Influence of single and binary doping of strontium and lithium on in vivo biological properties of bioactive glass scaffolds

Effects of strontium and lithium ion doping on the biological properties of bioactive glass (BAG) porous scaffolds have been checked in vitro and in vivo. BAG scaffolds were prepared by conventional glass melting route and subsequently, scaffolds were produced by evaporation of fugitive pore formers. After thorough physico-chemical and in vitro cell characterization, scaffolds were used for pre-clinical study. Soft and hard tissue formation in a rabbit femoral defect model after 2 and 4 months, were assessed using different tools. Histological observations showed excellent osseous tissue formation in Sr and Li + Sr scaffolds and moderate bone regeneration in Li scaffolds. Fluorochrome labeling studies showed wide regions of new bone formation in Sr and Li + Sr doped samples as compared to Li doped samples. SEM revealed abundant collagenous network and minimal or no interfacial gap between bone and implant in Sr and Li + Sr doped samples compared to Li doped samples. Micro CT of Li + Sr samples showed highest degree of peripheral cancellous tissue formation on periphery and cortical tissues inside implanted samples and vascularity among four compositions. Our findings suggest that addition of Sr and/or Li alters physico-chemical properties of BAG and promotes early stage in vivo osseointegration and bone remodeling that may offer new insight in bone tissue engineering

Fluoride inhibits the response of bone cells to mechanical loading

The response of bone cells to mechanical loading is mediated by the cytoskeleton. Since the bone anabolic agent fluoride disrupts the cytoskeleton, we investigated whether fluoride affects the response of bone cells to mechanical loading, and whether this is cytoskeleton mediated. The mechano-response of osteoblasts was assessed in vitro by measuring pulsating fluid flow-induced nitric oxide (NO) production. Osteocyte shape was determined in hamster mandibles in vivo as parameter of osteocyte mechanosensitivity. Pulsating fluid flow (0.7 ± 0.3 Pa, 5 Hz) stimulated NO production by 8-fold within 5 min. NaF (10-50 μM) inhibited pulsating fluid flow-stimulated NO production after 10 min, and decreased F-actin content by ~3-fold. Fluid flow-induced NO response was also inhibited after F-actin disruption by cytochalasin B. NaF treatment resulted in more elongated, smaller osteocytes in interdental bone in vivo. Our results suggest that fluoride inhibits the mechano-response of bone cells, which might occur via cytoskeletal changes. Since decreased mechanosensitivity reduces bone mass, the reported anabolic effect of fluoride on bone mass in vivo is likely mediated by other factors than changed bone cell mechanosensitivity. © 2011 The Society of The Nippon Dental University