Effects of Deletion of ERα in Osteoblast‐Lineage Cells on Bone Mass and Adaptation to Mechanical Loading Differ in Female and Male Mice

Estrogen receptor alpha (ERα) has been implicated in bone's response to mechanical loading in both males and females. ERα in osteoblast lineage cells is important for determining bone mass, but results depend on animal sex and the cellular stage at which ERα is deleted. We demonstrated previously that when ERα is deleted from mature osteoblasts and osteocytes in mixed‐background female mice, bone mass and strength are decreased. However, few studies exist examining the skeletal response to loading in bone cell–specific ERαKO mice. Therefore, we crossed ERα floxed (ERα^fl/fl) and osteocalcin‐Cre (OC‐Cre) mice to generate animals lacking ERα in mature osteoblasts and osteocytes (pOC‐ERαKO) and littermate controls (LC). At 10 weeks of age, the left tibia was loaded in vivo for 2 weeks. We analyzed bone mass through micro‐CT, bone formation rate by dynamic histomorphometry, bone strength from mechanical testing, and osteoblast and osteoclast activity by serum chemistry and immunohistochemistry. ERα in mature osteoblasts differentially regulated bone mass in males and females. Compared with LC, female pOC‐ERαKO mice had decreased cortical and cancellous bone mass, whereas male pOC‐ERαKO mice had equal or greater bone mass than LC. Bone mass results correlated with decreased compressive strength in pOC‐ERαKO female L₅ vertebrae and with increased maximum moment in pOC‐ERαKO male femora. Female pOC‐ERαKO mice responded more to mechanical loading, whereas the response of pOC‐ERαKO male animals was similar to their littermate controls. © 2015 American Society for Bone and Mineral Research. © 2015 American Society for Bone and Mineral Research.     

Modeling and analysis of pH-electric-stimuli-responsive hydrogels

A multiphysics model is presented in this paper, called the multi-effect-coupling pH-electric-stimuli (MECpHe) model, for analysis of smart hydrogels responding to the stimuli of solution pH coupled with electric voltage, when the hydrogels are placed into pH buffer solution subject to an externally applied electric field. The MECpHe model considers the chemo-electro-mechanical multiphysics effects and formulates the fixed charge density with the coupled effect of buffer solution pH and electric voltage. The model is formulated mathematically by a set of nonlinear partial differential governing equations for predicting the displacement and the swelling ratio, as well as the average curvature of hydrogel strip, and for simulating the distributive profiles of diffusive ionic species concentrations and the electric potential, as well as the fixed charge density. The model is validated by the comparison of the present computation results with experimental data extracted from open literature. The steady-state simulation of the smart hydrogels is then conducted for the pH-electric-coupled stimuli. The influences of the externally applied electric voltage are discussed in detail on the distributions of diffusive ionic species concentrations, the displacement, the swelling ratio and the average curvature of the hydrogel strip.     

Serial magnetic resonance imaging in experimental primate stroke: Validation of MRI for pre-clinical cerebroprotective trials

Abstract

Precise assessment of stroke outcome is critical for pre-clinical testing of cerebroprotective strategies. Differences in stroke volume measured by various magnetic resonance imaging (MRI) techniques are documented in humans, but not well described in experimental primate stroke. This study characterizes changes in stroke volume using serial MRI scans in a baboon model of reperfused cerebral ischemia. The location/area of hyperintensity on MRI corresponded with the TTC-stained infarct region. T2-weighted fast spin echo (T2W FSE), fluid attenuated inversion recovery (FLAIR), and diffusion weighted imaging (DWI) showed a decrease in infarct volume between 72 h and nine days post-ischemia (p = ns, p = 0.029, and p = 0.006). T2W FSE and FLAIR demonstrated an increase in infarct volume from 24 h to nine days postischemia, while DWI displayed a decrease over the same period. While early T2W FSE, FLAIR, and DWI all correlated with late infarct volume (p < 0.001), 72 h T2W FSE was the best direct measure (2.39% ± 1.40% unity deviation). Serial MRI in a nonhuman primate model of focal cerebral ischemia recapitulates findings in clinical stroke. MRI at 72 h accurately predicts late infarct volume.     

