Variation in Water-Holding Capacity in Sphagnum Species Depends on Both Plant and Colony Structure

Peatlands have become a focal point in climate mitigation strategies as these ecosystems have significant carbon sequestration capacities when healthy but release CO2 and other greenhouse gases when damaged. However, as drought episodes become more frequent and prolonged, organisms key to the functioning of some peatlands are increasingly under pressure from desiccation. The Sphagnum mosses, which tend to keep their ecosystem waterlogged and many of whom promote peat formation, are only mildly desiccation-tolerant in comparison to other mosses. The role of Sphagnum anatomy and colony structure is poorly understood in the context of desiccation resilience. Using four different Sphagnum species belonging to four different subgenera and positions along the gradient of the water table, we show that plant morphological traits and colony density are important determinants of water storage capacity. Our results show that, as previously postulated, the majority of the water is stored in an easily exchangeable form, probably extracellularly, and that plant morphological traits, specifically the type and presence of branches, are major contributors to water storage and can explain some of the interspecies variation. We also show that plant density is another important determinant for water storage capacity as higher densities hold larger quantities of water per unit of biomass for all four species, which increases resilience to desiccation. The results presented here suggest that species choice and planting density should receive more attention when considering peatland restoration strategies.

Breaking down barriers: comprehensive functional analysis of the Aspergillus niger chitin synthase repertoire

BACKGROUND

Members of the fungal kingdom are heterotrophic eukaryotes encased in a chitin containing cell wall. This polymer is vital for cell wall stiffness and, ultimately, cell shape. Most fungal genomes contain numerous putative chitin synthase encoding genes. However, systematic functional analysis of the full chitin synthase catalogue in a given species is rare. This greatly limits fundamental understanding and potential applications of manipulating chitin synthesis across the fungal kingdom.

RESULTS

In this study, we conducted in silico profiling and subsequently deleted all predicted chitin synthase encoding genes in the multipurpose cell factory Aspergillus niger. Phylogenetic analysis suggested nine chitin synthases evolved as three distinct groups. Transcript profiling and co-expression network construction revealed remarkably independent expression, strongly supporting specific role(s) for the respective chitin synthases. Deletion mutants confirmed all genes were dispensable for germination, yet impacted colony spore titres, chitin content at hyphal septa, and internal architecture of submerged fungal pellets. We were also able to assign specific roles to individual chitin synthases, including those impacting colony radial growth rates (ChsE, ChsF), lateral cell wall chitin content (CsmA), chemical genetic interactions with a secreted antifungal protein (CsmA, CsmB, ChsE, ChsF), resistance to therapeutics (ChsE), and those that modulated pellet diameter in liquid culture (ChsA, ChsB). From an applied perspective, we show chsF deletion increases total protein in culture supernatant over threefold compared to the control strain, indicating engineering filamentous fungal chitin content is a high priority yet underexplored strategy for strain optimization.

CONCLUSION

This study has conducted extensive analysis for the full chitin synthase encoding gene repertoire of A. niger. For the first time we reveal both redundant and non-redundant functional roles of chitin synthases in this fungus. Our data shed light on the complex, multifaceted, and dynamic role of chitin in fungal growth, morphology, survival, and secretion, thus improving fundamental understanding and opening new avenues for biotechnological applications in fungi.

A novel simplified approach for endodontic retrograde surgery in short single-rooted teeth

BACKGROUND

High technical thresholds, long operative times, and the need for expensive and specialized equipment impede the widespread adoption of endodontic microsurgery in many developing countries. This study aimed to compare the effects of a simplified, cost-effective, and time-efficient surgical approach involving orthograde obturation using biological ceramic material greater than 6 mm combined with apicoectomy for single-rooted teeth with short lengths with those of the conventional and current standard methods.

MATERIALS AND METHODS

Forty-five premolars equally categorized into three groups: conventional surgery group, standard surgery group, and modified surgery group. A µCT scan was used to calculate the volume of voids. A micro-leakage test and scanning electron microscope (SEM) were performed to assess the sealing effect. Additionally, four cases of chronic periapical periodontitis in the anterior region were selected, and the patients received either the modified approach or the standard surgery for endodontic microsurgery.

RESULTS

The volumes of voids in the apical 0-3 mm of the modified group and the standard group were comparable. The micro-leakage test and SEM examination demonstrated closely bonded fillings in the dentinal walls in both the modified surgery group and standard surgery group. The outcomes of the preliminary application of this modified procedure on patients were successful at the time of the follow-up cutoff.

CONCLUSIONS

The modified surgery group exhibited similar root canal filling and apical sealing abilities with the standard procedure for single-rooted teeth with short lengths (< 20 mm). The preliminary application of this modified surgical procedure achieved favorable results.

A fossil "Social Stomach": Micro-CT imaging unearths first fossil record of ant proventriculi and comparative analysis with recent species

Eusociality is an extreme form of social behavior found in some invertebrates, especially in ants, which allows them to thrive and dominate the environment through their cooperative and organized behavior. Their complex colony structure and social behavior is provided, among other things, by morphological adaptations, such as the unique structure and a huge variety of proventriculi relative to other insect groups. Here, we report the first discovery of proventriculus by X-ray microcomputed tomography (µCT) in the fossil ants †Oecophylla brischkei Mayr, 1868 and †Oecophylla crassinoda Wheeler, 1922. This is a remarkable fossil find, as it opens up new perspectives for research on phylogeny, the evolution of ant sociality and feeding behavior. We present a 3D model of the proventriculus in Oecophylla smaragdina (Fabricius, 1775) and a 3D model of the proventriculus in †Oe. brischkei and compare them. Fossil proventriculi are not fundamentally different in structure from the recent. Apparently, already in the late Eocene, the lifestyle and sociality of ants of the genus Oecophylla were similar to the one we are currently observing.

Can Different Parameter Sets Lead to Equivalent Optima between Geometric Accuracy and Mechanical Properties in Arburg Plastic Freeforming?

Technological advances have led to the increased use of plastic-based additive manufacturing processes for the production of consumer goods and spare parts. For this reason, the need for the best possible mechanical properties while maintaining geometric accuracy is becoming increasingly important. One of these additive manufacturing processes is the Arburg Plastic Freeforming process, which differs from the widely used Fused Filament Fabrication process in the way that droplets are discharged along a track instead of continuous extruded tracks. As with all other plastic-based additive manufacturing processes, due to the round shape of the tracks, voids occur between the individual tracks during manufacturing, which effects mechanical properties. In contrast to previous work, which mainly focused on how the mechanical properties change with a change in a single printing parameter, this work focused more closely on the interaction of three relevant printing parameters considered as a parameter set. Their influence on the mechanical properties was investigated by tensile tests, the influence on the residual porosity by density measurements and the influence on the geometric accuracy by surface roughness measurements. It was shown that by considering the parameters as a parameter set, states of high density and therefore high mechanical properties while reaching minimal surface roughness can be achieved for significantly more combinations than previously assumed. However, for these states the residual porosity was slightly different. This difference was explained by a parameter-dependent deformation factor of the droplets, which influences the maximal possible degree of filling during manufacturing. For the optimization of arbitrary parameter sets, an analytical model was derived.

