High Cortical Bone Mass Phenotype in Betacellulin Transgenic Mice Is EGFR Dependent

Signaling through the epidermal growth factor receptor (EGFR) by ligands such as epidermal growth factor (EGF), transforming growth factor α (TGFA), and amphiregulin (AREG) has been reported to have effects on skeletal growth. The role of betacellulin (BTC), another EGFR ligand, in skeletal development and bone metabolism is unknown. In previous experiments, transgenic mice overexpressing BTC ubiquitously under the control of the chicken β‐actin promoter (BTC‐tg) exhibited stunted growth and disproportionately sized long bones. In this study, we performed a detailed phenotypic analysis of BTC‐tg mice at 3, 6, and 9 wk of age. Osteoblastic cells from transgenic mice showed strong expression of BTC as determined by Western blots and by immunohistochemistry on bone sections. In femurs of male and female BTC‐tg mice, we found reduced longitudinal bone growth and a pronounced increase in total volumetric BMD. The increased femoral BMD was mainly caused by augmented endocortical bone apposition and subsequent cortical bone thickening. In contrast, vertebral BMD was reduced in BTC‐tg mice of both sexes. An overall similar phenotype was found in 6‐mo‐old BTC‐tg mice. The increase in cortical bone mass in the appendicular skeleton of BTC‐tg mice was largely blocked when they were crossed into the Egfr^Wa5 background characterized by a dominant negative EGFR. Our study showed that overexpression of BTC results in an EGFR‐dependent upregulation of cortical bone mass in the appendicular skeleton of mice, uncovering a potential novel anabolic pathway for cortical bone.     

Wie balanciert sollte eine kristalloide Lösung sein?

Die Anaesthesiologie -     

Disturbed function of the blood–cerebrospinal fluid barrier aggravates neuro-inflammation

Multiple sclerosis (MS) is a chronic neuro-inflammatory disorder, which is marked by the invasion of the central nervous system by monocyte-derived macrophages and autoreactive T cells across the brain vasculature. Data from experimental animal models recently implied that the passage of leukocytes across the brain vasculature is preceded by their traversal across the blood–cerebrospinal fluid barrier (BCSFB) of the choroid plexus. The correlation between the presence of leukocytes in the CSF of patients suffering from MS and the number of inflammatory lesions as detected by magnetic resonance imaging suggests that inflammation at the choroid plexus contributes to the disease, although in a yet unknown fashion. We here provide first insights into the involvement of the choroid plexus in the onset and severity of the disease and in particular address the role of the tight junction protein claudin-3 (CLDN3) in this process. Detailed analysis of human post-mortem brain tissue revealed a selective loss of CLDN3 at the choroid plexus in MS patients compared to control tissues. Importantly, mice that lack CLDN3 have an impaired BCSFB and experience a more rapid onset and exacerbated clinical signs of experimental autoimmune encephalomyelitis, which coincides with enhanced levels of infiltrated leukocytes in their CSF. Together, this study highlights a profound role for the choroid plexus in the pathogenesis of multiple sclerosis, and implies that CLDN3 may be regarded as a crucial and novel determinant of BCSFB integrity.     

Total alloplastic temporomandibular joint replacement: the Czech-Slovak initial experience

In 2004, total alloplastic temporomandibular joint (TMJ) replacement began in the Czech Republic and Slovakia. This paper presents initial subjective and objective data compiled between 2005 and 2009 from those cases. Data were collected from 27 patients (38 joints) reconstructed with the Biomet-Lorenz stock and custom TMJ prostheses during a mean follow-up period of 24 months. The variables of pain and mouth opening were evaluated pre- and postoperatively. Patients classified pain on a scale of 0-5 (none - unbearable). The extent of opening was investigated by a physician (the distance between the points of the incisors on the upper and lower jaw was measured). The most common indication for replacement was ankylosis. There was an improvement in pain score in 15 patients. 4 patients reported worsening of pain and 8 patients did not complain of pre- or postoperative pain. Mandibular opening increased from a mean of 17.7 mm preoperatively to a mean of 29.1mm postoperatively. There were complications related to the surgery, but no significant complications related to the devices. Total alloplastic TMJ replacement appears to be a safe and effective method of reconstruction in the patients in this initial study.     

Salidroside exerts angiogenic and cytoprotective effects on human bone marrowderived endothelial progenitor cells via Akt/mTOR/p70S6K and MAPK signalling pathways

Background and Purpose

With the increase of age, increased susceptibility to apoptosis and senescence may contribute to proliferative and functional impairment of endothelial progenitor cells (EPCs). The aim of this study was to investigate whether salidroside (SAL) can induce angiogenic differentiation and inhibit oxidative stress-induced apoptosis in bone marrow-derived EPCs (BM-EPCs), and if so, through what mechanism.