The effects of systemic and intratumoral interleukin-12 treatment in C6 rat glioma model

Abstract

Objective: Cytokine based immunotherapy has long been an exciting field for many investigators aiming to provide an effective alternative treatment modality for glioma management. Among these cytokines, interleukin-12 (IL-12) plays a crucial role in mediating inflammatory and antitumoral activity on the host defence. We have investigated the therapeutic role of systemic and local delivery of IL-12 in C6 rat glioma model and compared these two modalities.

Methods: The donor C6 glioma cells were injected stereotactically to 32 Wistar rats and right frontal tumor formation was established in all subjects. The rats were evenly divided into four groups as intratumoral (i.t.) control group (Group IA), intraperitoneal (i.p.) control group (Group IB), i.t. treatment group (Group II) and i.p. treatment group (Group III). Magnetic resonance imaging were performed to 12 rats (three from each group) on the seventh post-inoculation day. Recombinant mouse IL-12 (rmIL-12) was administered via i.t. (0.1 μg 5 μl/day/rat) and i.p. (0.1 μg 20 μl/day/rat) routes to treatment groups between days 9 and 11 following tumor inoculation, for 3 consecutive days. The rats which were unresponsive to the external stimuli, unable to feed themselves or having severe neurological impairment were decapitated and the specimens were histopathologically examined.

Results: The subjects of Group III (i.p.) showed a statistically significant prolongation in survival time (mean=39 days) when compared to the control group (mean=31.7 days) (p=0.035) and Group II (i.t.) (mean=24.5 days) (p=0.005). Histopathologic examination of Group III revealed markedly increased intratumoral and peritumoral lymphocyte infiltration compared with the other groups.

Conclusion: This study demonstrated that systemic administration of IL-12 in C6 glioma model in rats prolongs the survival, probably by stimulating the cellular immunity leading to lymphocytic infiltration.     

Periodontal disease and bisphosphonates induce osteonecrosis of the jaws in the rat

Bisphosphonates (BPs) are medications used commonly to treat primary and metastatic bone cancer, as well as osteoporosis. Although BPs improve bone mineral density, reduce fracture risk, and reduce hypercalcemia of malignancy, some patients develop BP‐related osteonecrosis of the jaws (BRONJ). This devastating complication is defined as clinically exposed bone in the maxillofacial region for more than 8 weeks. Despite an increasing number of BRONJ cases since first reported, the disease pathophysiology remains largely unknown. Since published studies suggest a significant role for dental disease in the pathophysiology of BRONJ, we developed a BRONJ animal model where aggressive periodontal disease is induced by ligature placement around the crown of the right maxillary first molar in the presence of vehicle (veh) or zoledronic acid (ZA), a potent BP. Ligature placement induced significant alveolar bone loss, which was attenuated by ZA treatment. Osteonecrosis was observed associated with ligature‐induced periodontitis in the ZA‐treated group. This was seen as sequestration and extensive periosteal alveolar bone formation on micro–computed tomography (µCT) in the ligated site of BP‐treated animals. Histologic examination confirmed these findings, seen as necrotic bone with diffuse loss of osteocytes and empty lacunae, rimming of the necrotic bone by squamous epithelium and inflammation, and exposure to the oral cavity. Importantly, the rat lesions were strikingly similar to those of BRONJ patients. Our data suggest that dental disease and potent BP therapy are sufficient for BRONJ development in the rat. © 2011 American Society for Bone and Mineral Research     

In vitro and in vivo response to nanotopographically-modified surfaces of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and polycaprolactone

