Effects of adipocyte-specific Dkk1 deletion on bone homeostasis and obesity-induced bone loss in male mice

The link between obesity and low bone strength has become a significant medical concern. The canonical Wnt signaling pathway is a key regulator of mesenchymal stem cell differentiation into either osteoblasts or adipocytes with active Wnt signaling promoting osteoblastogenesis. Our previous research indicated that Dickkopf-1 (Dkk1), a Wnt inhibitor, is upregulated in bone tissue in obesity and that osteoblast-derived Dkk1 drives obesity-induced bone loss. However, Dkk1 is also produced by adipocytes, but the impact of adipogenic Dkk1 on bone remodeling and its role in obesity-induced bone loss remain unclear. Thus, in this study, we investigated the influence of adipogenic Dkk1 on bone homeostasis and obesity-induced bone loss in mice. To that end, deletion of Dkk1 in adipocytes was induced by tamoxifen administration into 8-week-old male Dkk1fl/fl;AdipoQcreERT2 mice. Bone and fat mass were analyzed at 12 and 20 weeks of age. Obesity was induced in 8-week-old male Dkk1fl/fl;AdipoQcre mice with a high-fat diet (HFD) rich in saturated fats for 12 weeks. We observed that 12-week-old male mice without adipogenic Dkk1 had a significant increase in trabecular bone volume in the vertebrae and femoral bones. While histological and serological bone formation markers were not different, the number of osteoclasts and adipocytes was decreased in the vertebral bones of Dkk1fl/fl;AdipoQcre-positive mice. Despite the increased bone mass in 12-week-old male mice, at 20 weeks of age, there was no difference in the bone volume between the controls and Dkk1fl/fl;AdipoQcre-positive mice. Also, Dkk1fl/fl;AdipoQcre-positive mice were not protected from HFD-induced bone loss. Even though mRNA expression levels of Sost, another important Wnt inhibitor, in bone from Dkk1-deficient mice fed with HFD were decreased compared to Dkk1-sufficient mice on an HFD, this did not prevent the HFD-induced suppression of bone formation. In conclusion, adipogenic Dkk1 may play a transient role in bone mass regulation during adolescence, but it does not contribute to bone homeostasis or obesity-induced bone loss later in life.

Dickkopf1 fuels inflammatory cytokine responses

Many human diseases, including cancer, share an inflammatory component but the molecular underpinnings remain incompletely understood. We report that physiological and pathological Dickkopf1 (DKK1) activity fuels inflammatory cytokine responses in cell models, mice and humans. DKK1 maintains the elevated inflammatory tone of cancer cells and is required for mounting cytokine responses following ligation of toll-like and cytokine receptors. DKK1-controlled inflammation derives from cell-autonomous mechanisms, which involve SOCS3-restricted, nuclear RelA (p65) activity. We translate these findings to humans by showing that genetic DKK1 variants are linked to elevated cytokine production across healthy populations. Finally, we find that genetic deletion of DKK1 but not pharmacological neutralization of soluble DKK1 ameliorates inflammation and disease trajectories in a mouse model of endotoxemia. Collectively, our study identifies a cell-autonomous function of DKK1 in the control of the inflammatory response, which is conserved between malignant and non-malignant cells. Additional studies are required to mechanistically dissect cellular DKK1 trafficking and signaling pathways.

Epo/EpoR signaling in osteoprogenitor cells is essential for bone homeostasis and Epo-induced bone loss

High erythropoietin (Epo) levels are detrimental to bone health in adult organisms. Adult mice receiving high doses of Epo lose bone mass due to suppressed bone formation and increased bone resorption. In humans, high serum Epo levels are linked to fractures in elderly men. Our earlier studies indicated that Epo modulates osteoblast activity; however, direct evidence that Epo acts via its receptor (EpoR) on osteoblasts in vivo is still missing. Here, we created mice lacking EpoR in osteoprogenitor cells to specifically address this gap. Deletion of EpoR in osteoprogenitors (EpoR:Osx-cre, cKO) starting at 5 weeks of age did not alter red blood cell parameters but increased vertebral bone volume by 25% in 12-week-old female mice. This was associated with low bone turnover. Histological (osteoblast number, bone formation rate) and serum (P1NP, osteocalcin) bone formation parameters were all reduced, as were the number of osteoclasts and TRAP serum level. Differentiation of osteoblast precursors isolated from cKO versus control mice resulted in lower expression of osteoblast marker genes including Runx2, Alp, and Col1a1 on day 21, whereas the mineralization capacity was similar. Moreover, the RANKL/OPG ratio, which determines the osteoclast-supporting potential of osteoblasts, was substantially decreased by 50%. Similarly, coculturing cKO osteoblasts with control or cKO osteoclast precursors produced significantly fewer osteoclasts than coculture with control osteoblasts. Finally, exposing female mice to Epo pumps (10 U·d⁻¹) for 4 weeks resulted in trabecular bone loss (−25%) and increased osteoclast numbers (1.7-fold) in control mice only, not in cKO mice. Our data show that EpoR in osteoprogenitors is essential in regulating osteoblast function and osteoblast-mediated osteoclastogenesis via the RANKL/OPG axis. Thus, osteogenic Epo/EpoR signaling controls bone mass maintenance and contributes to Epo-induced bone loss.