Experimental Approach

BM-EPCs were isolated and treated with different concentrations of SAL for up to 4 days. Cell proliferation, migration and tube formation ability were detected by DNA content quantification, transwell assay and Matrigel-based angiogenesis assay. Gene and protein expression were assessed by qRT-PCR and Western blot respectively.

Key Results

Treatment with SAL promoted cellular proliferation and angiogenic differentiation of BM-EPCs, and increased VEGF and NO secretion, which in turn mediated the enhanced angiogenic differentiation of BM-EPCs. Furthermore, SAL significantly attenuated hydrogen peroxide (H₂O₂)-induced cell apoptosis, reduced the intracellular level of reactive oxygen species and restored the mitochondrial membrane potential of BM-EPCs. Moreover, SAL stimulated the phosphorylation of Akt, mammalian target of rapamycin and p70 S6 kinase, as well as ERK1/2, which is associated with cell migration and capillary tube formation. Additionally, SAL reversed the phosphorylation of JNK and p38 MAPK induced by H₂O₂ and suppressed the changes in the Bax/Bcl-xL ratio observed after stimulation with H₂O₂.

Conclusions and Implications

These findings identify novel mechanisms that regulate EPC function and suggest that SAL has therapeutic potential as a new agent to enhance vasculogenesis as well as protect against oxidative endothelial injury.     

Synthesis and thermal stability of ZrO2@SiO2 core–shell submicron particles

ZrO₂@SiO₂ core–shell submicron particles are promising candidates for the development of advanced optical materials. Here, submicron zirconia particles were synthesized using a modified sol–gel method and pre-calcined at 400 °C. Silica shells were grown on these particles (average size: ∼270 nm) with well-defined thicknesses (26 to 61 nm) using a seeded-growth Stöber approach. To study the thermal stability of bare ZrO₂ cores and ZrO₂@SiO₂ core–shell particles they were calcined at 450 to 1200 °C. After heat treatments, the particles were characterized by SEM, TEM, STEM, cross-sectional EDX mapping, and XRD. The non-encapsulated, bare ZrO₂ particles predominantly transitioned to the tetragonal phase after pre-calcination at 400 °C. Increasing the temperature to 600 °C transformed them to monoclinic. Finally, grain coarsening destroyed the spheroidal particle shape after heating to 800 °C. In striking contrast, SiO₂-encapsulation significantly inhibited grain growth and the t → m transition progressed considerably only after heating to 1000 °C, whereupon the particle shape, with a smooth silica shell, remained stable. Particle disintegration was observed after heating to 1200 °C. Thus, ZrO₂@SiO₂ core–shell particles are suited for high-temperature applications up to ∼1000 °C. Different mechanisms are considered to explain the markedly enhanced stability of ZrO₂@SiO₂ core–shell particles.

Silica encapsulation dramatically enhances the thermal stability of zirconia submicron particles by grain growth inhibition and tetragonal phase stabilization.     

The Osteogenic Effect of Erythropoietin on Human Mesenchymal Stromal Cells is Dose-Dependent and Involves Non-Hematopoietic Receptors and Multiple Intracellular Signaling Pathways

Erythropoietin (EPO) is a pleiotropic growth factor. Of interest for skeletal tissue engineering, the non-hematopoietic capabilities of EPO include its osteogenic and angiogenic potencies. The main aim of this study was to investigate the dose–response relationship and determine the lowest effective dose of EPO that reliably increases the osteogenic differentiation of human mesenchymal stromal cells (hMSCs). Additional aims were to elucidate the surface receptors and to investigate the role of the intracellular signaling pathways by blocking the mammalian target of rapamycin (mTOR), Jak-2 protein tyrosine kinase (JAK2), and phosphoinositide 3-kinases (PI3K). The primary outcome measures were two mineralization assays, Arsenazo III and alizarin red, applied after 10, 14, and 21 days. Moreover, alkaline phosphatase activity, cell number, and cell viability were determined after 2 and 7 days. A proportional dose–response relationship was observed. In vivo, the lowest effective dose of 20 IU/ml should be used for further research to accommodate safety concerns about adverse effects. Ex vivo, the most effective dose of 100 IU/ml could facilitate vascularization and bone ingrowth in cell-based scaffolds. The expression of non-hematopoietic receptors EPOR and CD131 was documented, and EPO triggered all three examined intracellular pathways. Future studies of the efficacy of EPO in cell-based tissue engineering can benefit from our findings.