Sclerostin antibody (Scl-Ab) improves osteomalacia phenotype in dentin matrix protein 1(Dmp1) knockout mice with little impact on serum levels of phosphorus and FGF23

Authors

Yinshi Rena, Xianglong Hana, Yan Jinga, Baozhi Yuanc, Huazhu Ked, Min Liud, Jian Q. Feng

Abstract

Unlike treatments for most rickets, the treatment using 1,25-(OH)2 vitamin D3 has little efficacy on patients with hypophosphatemic rickets, a set of rare genetic diseases. Thus, understanding the local cause for osteomalacia in hypophosphatemic rickets and developing an effective treatment to restore mineralization in this rare disease has been a longstanding goal in medicine. Here, we used Dmp1 knockout (KO) mice (whose mutations led to the same type of autosomal recessive hypophosphatemic rickets in humans) as the model in which the monoclonal antibody of sclerostin (Scl-Ab) was tested in two age groups for 8 weeks: the prevention group (starting at age 4 weeks) and the treatment group (starting at age 12 weeks). Applications of Scl-Ab greatly improved the osteomalacia phenotype (> 15%) and the biomechanical properties (3-point bending, ~ 60%) in the treated long-bone group. Our studies not only showed improvement of the osteomalacia in the alveolar bone, which has the highest bone metabolism rate, as well as the long bone phenotypes in treated mice. All these improvements attributed to the use of Scl-Ab are independent of the change in serum levels of phosphorus and FGF23, since Scl-Ab had little efficacy on those parameters. Finally, we propose a model to explain how Scl-Ab can improve the Dmp1 KO osteomalacia phenotype, in which the sclerostin level is already low.

Link to Article

http://dx.doi.org/10.1016/j.matbio.2015.12.009

Dihydroartemisinin, an Anti-Malaria Drug, Suppresses Estrogen Deficiency-Induced Osteoporosis, Osteoclast Formation, and RANKL-Induced Signaling Pathways

Authors

Lin Zhou, Qian Liu, Mingli Yang, Tao Wang, Jun Yao, Jianwen Cheng, Jinbo Yuan, Xixi Lin, Jinmin Zhao, Jennifer Tickner and Jiake Xu

Abstract

Osteoporosis is an osteolytic disease that features enhanced osteoclast formation and bone resorption. Identification of agents that can inhibit osteoclast formation and function is important for the treatment of osteoporosis. Dihydroartemisinin is a natural compound used to treat malaria but its role in osteoporosis is not known. Here, we found that dihydroartemisinin can suppress RANKL-induced osteoclastogenesis and bone resorption in a dose-dependent manner. Dihydroartemisinin inhibited the expression of osteoclast marker genes such as cathepsin K, calcitonin receptor, and tartrate-resistant acid phosphatase (TRAcP). Furthermore, dihydroartemisinin inhibited RANKL-induced NF-κB and NFAT activity. In addition, using an in vivo ovariectomized mouse model, we show that dihydroartemisinin is able to reverse the bone loss caused by ovariectomy. Together, this study shows that dihydroartemisinin attenuates bone loss in ovariectomized mice through inhibiting RANKL-induced osteoclast formation and function. This indicates that dihydroartemisinin, the first physiology or medicine nobel prize discovery of China, is a potential treatment option against osteolytic bone disease.

Sclerostin Antibody Treatment Improves the Bone Phenotype of Crtap-/- Mice, a Model of Recessive Osteogenesis Imperfecta

Authors

Ingo Grafe, Stefanie Alexander, Tao Yang, Caressa Lietman, Erica P Homan, Elda Munivez, Yuqing Chen, Ming Ming Jiang, Terry Bertin, Brian Dawson, Franklin Asuncion, Hua Zhu Ke, Michael S Ominsky and Brendan Lee

Abstract

Osteogenesis Imperfecta (OI) is characterized by low bone mass, poor bone quality and fractures. Standard treatment for OI patients is limited to bisphosphonates, which only incompletely correct the bone phenotype, and seem to be less effective in adults. Sclerostin neutralizing antibodies (Scl-Ab) have been shown to be beneficial in animal models of osteoporosis, and dominant OI resulting from mutations in the genes encoding type I collagen. However, Scl-Ab treatment has not been studied in models of recessive OI. Cartilage associated protein (CRTAP) is involved in posttranslational type I collagen modification, and its loss of function results in recessive OI. In this study, we treated 1 and 6 week old Crtap-/- mice with Scl-Ab for 6 weeks (25 mg/kg, s.c., twice per week), to determine the effects on the bone phenotype in models of “pediatric” and “young adult” recessive OI. Vehicle treated Crtap-/- and wildtype (WT) mice served as controls. Compared with control Crtap-/- mice, microCT analyses showed significant increases in bone volume and improved trabecular microarchitecture in Scl-Ab treated Crtap-/- mice in both age cohorts, in both vertebrae and femurs. Additionally, Scl-Ab improved femoral cortical parameters in both age cohorts. Biomechanical testing showed that Scl-Ab improved parameters of whole bone strength in Crtap-/- mice, with more robust effects in the week 6-12 cohort, but did not affect the increased bone brittleness. Additionally, Scl-Ab normalized the increased osteoclast numbers, stimulated bone formation rate (week 6-12 cohort only), but did not affect osteocyte density. Overall, our findings suggest that Scl-Ab treatment may be beneficial in the treatment of recessive OI caused by defects in collagen post-translational modification.

