Riboflavin crosslinked high-density collagen gel for the repair of annular defects in intervertebral discs: An in vivo study

Authors

Peter Grunert, Brandon H. Borde, Sara B. Towne, Yu Moriguchi, Katherine D. Hudson, Lawrence J. Bonassar, Roger Härtl

Abstract

Open annular defects compromise the ability of the annulus fibrosus to contain nuclear tissue in the disc space, and therefore lead to disc herniation with subsequent degenerative changes to the entire intervertebral disc. This study reports the use of riboflavin crosslinked high-density collagen gel for the repair of annular defects in a needle-punctured rat-tail model. High-density collagen has increased stiffness and greater hydraulic permeability than conventional low-density gels; riboflavin crosslinking further increases these properties. This study found that treating annular defects with crosslinked high-density collagen inhibited the progression of disc degeneration over 18 weeks compared to untreated control discs. Histological sections of FITC-labeled collagen gel revealed an early tight attachment to host annular tissue. The gel was subsequently infiltrated by host fibroblasts which remodeled it into a fibrous cap that bridged the outer disrupted annular fibers and partially repaired the defect. This repair tissue enhanced retention of nucleus pulposus tissue, maintained physiological disc hydration, and preserved hydraulic permeability, according to MRI, histological, and mechanical assessments. Degenerative changes were partially reversed in treated discs, as indicated by an increase in nucleus pulposus size and hydration between weeks 5 and 18. The collagen gel appeared to work as an instant sealant and by enhancing the intrinsic healing capabilities of the host tissue.

Link To Article

http://dx.doi.org/10.1016/j.actbio.2015.06.006

Alternative NF-κB Regulates RANKL-Induced Osteoclast Differentiation and Mitochondrial Biogenesis via Independent Mechanisms

Authors

Rong Zeng, Roberta Faccio, and Deborah V Novack

Abstract

Mitochondrial biogenesis, the generation of new mitochondrial DNA and proteins, has been linked to osteoclast (OC) differentiation and function. In this study we used mice with mutations in key alternative NF-κB pathway proteins, RelB and NIK, to dissect the complex relationship between mitochondrial biogenesis and osteoclastogenesis. OC precursors lacking either NIK or RelB, RANKL were unable to increase mitochondrial DNA or OxPhos protein expression, associated with lower oxygen consumption rates. Transgenic OC precursors expressing constitutively active NIK showed normal RANKL-induced mitochondrial biogenesis (OxPhos expression and mitochondria copy number) compared to controls, but larger mitochondrial dimensions and increased oxygen consumption rates, suggesting increased mitochondrial function. To deduce the mechanism for mitochondrial biogenesis defects in NIK- and RelB-deficient precursors, we examined expression of genes known to control this process. PGC-1β (Ppargc1b) expression, but not PGC-1α, PPRC1 or ERRα, was significantly reduced in RelB-/- and NIK-/- OCs. Because PGC-1β has been reported to positively regulate both mitochondrial biogenesis and differentiation in OCs, we retrovirally overexpressed PGC-1β in RelB-/- cells, but surprisingly found that it did not affect differentiation, nor restore RANKL-induced mitochondrial biogenesis. To determine whether the blockade in osteoclastogenesis in RelB-deficient cells precludes mitochondrial biogenesis, we rescued RelB-/- differentiation via overexpression of NFATc1. Mitochondrial parameters in neither WT nor RelB-deficient cultures were affected by NFATc1 overexpression, and bone resorption in RelB -/- was not restored. Furthermore, NFATc1 co-overexpression with PGC-1β, while allowing OC differentiation, did not rescue mitochondrial biogenesis or bone resorption in RelB-/- OCs, by CTX-I levels. Thus, our results indicate that the alternative NF-κB pathway plays dual, but distinct roles in controlling the independent processes of OC differentiation and OC mitochondrial biogenesis. Furthermore, the inability of PGC-1β to drive mitochondrial biogenesis in OCs without RelB indicates a cell-type specificity in mitochondria regulation.

Link To Article

http://dx.doi.org/10.1002/jbmr.2584

S-EQUOL PREVENTS LOSS OF BONE STRENGTH IN RAT OSTEOPOROSIS MODEL

Authors

J.A. Yu-Yahiro, C.B. Ruff, B.G. Parks, V.S. Sinkov, I. Merchenthaler

Abstract

Background: To investigate the effect of S-equol, a selective estrogen receptor ß agonist produced in certain individuals by biotransformation of the soy isoflavone daidzein, on bone structure, bone strength, and metabolism in overiectomized rats. Design: Controlled animal study. Participants: Total of 75 female rats. Intervention: Animals were divided into 5 groups: ovariectomized (OVX), OVX+17-beta estradiol benzoate (EB), OVX+S-equol (30 mg/kg), OVX+S-equol (100 mg/kg), and SHAM. Animals received drug or vehicle for 60 days. At sacrifice, right femora and vertebrae (L3 and L4) were excised. Measurements: Bone density and structural parameters were measured by pQCT. Mechanical testing and quantitative histomorphometry were done. Blood markers of bone metabolism and uterine weights were measured. Results: Higher dose S-equol preserved mechanical strength of bone. Vertebral compressive strength, femoral bending strength, and femoral cortical thickness were not different between the S- equol (100 mg/kg) , SHAM, and EB groups and all were significantly higher than OVX and S-equol (30 mg/kg) groups. No differences were found in osteoclast numbers or vertebral bone mineral composition, and serum markers of bone metabolism did not follow the pattern of strength measures differences. Uterine weight in the higher dose S-equol group was significantly lower than in SHAM and EB groups. Conclusions: Treatment of OVX rats with S-equol (100 mg/kg) resulted in preservation of vertebral and femoral bone strength and volume not different from that in SHAM or EB rats. Higher dose S-equol caused less uterine stimulation than did endogenous or synthetic estrogen. These results suggest that S-equol warrants further study as a possible alternative to estrogen replacement for treatment of osteoporosis.