Mice lacking DKK1 in T cells exhibit high bone mass and are protected from estrogen-deficiency-induced bone loss

The Wnt inhibitor Dickkopf-1 (DKK1) is a negative regulator of bone formation and bone mass and is dysregulated in various bone diseases. How DKK1 contributes to postmenopausal osteoporosis, however, remains poorly understood. Here, we show that mice lacking DKK1 in T cells are protected from ovariectomy-induced bone loss. Ovariectomy activated CD4+ and CD8+ T cells and increased their production of DKK1. Co-culture of activated T cells with osteoblasts inhibited Wnt signaling in osteoblasts, leading to impaired differentiation. Importantly, DKK1 expression in T cells also controlled physiological bone remodeling. T-cell-deficient Dkk1 knock-out mice had a higher bone mass with an increased bone formation rate and decreased numbers of osteoclasts compared with controls, a phenotype that was rescued by adoptive transfer of wild-type T cells. Thus, these findings highlight that T cells control bone remodeling in health and disease via their expression of DKK1.

Role of osteogenic Dickkopf-1 in bone remodeling and bone healing in mice with type I diabetes mellitus

Type 1 diabetes mellitus (T1DM) is associated with low bone mass and a higher risk for fractures. Dickkopf-1 (Dkk1), which inhibits Wnt signaling, osteoblast function, and bone formation, has been found to be increased in the serum of patients with T1DM. Here, we investigated the functional role of Dkk1 in T1DM-induced bone loss in mice. T1DM was induced in 10-week-old male mice with Dkk1-deficiency in late osteoblasts/osteocytes (Dkk1^f/f;Dmp1-Cre, cKO) and littermate control mice by 5 subsequent injections of streptozotocin (40 mg/kg). Age-matched, non-diabetic control groups received citrate buffer instead. At week 12, calvarial defects were created in subgroups of each cohort. After a total of 16 weeks, weight, fat, the femoral bone phenotype and the area of the bone defect were analyzed using µCT and dynamic histomorphometry. During the experiment, diabetic WT and cKO mice did not gain body weight compared to control mice. Further they lost their perigonadal and subcutaneous fat pads. Diabetic mice had highly elevated serum glucose levels and impaired glucose tolerance, regardless of their Dkk1 levels. T1DM led to a 36% decrease in trabecular bone volume in Cre− negative control animals, whereas Dkk1 cKO mice only lost 16%. Of note, Dkk1 cKO mice were completely protected from T1DM-induced cortical bone loss. T1DM suppressed the bone formation rate, the number of osteoblasts at trabecular bone, serum levels of P1NP and bone defect healing in both, Dkk1-deficient and sufficient, mice. This may be explained by increased serum sclerostin levels in both genotypes and the strict dependence on bone formation for bone defect healing. In contrast, the number of osteoclasts and TRACP 5b serum levels only increased in diabetic control mice, but not in Dkk1 cKO mice. In summary, Dkk1 derived from osteogenic cells does not influence the development of T1DM but plays a crucial role in T1DM-induced bone loss in male mice by regulating osteoclast numbers.

Pregnancy outcome in Charcot-Marie-Tooth disease: results of the CMT-NET cohort study in Germany

Background and purpose

Systematic research on the effect of Charcot–Marie–Tooth (CMT) disease on the outcome of pregnancy and conversely the effect of pregnancy on neuropathy is still sparse.

Methods

A clinical cohort study and cross‐sectional study within the German CMT‐NET was conducted between 2016 and 2019. Inclusion criteria were a confirmed diagnosis of CMT and at least one completed pregnancy after 1990. All participants agreed to fill in questionnaires and have their medical files reviewed.

Results

The study group comprised 54 women with a total of 98 pregnancies. The mean age at onset of CMT disease was 12.6 years (range 0–37 years). Fifty (92%) patients had autosomal dominant CMT; two patients each (4%) had X‐linked and autosomal recessive CMT. Forty patients (74%) had a PMP22 gene duplication (CMT1A). Obstetric complications did not differ significantly from a German reference population, neither in the whole group nor in the CMT1A group. Overall there was no increased newborn morbidity and mortality. About one‐third of patients reported exacerbation of CMT disease in or after pregnancy. No adverse effects of anaesthesia were reported. Most participants stressed a positive attitude and awareness of challenges associated with pregnancy. Important issues were assistance and support in caring for the family.

Discussion

In line with findings from our previous study undertaken in the 1990s, there were no increased complication rates for pregnancy and delivery. These results are reassuring for the vast majority of CMT patients and are important for family planning and clinical care.

Loss of Dkk-1 in Osteocytes Mitigates Alveolar Bone Loss in Mice With Periodontitis

Background: Periodontitis is a highly prevalent infection-triggered inflammatory disease that results in bone loss. Inflammation causes bone resorption by osteoclasts, and also by suppression of bone formation via increase of Dickkopf-1 (Dkk-1), an inhibitor of Wnt signaling. Here, we tested the hypothesis that osteocytic Dkk-1 is a key factor in the pathogenesis of periodontitis-induced alveolar bone loss (ABL).