Colloidal lithography and embossing master are new techniques of producing nanotopography, which have been recently applied to improve tissue response to biomaterials by modifying the surface topography on a nano-scale dimension. A natural polyester (Biopol^?), 8% 3-hydroxyvalerate-component (D400G) and a conventional biodegradable polycaprolactone (PCL) were studied, both nanostructured and native forms, in vitro and in vivo. Nanopits (100-nm deep, 120-nm diameter) on the D400G surface were produced by the embossing master technique (Nano-D400G), while nanocylinders (160-nm height, 100-nm diameter) on the PCL surface were made by the colloidal lithography technique (Nano-PCL). L929 fibroblasts were seeded on polyesters, and cell proliferation, cytotoxic effect, synthetic and cytokine production were assessed after 72 h and 7 days. Then, under general anesthesia, 3 Sprague–Dawley rats received dorsal subcutaneous implants of nanostructured and native polyesters. At 1, 4 and 12 weeks the animals were pharmacologically euthanized and implants with surrounding tissue studied histologically and histomorphometrically. In vitro results showed significant differences between D400G and PCL in Interleukin-6 production at 72 h. At 7 days, significant (P < 0.05) differences were found in Interleukin-1 β and tumor necrosis factor-α release for Nano-PCL when compared to Nano-D400G, and for PCL in comparison with D400G. In vivo results indicated that Nano-D400G implants produced a greater extent of inflammatory tissue than Nano-PCL at 4 weeks. The highest vascular densities were observed for Nano-PCL at 4 and 12 weeks. Chemical and topographical factors seem to be responsible for the different behaviour, and from the obtained results a prevalence of chemistry on in vitro data and nanotopography on soft tissue response in vivo are hypothesized, although more detailed investigations are necessary in this field.     

What Can Be Measured from Surface Electrogastrography (Computer Simulations)

The aims of this study were to investigate thedetectability of the propagation of the gastric slowwave from the cutaneous electrogastrogram (EGG) and thepatterns of the EGG when the gastric slow waves are uncoupled. A mathematical model wasestablished based on the volume conductor theory tosimulate the transfer of the serosal gastric slow wavefrom the stomach to the abdominal surface. A number of computer simulations were conducted using themodel, and the periodic cross-correlation function wasused to estimate the phase shift between the fourchannels. It was found that the propagation of the gastric slow wave was detectable from themultichannel EGG signals. The detectability of thepropagation was, however, associated with a number offactors, such as the thickness of the abdominal wall and the propagation velocity of the serosal slowwave. The amplitude of the EGG was found to beassociated with the coupling/uncoupling and propagationvelocity of the gastric slow wave. The amplitude of the EGG increased when the propagation velocity ofthe gastric slow wave increased. The amplitude of theEGG was substantially decreased when the gastric slowwaves were uncoupled. The uncoupling of the gastric slow wave at a frequency of 3 cpm produceddysrhythmias in the EGG, including tachygastria,bradygastria, and arrhythmia. The power spectra ofsimulated different positional EGG signals showedsimilar patterns when the gastric slow wave was coupled anddifferent and unpredictable patterns when the gastricslow wave was uncoupled. In conclusion, multichannel EGGrecordings may be necessary to obtain more information on gastric slow waves from the abdominalelectrodes. The propagation and coupling or uncouplingof the gastric slow wave may be detected frommultichannel EGG recordings.     

Muscular Architecture and Manometric Image of Gastroesophageal Barrier in the Rat

The two components of the gastroesophagealbarrier, the sphincter and the crural sling, closelyoverlap in humans, whereas they are widely separated inthe rat. This investigation correlates the anatomical components of the barrier and their manometriccounterparts in this animal. Sphincteric and cruralsling pressures were measured in four quadrants in 23rats. Muscle thickness was measured at nine levels of the gastroesophageal junction in the samequadrants in 12 rats and the muscular architecture ofthe region was studied in 10 fresh specimens. Themanometric sphincteric component is stronger on theright side where the thickest muscle fibers anchor tothe anterior and posterior borders of a mucosal ridgethat almost surround the cardia. Conversely, the slingpressure is highest towards the left where the muscular bundles straddle the esophagus. Inconclusion, there is a close correspondence between themanometric image and the muscular architecture of thecomponents of the gastroesophageal barrier in the rat. The anatomical arrangement of U-shapedmuscular bundles oriented in opposite directions createsa particularly powerful antireflux mechanism.     