Link To Article

http://www.jarcp.com/498-s-equol-prevents-loss-of-bone-strength-in-rat-osteoporosis-model.html

In vivo monitoring of activated macrophages and neutrophils in response to ischemic osteonecrosis in a mouse model

Authors

Matthew C. Phipps, YiHui Huang, Ryosuke Yamaguchi, Nobuhiro Kamiy, Naga S. Adapala, Liping Tang, and Harry K. W. Kim

Abstract

Ischemic osteonecrosis (IO) is caused by disruption of the blood supply to bone. It is a debilitating condition with pathological healing characterized by excessive bone resorption and delayed osteogenesis. Although the majority of research has focused on the role of osteoblasts and osteoclasts in the disease progression, we hypothesize that innate immune cells, macrophages and neutrophils, play a significant role. With the recent development of real-time imaging probes for neutrophils and macrophages, the purpose of this study was to investigate the kinetic immune cell response in a mouse model of IO. Our results show that induction of IO leads to a significant accumulation of activated neutrophils and macrophages at the affected tissue by 48 h after surgery. Additionally, the accumulation of these immune cells remained elevated in comparison to sham controls for up to 6 weeks, indicative of chronic inflammation. Immunohistochemistry confirmed the immune cell infiltration into the necrotic bone marrow and the increased presence of TNFα-positive cells, demonstrating, for the first time, a direct response of these cells to ischemia induced necrotic bone. These new findings support a hypothesis that IO is an osteoimmunologic condition where innate immune cells play a significant role in the chronic inflammation.

Link to Article

http://dx.doi.org/10.1002/jor.22952

The efficacy of a tissue-engineered xenograft in conjunction with sodium hyaluronate carrier in maxillary sinus augmentation: a clinical study

Authors

H.A. Emam, G. Behiri, M. El-Alaily, M. Sharawy

Abstract

PepGen P-15 Putty comprises anorganic bovine bone matrix (ABM) coupled with a synthetic cell-binding peptide, suspended in a sodium hyaluronate carrier. The P-15 portion exhibits a similar structure and properties to the cell-binding region of type I collagen. This study was performed to evaluate ABM/P-15 putty as the sole graft in sinus augmentation. Ten patients for whom both a sinus augmentation and two implants were indicated in the posterior maxilla were enrolled. Bone cores were harvested at 8 and 16 weeks, followed by placement of one implant at 8 weeks and the second at 16 weeks. Twenty collected bone cores were evaluated histologically and by micro-computed tomography. Results showed a significant increase (P < 0.05) in bone mineral density at 8 weeks (0.70 ± 0.13 g/cm3) and 16 weeks (0.97 ± 0.08 g/cm3) in the graft compared to native (control) bone (0.04 ± 0.02 g/cm3). There was no significant difference (P > 0.05) in the percentage bone volume at the two time intervals (PBV 21.14 ± 4.56 at 8 weeks and 26.33 ± 5.60 at 16 weeks). The average increase in bone height at 16 weeks was 10.55 ± 0.53 mm. It is concluded that PepGen P-15 Putty is capable of conducting and accelerating new bone formation and can successfully support dental implants.

Link To Article

http://dx.doi.org/10.1016/j.ijom.2015.04.011

The TGF-β Signaling Regulator PMEPA1 Suppresses Prostate Cancer Metastases to Bone

Authors

Pierrick G.J. Fournier, Patricia Juárez, Guanglong Jiang, Gregory A. Clines, Maria Niewolna, Hun Soo Kim, Holly W. Walton, Xiang Hong Peng, Yunlong Liu, Khalid S. Mohammad, Clark D. Wells, John M. Chirgwin, Theresa A. Guise

Abstract

Transforming growth factor-β (TGF-β) regulates the expression of genes supporting breast cancer cells in bone, but little is known about prostate cancer bone metastases and TGF-β. Our study reveals that the TGFBR1 inhibitor SD208 effectively reduces prostate cancer bone metastases. TGF-β upregulates in prostate cancer cells a set of genes associated with cancer aggressiveness and bone metastases, and the most upregulated gene was PMEPA1. In patients, PMEPA1 expression decreased in metastatic prostate cancer and low Pmepa1 correlated with decreased metastasis-free survival. Only membrane-anchored isoforms of PMEPA1 interacted with R-SMADs and ubiquitin ligases, blocking TGF-β signaling independently of the proteasome. Interrupting this negative feedback loop by PMEPA1 knockdown increased prometastatic gene expression and bone metastases in a mouse prostate cancer model.

Link To Article

http://dx.doi.org/10.1016/j.ccell.2015.04.009