Link to Article

http://dx.doi.org/10.1002/jbmr.2776

Skeletal Mineralization Deficits and Impaired Biogenesis and Function of Chondrocyte-Derived Matrix Vesicles in Phospho1-/- and Phospho1/Pit1 Double Knockout Mice

Authors

Manisha C. Yadav, Massimo Bottini., Esther Cory, Kunal Bhattacharya., Pia Kuss, Sonoko Narisawa, Robert L. Sah, Laurent Beck, Bengt Fadeel, Colin Farquharson and José Luis Millán

Abstract

We have previously shown that ablation of either the Phospho1 or Alpl gene, encoding PHOSPHO1 and tissue-nonspecific alkaline phosphatase (TNAP) respectively, lead to hyperosteoidosis but that their chondrocyte- and osteoblast-derived matrix vesicles (MVs) are able to initiate mineralization. In contrast, the double ablation of Phospho1 and Alpl completely abolish initiation and progression of skeletal mineralization. We argued that MVs initiate mineralization by a dual mechanism: PHOSPHO1-mediated intravesicular generation of Pi and phosphate transporter-mediated influx of Pi. To test this hypothesis, we generated mice with col2a1-driven cre-mediated ablation of Slc20a1, hereafter referred to as Pit1, alone or in combination with a Phospho1 gene deletion. Pit1col2/col2 mice did not show any major phenotypic abnormalities, while severe skeletal deformities were observed in the [Phospho1-/-; Pit1col2/col2] double knockout mice that were more pronounced than those observed in the Phospho1-/- mice. Histological analysis of [Phospho1-/-; Pit1col2/col2] bones showed growth plate abnormalities with a shorter hypertrophic chondrocyte zone and extensive hyperosteoidosis. The [Phospho1-/-; Pit1col2/col2] skeleton displayed significantly decreases in BV/TV%, trabecular number and bone mineral density, as well as decreased stiffness, decreased strength, and increased post-yield deflection compared to Phospho1-/- mice. Using atomic force microscopy we found that ∼80% of [Phospho1-/-; Pit1col2/col2] MVs were devoid of mineral in comparison to ∼50% for the Phospho1-/- MVs and ∼25% for the WT and Pit1col2/col2 MVs. We also found a significant decrease in the number of MVs produced by both Phospho1-/- and [Phospho1-/-; Pit1col2/col2] chondrocytes. These data support the involvement of PiT-1 in the initiation of skeletal mineralization and provide compelling evidence that PHOSPHO1 function is involved in MV biogenesis.

Link to Article

http://dx.doi.org/10.1002/jbmr.2790

Injury response of geriatric mouse patellar tendons

Authors

Michael J. Mienaltowski, Andrew A. Dunkman, Mark R. Buckley, David P. Beason, Sheila M. Adams, David E. Birk and Louis J. Soslowsky

Abstract

Injury adversely impacts the structure and mechanical properties of a tendon, thus causing pain and disability. Previously, we demonstrated that patellar tendons in mature (P150) and aged (P300) mice do not recover original functionality, even 6 weeks after injury, and that uninjured geriatric tendons (P570) are functionally inferior to uninjured mature tendons. In this study, we hypothesized that the repair response in injured geriatric mice would be further compromised, thus undermining patellar tendon function post-injury. Patellar tendons from wild-type mice were injured at 540 days. At 3 and 6 weeks post-surgery, structural, mechanical, and biochemical analyses were performed and compared to uninjured controls. Mechanical properties of geriatric tendons failed to improve after injury. When compared to mature and aged tendons post-injury, it was determined that at no age was there a suitable repair response. In previous studies, we were able to associate the absence of SLRPs with phenotypic changes both early and late in repair. Here we found that SLRPs were significantly decreased after injury, thus offering a possible explanation for why geriatric tendons were unable to mount an adequate repair response. Thus, we conclude that regardless of age after maturity, tendon healing ultimately results in a substandard outcome.

Link to Article

http://dx.doi.org/10.1002/jor.23144

Stromal-Initiated Changes in the Bone Promote Metastatic Niche Development

Authors

Xianmin Luo, Yujie Fu, Andrew J. Loza, Bhavna Murali, Kathleen M. Leahy, Megan K. Ruhland, Margery Gang, Xinming Su, Ali Zamani, Yu Shi, Kory J. Lavine, David M. Ornitz, Katherine N. Weilbaecher, Fanxin Long, Deborah V. Novack, Roberta Faccio, Gregory D. Longmore, Sheila A. Stewart

Abstract

More than 85% of advanced breast cancer patients suffer from metastatic bone lesions, yet the mechanisms that facilitate these metastases remain poorly understood. Recent studies suggest that tumor-derived factors initiate changes within the tumor microenvironment to facilitate metastasis. However, whether stromal-initiated changes are sufficient to drive increased metastasis in the bone remains an open question. Thus, we developed a model to induce reactive senescent osteoblasts and found that they increased breast cancer colonization of the bone. Analysis of senescent osteoblasts revealed that they failed to mineralize bone matrix and increased local osteoclastogenesis, the latter process being driven by the senescence-associated secretory phenotype factor, IL-6. Neutralization of IL-6 was sufficient to limit senescence-induced osteoclastogenesis and tumor cell localization to bone, thereby reducing tumor burden. Together, these data suggest that a reactive stromal compartment can condition the niche, in the absence of tumor-derived signals, to facilitate metastatic tumor growth in the bone.

Link to Article

http://dx.doi.org/10.1016/j.celrep.2015.12.016