Methods: Twelve-week-old female mice with a constitutive deletion of Dkk-1 specifically in osteocytes (Dkk-1^fl/fl;Dmp1:Cre) were subjected to experimental periodontitis (EP). Cre-negative littermates served as controls. EP was induced by placing a ligature around the upper 2nd left molar, the contralateral side was used as control. Mice were killed after 11 days and maxillae removed for micro-CT and histological analyses. The mRNA expression of Dkk-1, Runx2, Osteocalcin, OPG, RANKL, RANKL/OPG ratio, LEF-1, and TCF-7 were assessed in maxillae, while mRNA expressions of TNF and IL-1 were evaluated on gingiva using real-time PCR. Blood samples were collected for Dkk-1, CTX, and P1NP measurement by ELISA.

Results: The deletion of Dkk-1 in osteocytes prevented ABL in mice with EP, compared to Cre-negative control mice with EP. Micro-CT analysis showed a significant reduction of bone loss (−28.5%) in EP Dkk-1^fl/fl;Dmp1:Cre-positive mice compared to their littermate controls. These mice showed a greater alveolar bone volume, bone mineral density, trabecular number, and trabecular thickness after EP when compared to the Cre-negative controls. The local expression in maxillae as well as the serum levels of Dkk-1 were reduced in Dkk-1^fl/fl;Dmp1:Cre-positive mice with EP. The transgenic mice submitted to EP showed increase of P1NP and reduction of CTX-I serum levels, and increase of TCF-7 expression. Histological analysis displayed less inflammatory infiltrates, a reduction of TNF and IL-1 expressions in the gingiva and fewer osteoclasts in Cre-positive animals with EP. Moreover, in mice with EP, the osteocytic deletion of Dkk-1 enhanced bone formation due to increased expressions of Runx2 and Osteocalcin and decreased expression of RANKL in maxillae.

Conclusion: In summary, Dkk-1 derived from osteocytes plays a crucial role in ABL in periodontitis.

Osteogenic Dkk1 Mediates Glucocorticoid-Induced but Not Arthritis-Induced Bone Loss

Dickkopf-1 (Dkk1) is a negative regulator of bone formation and bone mass and is deregulated in bone loss induced by arthritis and glucocorticoid (GC) exposure. However, the role of Dkk1 in these pathological processes is still unknown. Here, we used conditional Dkk1 knock-out mice to determine the role of Dkk1 produced by osteolineage cells in the development of arthritis and GC-induced bone loss. Osteoprogenitor (Osx-Cre)- and osteocyte (Dmp1-Cre)-specific knock-out mice and their Cre-negative controls were subjected to two arthritis models, K/BxN and antigen-induced arthritis. Disease induction and progression were assessed. GC-induced bone loss was induced in 25-week-old female mice by implanting prednisolone (7.5 mg) slow-release pellets for 4 weeks. Dkk1^fl/fl ;Osx-Cre mice subjected to K/BxN arthritis showed mildly reduced disease severity with reduced infiltration of neutrophils and T cells into affected joints and reduced bone erosions compared with Cre-negative controls. Osteocyte-specific Dkk1 deletion did not affect disease severity or local bone erosions. However, systemic bone loss at the spine was less severe in both mouse lines. In contrast to arthritis, both lines were protected from GC-induced bone loss. Although the Cre-negative controls lost about 26% and 31% bone volume potentially caused by decreased bone formation, Cre-positive mice did not exhibit such alterations. Dkk-1 deficiency in osteolineage cells protects against GC-induced bone loss, whereas it had only minor effects in arthritis. Therefore, Dkk1 may be a promising therapeutic target especially for bone diseases in which inhibition of bone formation represents the predominant mechanism. © 2019 American Society for Bone and Mineral Research.

Regulation of sclerostin in glucocorticoid-induced osteoporosis (GIO) in mice and humans

Glucocorticoids (GC) are used for the treatment of inflammatory diseases, including various forms of arthritis. However, their use is limited, amongst others, by adverse effects on bone. The Wnt and bone formation inhibitor sclerostin was recently implicated in the pathogenesis of GC-induced osteoporosis. However, data are ambiguous. The aim of this study was to assess the regulation of sclerostin by GC using several mouse models with high GC levels and two independent cohorts of patients treated with GC. Male 24-week-old C57BL/6 and 18-week-old DBA/1 mice exposed to GC and 12-week-old mice with endogenous hypercortisolism displayed reduced bone formation as indicated by reduced levels of P1NP and increased serum sclerostin levels. The expression of sclerostin in femoral bone tissue and GC-treated bone marrow stromal cells, however, was not consistently altered. In contrast, GC dose- and time-dependently suppressed sclerostin at mRNA and protein levels in human mesenchymal stromal cells, and this effect was GC receptor dependent. In line with the human cell culture data, patients with rheumatoid arthritis (RA, n = 101) and polymyalgia rheumatica (PMR, n = 21) who were exposed to GC had lower serum levels of sclerostin than healthy age- and sex-matched controls (-40%, P < 0.01 and -26.5%, P < 0.001, respectively). In summary, sclerostin appears to be differentially regulated by GC in mice and humans as it is suppressed by GCs in humans but is not consistently altered in mice. Further studies are required to delineate the differences between GC regulation of sclerostin in mice and humans and assess whether sclerostin mediates GC-induced osteoporosis in humans.