Intestinal Vitamin D Receptor Is Dispensable for Maintaining Adult Bone Mass in Mice With Adequate Calcium Intake

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3)-mediated intestinal calcium (Ca) absorption supplies Ca for proper bone mineralization during growth. We tested whether vitamin D receptor (VDR)-mediated 1,25(OH)2D3 signaling is critical for adult Ca absorption and bone by using mice with inducible Vdr gene knockout in the whole intestine (villin-CreERT2+/- × Vdrf/f, WIK) or in the large intestine (Cdx2-CreERT2+/- ×Vdrf/f, LIK). At 4-month-old, Vdr alleles were recombined (0.05 mg tamoxifen/g BW, intraperitoneally [i.p.], 5 days) and mice were fed diets with either 0.5% (adequate) or 0.2% (low) Ca. Ca absorption was examined after 2 weeks while serum 1,25(OH)2D3, bone mass, and bone microarchitecture were examined after 16 weeks. Intestinal and renal gene expression was measured at both time points (n = 12/genotype/diet/time point). On the 0.5% Ca diet, all phenotypes in WIK and LIK mice were similar to the controls. Control mice adapted to the 0.2% low-Ca diet by increasing renal Cyp27b1 mRNA (3-fold), serum 1,25(OH)2D3 level (1.9-fold), and Ca absorption in the duodenum (Dd, + 131%) and proximal colon (PCo, + 28.9%), which prevented bone loss. In WIK mice, low-Ca diet increased serum 1,25(OH)2D3 (4.4-fold) but Ca absorption remained unaltered in the Dd and PCo. Consequently, significant bone loss occurred in WIK mice (e.g., cortical thickness, Ct.Th, -33.7%). LIK mice adapted to the low-Ca diet in the Dd but not the PCo, and the effect on bone phenotypes was milder (e.g., Ct.Th, -13.1%). Our data suggest intestinal VDR in adult mice prevents bone loss under low Ca intake but is dispensable under adequate calcium intake.

Early incisor lesions and Equine Odontoclastic Tooth Resorption and Hypercementosis: Reliability of radiographic findings

BACKGROUND

In clinical practice, early diagnosis of Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) and other resorptive incisor diseases is difficult to achieve. The radiographic appearance of subtle pathological changes has not been described in detail and might be confused with age-related changes.

OBJECTIVES

The study was performed to define typical radiographic signs of early incisor lesions and to evaluate the reliability of the radiographic findings.

STUDY DESIGN

Descriptive and comparative study using post mortem clinical, radiographic, macroscopic and µCT examination.

METHODS

The incisor region of 20 cadaveric horse heads, divided into three different age groups, was examined visually and by palpation. Intraoral radiographs were taken. After extraction, each incisor was macroscopically evaluated. Micro-computed tomography (µCT) scans were obtained. These scans were processed with Scry (v6.0, Kuchel & Sautter GbR) to obtain surface meshes which then were transferred to Meshlab (ISTI-CNR, version 2016.12). Attached tissues were virtually removed and surface curvature was computed to visualise and evaluate the quantity of unevenness (roughness) of the teeth's surface. Scoring systems for each diagnostic modality were developed. Scores were compared to describe and evaluate the radiographic appearance of early incisor lesions.

RESULTS

The prevalence and severity of incisor lesions increased with age. Early, subtle lesions develop on the palatal/lingual side of incisors. While radiographically detected lesions were confirmed macroscopically and on the µCT scans, numerous teeth which were radiographically classified as healthy displayed lesions by macroscopic inspection (13.7%) and µCT analysis (58.1%).

MAIN LIMITATIONS

Cadavers were studied and dental history was unknown.

CONCLUSIONS

The detection of early and subtle incisor lesions indicating first signs of EOTRH on dorsoventral intraoral radiographs is limited due to the typical localisation of the lesions on the palatal/lingual side of the incisors.

Morphological and Chemical Investigation of Ovarian Structures in a Bovine Model by Contrast-Enhanced X-ray Imaging and Microscopy

An improved understanding of an ovary's structures is highly desirable to support advances in folliculogenesis knowledge and reproductive medicine, with particular attention to fertility preservation options for prepubertal girls with malignant tumors. Although currently the golden standard for structural analysis is provided by combining histological sections, staining, and visible 2D microscopic inspection, synchrotron radiation phase-contrast microtomography is becoming a new challenge for three-dimensional studies at micrometric resolution. To this aim, the proper use of contrast agents can improve the visualization of internal structures in ovary tissues, which normally present a low radiopacity. In this study, we report a comparison of four staining protocols, based on iodine or tungsten containing agents, applied to bovine ovarian tissues fixed in Bouin's solution. The microtomography (microCT) analyses at two synchrotron facilities under different set-ups were performed at different energies in order to maximize the image contrast. While tungsten-based agents allow large structures to be well identified, Iodine ones better highlight smaller features, especially when acquired above the K-edge energy of the specific metal. Further scans performed at lower energy where the setup was optimized for overall quality and sensitivity from phase-contrast still provided highly resolved visualization of follicular and intrafollicular structures at different maturation stages, independent of the staining protocol. The analyses were complemented by X-ray Fluorescence mapping on 2D sections, showing that the tungsten-based agent has a higher penetration in this type of tissues.

A Feasibility Study of In-Situ Damage Visualization in Basalt-Fiber Reinforced Polymers with Open-Source Digital Volume Correlation

This work analyses damage formation within the bulk of basalt fiber-reinforced polymers (BFRP) by means of open-source Digital Volume Correlation (DVC). Volumetric image data were obtained from conventional in-situ X-Ray computed micro-tomography (µCT) of samples loaded in tension. The open-source image registration toolkit Elastix was employed to obtain full 3D displacement fields from the image data. We assessed the accuracy of the DVC results using the method of manufactured solution and showed that the approach followed here can detect deformation with a magnitude in the order of a fiber diameter which in the present case is 17 µm. The beneficial influence of regularization on DVC results is presented on the manufactured solution as well as on real in-situ tensile testing CT data of a BFRP sample. Results of the correlation showed that conventional µCT equipment in combination with DVC can be used to detect defects which could previously only be visualized using synchrotron facilities or destructive methods.

Microstructural and Mechanical Characterization of Newly Developed Zn-Mg-CaO Composite

In this study, the Zn-0.8Mg-0.28CaO wt.% composite was successfully prepared using different conditions of ball milling (rotations and time) followed by a direct extrusion process. These materials were characterized from the point of view of microstructure and compressive properties, and the correlation between those characteristics was found. Microstructures of individual materials possessed differences in grain size, where the grain size decreased with the intensified conditions (milling speed and time). However, the mutual relation between grain size and compressive strength was not linear. This was caused by the effect of other factors, such as texture, intermetallic phases, and pores. Material texture affects the mechanical properties by a different activity ratio between basal and pyramidal <c + a> slips. The properties of intermetallic particles and pores were determined in material volume using micro-computed tomography (µCT), enhancing the precision of our assumptions compared with commonly applied methods. Based on that, and the analysis after the compressive tests, we were able to determine the influence of aspect ratio, feret diameters, and volume content of intermetallic phases and pores on mechanical behavior. The influence of the aspects on mechanical behavior is described and discussed.

Green Tea Catechins Modulate Skeletal Development with Effects Dependent on Dose, Time, and Structure in a down Syndrome Mouse Model

Altered skeletal development in Down syndrome (DS) results in a brachycephalic skull, flattened face, shorter mandibular ramus, shorter limbs, and reduced bone mineral density (BMD). Our previous study showed that low doses of green tea extract enriched in epigallocatechin-3-gallate (GTE-EGCG), administered continuously from embryonic day 9 to postnatal day 29, reduced facial dysmorphologies in the Ts65Dn (TS) mouse model of DS, but high doses could exacerbate them. Here, we extended the analyses to other skeletal structures and systematically evaluated the effects of high and low doses of GTE-EGCG treatment over postnatal development in wild-type (WT) and TS mice using in vivo µCT and geometric morphometrics. TS mice developed shorter and wider faces, skulls, and mandibles, together with shorter and narrower humerus and scapula, and reduced BMD dynamically over time. Besides facial morphology, GTE-EGCG did not rescue any other skeletal phenotype in TS treated mice. In WT mice, GTE-EGCG significantly altered the shape of the skull and mandible, reduced the length and width of the long bones, and lowered the BMD. The disparate effects of GTE-EGCG depended on the dose, developmental timepoint, and anatomical structure analyzed, emphasizing the complex nature of DS and the need to further investigate the simultaneous effects of GTE-EGCG supplementation.

