In vivo evaluation of biofunctionalized implant surfaces with a synthetic peptide (P-15) and its impact on osseointegration. A preclinical animal study

Authors

Christian M. Schmitt, Markus Koepple, Tobias Moest, Konrad Neumann, Tamara Weisel, Karl Andreas Schlegel

Abstract

The overall aim of the study was to investigate a biofunctionalized implant surface with electrochemically deposition of hydroxyapatite and the synthetic peptide (P-15) and its effect on osseointegration.

Three modified implant types of ANKYLOS® C/X implants were used; (1) machined implants used as negative control (M, n = 20), (2) implants with the FRIADENT® plus surface (grit blasted and acid-etched) used as positive control (P, n = 20), and (3) implants with a biomimetic surface consisting of hydroxyapatite and the synthetic 15 aminoacids containing peptide P-15 (BP, n = 40). The implants were randomly inserted in the mandibles of 10 beagle dogs following 4 months after tooth extraction (P1-P4). Three animals were sacrificed 2 and 7 days after implant insertion, respectively, and four animals were sacrificed 6 months post implant insertion. Bone-to-implant contacts (BICs) were analyzed via histomorphometrical analyses at five different region of interests (ROIs); two at the middle part on either side of the implant (ROI 1/4), two at the apical part of the implant at each side (ROI 2/3), and one at the tip of the implant (ROI 5).

All implant surfaces showed a high level of osseointegration and osteoconductivity. The cumulative implant survival rate (CSR) was 93.8%, 100% in the M, 85% in the P, and 95% in the BP group. No statistical difference in BICs at ROI 1/4, 2/3, and 5 could be shown between implant types following 2 and 7 days of healing. BIC values increased in all groups over time. After 6 months of healing the BP group showed superiority in BIC in ROI 2/3 (73.2 ± 15.6%) compared to the P (48.3 ± 10.6%) and M group (66.3 ± 30.2%) with a significant difference between BP and P (P = 0.002).

It is hypothesized, that the surface biofunctionalization improves peri-implant bone formation and remodeling, leading to an increased bone-to implant contact. However, within the limitations of the study set-up no benefit in the early phase of osseointegration could be established for dental implants with P-15 containing surface in this study.

Link to Article

http://dx.doi.org/10.1111/clr.12723

A comprehensive study of long-term skeletal changes after spinal cord injury in adult rats

Authors

Tiao Lin, Wei Tong, Abhishek Chandra, Shao-Yun Hsu, Haoruo Jia, Ji Zhu, Wei-Ju Tseng, Michael A Levine, Yejia Zhang, Shi-Gui Yan, X Sherry Liu, Dongming Sun, Wise Young & Ling Qin

Abstract

Spinal cord injury (SCI)-induced bone loss represents the most severe osteoporosis with no effective treatment. Past animal studies have focused primarily on long bones at the acute stage using adolescent rodents. To mimic chronic SCI in human patients, we performed a comprehensive analysis of long-term structural and mechanical changes in axial and appendicular bones in adult rats after SCI. In this experiment, 4-month-old Fischer 344 male rats received a clinically relevant T13 contusion injury. Sixteen weeks later, sublesional femurs, tibiae, and L4 vertebrae, supralesional humeri, and blood were collected from these rats and additional non-surgery rats for micro-computed tomography (µCT), micro-finite element, histology, and serum biochemical analyses. At trabecular sites, extreme losses of bone structure and mechanical competence were detected in the metaphysis of sublesional long bones after SCI, while the subchondral part of the same bones showed much milder damage. Marked reductions in bone mass and strength were also observed in sublesional L4 vertebrae but not in supralesional humeri. At cortical sites, SCI induced structural and strength damage in both sub- and supralesional long bones. These changes were accompanied by diminished osteoblast number and activity and increased osteoclast number and activity. Taken together, our study revealed site-specific effects of SCI on bone and demonstrated sustained inhibition of bone formation and elevation of bone resorption at the chronic stage of SCI.

Link to Article

http://dx.doi.org/10.1038%2Fboneres.2015.28

Prolonged performance of a high repetition low force task induces bone adaptation in young adult rats, but loss in mature rats

Authors

Vicky S. Massicotte, Nagat Frara, Michele Y. Harris, Mamta Amin, Christine K. Wade, Steven N. Popoff, Mary F. Barbe

Abstract

We have shown that prolonged repetitive reaching and grasping tasks lead to exposure-dependent changes in bone microarchitecture and inflammatory cytokines in young adult rats. Since aging mammals show increased tissue inflammatory cytokines, we sought here to determine if aging, combined with prolonged performance of a repetitive upper extremity task, enhances bone loss. We examined the radius, forearm flexor muscles, and serum from 16 mature (14–18 months of age) and 14 young adult (2.5–6.5 months of age) female rats after performance of a high repetition low force (HRLF) reaching and grasping task for 12 weeks. Young adult HRLF rats showed enhanced radial bone growth (e.g., increased trabecular bone volume, osteoblast numbers, bone formation rate, and mid-diaphyseal periosteal perimeter), compared to age-matched controls. Mature HRLF rats showed several indices of radial bone loss (e.g., decreased trabecular bone volume, and increased cortical bone thinning, porosity, resorptive spaces and woven bone formation), increased osteoclast numbers and inflammatory cytokines, compared to age-matched controls and young adult HRLF rats. Mature rats weighed more yet had lower maximum reflexive grip strength, than young adult rats, although each age group was able to pull at the required reach rate (4 reaches/min) and required submaximal pulling force (30 force-grams) for a food reward. Serum estrogen levels and flexor digitorum muscle size were similar in each age group. Thus, mature rats had increased bone degradative changes than in young adult rats performing the same repetitive task for 12 weeks, with increased inflammatory cytokine responses and osteoclast activity as possible causes.

