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

Attenuation of hind-limb suspension-induced bone loss by curcumin is associated with reduced oxidative stress and increased vitamin D receptor expression

Authors

M. Xin, Y. Yang, D. Zhang, J. Wang, S. Chen, D. Zhou

Abstract

Summary Treatment with curcumin attenuated modeled microgravity-induced bone loss, possibly through abating oxidative stress and activating vitamin D receptor. Curcumin might be an effective countermeasure for microgravity-induced bone loss but remains to be tested in humans.

Introduction Bone loss is one of the most important complications for human crewmembers who are exposed to long-term microgravity in space and also for bedridden people. The aim of the current study was to elucidate whether treatment with curcumin attenuated bone loss induced by microgravity.

Methods We used hind-limb suspension (HLS) and rotary wall vessel bioreactor (RWVB) to model microgravity in vivo and in vitro, respectively. We investigated the effects of curcumin consumption (40 mg kg−1 body weight day−1, via daily oral gavages) on Sprague–Dawley (SD) rats exposed to HLS for 6 weeks. Then, we investigated the effects of incubation with curcumin (4 μM) on MC3T3-E1 and RAW264.7 cells cultured in RWVB.

Results Curcumin alleviated HLS-induced reduction of bone mineral density in tibiae and preserved bone structure in tibiae and mechanical strength in femurs. Curcumin alleviated HLS-induced oxidative stress marked by reduced malondialdehyde content and increased total sulfhydryl content in femurs. In cultured MC3T3-E1 cells, curcumin inhibited modeled microgravity-induced reactive oxygen species (ROS) formation and enhanced osteoblastic differentiation. In cultured RAW264.7 cells, curcumin reduced modeled microgravity-induced ROS formation and attenuated osteoclastogenesis. In addition, curcumin upregulated vitamin D receptor (VDR) expression in femurs of rats exposed to HLS and MC3T3-E1 cells exposed to modeled microgravity.

Conclusion Curcumin alleviated HLS-induced bone loss in rats, possibly via suppressing oxidative stress and upregulating VDR expression.

Link To Article

http://dx.doi.org/10.1007/s00198-015-3153-7

The receptor CD44 is associated with systemic insulin resistance and proinflammatory macrophages in human adipose tissue

Authors

Li Fen Liu, Keiichi Kodama, Ke Wei, Lorna L. Tolentino, Okmi Choi, Edgar G. Engleman, Atul J. Butte, Tracey McLaughlin

Abstract

Aims/hypothesis Proinflammatory immune cell infiltration in human adipose tissue is associated with the development of insulin resistance. We previously identified, via a gene expression-based genome-wide association study, the cell-surface immune cell receptor CD44 as a functionally important gene associated with type 2 diabetes. We then showed that, compared with controls, Cd44 knockout mice were protected from insulin resistance and adipose tissue inflammation during diet-induced obesity. We thus sought to test whether CD44 is associated with adipose tissue inflammation and insulin resistance in humans.

Methods Participants included 58 healthy, overweight/moderately obese white adults who met predetermined criteria for insulin resistance or insulin sensitivity based on the modified insulin-suppression test. Serum was collected from 43 participants to measure circulating concentrations of CD44. Subcutaneous adipose tissue was obtained from 17 participants to compare CD44, its ligand osteopontin (OPN, also known as SPP1) and pro-inflammatory gene expression. CD44 expression on adipose tissue macrophage (ATM) surfaces was determined by flow cytometry.

Results Serum CD44 concentrations were significantly increased in insulin-resistant (IR) participants. CD44 gene expression in subcutaneous adipose tissue was threefold higher in the IR subgroup. The expression of OPN, CD68 and IL6 was also significantly elevated in IR individuals. CD44 gene expression correlated significantly with CD68 and IL6 expression. CD44 density on ATMs was associated with proinflammatory M1 polarisation.

Conclusions/interpretation CD44 and OPN in human adipose tissue are associated with localised inflammation and systemic insulin resistance. This receptor–ligand pair is worthy of further research as a potentially modifiable contributor to human insulin resistance and type 2 diabetes.

Link To Article

http://dx.doi.org/10.1007/s00125-015-3603-y

Immediate effects of retinoic acid on gene expression in primary murine osteoblasts

Authors

Timur A. Yorgan, Timo Heckt, Carsten Rendenbach, Christina Helmis, Sebastian Seitz, Thomas Streichert, Michael Amling, Thorsten Schinke

Abstract

Consistent with clinical observations demonstrating that hypervitaminosis A is associated with increased skeletal fracture risk, we have previously found that dietary retinol deprivation partially corrects the bone mineralization defects in a mouse model of X-linked hypophosphatemic rickets. That retinol-dependent signaling pathways impact the skeleton is further supported by various findings demonstrating a negative influence of retinoic acid (RA) on bone-forming osteoblasts. We hypothesized that RA would directly regulate the expression of specific target genes in osteoblasts, and we aimed to identify these by genome-wide expression analyses. Here we show that high dietary retinol intake in mice causes low bone mass associated with increased osteoclastogenesis and decreased osteoblastogenesis, but intact bone matrix mineralization. We additionally found that short-term treatment of primary osteoblasts with RA causes a rapid induction of specific genes involved in either retinol-dependent signaling (i.e. Rara, Crabp2) or skeletal remodeling (i.e. Twist2,Tnfsf11). In contrast, neither expression of established osteoblast differentiation markers nor the proliferation rate was immediately affected by RA administration. Collectively, our data suggest that the negative effects of vitamin A on skeletal integrity are explainable by an immediate influence of RA signaling on specific genes in osteoblasts that in turn influence bone remodeling.

Link To Article

http://dx.doi.org/10.1007/s00774-015-0666-2