Spin Freezing and Its Impact on Pore Size, Tortuosity and Solid State

Spin freeze-drying, as a part of a continuous freeze-drying technology, is associated with a much higher drying rate and a higher level of process control in comparison with batch freeze-drying. However, the impact of the spin freezing rate on the dried product layer characteristics is not well understood at present. This research focuses on the relation between spin-freezing and pore size, pore shape, dried product mass transfer resistance and solid state of the dried product layer. This was thoroughly investigated via high-resolution X-ray micro-computed tomography (µCT), scanning electron microscopy (SEM), thermal imaging and solid state X-ray diffraction (XRD). It was concluded that slow spin-freezing rates resulted in the formation of highly tortuous structures with a high dried-product mass-transfer resistance, while fast spin-freezing rates resulted in lamellar structures with a low tortuosity and low dried-product mass-transfer resistance.

Understanding the Microstructure of Mortars for Cultural Heritage Using X-ray CT and MIP

In this study, the microstructure of mock-up mortar specimens for a historic environment, composed of different mixtures, was studied using mercury intrusion porosity (MIP) and microcomputed tomography (µCT), highlighting the advantages and drawbacks of both techniques. Porosity, sphericity, and pores size distribution were studied, evaluating changes according to mortar composition (aerial and hydraulic binders, quartz sand, and crushed limestone aggregate). The µCT results were rendered using 3D visualization software, which provides complementary information for the interpretation of the data obtained using 3D data-analysis software. Moreover, µCT contributes to the interpretation of MIP results of mortars. On the other hand, MIP showed significant ink-bottle effects in lime and cement mortars samples that should be taken into account when interpreting the results. Moreover, the MIP results highlighted how gypsum mortar samples display a porosity distribution that is best studied using this technique. This multi-analytical approach provides important insights into the interpretation of the porosimetric data obtained. This is crucial in the characterization of mortars and provides key information for the study of building materials and cultural heritage conservation.

Insights into the Development of Phototrophic Biofilms in a Bioreactor by a Combination of X-ray Microtomography and Optical Coherence Tomography

As productive biofilms are increasingly gaining interest in research, the quantitative monitoring of biofilm formation on- or offline for the process remains a challenge. Optical coherence tomography (OCT) is a fast and often used method for scanning biofilms, but it has difficulty scanning through more dense optical materials. X-ray microtomography (μCT) can measure biofilms in most geometries but is very time-consuming. By combining both methods for the first time, the weaknesses of both methods could be compensated. The phototrophic cyanobacterium Tolypothrix distorta was cultured in a moving bed photobioreactor inside a biocarrier with a semi-enclosed geometry. An automated workflow was developed to process µCT scans of the biocarriers. This allowed quantification of biomass volume and biofilm-coverage on the biocarrier, both globally and spatially resolved. At the beginning of the cultivation, a growth limitation was detected in the outer region of the carrier, presumably due to shear stress. In the later phase, light limitations could be found inside the biocarrier. µCT data and biofilm thicknesses measured by OCT displayed good correlation. The latter could therefore be used to rapidly measure the biofilm formation in a process. The methods presented here can help gain a deeper understanding of biofilms inside a process and detect any limitations.

Management of oral biofilms by nisin delivery in adhesive microdevices

Numerous beneficial microbes thrive in the oral cavity where they form biofilms on dental and mucosal surfaces to get access to nutrients, and to avoid being carried away with the saliva. However, biofilm formation is also a virulence factor as it also protects pathogenic bacteria, providing them with an environment for proliferation causing oral infections. Oral hygiene relies on mechanical removal of biofilms. Some oral care products also contain antimicrobials, but effective eradication of biofilms with antimicrobials requires both a high concentration and long exposure time. In the present communication, we investigate the potential of using miniaturized drug delivery devices, known as microcontainers (MCs), to deliver the antimicrobial peptide, nisin to an oral multi-species biofilm. MCs are loaded with nisin and X-ray micro-computed tomography reveals a full release of nisin through a chitosan lid within 15 min. Chitosan-coated MCs display substantial bioadhesion to the buccal mucosa compared to non-coated MCs (68.6 ± 14.3% vs 33.8 ± 5.2%). Confocal monitoring of multi-species biofilms reveals antibacterial effects of nisin-loaded chitosan-coated MCs with a faster onset (after 3 h) compared to solution-based delivery (after 9 h). Our study shows the potential of using MCs for treatment of multi-species oral biofilms and is encouraging for further design of drug delivery devices to treat oral diseases.

Myeloid HIF1α Is Involved in the Extent of Orthodontically Induced Tooth Movement

During orthodontic tooth movement, transcription factor hypoxia-inducible factor 1α (HIF1α) is stabilised in the periodontal ligament. While HIF1α in periodontal ligament fibroblasts can be stabilised by mechanical compression, in macrophages pressure application alone is not sufficient to stabilise HIF1α. The present study was conducted to investigate the role of myeloid HIF1α during orthodontic tooth movement. Orthodontic tooth movement was performed in wildtype and Hif1α^Δmyel mice lacking HIF1α expression in myeloid cells. Subsequently, µCT images were obtained to determine periodontal bone loss, extent of orthodontic tooth movement and bone density. RNA was isolated from the periodontal ligament of the control side and the orthodontically treated side, and the expression of genes involved in bone remodelling was investigated. The extent of tooth movement was increased in Hif1α^Δmyel mice. This may be due to the lower bone density of the Hif1α^Δmyel mice. Deletion of myeloid Hif1α was associated with increased expression of Ctsk and Acp5, while both Rankl and its decoy receptor Opg were increased. HIF1α from myeloid cells thus appears to play a regulatory role in orthodontic tooth movement.

FasL Is Required for Osseous Healing in Extraction Sockets in Mice

Fas ligand (FasL) is a member of the tumor necrosis factor (TNF) superfamily involved in the activation of apoptosis. Assuming that apoptosis is initiated after tooth extraction it is reasonable to suggest that FasL may play a pivotal role in the healing of extraction sockets. Herein, we tested the hypothesis of whether the lack of FasL impairs the healing of extraction sockets. To this end, we extracted upper right incisors of FasL knockout (KO) mice and their wildtype (WT) littermates. After a healing period of two weeks, bone volume over total volume (BV/TV) via µCT and descriptive histological analyses were performed. µCT revealed that BV/TV in the coronal region of the socket amounted to 39.4% in WT and 21.8% in KO, with a significant difference between the groups (p=0.002). Likewise, in the middle region of the socket, BV/TV amounted to 50.3% in WT and 40.8% in KO (p<0.001). In the apical part, however, no difference was noticed. Consistently, WT mice displayed a significantly higher median trabecular thickness and a lower trabecular separation when compared to the KO group at the coronal and central region of the socket. There was the overall tendency that in both, female and male mice, FasL affects bone regeneration. Taken together, these findings suggest that FasL deficiency may reduce bone regeneration during the healing process of extraction sockets.

A new species group of Strumigenys (Hymenoptera, Formicidae) from Ecuador, with a description of its mandible morphology

Strumigenys is one of the most diverse ant genera in the world and arguably the most morphologically diverse, exhibiting an exceptional range of mandible shape and function. A new species, Strumigenysayerstheysp. nov., discovered in the Chocó region of Ecuador is described. With two morphological characters, this species is shown to be a morphologically unique outlier among Strumigenys globally, having predominately smooth and shining cuticle surface sculpturing and long trap-jaw mandibles. Using µCT scans, we produced 3D images of the worker ant and static images to examine and compare mandible articular morphologies with most morphologically similar members of the mandibularis species group. Cuticular, pilosity, and articular mandible morphological differences supports placing the new species in its own new species group.

