Accelerated bone ingrowth by local delivery of Zinc from bioactive glass: oxidative stress status, mechanical property, and microarchitectural characterization in an ovariectomized rat model.

BACKGROUND: Synthetic bone graft substitutes such as bioactive glass (BG) material are developed in order to achieve successful bone regeneration. Zn plays an important role in the proper bone growth, development, and maintenance of healthy bones. AIMS: This study aims to evaluate in vivo the performance therapy of zinc-doped bioactive glass (BG-Zn) and its applications in biomedicine. METHODS: Female Wistar rats were ovariectomized. BG and BG-Zn were implanted in the femoral condyles of Wistar rats and compared to that of control group. Grafted bone tissues were carefully removed to evaluate the oxidative stress status, histomorphometric profile, mechanical property, and mineral bone distribution by using inductively coupled plasma optical emission spectrometry. RESULTS: A significant decrease of thiobarbituric acid-reactive substances was observed after BG-Zn implantation. Superoxide dismutase, catalase (CAT), and glutathione peroxidase (GPx) activities significantly increased in ovariectomized group implanted with Zinc-doped bioactive glass (OVX-BG-Zn) as compared to ovariectomized group implanted with bioactive glass (OVX-BG). An improved mechanical property was noticed in contact of OVX-BG-Zn (39±6 HV) when compared with that of OVX-BG group (26±9 HV). After 90 days of implantation, the histomorphometric analysis showed that trabecular thickness (Tb.Th) and trabecular number (Tb.N) were significantly increased with 28 and 24%, respectively, in treated rats of OVX-BG-Zn group as compared to those of OVX-BG groups. Trabecular separation (Tb.Sp) and trabecular bone pattern factor (TBPf) were significantly decreased in OVX-BG-Zn group with 29.5 and 54% when compared with those of OVX-BG rat groups. On the other hand, a rise in Ca and P ion concentrations in the implanted microenvironment was shown and lead to the formation/deposition of Ca-P phases. The ratio of pyridinoline [Pyr] to dihydroxylysinonorleucine [DHLNL] cross-links was normalized to the control level. CONCLUSION: Our findings suggested that BG-Zn might have promising potential applications for osteoporosis therapy.

Cytocompatibility, gene-expression profiling, apoptotic, mechanical and (29)Si, (31)P solid-state nuclear magnetic resonance studies following treatment with a bioglass-chitosan composite.

The performance therapy of chitosan (CH)-doped bioactive glass (BG) has been evaluated in vitro and in vivo. In vitro, the effect of CH-BG was assessed on human Saos-2 osteoblast cells. In vivo, Wistar rats were ovariectomized (OVX) and CH, BG and CH-BG were implanted in bone tissue. After 3 days of CH-BG contact, cell viability of Saos-2 osteoblast increased by 16.4% as compared to the control group. The runt-related transcription factor 2 (RUNX2/Cbfa1) and osteocalcin (OC) gene expressions were significantly increased with 600 and 300%, respectively, in contact of CH-BG as compared with CH. In vivo, the apoptotic index in the OVX-CH-BG group was decreased by 80%. A mechanical hardness test showed a significant bone strength improvement after CH-BG implantation (40%). The CH-BG composite may therefore prove clinically useful as a bioactive bone substitute.

Biologic Response to Carbonated Hydroxyapatite Associated with Orthopedic Device: Experimental Study in a Rabbit Model

BACKGROUND: Carbonated hydroxyapatite (CHA) and related calcium phosphates have been studied for many years as implant materials due to their similarity with the mineral phase of bone. The main limitation of CHA ceramics as well as other bioactive materials is that they have poor mechanical proprieties. It is thought that the mechanical device can cause an increase in metabolic activity and bone healing. In this study we investigated the reactivity and tissue behaviour of implanted CHA biomaterial reinforced by mini external fixator. METHODS: The evaluation of biomaterial biocompatibility and osteogenesis was performed on a rabbit model over a period of 6 weeks by radiological, histological and scanning electron microscopy (SEM) coupled with energy dispersive X-ray SEM-energy-dispersive X-ray (EDX) analysis. RESULTS: While rabbits treated with CHA exhibited more bone formation, and fibrous tissue was observed when empty bone defects were observed. EDX analysis detected little calcium and phosphorus on the surface of the bone that was not implanted, while high content of calcium (62.7%) and phosphorus (38%) was found on the interface bone cement. CONCLUSIONS: Bone repairing showed that the mini external fixator stimulated the ossification which was pushed when grafted by CHA. This effect may play an important role in the prevention of implant loosening.

Effect of hydroxyapatite and beta-tricalcium phosphate nanoparticles on promonocytic U937 cells.

OBJECTIVES: Nanoparticles from implanted materials are reported as the main cause of implant failure. Monocytes are among the first cells to colonize the inflammatory site. We evaluated the biological effects of bone substitutes presented to U937 cells in vitro as micron- or nanometer-sized particles. METHODS: The HA (550 nm) and beta-TCP (550 nm) nanoparticles were incubated with U937 cells. Cell cycle modification, specific antigens expression, and the extent of cell death were determined. RESULTS: Firstly, by using the sulforhodamine B (SRB) test and the annexin V-FITC analysis by flow cytometry, our results provide evidence of the absence of cytotoxicity, and show that nanoparticles do not induce more apoptosis than microparticles in U937 cells. Secondly, although morphologic evidence of stimulation of U937-cells was found by confocal microscopy, neither bone substitute altered the distribution of the cells into different phases of the cell cycle (Kit Cycle Test Plus DNA). These results suggest that nanoparticles do not cause promonocyte maturation in macrophages. Thirdly, the flow cytometry results showed no differences in the expression of the adherence and activation markers. SIGNIFICANCE: The results suggest that nanoparticles do not promote the differentiation of promonocytic U937 cells into macrophages and do not induce an enhanced inflammatory response.