Trabectedin Reduces Skeletal Prostate Cancer Tumor Size in Association with Effects on M2 Macrophages and Efferocytosis

Macrophages play a dual role in regulating tumor progression. They can either reduce tumor growth by secreting antitumorigenic factors or promote tumor progression by secreting a variety of soluble factors. The purpose of this study was to define the monocyte/macrophage population prevalent in skeletal tumors, explore a mechanism employed in supporting prostate cancer (PCa) skeletal metastasis, and examine a novel therapeutic target. Phagocytic CD68+ cells were found to correlate with Gleason score in human PCa samples, and M2-like macrophages (F4/80⁺CD206⁺) were identified in PCa bone resident tumors in mice. Induced M2-like macrophages in vitro were more proficient at phagocytosis (efferocytosis) of apoptotic tumor cells than M1-like macrophages. Moreover, soluble factors released from efferocytic versus nonefferocytic macrophages increased PC-3 prostate cancer cell numbers in vitro. Trabectedin exposure reduced M2-like (F4/80+CD206+) macrophages in vivo. Trabectedin administration after PC-3 cell intracardiac inoculation reduced skeletal metastatic tumor growth. Preventative pretreatment with trabectedin 7 days prior to PC-3 cell injection resulted in reduced M2-like macrophages in the marrow and reduced skeletal tumor size. Together, these findings suggest that M2-like monocytes and macrophages promote PCa skeletal metastasis and that trabectedin represents a candidate therapeutic target.

Postnatal Skeletal Deletion of Dickkopf-1 Increases Bone Formation and Bone Volume in Male and Female Mice, Despite Increased Sclerostin Expression

The Wnt antagonist Dickkopf-1 (Dkk1) is a negative regulator of osteoblast function and bone mass. However, because of the lack of appropriate models, many aspects of its role in the regulation of postnatal bone turnover and its cellular source have remained unknown. In this study, we deleted Dkk1 postnatally and in different cell types using various Cre-drivers (Rosa26-ERT2-Cre, Osx-cre, Dmp1-Cre) and assessed to which extent cells of the osteoblastic lineage contribute to the effects of Dkk1 on bone turnover and homeostasis. Female and male mice were examined at 12 weeks of age. Mice with a global or cell type-specific deletion of Dkk1 showed a two- to threefold higher bone volume compared with their Cre-negative littermates. The mineral apposition rate and the bone formation rate were increased two- to fourfold in all three mouse lines, despite a significant increase in systemic and skeletal levels of sclerostin. Dkk1 deletion further reduced the number of osteoclasts about twofold, which was accompanied by a strong decrease in the receptor activator of nuclear factor-κB ligand/osteoprotegerin mRNA ratio in femoral bone. Despite similar increases in bone mass, the deletion of Dkk1 in osterix-expressing cells reduced circulating Dkk1 significantly (males, -79%; females, -77%), whereas they were not changed in Dkk1^fl/fl ;Dmp1-Cre mice. However, both lines showed significantly reduced Dkk1 mRNA levels in bone. In summary, we show that lack of Dkk1 in cells of the osteoblastic lineage leads to high bone mass with increased bone formation, despite increased levels of sclerostin. Moreover, the majority of systemic Dkk1 appears to originate from osteoprogenitors but not from mature osteoblasts or osteocytes. Nevertheless, the amount of Dkk1 produced locally by more mature osteogenic cells is sufficient to modulate bone mass. Thus, this study highlights the importance of local Wnt signaling on postnatal bone homeostasis. © 2018 American Society for Bone and Mineral Research.

Communication Architecture for AAL

Introduction: This article is part of the Focus Theme of Methods of Information in Medicine on “Using Data from Ambient Assisted Living and Smart Homes in Electronic Health Records”.

Background: Concepts of Ambient Assisted Living (AAL) support a long-term health monitoring and further medical and other services for multi-morbid patients with chronic diseases. In Germany many AAL and telemedical applications exist. Synergy effects by common agreements for essential application components and standards are not achieved.

Objectives: It is necessary to define a communication architecture which is based on common definitions of communication scenarios, application components and communication standards.

Methods: The development of a communication architecture requires different steps. To gain a reference model for the problem area different AAL and telemedicine projects were compared and relevant data elements were generalized. The derived reference model defines standardized communication links.

Results: As a result the authors present an approach towards a reference architecture for AAL-communication. The focus of the architecture lays on the communication layer. The necessary application components are identified and a communication based on standards and their extensions is highlighted.

Conclusion: The exchange of patient in -dividual events supported by an event classification model, raw and aggregated data from the personal home area over a tele-medicine center to health care providers is possible.