Characterization of Open-Cell Sponges via Magnetic Resonance and X-ray Tomography

The applications of polymeric sponges are varied, ranging from cleaning and filtration to medical applications. The specific properties of polymeric foams, such as pore size and connectivity, are dependent on their constituent materials and production methods. Nuclear magnetic resonance imaging (MRI) and X-ray micro-computed tomography (µCT) offer complementary information about the structure and properties of porous media. In this study, we employed MRI, in combination with µCT, to characterize the structure of polymeric open-cell foam, and to determine how it changes upon compression, µCT was used to identify the morphology of the pores within sponge plugs, extracted from polyurethane open-cell sponges. MRI T2 relaxation maps and bulk T2 relaxation times measurements were performed for 7° dH water contained within the same polyurethane foams used for µCT. Magnetic resonance and µCT measurements were conducted on both uncompressed and 60% compressed sponge plugs. Compression was achieved using a graduated sample holder with plunger. A relationship between the average T2 relaxation time and maximum opening was observed, where smaller maximum openings were found to have a shorter T2 relaxation times. It was also found that upon compression, the average maximum opening of pores decreased. Average pore size ranges of 375-632 ± 1 µm, for uncompressed plugs, and 301-473 ± 1 µm, for compressed plugs, were observed. By determining maximum opening values and T2 relaxation times, it was observed that the pore structure varies between sponges within the same production batch, as well as even with a single sponge.

Biocompatibility and degradation of the open-pored magnesium scaffolds LAE442 and La2

Porous magnesium implants are of particular interest for application as resorbable bone substitutes, due to their mechanical strength and a Young's modulus similar to bone. The objective of the present study was to compare the biocompatibility, bone and tissue ingrowth, and the degradation behaviour of scaffolds made from the magnesium alloys LAE442 (n= 40) and Mg-La2 (n= 40)in vivo. For this purpose, cylindrical magnesium scaffolds (diameter 4 mm, length 5 mm) with defined, interconnecting pores were produced by investment casting and coated with MgF₂. The scaffolds were inserted into the cancellous part of the greater trochanter ossis femoris of rabbits. After implantation periods of 6, 12, 24 and 36 weeks, the bone-scaffold compounds were evaluated usingex vivo µCT80 images, histological examinations and energy dispersive x-ray spectroscopy analysis. The La2 scaffolds showed inhomogeneous and rapid degradation, with inferior osseointegration as compared to LAE442. For the early observation times, no bone and tissue could be observed in the pores of La2. Furthermore, the excessive amount of foreign body cells and fibrous capsule formation indicates insufficient biocompatibility of the La2 scaffolds. In contrast, the LAE442 scaffolds showed slow degradation and better osseointegration. Good vascularization, a moderate cellular response, bone and osteoid-like bone matrix at all implantation periods were observed in the pores of LAE442. In summary, porous LAE442 showed promise as a degradable scaffold for bone defect repair, based on its degradation behaviour and biocompatibility. However, further studies are needed to show it would have the necessary mechanical properties required over time for weight-bearing bone defects.

Using µCT in live larvae of a large wood-boring beetle to study tracheal oxygen supply during development

How respiratory structures vary with, or are constrained by, an animal's environment is of central importance to diverse evolutionary and comparative physiology hypotheses. To date, quantifying insect respiratory structures and their variation has remained challenging due to their microscopic size, hence only a handful of species have been examined. Several methods for imaging insect respiratory systems are available, in many cases however, the analytical process is lethal, destructive, time consuming and labour intensive. Here, we explore and test a different approach to measuring tracheal volume using X-ray micro-tomography (µCT) scanning (at 15 µm resolution) on living, sedated larvae of the cerambycid beetle Cacosceles newmannii across a range of body sizes at two points in development. We provide novel data on resistance of the larvae to the radiation dose absorbed during µCT scanning, repeatability of imaging analyses both within and between time-points and, structural tracheal trait differences provided by different image segmentation methods. By comparing how tracheal dimension (reflecting metabolic supply) and basal metabolic rate (reflecting metabolic demand) increase with mass, we show that tracheal oxygen supply capacity increases during development at a comparable, or even higher rate than metabolic demand. Given that abundant gas delivery capacity in the insect respiratory system may be costly (due to e.g. oxygen toxicity or space restrictions), there are probably balancing factors requiring such a capacity that are not linked to direct tissue oxygen demand and that have not been thoroughly elucidated to date, including CO₂ efflux. Our study provides methodological insights and novel biological data on key issues in rapidly quantifying insect respiratory anatomy on live insects.

Programming Effect of the Parental Obesity on the Skeletal System of Offspring at Weaning Day

Simple Summary

Overweight and obesity can cause many diseases, and several studies indicate a close relationship between the obesity of parents and the health of their offspring. Our aim was to investigate whether there is a programming influence of parental obesity on the skeletal system in weaned female and male offspring rats. In undertaking this, analysis of bone material was carried out using isolated tibia, and densitometry (DXA), peripheral (pQCT) and micro (µCT) computed tomography were performed. Mechanical tests and blood serum biochemistry were also carried out. Our work showed a significant programming influence of parental obesity on neonatal skeletal development. The tibiae isolated from offspring originating from obese parents were characterized by more intense mineralization and higher fracture resistance. However, numerous studies demonstrate the destructive effect of obesity on the skeletal system. Our research and the available literature suggest the existence of a “fat threshold”, the exceeding of which changes of the osteotropic effect of adipose tissue to become unfavorable. Therefore, there is a need for further research to determine the time-dependent metabolic relationship between adipose tissue and bone in both animals and humans.

Abstract

Our study aimed to verify the hypothesis of the existence of a programming effect of parental obesity on the growth, development and mineralization of the skeletal system in female and male rat offspring on the day of weaning. The study began with the induction of obesity in female and male rats of the parental generation, using a high-energy diet (group F). Females and males of the control group received the standard diet (group S). After 90 days of dietary-induced obesity, the diet in group F was changed into the standard. Rats from groups F and S were mated to obtain offspring which stayed with their mothers until 21 days of age. Tibia was tested using dual-energy X-ray absorptiometry (DXA), peripheral quantitative computed tomography (pQCT), micro-computed tomography (µCT) and mechanical strength using the three-point bending test. Biochemical analysis of blood serum bone metabolism markers was performed. DXA analysis showed higher tibia bone mineral content (BMC) and area. pQCT measurements of cortical and trabecular tissue documented the increase of the volumetric bone mineral density and BMC of both bone compartments in offspring from the F group, while µCT of the trabecular tissue showed an increase in trabecular thickness and a decrease of its separation. Parental obesity, hence, exerts a programming influence on the development of the skeletal system of the offspring on the day of the weaning, which was reflected in the intensification of mineralization and increased bone strength.

Effects of Histamine Receptor Antagonist Cetirizine on Orthodontic Tooth Movement

Many patients regularly take histamine receptor antagonists, such as cetirizine, to prevent allergic reactions, but these antiallergic drugs may have inadvertent effects on orthodontic treatment. In previous studies, histamine has been shown to modulate the sterile inflammatory reaction underlying orthodontic tooth movement. Pertinent effects of histamine antagonization via cetirizine during orthodontic treatment, however, have not been adequately investigated. We thus treated male Fischer344 rats either with tap water (control group) or cetirizine by daily oral gavage corresponding to the clinically used human dosage adjusted to the rat metabolism (0.87 mg/kg) or to a previously published high dosage of cetirizine (3 mg/kg). Experimental anterior movement of the first upper left molar was induced by insertion of a nickel-titanium (NiTi) coil spring (0.25 N) between the molar and the upper incisors. Cone-beam computed tomography (CBCT), micro-computed tomography (µCT) images, as well as histological hematoxylin-eosin (HE), and tartrate-resistant acid phosphatase (TRAP) stainings were used to assess the extent of tooth movement, cranial growth, periodontal bone loss, root resorptions, and osteoclast activity in the periodontal ligament. Both investigated cetirizine dosages had no impact on the weight gain of the animals and, thus, animal welfare. Neither the extent of tooth movement, nor cranial growth, nor root resorption, nor periodontal bone loss were significantly influenced by the cetirizine dosages investigated. We, thus, conclude that histamine receptor antagonist cetirizine can be used during orthodontic treatment to prevent allergic reactions without clinically relevant side effects on orthodontic tooth movement.