Link to Article

http://dx.doi.org/10.1016/j.exger.2015.10.014

Excess TGF-β mediates muscle weakness associated with bone metastases in mice

Authors

David L Waning, Khalid S Mohammad, Steven Reiken, Wenjun Xie, Daniel C Andersson, Sutha John, Antonella Chiechi, Laura E Wright, Alisa Umanskaya, Maria Niewolna, Trupti Trivedi, Sahba Charkhzarrin, Pooja Khatiwada, Anetta Wronska, Ashley Haynes, Maria Serena Benassi, Frank A Witzmann, Gehua Zhen, Xiao Wang, Xu Cao, G David Roodman, Andrew R Marks & Theresa A Guise

Abstract

Cancer-associated muscle weakness is a poorly understood phenomenon, and there is no effective treatment. Here we find that seven different mouse models of human osteolytic bone metastases—representing breast, lung and prostate cancers, as well as multiple myeloma—exhibited impaired muscle function, implicating a role for the tumor-bone microenvironment in cancer-associated muscle weakness. We found that transforming growth factor (TGF)-β, released from the bone surface as a result of metastasis-induced bone destruction, upregulated NADPH oxidase 4 (Nox4), resulting in elevated oxidization of skeletal muscle proteins, including the ryanodine receptor and calcium (Ca2+) release channel (RyR1). The oxidized RyR1 channels leaked Ca2+, resulting in lower intracellular signaling, which is required for proper muscle contraction. We found that inhibiting RyR1 leakage, TGF-β signaling, TGF-β release from bone or Nox4 activity improved muscle function in mice with MDA-MB-231 bone metastases. Humans with breast- or lung cancer–associated bone metastases also had oxidized skeletal muscle RyR1 that is not seen in normal muscle. Similarly, skeletal muscle weakness, increased Nox4 binding to RyR1 and oxidation of RyR1 were present in a mouse model of Camurati-Engelmann disease, a nonmalignant metabolic bone disorder associated with increased TGF-β activity. Thus, pathological TGF-β release from bone contributes to muscle weakness by decreasing Ca2+-induced muscle force production.

Link to Article

http://dx.doi.org/10.1038/nm.3961

Inhibition of osteoclastogenesis and inflammatory bone resorption by targeting BET proteins and epigenetic regulation

Authors

Kyung-Hyun Park-Min, Elisha Lim, Min Joon Lee, Sung Ho Park, Eugenia Giannopoulou, Anna Yarilina, Marjolein van der Meulen, Baohong Zhao, Nicholas Smithers, Jason Witherington, Kevin Lee, Paul P. Tak, Rab K. Prinjha & Lionel B Ivashkiv

Abstract

Emerging evidence suggests that ANKL-induced changes in chromatin state are important for osteoclastogenesis, but these epigenetic mechanisms are not well understood and have not been therapeutically targeted. In this study, we find that the small molecule -BET151 that targets bromo and extra-terminal (BET) proteins that ‘read’ chromatin states by binding to acetylated histones strongly suppresses osteoclastogenesis. -BET151 suppresses pathologic bone loss in NF-induced inflammatory osteolysis, inflammatory arthritis and post-ovariectomy models. Transcriptome analysis identifies a YC-NFAT axis important for osteoclastogenesis. Mechanistically, -BET151 inhibits expression of the master osteoclast regulator FATC1 by suppressing expression and recruitment of its newly identified upstream regulator YC. YC is elevated in rheumatoid arthritis macrophages and its induction by ANKL is important for osteoclastogenesis and NF-induced bone resorption. These findings highlight the importance of an -BET151-inhibited YC-NFAT axis in osteoclastogenesis, and suggest targeting epigenetic chromatin regulators holds promise for treatment of inflammatory and oestrogen deficiency-mediated pathologic bone resorption.

Link to Article

http://dx.doi.org/10.1038/ncomms6418

Covalently immobilised type I collagen facilitates osteoconduction and osseointegration of titanium coating implants

Authors

Haiyong Ao, Youtao Xie, Shengbin Yang, Xiaodong Wu, Kai Li, Xuebin Zheng, Tingting Tang

Abstract

Background/Objective

Plasma-sprayed titanium coating (TC) with rough surfaces has been successfully applied in hip or knee prostheses. This study aimed to investigate the osteoconduction and osseointegration of Type I collagen covalently immobilised on TC (TC-AAC) compared with those of TC.

Methods

In vitro, the migration of human mesenchymal stem cells (hMSCs) on TC and TC-AAC was observed by scanning electron microscopy and visualised fluorescent live/dead assay. In vivo, a rabbit model with femur condyle defect was employed, and implants of TC and TC-AAC were embedded into the femur condyles.

Results

Collagen immobilised on TC could promote hMSCs' migration into the porous structure of the TC. Micro computed tomography images showed that bone trabeculae were significantly more abundant around TC-AAC implants than around TC implants. Fluorescence micrographs indicated more active new-bone formation around implants in the TC-AAC group than in the TC group. The measurement of bone–implant contact on histological sections indicated significantly greater osteointegration around TC-AAC implants than around TC ones.

Conclusion

Immobilised Type I collagen could improve the osteoconduction and osseointegration of TC implants.

Link to Article

http://dx.doi.org/10.1016/j.jot.2015.08.005