Effects of bleaching on osteoclast activity and their modulation by osteostatin and fibroblast growth factor 2

Hypothesis: Dental bleaching with H2O2 is a common daily practice in dentistry to correct discoloration of anterior teeth. The aim of this study has been to determine whether this treatment of human teeth affects growth, differentiation and activity of osteoclast-like cells, as well as the putative modulatory action of osteostatin and fibroblast growth factor 2 (FGF-2). Experiments: Previously to the in vitro assays, structural, physical-chemical and morphological features of teeth after bleaching were studied. Osteoclast-like cells were cultured on human dentin disks, pre-treated or not with 38% H2O2 bleaching gel, in the presence or absence of osteostatin (100 nM) or FGF-2 (1 ng/ml). Cell proliferation and viability, intracellular content of reactive oxygen species (ROS), pro-inflammatory cytokine (IL-6 and TNF alpha) secretion and resorption activity were evaluated. Findings: Bleaching treatment failed to affect either the structural or the chemical features of both enamel and dentin, except for slight morphological changes, increased porosity in the most superficial parts (enamel), and a moderate increase in the wettability degree. In this scenario, bleaching produced an increased osteoclast-like cell proliferation but decreased cell viability and cytokine secretion, while it augmented resorption activity on dentin. The presence of either osteostatin or FGF-2 reduced the osteoclast-like cell proliferation induced by bleaching. FGF-2 enhanced ROS content, whereas osteostatin decreased ROS but increased TNF alpha secretion. The bleaching effect on resorption activity was increased by osteostatin, but this effect was less evident with FGF-2. Conclusions: These findings further confirm the deleterious effects of tooth bleaching by affecting osteoclast growth and function as well as different modulatory actions of osteostatin and FGF-2. (C) 2015 Elsevier Inc. All rights reserved

Effects of immobilized VEGF on endothelial progenitor cells cultured on silicon substituted and nanocrystalline hydroxyapatites

Vascular endothelial growth factor (VEGF) plays an essential role in angiogenesis and vascular homeostasis. Endothelial progenitor cells (EPCs) are primitive bone marrow cells participating in neovascularization and revascularization processes, which also promote bone regeneration. Synthetic hydroxyapatite (HA) has been widely used in bone repair and implant coatings. In HA-based materials, small levels of ionic substitution by silicon (Si) have significant effects on osteoclastic and osteoblastic responses. Moreover, nanocrystalline hydroxyapatites (nano-HA) display enhanced bioreactivity and beneficial effects in bone formation. In this work, the angiogenic potential of VEGF-121 adsorbed on crystalline and nanocrystalline HAs with different Si proportion is evaluated with endothelial-like cells derived from EPCs cultured on nano-HA, nano-SiHA0.25, nano-SiHA0.4, HA, SiHA0.25 and SiHA0.4 disks. The Si amount incorporated for x ¼ 0.25 is enough to yield changes in the textural parameters and surface charge without decomposing the HA phase. Si substitution for x ¼ 0.4 does not result in pure Si-substituted apatites. Si probably remains at the grain boundaries as amorphous silica in nano-SiHA0.4 and SiHA0.4 is decomposed in a-TCP and HA after 1150 �C treatment. Immobilized VEGF on nano-HA, nano-SiHA0.25, nano-SiHA0.4, HA, SiHA0.25 and SiHA0.4 maintains its function exerting a local regulation of the cell response. The crystallite size and topography of nanocrystalline HAs could produce insufficient and weak contacts with endothelial-like cells triggering anoikis. Concerning Si proportion, the best results are obtained with SiHA0.25/VEGF and nano- SiHA0.25/VEGF disks. All these results suggest the potential utility of SiHA0.25/VEGF and nano-SiHA0.25/VEGF for bone repair and tissue engineering by promoting angiogenesis

Synthesis, characterization and biocompatibility of mesolamellar calcium phosphate hybrids prepared via anionic surfactant templating

Calcium phosphate (CaP) based hybrid materials have been synthesized through a precipitation method in aqueous medium in the presence of the anionic surfactant sodium dodecylbenzene sulfonate (SDBS) as structure directing agent. Parameters of synthesis, such as Ca/P molar ratio, surfactant concentration and initial pH, have been investigated trying to get mesostructured CaP phases. A lamellar-like hybrid mesophase consisting in several wavy layers of apatite or apatite-brushite nanoplates was successfully obtained. Materials have been characterized by several physico- chemical techniques. A potential application of these lamellar calcium phosphate based hybrids can be as matrixes in drug delivery systems with the possibility of loading hydrophobic drugs in the organic interlayers. To evaluate their potential as biomaterials, the biocompatibility of two hybrids has been studied in vitro with human Saos-2 osteoblasts. Cell assays showed that, upon the appropriate synthesis and stabilization conditions, a biocompatible CaP and SDBS mesolamellar hybrid can be prepared