Heterogeneity of the osteocyte lacuno-canalicular network architecture and material characteristics across different tissue types in healing bone

Various tissue types, including fibrous connective tissue, bone marrow, cartilage, woven and lamellar bone, coexist in healing bone. Similar to most bone tissue type, healing bone contains a lacuno-canalicular network (LCN) housing osteocytes. These cells are known to orchestrate bone remodeling in healthy bone by sensing mechanical strains and translating them into biochemical signals. The structure of the LCN is hypothesized to influence mineralization processes. Hence, the aim of the present study was to visualize and match spatial variations in the LCN topology with mineral characteristics, within and at the interfaces of the different tissue types that comprise healing bone. We applied a correlative multi-method approach to visualize the LCN architecture and quantify mineral particle size and orientation within healing femoral bone in a mouse osteotomy model (26 weeks old C57BL/6 mice). This approach revealed structural differences across several length scales during endochondral ossification within the following regions: calcified cartilage, bony callus, cortical bone and a transition zone between the cortical and callus region analyzed 21 days after the osteotomy. In this transition zone, we observed a continuous convergence of mineral characteristics and osteocyte lacunae shape as well as discontinuities in the lacunae volume and LCN connectivity. The bony callus exhibits a 34% higher lacunae number density and 40% larger lacunar volume compared to cortical bone. The presented correlations between LCN architecture and mineral characteristics improves our understanding of how bone develops during healing and may indicate a contribution of osteocytes to bone (re)modeling.

Molding Binder Influence on the Porosity and Gas Permeability of Ceramic Casting Molds

The investment casting process is widely used in the aerospace industry to produce complex engine parts. The article determines the properties of quartz powders, nanosilica dioxide binders, and multilayer samples of ceramic casting molds. The properties of spherical molds obtained using an alcohol-water system derived from hydrolyzed ethyl silicate (ZKE) and LUDOX PX-30 (type Q1) were compared with those obtained in water systems derived from Remasol Plus and Remasol Premium binders (type Q2). The spherical samples are composed of seven layers made with the use of an immersion-sprinkling method. To assess the properties of the molds, X-ray microscopy (µCT), scanning electron microscopy (SEM), and gas permeability analysis over a temperature range of 20–950 °C were utilized. The binder type is proven to affect the properties of the casting mold samples. The material obtained in the water system, Q2, has advantageous properties such as a high porosity and gas permeability.

The visible skeleton 2.0: phenotyping of cartilage and bone in fixed vertebrate embryos and foetuses based on X-ray microCT

For decades, clearing and staining with Alcian Blue and Alizarin Red has been the gold standard to image vertebrate skeletal development. Here, we present an alternate approach to visualise bone and cartilage based on X-ray microCT imaging, which allows the collection of genuine 3D data of the entire developing skeleton at micron resolution. Our novel protocol is based on ethanol fixation and staining with Ruthenium Red, and efficiently contrasts cartilage matrix, as demonstrated in whole E16.5 mouse foetuses and limbs of E14 chicken embryos. Bone mineral is well preserved during staining, thus the entire embryonic skeleton can be imaged at high contrast. Differences in X-ray attenuation of ruthenium and calcium enable the spectral separation of cartilage matrix and bone by dual energy microCT (microDECT). Clearing of specimens is not required. The protocol is simple and reproducible. We demonstrate that cartilage contrast in E16.5 mouse foetuses is adequate for fast visual phenotyping. Morphometric skeletal parameters are easily extracted. We consider the presented workflow to be a powerful and versatile extension to the toolkit currently available for qualitative and quantitative phenotyping of vertebrate skeletal development.

PAK1 inhibitor IPA-3 mitigates metastatic prostate cancer-induced bone remodeling

Metastatic prostate cancer (PCa) has high mortality and a poor 5-year survival rate primarily due to the lack of effective treatments. Bone is the primary site of PCa metastasis in humans and the development of reliable therapeutic options for bone metastatic PCa will make a huge impact in reducing the mortality among these patients. Although P21 activated kinases (PAKs) have been studied in the past for their role in cancer, the efficacy of targeting PAKs to treat lung and bone metastatic PCa has not been tested yet. In the current study, we report that targeting PAK1 using IPA-3, an allosteric inhibitor of PAK1 kinase activity, significantly inhibits the murine metastatic PCa (RM1) cell proliferation and motility in vitro, and metastasis to the lungs in vivo. More importantly, we demonstrate for the first time that treatment with IPA-3 can blunt metastatic PCa-induced bone remodeling in vivo as analyzed by the 3-dimensional microcomputer tomography analysis. Our study has identified IPA-3 as a potential drug to treat bone metastatic PCa.

Evidence for convergent evolution of ultrasonic hearing in toothed whales (Cetacea: Odontoceti)

Toothed whales (Cetacea: Odontoceti) are the most diverse group of modern cetaceans, originating during the Eocene/Oligocene transition approximately 38 Ma. All extant odontocetes echolocate; a single origin for this behaviour is supported by a unique facial source for ultrasonic vocalizations and a cochlea adapted for hearing the corresponding echoes. The craniofacial and inner ear morphology of Oligocene odontocetes support a rapid (less than 5 Myr) early evolution of echolocation. Although some cranial features in the stem odontocetes Simocetus and Olympicetus suggest an ability to generate ultrasonic sound, until now, the bony labyrinths of taxa of this grade have not been investigated. Here, we use µCT to examine a petrosal of a taxon with clear similarities to Olympicetus avitus. Measurements of the bony labyrinth, when added to an extensive dataset of cetartiodactyls, resulted in this specimen sharing a morphospace with stem whales, suggesting a transitional inner ear. This discovery implies that either the lineage leading to this Olympicetus--like taxon lost the ability to hear ultrasonic sound, or adaptations for ultrasonic hearing evolved twice, once in xenorophids and again on the stem of the odontocete crown group. We favour the latter interpretation as it matches a well-documented convergence of craniofacial morphology between xenorophids and extant odontocetes.

Surface Pre-Reacted Glass Filler Contributes to Tertiary Dentin Formation through a Mechanism Different Than That of Hydraulic Calcium-Silicate Cement

The induction of tissue mineralization and the mechanism by which surface pre-reacted glass-ionomer (S-PRG) cement influences pulpal healing remain unclear. We evaluated S-PRG cement-induced tertiary dentin formation in vivo, and its effect on the pulp cell healing process in vitro. Induced tertiary dentin formation was evaluated with micro-computed tomography (μCT) and scanning electron microscopy (SEM). The distribution of elements from the S-PRG cement in pulpal tissue was confirmed by micro-X-ray fluorescence (μXRF). The effects of S-PRG cement on cytotoxicity, proliferation, formation of mineralized nodules, and gene expression in human dental pulp stem cells (hDPSCs) were assessed in vitro. μCT and SEM revealed that S-PRG induced tertiary dentin formation with similar characteristics to that induced by hydraulic calcium-silicate cement (ProRoot mineral trioxide aggregate (MTA)). μXRF showed Sr and Si ion transfer into pulpal tissue from S-PRG cement. Notably, S-PRG cement and MTA showed similar biocompatibility. A co-culture of hDPSCs and S-PRG discs promoted mineralized nodule formation on surrounding cells. Additionally, S-PRG cement regulated the expression of genes related to osteo/dentinogenic differentiation. MTA and S-PRG regulated gene expression in hDPSCs, but the patterns of regulation differed. S-PRG cement upregulated CXCL-12 and TGF-β1 gene expression. These findings showed that S-PRG and MTA exhibit similar effects on dental pulp through different mechanisms.

A micro X-ray computed tomography dataset of fossil echinoderms in an ancient obrution bed: a robust method for taphonomic and palaeoecologic analyses

BACKGROUND

Taphonomic and palaeoecologic studies of obrution beds often employ conventional methods of investigation such as physical removal and extraction of fossils from their host rock (matrix) by mechanical preparation. This often-destructive method is not suitable for studying mold fossils, which are voids left in host rocks due to dissolution of the original organism in post-depositional processes.