Olfactory discrimination and memory deficits in the Flinders Sensitive Line rodent model of depression

Major Depressive Disorder (MDD) is a heterogeneous psychiatric disorder with broad symptomatic manifestations. The current study examined, for the first time, olfactory memory and discrimination in the Flinders Sensitive Line (FSL) rodent model of depression. Male FSL rats and controls were trained on an Olfactory Discrimination (OD) and a Social Interaction (SI) test. On the OD test, the FSL and controls performed similarly at the shortest inter-trial interval (5min), however, with extended delay of 30min, the FSLs had a recall and odour discrimination deficit. At the longest delay (60min) both groups performed poorly. The FSL rats i.) had a deficit in olfactory discrimination suggesting impairment in olfactory memory and recall; ii.) were less likely to socialize with unfamiliar rats. The data suggests that FSL animals have an impaired olfactory information processing capacity.

Landau-Zener Transition in a Continuously Measured Single-Molecule Spin Transistor

We monitor the Landau-Zener dynamics of a single-ion magnet inserted into a spin-transistor geometry. For increasing field-sweep rates, the spin reversal probability shows increasing deviations from that of a closed system. In the low-conductance limit, such deviations are shown to result from a dephasing process. In particular, the observed behaviors are successfully simulated by means of an adiabatic master equation, with time averaged dephasing (Lindblad) operators. The time average is tentatively interpreted in terms of the finite time resolution of the continuous measurement.

Rotationally symmetric formulation of the wave propagation method-application to the straylight analysis of diffractive lenses

We introduce a modified formulation of the wave propagation method for the efficient simulation of rotationally symmetric micro-optical components. The reformulated algorithm provides an increased computational performance of approximately two orders of magnitude and strongly reduced memory requirements, in comparison to the original formulation. This enables the efficient wave optical simulation of extended micro-optical structures beyond the common thin-element approximation. As a prototypical example, we assess the modified algorithm for the evaluation of straylight induced by diffractive lenses. We find an excellent accuracy, while comparing to rigorous simulations, which justifies the ability to overcome the limitations of the thin-element approximation.

Role of milk fat globule-epidermal growth factor 8 in osteoimmunology

Milk fat globule-epidermal growth factor 8 (MFG-E8) is a glycoprotein that is abundantly expressed in various tissues and has a pivotal role in the phagocytic clearance of apoptotic cells. However, MFG-E8 has also gained significant attention because of its wide range of functions in autoimmunity, inflammation and tissue homeostasis. More recently, MFG-E8 has been identified as a critical regulator of bone homeostasis, being expressed in both, osteoblasts and osteoclasts. In addition, it was shown that MFG-E8 fulfils an active role in modulating inflammatory processes, suggesting an anti-inflammatory role of MFG-E8 and proposing it as a novel therapeutic target for inflammatory diseases. This concise review focusses on the expression and regulation of MFG-E8 in the context of inflammatory bone diseases, highlights its role in the pathophysiology of osteoimmune diseases and discusses the therapeutic potential of MFG-E8.

Bimodal endoscopic probe combining white-light microscopy and optical coherence tomography

We present a novel bimodal endoscopic imaging probe that can simultaneously provide full-field white-light video microscopy and confocal optical coherence tomography (OCT) depth scans. The two modalities rely on spectrally separated optical paths that run partially in parallel through a micro-optical bench system, which has a cross-section of only 2  mm×2.76  mm and is realized via standard silicon micromachining techniques. With a numerical aperture of 0.061, the video modality has a resolution and field of view of 9.3 and 1240  μm×1080  μm, respectively. The resolution is limited by the pixel spacing of the coherent fiber bundle, which relays the acquired image from the distal to the proximal end. A custom-designed diffractive optical element placed within the video imaging path significantly improves the image contrast by up to 45% in the medium frequency range. The OCT modality is optimized for 830 nm center wavelength, and works in a confocal arrangement with an NA of 0.018. It provides single-point depth probing at the center of the video image with a lateral resolution of 20 μm. Through its compact footprint and enhanced functionality, the probe can provide depth-resolved guiding capability for existing laparoscopes and represents a major step toward a new class of multimodal endoscopic imaging probes.

Milk Fat Globule-Epidermal Growth Factor 8 (MFG-E8) Is a Novel Anti-inflammatory Factor in Rheumatoid Arthritis in Mice and Humans

