of trabecular and cortical bone were lower in the high-dose UFH (H-UFH) CKD group than in the CKD control group (P < 0.05 and P < 0.01, respectively). The BMD of the femoral ROI constituted of cortical bone did not differ between the H-UFH CKD group and the CKD control group. Histomorphometrical changes in the CKD rats indicated secondary hyperparathyroidism, and the femoral trabecular bone volume, but not cortical bone volume, significantly decreased with increasing UFH dose. The same decreasing trend was found in osteoblast parameters, and an increasing trend was found in osteoclast parameters; however, most differences were not significant. Moreover, no distinct statistical differences were found in the comparison of vascular calcium or phosphorus content among the CKD control group and the two UFH CKD groups. Therefore, we concluded that UFH could induce bone loss in CKD rats with secondary hyperparathyroidism, mainly by reducing the trabecular volume and had little effect on cortical bone volume. The underlying mechanism might involve inhibition of osteoblast activity and promotion of osteoclast activity by UFH. We did not find any effect of UFH on vascular calcification in CKD rats with secondary hyperparathyroidism.

Link to Article

http://dx.doi.org/10.1016/j.bone.2013.10.010

The tyrosine kinase inhibitor GNF-2 suppresses osteoclast formation and activity

Authors

Hyun-Ju Kim, Hye-Jin Yoon, Je-Yong Choi, In-Kyu Lee and Shin-Yoon Kim

Abstract

GNF-2, a tyrosine kinase inhibitor, was developed to overcome imatinib-resistant mutations found in CML patients. Osteoclasts are the principal bone-resorbing cells that are responsible for bone diseases, such as osteoporosis, tumor-induced osteolysis, and metastatic cancers. In this study, we investigated the effect of GNF-2 on osteoclast development induced by RANKL and M-CSF. We found that GNF-2 inhibited osteoclast differentiation from BMMs. GNF-2 suppressed RANKL-induced NF-κB transcriptional activity and the induction of c-Fos and NFATc1, which are two key transcription factors in osteoclastogenesis. We also observed that GNF-2 dose-dependently inhibited the proliferation of osteoclast precursors through the suppression of the M-CSFR c-Fms. In addition, GNF-2 accelerated osteoclast apoptosis by inducing caspase-3 and Bim expression. Furthermore, GNF-2 interfered with actin cytoskeletal organization and subsequently blocked the bone-resorbing activity of mature osteoclasts. In agreement with its in vitro effects, GNF-2 reduced osteoclast number and bone loss in a mouse model of LPS-induced bone destruction. Taken together, our data reveal that GNF-2 possesses anti-bone-resorptive properties, suggesting that GNF-2 may have therapeutic value for the treatment of bone-destructive disorders that can occur as a result of excessive osteoclastic bone resorption.

Link to Article

http://dx.doi.org/10.1189/jlb.0713356

Evaluation of the effects of systemic treatment with a sclerostin neutralizing antibody on bone repair in a rat femoral defect model

Authors

Farhang Alaee, Mandeep S. Virk, Hezhen Tang, Osamu Sugiyama, Douglas J. Adams, Marina Stolina, Denise Dwyer, Michael S. Ominsky, Hua Zhu Ke, Jay R. Lieberman

Abstract

Systemic administration of a sclerostin neutralizing antibody (Scl-Ab) has been shown to enhance fracture callus density and strength in several animal models. In order to further evaluate the potential of Scl-Ab to improve healing in a bone defect model, we evaluated Scl-Ab in a 3 mm femoral defect in young male outbred rats. Scl-Ab was given either continuously for 6 or 12 weeks after surgery or with 2 weeks of delay for 10 weeks. Bone formation was assessed by radiographs, µ-CT, and histology. Complete bony union was achieved in only a few defects after 12 weeks of healing (Scl-Ab treated 5/30, vehicle treated 1/15). µ-CT evaluation demonstrated a significant increase in the BV/TV in the defect in the delayed treatment group (65%, p < 0.05), but a non-significant increase in the continuous group (35%, p = 0.11) compared to control. However, both regimens induced an anabolic response in the bone proximal and distal to the defect and in the un-operated femurs. We demonstrate that treatment with Scl-Ab can enhance bone repair in a bone defect and in the surrounding host bone, but lacks the osteoinductive activity to heal it. This agent seems to be most effective in bone repair scenarios where there is cortical integrity.