FINDINGS

Microcomputed tomography (µCT) scan data of 24 fossiliferous rock samples revealed thousands of Paleozoic echinoderms. Digitally "stitching" together individually µCT scanned rock samples within three-dimensional (3D) space allows for quantifiable taphonomic data on a fossil echinoderm-rich obrution deposit from the Devonian (Emsian) of South Africa. Here, we provide a brief step-by-step guide on creating, segmenting, and ultimately combining sections of richly fossiliferous beds to create virtual models suited for the quantitative and qualitative taphonomic analyses of fossil invertebrate assemblages.

CONCLUSIONS

Visualizing the internal features of fossiliferous beds in 3D is an invaluable taphonomic tool for analyzing delicate fossils, accounting for all specimens irrespective of their preservation stages and with minimal damage. This technique is particularly useful for analyzing fossiliferous deposits with mold fossils that prove to be difficult to study with traditional methods, because the method relies on the large density contrast between the mold and host rock.

Effect of total occlusal convergence on fit and fracture resistance of zirconia-reinforced lithium silicate crowns

Introduction

Computer-aided design (CAD) and computer-aided manufacturing (CAM) monolithic crowns are gaining momentum. Limited evidence exists about the effect of tooth preparation total occlusal convergence (TOC) on marginal and internal gap distances in addition to load to fracture values.

Aim

The aim of this study was to evaluate, by microcomputed tomography (µCT), the influence of 12° and 20° TOC on marginal and internal adaptation of zirconia-reinforced lithium silicate (ZLS) crowns. Moreover, values of load to fracture with and without initial cyclic loading (CL) were compared.

Material and methods

Forty ZLS crowns were fabricated on dies with TOC of 12° and 20°, 20 crowns for each group. µCT was used to compare marginal and internal adaptation. Each specimen was measured at 140 points distributed on all tooth preparation surfaces for 2D gap distance assessment. 3D gap volume was also evaluated. Crowns were then cemented and divided into two subgroups; the first was stored in distilled water (no cyclic loading [NCL] subgroup), the second was subjected to CL (CL subgroup).

Results

Factorial repeated measures ANOVA followed by Bonferroni post hoc in addition to independent and dependent t-tests were used for statistical analysis. Marginal gap, absolute marginal discrepancy, and occlusal gap measurements showed significant differences between the measurement sites. Static load to fracture values showed significant differences between TOC groups for both NCL (P=0.011) and CL (P=0.025) subgroups.

Conclusion

An increase of TOC from 12° to 20° did not affect marginal and internal adaptation but resulted in higher values of load to fracture of ZLS crowns. CL simulating 1 year of service did not result in fatigue failure.

Early Fracture Healing is Delayed in the Col1a2+/G610C Osteogenesis Imperfecta Murine Model

Osteogenesis imperfecta (OI) is a rare heritable skeletal dysplasia mainly caused by type I collagen abnormalities and characterized by bone fragility and susceptibility to fracture. Over 85% of the patients carry dominant mutations in the genes encoding for the collagen type I α1 and α2 chains. Failure of bone union and/or presence of hyperplastic callus formation after fracture were described in OI patients. Here we used the Col1a2^+/G610C mouse, carrying in heterozygosis the α2(I)-G610C substitution, to investigate the healing process of an OI bone. Tibiae of 2-month-old Col1a2^+/G610C and wild-type littermates were fractured and the healing process was followed at 2, 3, and 5 weeks after injury from fibrous cartilaginous tissue formation to its bone replacement by radiography, micro-computed tomography (µCT), histological and biochemical approaches. In presence of similar fracture types, in Col1a2^+/G610C mice an impairment in the early phase of bone repair was detected compared to wild-type littermates. Smaller callus area, callus bone surface, and bone volume associated to higher percentage of cartilage and lower percentage of bone were evident in Col1a2^+/G610C at 2 weeks post fracture (wpf) and no change by 3 wpf. Furthermore, the biochemical analysis of collagen extracted from callus 2 wpf revealed in mutants an increased amount of type II collagen, typical of cartilage, with respect to type I, characteristic of bone. This is the first report of a delay in OI bone fracture repair at the modeling phase.

Allogeneic yet major histocompatibility complex-matched bone marrow transplantation in mice results in an impairment of osteoblasts and a significantly reduced trabecular bone

Secondary osteopenia following allogeneic bone marrow or stem cell transplantation (BMT or HSCT) is a significant source of morbidity in patients. It is believed to be caused by a number of factors related to the myeloablative conditioning and subsequent therapy regimen. We here aimed to investigate whether the allogeneic bone marrow by itself directly impacts on the bone mass of the patient. We thus performed syn- and allogeneic BMT between two inbred mouse strains, which share an identical major histocompatibility complex background yet differ in their bone phenotypes. BMT was well tolerated, yielded survival rates of 97% and allowed for a regular physiological development. However, allogeneic BMT led to a significant reduction of trabecular bone mass that was independent of strain, sex, immunosuppressive medication, complications resulting from graft versus host disease, underlying bone phenotype and numbers of osteoclasts. Instead, reduced trabecular bone mass correlated with reduced plasma levels of amino-terminal propeptide of type I collagen. Our results suggest that osteopenia following allogeneic BMT is significantly influenced by an impaired osteoblast activity that may stem from a lack of communication between the resident osteoblasts and an allogeneic bone marrow-derived cell type. Elucidating this incompatibility will open new approaches for the therapy of secondary osteopenia.

The influence of biodegradable magnesium implants on the growth plate

Mg-based biodegradable materials are considered promising candidates in the paediatric field due to their favourable mechanical and biological properties and their biodegrading potential that makes a second surgery for implant removal unnecessary. In many cases the surgical fixation technique requires a crossing of the growth plate by the implant in order to achieve an adequate fragment replacement or fracture stabilisation. This study investigates the kinetics of slowly and rapidly degrading Mg alloys in a transphyseal rat model, and also reports on their dynamics in the context of the physis and consecutive bone growth. Twenty-six male Sprague-Dawley rats received either a rapidly degrading (ZX50; n = 13) or a slowly degrading (WZ21; n = 13) Mg alloy, implanted transphyseal into the distal femur. The contralateral leg was drilled in the same manner and served as a direct sham specimen. Degradation behaviour, gas formation, and leg length were measured by continuous in vivo micro CT for up to 52 weeks, and additional high-resolution µCT (HRS) scans and histomorphological analyses of the growth plate were performed. The growth plate was locally destroyed and bone growth was significantly diminished by the fast degradation of ZX50 implants and the accompanying release of large amounts of hydrogen gas. In contrast, WZ21 implants showed homogenous and moderate degradation performance, and the effect on bone growth did not differ significantly from a single drill-hole defect.

STATEMENT OF SIGNIFICANCE

This study is the first that reports on the effects of degrading magnesium implants on the growth plate in a living animal model. The results show that high evolution of hydrogen gas due to rapid Mg degradation can damage the growth plate substantially. Slow degradation, however, such as seen for WZ21 alloys, does not affect the growth plate more than drilling alone, thus meeting one important prerequisite for deployment in paediatric osteosynthesis.