Milk fat globule-epidermal growth factor 8 (MFG-E8) is an anti-inflammatory glycoprotein that mediates the clearance of apoptotic cells and is implicated in the pathogenesis of autoimmune and inflammatory diseases. Because MFG-E8 also controls bone metabolism, we investigated its role in rheumatoid arthritis (RA), focusing on inflammation and joint destruction. The regulation of MFG-E8 by inflammation was assessed in vitro using osteoblasts, in arthritic mice and in patients with RA. K/BxN serum transfer arthritis (STA) was applied to MFG-E8 knock-out mice to assess its role in the pathogenesis of arthritis. Stimulation of osteoblasts with lipopolysaccharide (LPS) and tumor necrosis factor (TNF)-α downregulated the expression of MFG-E8 by 30% to 35%. MFG-E8-deficient osteoblasts responded to LPS with a stronger production of pro-inflammatory cytokines. In vivo, MFG-E8 mRNA levels were 52% lower in the paws of collagen-induced arthritic (CIA) mice and 24% to 42% lower in the serum of arthritic mice using two different arthritis models (CIA and STA). Similarly, patients with RA (n = 93) had lower serum concentrations of MFG-E8 (-17%) compared with healthy controls (n = 140). In a subgroup of patients who had a moderate to high disease activity (n = 21), serum concentrations of MFG-E8 rose after complete or partial remission had been achieved (+67%). Finally, MFG-E8-deficient mice subjected to STA exhibited a stronger disease burden, an increased number of neutrophils in the joints, and a more extensive local and systemic bone loss. This was accompanied by an increased activation of osteoclasts and a suppression of osteoblast function in MFG-E8-deficient mice. Thus, MFG-E8 is a protective factor in the pathogenesis of RA and subsequent bone loss. Whether MFG-E8 qualifies as a novel biomarker or therapeutic target for the treatment of RA is worth addressing in further studies.

p38 MAPK regulates the Wnt inhibitor Dickkopf-1 in osteotropic prostate cancer cells

The Wnt inhibitor Dickkopf-1 (DKK-1) has been associated with the occurrence of bone metastases in osteotropic prostate cancer by inhibiting osteoblastogenesis. P38 mitogen-activated protein kinase (MAPK) activity is also dysregulated in advanced prostate cancer. However, the impact of p38 MAPK signaling on DKK-1 remains unknown. Inhibition of p38 MAPK signaling in osteolytic PC3 cells by small molecule inhibitors (doramapimod, LY2228820 and SB202190) suppressed DKK-1 expression, whereas activation of p38 MAPK by anisomycin increased DKK-1. Further dissection by targeting individual p38 MAPK isoforms with siRNA revealed a stronger role for MAPK11 than MAPK14 and MAPK12 in the regulation of DKK-1. Moreover, prostate cancer cells with a predominantly osteolytic phenotype produced sufficient amounts of DKK-1 to inhibit Wnt3a-induced osteoblastic differentiation in C2C12 cells. This inhibition was blocked directly by neutralizing DKK-1 using a specific antibody and also indirectly by blocking p38 MAPK. Furthermore, tissue expression in human prostate cancer revealed a correlation between p38 MAPK and DKK-1 expression with higher expression in tumor compared with normal tissues. These results reveal that p38 MAPK regulates DKK-1 in prostate cancer and may present a potential target in osteolytic prostate cancers.

Three-dimensional morphology of the interface between micro porous layer and catalyst layer in a polymer electrolyte membrane fuel cell

FIB/SEM tomography and ALD infiltration are combined to analyse the interface between MPL and CL in a PEM fuel cell.

Adult osteochondritis dissecans and focussed ESWT: A successful treatment option

Extracorporeal shockwave therapy (ESWT) has gained acceptance in the medical field and in the treatment of non-unions and delayed bone healing. ESWT has been used effectively for many years as a noninvasive surgical procedure. The idea of treating Osteochondritis dissecans of knee and talus arose in the middle of the 1990's. OCD is known as a pre-arthritic factor in the long-term and still there is no consistent treatment. In the literature there is still only a small number of publications but international societies for shockwave treatment are convinced that ESWT on OCD shows to be an effective and safe method in the treatment of OCD in the early stages. We want to summarize the actual data on the treatment of OCD by ESWT.

Lateral epicondylitis: This is still a main indication for extracorporeal shockwave therapy

Extracorporeal shockwave therapy (ESWT) is used in a number of indications in the medical field. A number of tendinopathies show good and excellent results due to evidence based medicine. The treatment of lateral epicondylitis is known to show conflicting results. This overview of the published RCT's on ESWT for lateral epicondylitis tries to show the reasons for this conflicting data-base and point out, why we think that this is still a main indication for extracorporeal shockwave therapy.

Determination of the binding mode for the cyclopentapeptide CXCR4 antagonist FC131 using a dual approach of ligand modifications and receptor mutagenesis

BACKGROUND AND PURPOSE

The cyclopentapeptide FC131 (cyclo(-L-Arg(1) -L-Arg(2) -L-2-Nal(3) -Gly(4) -D-Tyr(5) -)) is an antagonist at the CXC chemokine receptor CXCR4, which plays a role in human immunodeficiency virus infection, cancer and stem cell recruitment. Binding modes for FC131 in CXCR4 have previously been suggested based on molecular docking guided by structure-activity relationship (SAR) data; however, none of these have been verified by in vitro experiments.

EXPERIMENTAL APPROACH

Heterologous (125) I-12G5-competition binding and functional assays (inhibition of CXCL12-mediated activation) of FC131 and three analogues were performed on wild-type CXCR4 and 25 receptor mutants. Computational modelling was used to rationalize the experimental data.