Link to Article

http://onlinelibrary.wiley.com/doi/10.1002/jor.22498/abstract

A comparative study of the bone metabolic response to dried plum supplementation and PTH treatment in adult, osteopenic ovariectomized rat

Authors

Brenda J. Smith, So Young Bu, Yan Wang, Elizabeth Rendina, Yin F. Lim, Denver Marlow, Stephen L. Clarke, Diane M. Cullen, Edralin A. Lucas

Abstract

Dried plum has been reported to have potent effects on bone in osteopenic animal models, but the mechanisms through which bone metabolism is altered in vivo remain unclear. To address this issue, a study comparing the metabolic response of dried plum to the anabolic agent, parathyroid hormone (PTH), was undertaken. Six month-old female Sprague Dawley rats (n = 84) were sham-operated (SHAM) or ovariectomized (OVX) and maintained on a control diet for 6 wks until osteopenia was confirmed. Treatments were initiated consisting of a control diet (AIN-93M) supplemented with dried plum (0, 5, 15 or 25%; w/w) or a positive control group receiving PTH. At the end of 6 wks of treatment, whole body and femoral bone mineral density (BMD) were restored by the two higher doses of dried plum to the level of the SHAM group. Trabecular bone volume and cortical thickness were also improved with these two doses of dried plum. Dried plum suppressed the OVX-induced increase in bone turnover as indicated by systemic biomarkers of bone metabolism, N-terminal procollagen type 1 (P1NP) and deoxypyridinoline (DPD). Dynamic bone histomorphometric analysis of the tibial metaphysis revealed that dried plum restored the OVX-induced increase in cancellous bone formation rate (BFR) and mineralizing surface (MS/BS) to the SHAM group, but some doses of dried plum increased endocortical mineral apposition rate (MAR). As expected, PTH significantly increased endocortical MAR and BFR, periosteal BFR, and trabecular MAR and BFR beyond that of the OVX and maintained the accelerated rate of bone resorption associated with OVX. Dried plum up-regulated bone morphogenetic protein 4 (Bmp4) and insulin-like growth factor 1 (Igf1) while down-regulating nuclear factor T cell activator 1 (Nfatc1). These findings demonstrate that in the adult osteopenic OVX animal, the effects of dried plum differ from that of PTH in that dried plum primarily suppressed bone turnover with the exception of the indices of bone formation at the endocortical surface.

Link to Article

http://dx.doi.org/10.1016/j.bone.2013.10.005

Bone quality and strength are greater in growing male rats fed fructose compared with glucose

Authors

Erica F. Bass, Clifton A. Bailee, Richard D. Lewis, Silvia Q. Giraudo

Abstract

Optimization of peak bone mass during adolescence is important for osteoporosis prevention. Studies in rodents and humans have demonstrated the harmful effects of sugar intake on bone health. With the high levels of sucrose in the diets of adolescents, it is necessary to understand the influence of glucose and fructose on growing bones. This study compared the effects of dietary glucose and fructose on bone formation, microarchitecture, and strength. Because of the different metabolic effects of glucose and fructose, we hypothesized that their individual effects on bone would be different. Eighteen male Sprague-Dawley rats (age, 60 days) were randomly assigned to high-fructose (n = 9; 40% fructose, 10% glucose) or high-glucose diet (n = 9; 50% glucose) for 12 weeks. Bone measurements included histology and histomorphometry of trabecular bone in the distal femur and a 3-point bending test of the whole tibia. Whole liver mass and postprandial serum glucose, insulin, and triglycerides were used to assess differences in energy metabolism between the diets. There were no differences in food intake, body weight, or visceral adiposity between groups, but fructose consumption led to heavier livers (P = .001) and elevated serum triglycerides (P = .00). The distal femurs of fructose-fed rats had greater bone volume (bone volume/total volume; P = .03), lower bone surface (bone surface/bone volume; P = .02), and thicker trabeculae (trabecular thickness; P = .01). The tibias of the fructose-fed rats also withstood a greater maximum flexure load (P = .032). These results indicate that consumption of the high-fructose diet resulted in stronger bones with enhanced microarchitecture than consumption of the high-glucose diet.

Link to Article

http://dx.doi.org/10.1016/j.nutres.2013.08.006