Micro-Computed-Tomography-Guided Analysis of In Vitro Structural Modifications in Two Types of 45S5 Bioactive Glass Based Scaffolds

Three-dimensional 45S5 bioactive glass (BG)-based scaffolds are being investigated for bone regeneration. Besides structural properties, controlled time-dependent alteration of scaffold morphology is crucial to achieve optimal scaffold characteristics for successful bone repair. There is no in vitro evidence concerning the dependence between structural characteristics and dissolution behavior of 45S5 BG-based scaffolds of different morphology. In this study, the dissolution behavior of scaffolds fabricated by the foam replica method using polyurethane foam (Group A) and maritime sponge Spongia Agaricina (Group B) as sacrificial templates was analyzed by micro-computed-tomography (µCT). The scaffolds were immersed in Dulbecco’s Modified Eagle Medium for 56 days under static cell culture conditions and underwent µCT-analysis initially, and after 7, 14, and 56 days. Group A showed high porosity (91%) and trabecular structure formed by macro-pores (average diameter 692 µm ± 72 µm). Group-B-scaffolds were less porous (51%), revealing an optimal pore size distribution within the window of 110–500 µm pore size diameter, combined with superior mechanical stability. Both groups showed similar structural alteration upon immersion. Surface area and scaffold volume increased whilst density decreased, reflecting initial dissolution followed by hydroxycarbonate-apatite-layer-formation on the scaffold surfaces. In vitro- and/or in vivo-testing of cell-seeded BG-scaffolds used in this study should be performed to evaluate the BG-scaffolds’ time-dependent osteogenic properties in relation to the measured in vitro structural changes.

Deletion of a Distal RANKL Gene Enhancer Delays Progression of Atherosclerotic Plaque Calcification in Hypercholesterolemic Mice

Receptor activator of NF-κB ligand (RANKL) is a TNF-like cytokine which mediates diverse physiological functions including bone remodeling and immune regulation. RANKL has been identified in atherosclerotic lesions; however, its role in atherosclerotic plaque development remains elusive. An enhancer located 75 kb upstream of the murine Rankl gene's transcription start site designated D5 is important for its calciotropic hormone- and cytokine-mediated expression. Here, we determined the impact of RANKL levels in atherosclerotic plaque development in the D5 enhancer-null (D5^-/- ) mice in an atherogenic Apoe^-/- background fed a high-fat diet (HFD). Rankl mRNA transcripts were increased in aortic arches and thoracic aortae of Apoe^-/- mice; however, this increase was blunted in Apoe^-/- ;D5^-/- mice. Similarly, higher Rankl transcripts were identified in splenic T lymphocytes in Apoe^-/- mice, and their levels were reduced in Apoe^-/- ;D5^-/- mice. When analyzed by micro-computed tomography (µCT), atherosclerotic plaque calcification was identified in six out of eight Apoe^-/- mice, whereas only one out of eight Apoe^-/- ;D5^-/- mice developed plaque calcification after 12 weeks of HFD. However, following 18 weeks of HFD challenge, all of Apoe^-/- and Apoe^-/- ;D5^-/- animals developed atherosclerotic plaque calcification. Likewise, atherosclerotic lesion sizes were site-specifically reduced in the aortic arch of Apoe^-/- ;D5^-/- mice at initial stage of atherosclerosis and this effect was diminished as atherosclerosis proceeded to a more advanced stage. Our data suggest that deletion of the RANKL D5 enhancer delays the progression of atherosclerotic plaque development and plaque calcification in hypercholesterolemic mice. This work provides important insight into RANKL's regulatory role in atherosclerosis. J. Cell. Biochem. 118: 4240-4253, 2017. © 2017 Wiley Periodicals, Inc.

Micro-CT evaluation of asymmetrical ovine intervertebral disc height loss from surgical approach

PURPOSE

The primary goal of this study is to clearly define and evaluate new intervertebral disc height parameters in analysing the morphological pathology of disc degeneration for application in damage model and regeneration therapy development, as well as applying traditional variables to 3-D characterization methods.

METHODS

A posterolateral surgical approach was used to induce disc degeneration in an ovine model. At 12-months post-operation, sheep vertebral segments were removed and characterized using micro-CT to evaluate disc height parameters in regard to injury localization.

RESULTS

Statistically significant differences between the disc height loss of the left and right side of the disc, consistent with the lateral surgical approach used were seen using the modified average disc height method by Dabbs et al. However, convexity index and the newly proposed Cross Tilt Index did not conclusively demonstrate a difference.

CONCLUSION

Two-dimensional morphological evaluations can be applied in 3-D to provide a more complete picture of disc height loss for injury models. New 3-D parameters that are tailored to the type of surgical approach used should be investigated, with the 9-point system described herein providing a useful basis for derived values. Additionally, the surgical approach chosen when artificially injuring the disc can result in asymmetrical degeneration, as indicated by uneven disc height loss.

Absence of the Vitamin D Receptor Inhibits Atherosclerotic Plaque Calcification in Female Hypercholesterolemic Mice

Epidemiological and clinical data suggest adverse cardiovascular outcomes with respect to vitamin D deficiency. Here, we explored the effects of vitamin D in atherosclerotic plaque calcification in vivo by utilizing vitamin D receptor (Vdr)-deficient mice in an Apoe^-/- background. Animals were fed a high-fat diet (HFD) for either 12 or 18 weeks and then examined for atherosclerotic plaque development. In order to prevent calcium deficiency, Vdr^-/- and Apoe^-/- ;Vdr^-/- animals were fed a high-calcium rescue diet prior to initiation of the HFD feeding and supplemented with high-calcium water during HFD feeding. Although calcium supplementation improved bone mass in Vdr^-/- and Apoe^-/- ;Vdr^-/- mice, neither strain was fully rescued. Systemic inflammatory responses observed in the absence of VDR were exaggerated in Apoe^-/- mice. Whereas, hyperlipidemic profiles seen in Apoe^-/- mice were ameliorated in the absence of VDR. Micro-computed tomography (µCT) analysis revealed that six out of eight Apoe^-/- animals developed atherosclerotic plaque calcification following 12 weeks of HFD feeding and 100% of the mice developed plaque calcification after 18 weeks. In contrast, although atherosclerotic lesions were evident in Apoe^-/- ;Vdr^-/- mice at 12 and 18 weeks of HFD challenge, none of these animals developed plaque calcification at either time point. The active vitamin D hormone, 1,25(OH)₂ D₃ likely increased calcification in aortic smooth muscle cells perhaps by directly modulating expression of Alpl, Rankl, and Opg. Our data suggest that the absence of VDR inhibits atherosclerotic plaque calcification in hypercholesterolemic Apoe^-/- mice, providing additional insight into the role of vitamin D in atherosclerotic plaque calcification. J. Cell. Biochem. 118: 1050-1064, 2017. © 2016 Wiley Periodicals, Inc.

Effects of letrozole on breast cancer micro-metastatic tumor growth in bone and lung in mice inoculated with murine 4T1 cells

Breast cancer (BC) is the leading cancer in women worldwide. Metastasis occurs in stage IV BC with bone and lung being common metastatic sites. Here we evaluate the effects of the aromatase inhibitor letrozole on BC micro-metastatic tumor growth in bone and lung metastasis in intact and ovariectomized (OVX) mice with murine estrogen receptor negative (ER-) BC cells inoculated in tibia. Forty-eight BALB/c mice were randomly assigned to one of four groups: OVX, OVX + Letrozole, Intact, and Intact + Letrozole, and injected with 4T1 cells intra-tibially. Letrozole was subcutaneously injected daily for 23 days at a dose of 1.75 µg/g body weight. Tumor progression was monitored by bioluminescence imaging (BLI). Following necropsy, inoculated tibiae were scanned via µCT and bone response to tumor was scored from 0 (no ectopic mineralization/osteolysis) to 5 (extensive ectopic mineralization/osteolysis). OVX mice had higher tibial pathology scores indicative of more extensive bone destruction than intact mice, irrespective of letrozole treatment. Letrozole decreased serum estradiol levels and reduced lung surface tumor numbers in intact animals. Furthermore, mice receiving letrozole had significantly fewer tumor colonies and fewer proliferative cells in the lung than OVX and intact controls based on H&E and Ki-67 staining, respectively. In conclusion, BC-inoculated OVX animals had higher tibia pathology scores than BC-inoculated intact animals and letrozole reduced BC metastases to lungs. These findings suggest that, by lowering systemic estrogen level and/or by interacting with the host organ, the aromatase inhibitor letrozole has the potential to reduce ER- BC metastasis to lung.