KEY RESULTS

The Arg(2) and 2-Nal(3) side chains of FC131 interact with residues in TM-3 (His(113) , Asp(171) ) and TM-5 (hydrophobic pocket) respectively. Arg(1) forms charge-charge interactions with Asp(187) in ECL-2, while D-Tyr(5) points to the extracellular side of CXCR4. Furthermore, the backbone of FC131 interacts with the chemokine receptor-conserved Glu(288) via two water molecules. Intriguingly, Tyr(116) and Glu(288) form a H-bond in CXCR4 crystal structures and mutation of either residue to Ala abolishes CXCR4 activity.

CONCLUSIONS AND IMPLICATIONS

Ligand modification, receptor mutagenesis and computational modelling approaches were used to identify the binding mode of FC131 in CXCR4, which was in agreement with binding modes suggested from previous SAR studies. Furthermore, insights into the mechanism for CXCR4 activation by CXCL12 were gained. The combined findings will facilitate future design of novel CXCR4 antagonists.

Loss of milk fat globule-epidermal growth factor 8 (MFG-E8) in mice leads to low bone mass and accelerates ovariectomy-associated bone loss by increasing osteoclastogenesis

Milk fat globule-epidermal growth factor 8 (MFG-E8) is a glycoprotein that controls the engulfment of apoptotic cells and exerts inflammation-modulatory effects. Recently, it has been implicated in osteoclastogenesis and the pathogenesis of inflammatory periodontal bone loss, but its role in physiological bone homeostasis is still not well defined. Here, we evaluated the influence of MFG-E8 on osteoblasts and osteoclasts and its impact on bone remodeling in healthy and ovariectomized mice as a model for post-menopausal osteoporosis. Total and trabecular bone mineral densities at the lumbar spine in 6-week-old MFG-E8 KO mice were reduced by 11% (p < 0.05) and 17% (p < 0.01), respectively, as compared to wild-type (WT) mice. Accordingly, serum levels of the bone formation marker P1NP were decreased by 37% (p < 0.01) in MFG-E8 KO mice as were the ex vivo mineralization capacity and expression of osteoblast genes (Runx2, alkaline phosphatase, osteocalcin) in MFG-E8 KO osteoblasts. In contrast, serum bone resorption markers CTX1 and TRAP5b were increased by 30% and 60% (p < 0.05), respectively, in MFG-E8 KO mice. Furthermore, bone marrow macrophages from MFG-E8-KO mice differentiated more effectively into osteoclasts, as compared to WT cells. MFG-E8-deficient osteoclasts displayed increased bone resorption ex vivo, which could be reversed by the presence of recombinant MFG-E8. To determine the significance of the enhanced osteoclastogenesis in MFG-E8 KO mice, we performed an ovariectomy, which is associated with bone loss due to increased osteoclast activity. Indeed, MFG-E8 KO mice lost 12% more trabecular bone density than WT mice after ovariectomy. Together, these data indicate that MFG-E8 controls steady-state and pathological bone turnover and may therefore represent a new target gene in the treatment of bone diseases.

Loss of bone strength in HLA-B27 transgenic rats is characterized by a high bone turnover and is mainly osteoclast-driven

OBJECTIVE

Although osteopenia is frequent in spondyloarthritis (SpA), the underlying cellular mechanisms and association with other symptoms are poorly understood. This study aimed to characterize bone loss during disease progression, determine cellular alterations, and assess the contribution of inflammatory bowel disease (IBD) to bone loss in HLA-B27 transgenic rats.

METHODS

Bones of 2-, 6-, and 12-month-old non-transgenic, disease-free HLA-B7 and disease-associated HLA-B27 transgenic rats were examined using peripheral quantitative computed tomography, μCT, and nanoindentation. Cellular characteristics were determined by histomorphometry and ex vivo cultures. The impact of IBD was determined using [21-3 x 283-2]F1 rats, which develop arthritis and spondylitis, but not IBD.

RESULTS

HLA-B27 transgenic rats continuously lost bone mass with increasing age and had impaired bone material properties, leading to a 3-fold decrease in bone strength at 12 months of age. Bone turnover was increased in HLA-B27 transgenic rats, as evidenced by a 3-fold increase in bone formation and a 6-fold increase in bone resorption parameters. Enhanced osteoclastic markers were associated with a larger number of precursors in the bone marrow and a stronger osteoclastogenic response to RANKL or TNFα. Further, IBD-free [21-3 x 283-2]F1 rats also displayed decreased total and trabecular bone density.

CONCLUSIONS

HLA-B27 transgenic rats lose an increasing amount of bone density and strength with progressing age, which is primarily mediated via increased bone remodeling in favor of bone resorption. Moreover, IBD and bone loss seem to be independent features of SpA in HLA-B27 transgenic rats.