A Meta‐Analysis of the Association of Fracture Risk and Body Mass Index in Women

Several recent studies suggest that obesity may be a risk factor for fracture. The aim of this study was to investigate the association between body mass index (BMI) and future fracture risk at different skeletal sites. In prospective cohorts from more than 25 countries, baseline data on BMI were available in 398,610 women with an average age of 63 (range, 20–105) years and follow up of 2.2 million person‐years during which 30,280 osteoporotic fractures (6457 hip fractures) occurred. Femoral neck BMD was measured in 108,267 of these women. Obesity (BMI ≥ 30 kg/m²) was present in 22%. A majority of osteoporotic fractures (81%) and hip fractures (87%) arose in non‐obese women. Compared to a BMI of 25 kg/m², the hazard ratio (HR) for osteoporotic fracture at a BMI of 35 kg/m² was 0.87 (95% confidence interval [CI], 0.85–0.90). When adjusted for bone mineral density (BMD), however, the same comparison showed that the HR for osteoporotic fracture was increased (HR, 1.16; 95% CI, 1.09–1.23). Low BMI is a risk factor for hip and all osteoporotic fracture, but is a protective factor for lower leg fracture, whereas high BMI is a risk factor for upper arm (humerus and elbow) fracture. When adjusted for BMD, low BMI remained a risk factor for hip fracture but was protective for osteoporotic fracture, tibia and fibula fracture, distal forearm fracture, and upper arm fracture. When adjusted for BMD, high BMI remained a risk factor for upper arm fracture but was also a risk factor for all osteoporotic fractures. The association between BMI and fracture risk is complex, differs across skeletal sites, and is modified by the interaction between BMI and BMD. At a population level, high BMI remains a protective factor for most sites of fragility fracture. The contribution of increasing population rates of obesity to apparent decreases in fracture rates should be explored. © 2014 American Society for Bone and Mineral Research.     

Effects of Neonatal Enzyme Replacement Therapy and Simvastatin Treatment on Cervical Spine Disease in Mucopolysaccharidosis I Dogs

Mucopolysaccharidosis I (MPS I) is a lysosomal storage disease characterized by deficient α‐L‐iduronidase activity, leading to the accumulation of poorly degraded glycosaminoglycans (GAGs). Children with MPS I exhibit high incidence of spine disease, including accelerated disc degeneration and vertebral dysplasia, which in turn lead to spinal cord compression and kyphoscoliosis. In this study we investigated the efficacy of neonatal enzyme replacement therapy (ERT), alone or in combination with oral simvastatin (ERT + SIM) for attenuating cervical spine disease progression in MPS I, using a canine model. Four groups were studied: normal controls; MPS I untreated; MPS I ERT‐treated; and MPS I ERT + SIM–treated. Animals were euthanized at age 1 year. Intervertebral disc condition and spinal cord compression were evaluated from magnetic resonance imaging (MRI) images and plain radiographs, vertebral bone condition and odontoid hypoplasia were evaluated using micro–computed tomography (µCT), and epiphyseal cartilage to bone conversion was evaluated histologically. Untreated MPS I animals exhibited more advanced disc degeneration and more severe spinal cord compression than normal animals. Both treatment groups resulted in partial preservation of disc condition and cord compression, with ERT + SIM not significantly better than ERT alone. Untreated MPS I animals had significantly lower vertebral trabecular bone volume and mineral density, whereas ERT treatment resulted in partial preservation of these properties. ERT + SIM treatment demonstrated similar, but not greater, efficacy. Both treatment groups partially normalized endochondral ossification in the vertebral epiphyses (as indicated by absence of persistent growth plate cartilage), and odontoid process size and morphology. These results indicate that ERT begun from a very early age attenuates the severity of cervical spine disease in MPS I, particularly for the vertebral bone and odontoid process, and that additional treatment with simvastatin does not provide a significant additional benefit over ERT alone. © 2014 American Society for Bone and Mineral Research.