High-acceleration whole body vibration stimulates cortical bone accrual and increases bone mineral content in growing mice

Whole body vibration (WBV) is a promising tool for counteracting bone loss. Most WBV studies on animals have been performed at acceleration <1g and frequency between 30 and 90Hz. Such WBV conditions trigger bone growth in osteopenia models, but not in healthy animals. In order to test the ability of WBV to promote osteogenesis in young animals, we exposed seven-week-old male mice to vibration at 90Hz and 2g peak acceleration for 15min/day, 5 days/week. We examined the effects on skeletal tissues with micro-computed tomography and histology. We also quantified bone vascularization and mechanosensitive osteocyte proteins, sclerostin and DMP1. Three weeks of WBV resulted in an increase of femur cortical thickness (+5%) and area (+6%), associated with a 25% decrease of sclerostin expression, and 35% increase of DMP1 expression in cortical osteocytes. Mass-structural parameters of trabecular bone were unaltered in femur or vertebra, while osteoclastic parameters and bone formation rate were increased at both sites. Three weeks of WBV resulted in higher blood vessel numbers (+23%) in the distal femoral metaphysis. After 9-week WBV, we have not observed the difference in structural cortical or trabecular parameters. However, the tissue mineral density of cortical bone was increased by 2.5%. Three or nine weeks of 2g/90Hz WBV treatment did not affect longitudinal growth rate or body weight increase under our experimental conditions, indicating that these are safe to use. These results validate a potential of 2g/90Hz WBV to stimulate trabecular bone cellular activity, accelerate cortical bone growth, and increase bone mineral density.

The anti-fibrotic effect of inhibition of TGFβ-ALK5 signalling in experimental pulmonary fibrosis in mice is attenuated in the presence of concurrent γ-herpesvirus infection

TGFβ-ALK5 pro-fibrotic signalling and herpesvirus infections have been implicated in the pathogenesis and exacerbation of pulmonary fibrosis. In this study we addressed the role of TGFβ-ALK5 signalling during the progression of fibrosis in a two-hit mouse model of murine γ-herpesvirus 68 (MHV-68) infection on the background of pre-existing bleomycin-induced pulmonary fibrosis. Assessment of total lung collagen levels in combination with ex vivo micro-computed tomography (µCT) analysis of whole lungs demonstrated that MHV-68 infection did not enhance lung collagen deposition in this two-hit model but led to a persistent and exacerbated inflammatory response. Moreover, µCT reconstruction and analysis of the two-hit model revealed distinguishing features of diffuse ground-glass opacities and consolidation superimposed on pre-existing fibrosis that were reminiscent of those observed in acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF). Virally-infected murine fibrotic lungs further displayed evidence of extensive inflammatory cell infiltration and increased levels of CCL2, TNFα, IL-1β and IL-10. Blockade of TGFβ-ALK5 signalling attenuated lung collagen accumulation in bleomycin-alone injured mice, but this anti-fibrotic effect was reduced in the presence of concomitant viral infection. In contrast, inhibition of TGFβ-ALK5 signalling in virally-infected fibrotic lungs was associated with reduced inflammatory cell aggregates and increased levels of the antiviral cytokine IFNγ. These data reveal newly identified intricacies for the TGFβ-ALK5 signalling axis in experimental lung fibrosis, with different outcomes in response to ALK5 inhibition depending on the presence of viral infection. These findings raise important considerations for the targeting of TGFβ signalling responses in the context of pulmonary fibrosis.

The 3D structure of the collagen fibril network in human trabecular bone: relation to trabecular organization

Trabecular bone is morphologically and functionally different from compact bone at the tissue level, but both are composed of lamellae at the micrometer-scale level. We present a three-dimensional study of the collagenous network of human trabecular lamellar bone from the proximal femur using the FIB-SEM serial surface view method. The results are compared to human compact lamellar bone of the femoral shaft, studied by the same method. Both demineralized trabecular and compact lamellar bone display the same overall structural organization, namely the presence of ordered and disordered materials and the confinement of the canalicular network to the disordered material. However, in trabecular bone lamellae a significant proportion of the ordered collagen fibril arrays is aligned with the long axis of the trabecula and, unlike in compact bone, is not related to the anatomical axis of the whole femur. The remaining ordered collagen fibrils are offset from the axis of a trabecula either by about 30° or 70°. Interestingly, at the tissue scale of millimeters, the most abundant angles between any two connected trabeculae - the inter-trabecular angles - center around 30° and 70°. This implies that within a framework of interconnected trabeculae the same lamellar structure will always have a significant component of the fibrils aligned with the long axes of connected trabeculae. This structural complementarity at different hierarchical levels presumably reflects an adaptation of trabecular bone to function.

3D assessment of cortical bone porosity and tissue mineral density using high-resolution µCT: effects of resolution and threshold method

Current micro-computed tomography (µCT) systems allow scanning bone at resolutions capable of three-dimensional (3D) characterization of intracortical vascular porosity and osteocyte lacunae. However, the scanning and reconstruction parameters along with the image segmentation method affect the accuracy of the measurements. In this study, the effects of scanning resolution and image threshold method in quantifying small features of cortical bone (vascular porosity, vascular canal diameter and separation, lacunar porosity and density, and tissue mineral density) were analyzed. Cortical bone from the tibia of Sprague-Dawley rats was scanned at 1-µm and 4-µm resolution, reconstructions were density-calibrated, and volumes of interest were segmented using approaches based on edge-detection or histogram analysis. In 1-µm resolution scans, the osteocyte lacunar spaces could be visualized, and it was possible to separate the lacunar porosity from the vascular porosity. At 4-µm resolution, the vascular porosity and vascular canal diameter were underestimated, and osteocyte lacunae were not effectively detected, whereas the vascular canal separation and tissue mineral density were overestimated compared to 1-µm resolution. Resolution had a much greater effect on the measurements than did threshold method, showing partial volume effects at resolutions coarser than 2 µm in two separate analyses, one of which assessed the effect of resolution on an object of known size with similar architecture to a vascular pore. Although there was little difference when using the edge-detection versus histogram-based threshold approaches, edge-detection was somewhat more effective in delineating canal architecture at finer resolutions (1-2 µm). In addition, use of a high-resolution (1 µm) density-based threshold on lower resolution (4 µm) density-calibrated images was not effective in improving the lower-resolution measurements. In conclusion, if measuring cortical vascular microarchitecture, especially in small animals, a µCT resolution of 1 to 2 µm is appropriate, whereas a resolution of at least 1 µm is necessary when assessing osteocyte lacunar porosity.

Tendon mineralization is accelerated bilaterally and creep of contralateral tendons is increased after unilateral needle injury of murine achilles tendons

Heterotopic mineralization may result in tendon weakness, but effects on other biomechanical responses have not been reported. We used a needle injury, which accelerates spontaneous mineralization of murine Achilles tendons, to test two hypotheses: that injured tendons would demonstrate altered biomechanical responses; and that unilateral injury would accelerate mineralization bilaterally. Mice underwent left hind (LH) injury (I; n = 11) and were euthanized after 20 weeks along with non-injured controls (C; n = 9). All hind limbs were examined by micro computed tomography followed by biomechanical testing (I = 7 and C = 6). No differences were found in the biomechanical responses of injured tendons compared with controls. However, the right hind (RH) tendons contralateral to the LH injury exhibited greater static creep strain and total creep strain compared with those LH tendons (p ≤ 0.045) and RH tendons from controls (p ≤ 0.043). RH limb lesions of injured mice were three times larger compared with controls (p = 0.030). Therefore, despite extensive mineralization, changes to the responses we measured were limited or absent 20 weeks postinjury. These results also suggest that bilateral occurrence should be considered where tendon mineralization is identified clinically. This experimental system may be useful to study the mechanisms of bilateral new bone formation in tendinopathy and other conditions.