Sulfated glycosaminoglycans support osteoblast functions and concurrently suppress osteoclasts

In order to improve bone regeneration, development and evaluation of new adaptive biomaterials is warranted. Glycosaminoglycans (GAGs) such as hyaluronan (HA) and chondroitin sulfate (CS) are major extracellular matrix (ECM) components of bone, and display osteogenic properties that are potentially useful for biomaterial applications. Using native and synthetic sulfate-modified GAGs, we manufactured artificial collagen/GAG ECM (aECMs) coatings, and evaluated how the presence of GAGs and their degree of sulfation affects the differentiation of murine mesenchymal stem cells to osteoblasts (OB) cultivated on these aECMs. GAG sulfation regulated osteogenesis at all key steps of OB development. Adhesion, but not migration, was diminished by 50% (P < 0.001). Proliferation and metabolic activity were slightly (P < 0.05) and cell death events strongly (P < 0.001) down-regulated due to a switch from proliferative to matrix synthesis state. When exposed to sulfated GAGs, OB marker genes, such as alkaline phosphatase, osteoprotegerin (OPG), and osteocalcin increased by up to 28-fold (P < 0.05) and calcium deposition up to 4-fold (P < 0.05). Furthermore, GAG treatment of OBs suppressed their ability to support osteoclast (OC) differentiation and resorption. In conclusion, GAG sulfation controls bone cell homeostasis by concurrently promoting osteogenesis and suppressing their paracrine support of OC functions, thus displaying a favorable profile on bone remodeling. Whether these cellular properties translate into improved bone regeneration needs to be validated in vivo.

Gating function of isoleucine-116 in TM-3 (position III:16/3.40) for the activity state of the CC-chemokine receptor 5 (CCR5)

BACKGROUND AND PURPOSE

A conserved amino acid within a protein family indicates a significance of the residue. In the centre of transmembrane helix (TM)-5, position V:13/5.47, an aromatic amino acid is conserved among class A 7TM receptors. However, in 37% of chemokine receptors - a subgroup of 7TM receptors - it is a leucine indicating an altered function. Here, we describe the significance of this position and its possible interaction with TM-3 for CCR5 activity.

EXPERIMENTAL APPROACH

The effects of [L203F]-CCR5 in TM-5 (position V:13/5.47), [I116A]-CCR5 in TM-3 (III:16/3.40) and [L203F;G286F]-CCR5 (V:13/5.47;VII:09/7.42) were determined in G-protein- and β-arrestin-coupled signalling. Computational modelling monitored changes in amino acid conformation.

KEY RESULTS

[L203F]-CCR5 increased the basal level of G-protein coupling (20-70% of Emax ) and β-arrestin recruitment (50% of Emax ) with a threefold increase in agonist potency. In silico, [I116A]-CCR5 switched χ1-angle in [L203F]-CCR5. Furthermore, [I116A]-CCR5 was constitutively active to a similar degree as [L203F]-CCR5. Tyr(244) in TM-6 (VI:09/6.44) moved towards TM-5 in silico, consistent with its previously shown function for CCR5 activation. On [L203F;G286F]-CCR5 the antagonist aplaviroc was converted to a superagonist.

CONCLUSIONS AND IMPLICATIONS

The results imply that an aromatic amino acid in the centre of TM-5 controls the level of receptor activity. Furthermore, Ile(116) acts as a gate for the movement of Tyr(244) towards TM-5 in the active state, a mechanism proposed previously for the β2 -adrenoceptor. The results provide an understanding of chemokine receptor function and thereby information for the development of biased and non-biased antagonists and inverse agonists.

Wave-optical design of a combined refractive-diffractive varifocal lens

A novel type of integrated refractive-diffractive varifocal membrane lens is designed and analyzed by wave-optical methods. In contrast to other hybrid devices, the diffractive microstructure is directly imprinted onto the soft deflecting membrane, allowing for a high level of integration. Elastic deformation is taken into account by mechanical simulations with the finite element method (FEM). We show, that the superimposed structure can considerably suppress chromatic and spherical aberration. Furthermore, our algorithm is successfully applied to design a confocal hyperspectral lens.

Somatropin treatment of spinal muscular atrophy: a placebo-controlled, double-blind crossover pilot study

In preclinical studies growth hormone and its primary mediator IGF-1 have shown potential to increase muscle mass and strength. A single patient with spinal muscular atrophy reported benefit after compassionate use of growth hormone. Therefore we evaluated the efficacy and safety of growth hormone treatment for spinal muscular atrophy in a multicenter, randomised, double-blind, placebo-controlled, crossover pilot trial. Patients (n = 19) with type II/III spinal muscular atrophy were randomised to receive either somatropin (0.03 mg/kg/day) or placebo subcutaneously for 3 months, followed by a 2-month wash-out phase before 3 months of treatment with the contrary remedy. Changes in upper limb muscle strength (megascore for elbow flexion and hand-grip in Newton) were assessed by hand-held myometry as the primary measure of outcome. Secondary outcome measures included lower limb muscle strength, motor function using the Hammersmith Functional Motor Scale and other functional tests for motor function and pulmonary function. Somatropin treatment did not significantly affect upper limb muscle strength (point estimate mean: 0.08 N, 95% confidence interval (CI:-3.79;3.95, p = 0.965), lower limb muscle strength (point estimate mean: 2.23 N, CI:-2.19;6.63, p = 0.302) or muscle and pulmonary function. Side effects occurring during somatropin treatment corresponded with well-known side effects of growth hormone substitution in patients with growth hormone deficiency. In this pilot study, growth hormone treatment did not improve muscle strength or function in patients with spinal muscular atrophy type II/III.