Beta-nerve growth factor promotes neurogenesis and angiogenesis during the repair of bone defects

We previously showed that the repair of bone defects is regulated by neural and vascular signals. In the present study, we examined the effect of topically applied β-nerve growth factor（β-NGF） on neurogenesis and angiogenesis in critical-sized bone defects filled with collagen bone substitute. We created two symmetrical defects, 2.5 mm in diameter, on either side of the parietal bone of the skull, and filled them with bone substitute. Subcutaneously implanted osmotic pumps were used to infuse 10 μgβ-NGF in PBS（β-NGF ＋ PBS） into the right-hand side defect, and PBS into the left（control） defect, over the 7 days following surgery. Immunohistochemical staining and hematoxylin-eosin staining were carried out at 3, 7, 14, 21 and 28 days postoperatively. On day 7, expression of β III-tubulin was lower on the β-NGF ＋ PBS side than on the control side, and that of neurofilament 160 was greater. On day 14, β III-tubulin and protein gene product 9.5 were greater on the β-NGF ＋ PBS side than on the control side. Vascular endothelial growth factor expression was greater on the experimental side than the control side at 7 days, and vascular endothelial growth factor receptor 2 expression was elevated on days 14 and 21, but lower than control levels on day 28. However, no difference in the number of blood vessels was observed between sides. Our results indicate that topical application of β-NGF promoted neurogenesis, and may modulate angiogenesis by promoting nerve regeneration in collagen bone substitute-filled defects.

Sintering effects on chemical and physical properties of bioactive ceramics

The objective of this study was to characterize the chemical and physical properties of bioactive ceramics prepared from an aqueous paste containing hydroxyapatite(HA)and beta tri-calcium phosphate(β-TCP).Prior to formulating the paste,HA andβ-TCP were calcined at 800℃and 975℃(11 h),milled,and blended into 15%/85%HA/β-TCP volume-mixed paste.Fabricated cylindrical rods were subsequently sintered to 900℃,1100℃or 1250℃.The sintered specimens were characterized by helium pycnometry,X-ray diffraction(XRD),Fourier transform-infrared(FT-IR),and inductively coupled plasma(ICP)spectroscopy for evaluation of porosity,crystalline phase,functional-groups,and Ca:P ratio,respectively.Mechanical properties were assessed via 3-point bending and diametral compression.Qualitative microstructural evaluation using scanning electron microscopy(SEM)showed larger pores and a broader pore size distribution(PSD)for materials sintered at 900℃and 1100℃,whereas the 1250℃samples showed more uniform PSD.Porosity quantification showed significantly higher porosity for materials sintered to 900℃and 1250℃(p<0.05).XRD indicated substantial deviations from the 15%/85%HA/β-TCP formulation following sintering where lower amounts of HA were observed when sintering temperature was increased.Mechanical testing demonstrated significant differences between calcination temperatures and different sintering regimes(p<0.05).Variation in chemical composition and mechanical properties of bioactive ceramics were direct consequences of calcination and sintering.