Natural bone-mimicking nanopore-incorporated hydroxyapatite scaffolds for enhanced bone tissue regeneration.

BACKGROUND: A considerable number of studies has been carried out to develop alloplastic bone graft materials such as hydroxyapatite (HAP) that mimic the hierarchical structure of natural bones with multiple levels of pores: macro-, micro-, and nanopores. Although nanopores are known to play many essential roles in natural bones, only a few studies have focused on HAPs containing them; none of those studies investigated the functions of nanopores in biological systems. METHOD: We developed a simple yet powerful method to introduce nanopores into alloplastic HAP bone graft materials in large quantities by simply pressing HAP nanoparticles and sintering them at a low temperature. RESULTS: The size of nanopores in HAP scaffolds can be controlled between 16.5 and 30.2 nm by changing the sintering temperature. When nanopores with a size of ~ 30.2 nm, similar to that of nanopores in natural bones, are introduced into HAP scaffolds, the mechanical strength and cell proliferation and differentiation rates are significantly increased. The developed HAP scaffolds containing nanopores (SNPs) are biocompatible, with negligible erythema and inflammatory reactions. In addition, they enhance the bone regeneration when are implanted into a rabbit model. Furthermore, the bone regeneration efficiency of the HAP-based SNP is better than that of a commercially available bone graft material. CONCLUSION: Nanopores of HAP scaffolds are very important for improving the bone regeneration efficiency and may be one of the key factors to consider in designing highly efficient next-generation alloplastic bone graft materials.

DNA aptamer immobilized hydroxyapatite for enhancing angiogenesis and bone regeneration.

In this study, we developed aptamer-conjugated hydroxyapatite (Apt-HA) that promotes bone regeneration and angiogenesis. The 3R02 bivalent aptamer specific to vascular endothelial growth factor (VEGF) was grafted to the hydroxyapatite (HA) surface. Apt-HA was tested for its VEGF protein capture ability to determine the optimal aptamer concentration immobilized on the HA. Apt-HA showed higher VEGF protein capture ability, and faster growth of human umbilical vein endothelial cell (HUVEC) compared to a neat HA with no cytotoxic effects on human osteoblasts. To examine in vivo angiogenesis and bone regeneration, Apt-HA and HA were bilaterally implanted into rabbit tibial metaphyseal defects and analyzed after eight weeks using micro-CT, histology, and histomorphometry. Apt-HA showed significantly increased the volume of new bones, the percentage of bone, and the density of bone mineral in cortical bone. Apt-HA also exhibited the enhanced bone formation at the cortical region in a histomorphometric analysis. Finally, Apt-HA showed significantly increased blood vessel number compared to a neat HA. In summary, the engineered Apt-HA has potential as a bone graft material that may simultaneously promote bone regeneration and angiogenesis. STATEMENT OF SIGNIFICANCE: This work presents a functional hydroxyapatite bone graft using a DNA-based aptamer which overcomes the limitations of existing bone graft materials, which use bound signaling peptides. DNA aptamer immobilized hydroxyapatite enhances the in vitro proliferation of human umbilical vascular endothelial cells as well as in vivo angiogenesis and bone regeneration. DNA aptamer immobilized hydroxyapatite shows no cytotoxic effect on human osteoblasts.

Dental Hetero-Graft Materials with Nano Hydroxyapatite Surface Treatment.

We report the development of hydroxyapatite nanoparticle (HAp NP)-functionalized hetero-graft materials (HGMs) for dental applications. These HGMs were prepared by attaching platelet-, needle-, and sphere-shaped HAp NPs to the surface of xenograft materials through chemical conjugation. Although all three HAp NPs contributed to increase the surface area of bone graft material (BGM), the shape of the HAp NPs was a determining factor. Platelet HAp NPs were most effective, because they caused a 48.9% increase in BGM surface area whereas the influence of the spherical NP was only a 6.7% increase. This suggests that geometric factors regarding both the attached HAp NPs and graft material surface are essential in controlling the surface roughness of graft materials. Among the three HAp NPs, it was the platelet HAp NPs that helped to increase the efficacy of the BGM most significantly. Compared with BGM with no HAp NP attachment, HGM with platelet HAp NP ('platelet-HGM) treatment had ~46.1% higher cell attachment and proliferation rate. The MTT assay also showed that the HAp NP-treated hetero-graft materials had negligible cytotoxicity.

Scutellaria baicalensis attenuates blood-brain barrier disruption after intracerebral hemorrhage in rats.

Disruption of the blood-brain barrier (BBB) contributes to the inflammatory response and edema formation in the brain, exacerbating brain damage. The present study evaluated the effects of Scutellaria baicalensis (SR) water extracts on BBB disruption after intracerebral hemorrhage (ICH) in rats. ICH was induced by stereotaxic intrastriatal injection of bacterial type VII collagenase, and SR was administrated orally three times (50 mg/ml/kg) during the 48 h after ICH onset. SR treatment significantly reduced the degree of (1) hemorrhage volume and edema percentage of the ipsilateral hemisphere, (2) brain water content, (3) MPO-positive neutrophil infiltration in the peri-hematoma, and (4) BBB permeability measured by Evans blue leakage. In addition, expression of matrix metalloproteinase (MMP)-9, MMP-12, and tissue inhibitor of MMPs (TIMP)-1 were investigated with immunohistochemistry. SR treatment reduced MMP-9 and MMP-12 expression in the peri-hematoma after ICH. These results indicate that SR attenuates the BBB disruption through anti-inflammatory effects and suppression of MMP expression. These findings provide a pharmacological basis for the use of SR in the treatment of the BBB disruption following stroke and trauma.

Protective effects of natrii sulfas on cerebral focal ischemia induced by MCAO in rats.

This study examined the effect of Natrii sulfas, a treatment for stroke patients suffering constipation in Oriental medicine, on the physiological indices and brain edema of rats. Brain edema was induced by a middle cerebral artery occlusion (MCAO), Natrii sulfas was administered after the MCAO. At 3, 6, 15, 24, and 48 hours after reperfusion, the physiological indices such as the fecal weight, urine volume and water content in the stools were assessed. The edema index was measured 48 hours after reperfusion. At 48 hours, the expressions of iNOS, MMP9, VEGF, GFAP, Bax, Bcl-2, c-Fos, and HSP72 positive astrocytes were observed on the brain tissues by immunohistochemistry. Natrii sulfas significantly improved the decrease in fecal weight, urine volume and water content in the stool caused by the ischemic insult (p < 0.05) and attenuated the brain edema caused by the ischemia insult (p < 0.05). Natrii sulfas significantly down-regulated iNOS and MMP9 expressions and attenuated the astrocyte swelling due to brain edema in the penumbra of the cerebral cortex of MCAO rats. Natrii sulfas reduced the excess Bax and HSP72 expressions in ischemic brain, which was statistically significant in the penumbra of the cerebral cortex but not in the caudate putamen. These results suggest Natrii sulfas has a protective effect on ischemia-induced brain edema and improves the physiological symptoms.