Sclerostin antibody improves skeletal parameters in a Brtl/+ mouse model of osteogenesis imperfecta

Authors

Benjamin P. Sinder, Mary M. Eddy, Michael S Ominsky, Michelle S. Caird, Joan C. Marini, Kenneth M. Kozloff

Abstract

Osteogenesis imperfecta (OI) is a genetic bone dysplasia characterized by osteopenia and easy susceptibility to fracture. Symptoms are most prominent during childhood. Although anti-resorptive bisphosphonates have been widely used to treat pediatric OI, controlled trials showed improved vertebral parameters but equivocal effects on long-bone fracture rates. New treatments for OI are needed to increase bone mass throughout the skeleton. Sclerostin antibody (Scl-Ab) therapy is potently anabolic in the skeleton by stimulating osteoblasts via the canonical wnt signaling pathway, and may be beneficial for treating OI. In this study, Scl-Ab therapy was investigated in mice heterozygous for a typical OI-causing Gly- > Cys substitution incol1a1. Two weeks of Scl-Ab successfully stimulated osteoblast bone formation in Brtl/+ and WT mice, leading to improved bone mass and reduced long-bone fragility. Image-guided nanoindentation revealed no alteration in local tissue mineralization dynamics with Scl-Ab. These results contrast with previous findings of antiresorptive efficacy in OI both in mechanism and potency of effects on fragility. In conclusion, short-term Scl-Ab was successfully anabolic in osteoblasts harboring a typical OI-causing collagen mutation and represents a potential new therapy to improve bone mass and reduce fractures in pediatric OI.

Link to Article

http://dx.doi.org/10.1002/jbmr.1717

In vivo bone-specific EphB4 overexpression in mice protects both subchondral bone and cartilage during osteoarthritis

Authors

Gladys Valverde-Franco PhD, Jean-Pierre Pelletier MD, Hassan Fahmi PhD, David Hum MSc, Koichi Matsuo MD, PhD, Bertrand Lussier DVM, MSc, Dipl. ACVS, Mohit Kapoor PhD, Johanne Martel-Pelletier PhD

Abstract

In vitro activation of the receptor EphB4 positively impacts human osteoarthritis (OA) articular cell metabolism. However, the specific in vivo role of this ephrin receptor in OA remains unknown. We investigated in mice the in vivo effect of bone-specific EphB4 overexpression on OA pathophysiology. Morphometric, morphological, and radiological evaluations were performed on postnatal day 5 (P5) and on 10-week-old mice. Knee OA was surgically induced (DMM) in 10-week-old male EphB4 homozygous (TgEphB4) and wild-type (WT) mice. Medial compartment evaluations of cartilage were performed using histology and immunohistochemistry, and of subchondral bone using histomorphometry, osteoclast staining, and micro-computed tomography. There was no obvious phenotypic difference in skeletal development between TgEphB4 and WT mice at P5 and 10 weeks. At 8 and 12 weeks post-DMM surgery, TgEphB4 mice demonstrated significantly less cartilage alteration than the WT in the medial tibial plateau and the femoral condyle. This was associated with a significant reduction in the operated TgEphB4 mice of aggrecan and type II collagen degradation products, type X collagen and collagen fibril disorganization. The medial tibial subchondral bone demonstrated at both times post-DMM surgery that, compared to the WT, the TgEphB4 mice had a significant reduction in sclerosis, bone volume, trabecular thickness, and number of tartrate resistant acid phosphatase positive osteoclasts.This is the first in vivo evidence that bone-specific EphB4 overexpression exerts a protective effect on OA joint structural changes. This study stresses the in vivo importance of subchondral bone biology in cartilage integrity.

Link to Article

http://dx.doi.org/10.1002/art.34638

BMP-2 tethered hydroxyapatite for bone tissue regeneration: Coating chemistry and osteoblast attachment

Authors

Stefanie M. Shiels, Kimberly D. Solomon, Marcello Pilia, Mark R. Appleford, Joo L. Ong

Abstract

The goal of this study was to determine the effectiveness of using polyethyleneimine (PEI) and a polyethylene glycol (PEG) tether to bind human recombinant bone morphogenetic protein-2 (rhBMP-2) to hydroxyapatite (HAp) to enhance rhBMP-2 loading, alter its release properties, and enhance cellular interaction with the material. By using a branched PEI that was derived to express free thiols, rhBMP-2 was coated onto dense HAp surfaces at ∼43 ng/cm2. Using this novel attachment methodology, it was observed that the PEI-SH coating did not change the morphology of the HAp surfaces and that the amount of rhBMP-2 loaded was comparable to a direct adsorption method. In addition, it was also observed that the PEI and PEG tether significantly retained the rhBMP-2 to the HAp surface, inhibiting the burst release effect. Using human fetal osteoblast cells, the PEI- and PEG-tethered BMP-2 was also observed to increase cellular attachment by 10-fold when compared with uncoated HAp and adsorbed rhBMP-2. It was concluded from this study that PEI and PEG tether significantly reduce the initial burst release effect of rhBMP-2. It was also concluded that the rhBMP-2 conjugation to PEI and PEG tether promoted an increase in cellular attachment to the HAp surface.