Treatment of rats with a self-selected hyperlipidic diet, increases the lipid content of the main adipose tissue sites in a proportion similar to that of the lipids in the rest of organs and tissues

Adipose tissue (AT) is distributed as large differentiated masses, and smaller depots covering vessels, and organs, as well as interspersed within them. The differences between types and size of cells makes AT one of the most disperse and complex organs. Lipid storage is partly shared by other tissues such as muscle and liver. We intended to obtain an approximate estimation of the size of lipid reserves stored outside the main fat depots. Both male and female rats were made overweight by 4-weeks feeding of a cafeteria diet. Total lipid content was analyzed in brain, liver, gastrocnemius muscle, four white AT sites: subcutaneous, perigonadal, retroperitoneal and mesenteric, two brown AT sites (interscapular and perirenal) and in a pool of the rest of organs and tissues (after discarding gut contents). Organ lipid content was estimated and tabulated for each individual rat. Food intake was measured daily. There was a surprisingly high proportion of lipid not accounted for by the main macroscopic AT sites, even when brain, liver and BAT main sites were discounted. Muscle contained about 8% of body lipids, liver 1-1.4%, four white AT sites lipid 28-63% of body lipid, and the rest of the body (including muscle) 38-44%. There was a good correlation between AT lipid and body lipid, but lipid in"other organs" was highly correlated too with body lipid. Brain lipid was not. Irrespective of dietary intake, accumulation of body fat was uniform both for the main lipid storage and handling organs: large masses of AT (but also liver, muscle), as well as in the"rest" of tissues. These storage sites, in specialized (adipose) or not-specialized (liver, muscle) tissues reacted in parallel against a hyperlipidic diet challenge. We postulate that body lipid stores are handled and regulated coordinately, with a more centralized and overall mechanisms than usually assumed

Silicon substituted hydroxyapatite/VEGF scaffolds stimulate bone regeneration in osteoporotic sheep.

Silicon-substituted hydroxyapatite (SiHA) macroporous scaffolds have been prepared by robocasting. In order to optimize their bone regeneration properties, we have manufactured these scaffolds presenting different microstructures: nanocrystalline and crystalline. Moreover, their surfaces have been decorated with vascular endothelial growth factor (VEGF) to evaluate the potential coupling between vascularization and bone regeneration. In vitro cell culture tests evidence that nanocrystalline SiHA hinders pre-osteblast proliferation, whereas the presence of VEGF enhances the biological functions of both endothelial cells and pre-osteoblasts. The bone regeneration capability has been evaluated using an osteoporotic sheep model. In vivo observations strongly correlate with in vitro cell culture tests. Those scaffolds made of nanocrystalline SiHA were colonized by fibrous tissue, promoted inflammatory response and forested osteoclast recruitment. These observations discard nanocystalline SiHA as a suitable material for bone regeneration purposes. On the contrary, those scaffolds made of crystalline SiHA and decorated with VEGF exhibited bone regeneration properties, with high ossification degree, thicker trabeculae and higher presence of osteoblasts and blood vessels. Considering these results, macroporous scaffolds made of SiHA and decorated with VEGF are suitable bone grafts for regeneration purposes, even in adverse pathological scenarios such as osteoporosis

Subacute Tissue Response to 3D Graphene Oxide Scaffolds Implanted in the Injured Rat Spinal Cord

The increasing prevalence and high sanitary costs of lesions affecting the central nervous system (CNS) at the spinal cord are encouraging experts in different fields to explore new avenues for neural repair. In this context, graphene and its derivatives are attracting significant attention, although their toxicity and performance in the CNS in vivo remains unclear. Here, the subacute tissue response to 3D flexible and porous scaffolds composed of partially reduced graphene oxide is investigated when implanted in the injured rat spinal cord. The interest of these structures as potentially useful platforms for CNS regeneration mainly relies on their mechanical compliance with neural tissues, adequate biocompatibility with neural cells in vitro and versatility to carry topographical and biological guidance cues. Early tissue responses are thoroughly investigated locally (spinal cord at C6 level) and in the major organs (i.e., kidney, liver, lung, and spleen). The absence of local and systemic toxic responses, along with the positive signs found at the lesion site (e.g., filler effect, soft interface for no additional scaring, preservation of cell populations at the perilesional area, presence of M2 macrophages), encourages further investigation of these materials as promising components of more efficient material-based platforms for CNS repair.This work was supported by the Instituto de Salud Carlos III (ISCIII) and Ministerio de Economía y Competitividad (MINECO) (Grant CP13/00060), co‐financed by FEDER funding, and MINECO (Grants MAT2011‐25329 and MAT2013‐43229‐R). AGM and MCS acknowledge ISCIII‐MINECO for respective contracts associated to project CP13/00060