Link to Article

http://dx.doi.org/10.1002/jbm.a.34241

Stable Size Distribution of Amyloid Plaques Over the Course of Alzheimer Disease

Authors

Serrano-Pozo, Alberto MD; Mielke, Matthew L. BS; Muzitansky, Alona; Gómez-Isla, Teresa MD, PhD; Growdon, John H. MD; Bacskai, Brian J. PhD; Betensky, Rebecca A. PhD, MPH; Frosch, Matthew P. MD, PhD; Hyman, Bradley T. MD, PhD

Abstract

Amyloid β plaques are a key pathologic feature of Alzheimer disease (AD), but whether plaque sizes increase or stabilize over thecourse of AD is unknown. We measured the size distribution of total immunoreactive (10D5-positive) and dense-core (Thioflavin S-positive) plaques in the temporal neocortex of a large group of subjects with AD and age-matched plaque-bearing subjects without dementia to test the hypothesis that amyloid plaques continue to grow along with the progression of the disease. The size of amyloid β (10D5)-positive plaques did not differ between groups, whereas dense-core plaques from the group with AD were slightly larger than those from the group without dementia (∼25%-30%, p = 0.01). Within the group with AD, dense-core plaque size did not independently correlate with duration of clinical disease (from 4 to 21 years, p = 0.68), whereas 10D5-positive plaque size correlated negatively with disease duration (p = 0.01). By contrast, an earlier age of symptom onset strongly predicted a larger postmortem plaque size; this effect was independent of disease duration and the presence of the APOE[Latin Small Letter Open E]4 allele (p = 0.0001). We conclude that plaques vary in size among patients, with larger size distributions correlating with an earlier age of onset, but plaques do not substantially increase in size over the clinical course of the disease.

Link to Article

http://dx.doi.org/10.1097/NEN.0b013e31825e77de

Stimulation of Host Bone Marrow Stromal Cells by Sympathetic Nerves Promotes Breast Cancer Bone Metastasis in Mice

Authors

J. Preston Campbell, Matthew R. Karolak, Yun Ma,Daniel S. Perrien, S. Kathryn Masood-Campbell, Niki L. Penner, Steve A. Munoz, Andries Zijlstra, Xiangli Yang, Julie A. Sterling, Florent Elefteriou

Abstract

Bone and lung metastases are responsible for the majority of deaths in patients with breast cancer. Following treatment of the primary cancer, emotional and psychosocial factors within this population precipitate time to recurrence and death, however the underlying mechanism(s) remain unclear. Using a mouse model of bone metastasis, we provide experimental evidence that activation of the sympathetic nervous system, which is one of many pathophysiological consequences of severe stress and depression, promotes MDA-231 breast cancer cell colonization of bone via a neurohormonal effect on the host bone marrow stroma. We demonstrate that induction of RANKL expression in bone marrow osteoblasts, following β2AR stimulation, increases the migration of metastatic MDA-231 cells in vitro, independently of SDF1-CXCR4 signaling. We also show that the stimulatory effect of endogenous (chronic stress) or pharmacologic sympathetic activation on breast cancer bone metastasis in vivo can be blocked with the β-blocker propranolol, and by knockdown of RANK expression in MDA-231 cells. These findings indicate that RANKL promotes breast cancer cell metastasis to bone via its pro-migratory effect on breast cancer cells, independently of its effect on bone turnover. The emerging clinical implication, supported by recent epidemiological studies, is that βAR-blockers and drugs interfering with RANKL signaling, such as Denosumab, could increase patient survival if used as adjuvant therapy to inhibit both the early colonization of bone by metastatic breast cancer cells and the initiation of the “vicious cycle” of bone destruction induced by these cells.

Link to Article

http://dx.doi.org/10.1371/journal.pbio.1001363

Evaluation of BMP-2 tethered polyelectrolyte coatings on hydroxyapatite scaffolds in vivo

Authors

Stefanie Shiels, Sunho Oh, Chunsik Bae, Teja Guda, Brian Singleton, David D. Dean, Joseph C. Wenke, Mark R. Appleford, Joo L. Ong

Abstract

The goal of this in vivo study was to evaluate the osteoinductive and angio-inductive properties of a porous hydroxyapatite (HAp) scaffold with immobilized recombinant bone morphogenetic protein-2 (rhBMP-2) on the surface. It was hypothesized in this study that the use of a rhBMP-2 incorporated polyelectrolyte coating on the HAp scaffold would allow for controlled exposure of rhBMP-2 into the tissue and would provide a sound platform for tissue growth. The scaffolds were characterized for porosity and interconnectivity using pycnometry, scanning electron microscopy and micro-ct. These scaffolds were then divided into the following four groups: (a) HAp scaffold (n-HAp group), (b) rhBMP-2 physically adsorbed on HAp scaffold (HAp-BMP-2 Group), (c) polyelectrolyte coating on HAp scaffold without rhBMP-2 (HAp-PEI Scaffold Group), and (d) polyelectrolyte coating tethered with rhBMP-2 on HAp scaffold (HAp-PEI-BMP-2 Scaffold Group). Using 18 skeletally matured New Zealand white rabbits, these scaffolds were evaluated in a nonload bearing femoral condyle plug model. The negative controls for this study have defects that were left untreated and the positive controls have defects that were filled with autologous bone graft harvested from epsilateral iliac crest. Bone induction, vessel growth, and scaffold-bone contact were analyzed after 8-week implantation using micro-CT and histomorphometry. It was concluded from this study that the use of scaffold with an attached rhBMP-2 increased the vascularization around the implant when compared with the uncoated n-HAp scaffold, a necessary step of bone regeneration. The open-pore HAp scaffold was also concluded to provide a platform for tissue growth, drug loading, and tissue interaction.

Link to Article

http://dx.doi.org/10.1002/jbm.b.32745