Botulinum neurotoxin type A responders among children with spastic cerebral palsy: Pattern-specific effects

AIM

To identify short-term effects of botulinum neurotoxin type A (BoNT) injections on gait and clinical impairments, in children with spastic cerebral palsy (CP), based on baseline gait pattern-specific subgroups.

METHOD

Short-term effects of BoNT injections in the medial hamstrings and gastrocnemius were defined in a retrospective convenience sample of 117 children with CP (median age: 6 years 4 months; GMFCS I/II/III: 70/31/16; unilateral/bilateral: 56/61) who had received gait analyses before and 2 months post-BoNT. First, baseline gait patterns were classified. Statistical and meaningful changes were calculated between pre- and post-BoNT lower limb sagittal plane kinematic waveforms, the gait profile score, and non-dimensional spatiotemporal parameters for the entire sample and for pattern-specific subgroups. These gait waveforms per CP subgroup at pre- and post-BoNT were also compared to typically developing gait and composite scores for spasticity, weakness, and selectivity were compared between the two conditions.

RESULTS

Kinematic improvements post-BoNT were identified at the ankle and knee for the entire sample, and for subgroups with apparent equinus and jump gait. Limbs with baseline patterns of dropfoot and to a lesser extent true equinus showed clear improvements only at the ankle. In apparent equinus, jump gait, and dropfoot, spasticity improved post-BoNT, without leading to increased weakness or diminished selectivity. Compared to typical gait, knee and hip motion improved in the crouch gait subgroup post-BoNT.

CONCLUSION

This comprehensive analysis highlighted the importance of investigating BoNT effects on gait and clinical impairments according to baseline gait patterns. These findings may help identify good treatment responders.

Impact of Collagen Crosslinking on Dislocated Human Shoulder Capsules-Effect on Structural and Mechanical Properties

Classical treatments of shoulder instability are associated with recurrence. To determine whether the modification of the capsule properties may be an alternative procedure, the effect of crosslinking treatment on the structure and mechanical properties of diseased human shoulder capsules was investigated. Joint capsules harvested from patients during shoulder surgery (n = 5) were treated or not with UV and/or riboflavin (0.1%, 1.0% and 2.5%). The structure and the mechanical properties of the capsules were determined by atomic force microscopy. The effect of treatments on cell death was investigated. Collagen fibrils were well-aligned and adjacent to each other with a D-periodicity of 66.9 ± 3.2 nm and a diameter of 71.8 ± 15.4 nm in control untreated capsules. No effect of treatments was observed on the organization of the collagen fibrils nor on their intrinsic characteristics, including D-periodicity or their mean diameter. The treatments also did not induce cell death. In contrast, UV + 2.5% riboflavin induced capsule stiffness, as revealed by the increased Young's modulus values (p < 0.0001 for each patient). Our results showed that the crosslinking procedure changed the biomechanics of diseased capsules, while keeping their structural organisation unchanged at the single fibril level. The UV/riboflavin crosslinking procedure may be a promising way to preserve the functions of collagen-based tissues and tune their elasticity for clinically relevant treatments.

Osteocytes Influence on Bone Matrix Integrity Affects Biomechanical Competence at Bone-Implant Interface of Bioactive-Coated Titanium Implants in Rat Tibiae

Osseointegration is a prerequisite for the long-term success of implants. Titanium implants are preferred for their biocompatibility and mechanical properties. Nonetheless, the need for early and immediate loading requires enhancing these properties by adding bioactive coatings. In this preclinical study, extracellular matrix properties and cellular balance at the implant/bone interface was examined. Polyelectrolyte multilayers of chitosan and gelatin or with chitosan and Hyaluronic acid fabricated on titanium alloy using a layer-by-layer self-assembly process were compared with native titanium alloy. The study aimed to histologically evaluate bone parameters that correlate to the biomechanical anchorage enhancement resulted from bioactive coatings of titanium implants in a rat animal model. Superior collagen fiber arrangements and an increased number of active osteocytes reflected a significant improvement of bone matrix quality at the bone interface of the chitosan/gelatin-coated titan implants over chitosan/hyaluronic acid-coated and native implants. Furthermore, the numbers and localization of osteoblasts and osteoclasts in the reparative and remodeling phases suggested a better cellular balance in the chitosan/Gel-coated group over the other two groups. Investigating the micro-mechanical properties of bone tissue at the interface can elucidate detailed discrepancies between different promising bioactive coatings of titanium alloys to maximize their benefit in future medical applications.

Animal Model for Glucocorticoid Induced Osteoporosis: A Systematic Review from 2011 to 2021

Clinical and experimental data have shown that prolonged exposure to GCs leads to bone loss and increases fracture risk. Special attention has been given to existing emerging drugs that can prevent and treat glucocorticoid-induced osteoporosis GIOP. However, there is no consensus about the most relevant animal model treatments on GIOP. In this systematic review, we aimed to examine animal models of GIOP centering on study design, drug dose, timing and size of the experimental groups, allocation concealment, and outcome measures. The present review was written according to the PRISMA 2020 statement. Literature searches were performed in the PubMed electronic database via Mesh with the publication date set between April, 2011, and February 2021. A total of 284 full-text articles were screened and 53 were analyzed. The most common animal species used to model GIOP were rats (66%) and mice (32%). In mice studies, males (58%) were preferred and genetically modified animals accounted for 28%. Our work calls for a standardization of the establishment of the GIOP animal model with better precision for model selection. A described reporting design, conduction, and selection of outcome measures are recommended.

Axonal growth on surfaces with periodic geometrical patterns

The formation of neuron networks is a complex phenomenon of fundamental importance for understanding the development of the nervous system, and for creating novel bioinspired materials for tissue engineering and neuronal repair. The basic process underlying the network formation is axonal growth, a process involving the extension of axons from the cell body towards target neurons. Axonal growth is guided by environmental stimuli that include intercellular interactions, biochemical cues, and the mechanical and geometrical features of the growth substrate. The dynamics of the growing axon and its biomechanical interactions with the growing substrate remains poorly understood. In this paper, we develop a model of axonal motility which incorporates mechanical interactions between the axon and the growth substrate. We combine experimental data with theoretical analysis to measure the parameters that describe axonal growth on surfaces with micropatterned periodic geometrical features: diffusion (cell motility) coefficients, speed and angular distributions, and axon bending rigidities. Experiments performed on neurons treated Taxol (inhibitor of microtubule dynamics) and Blebbistatin (disruptor of actin filaments) show that the dynamics of the cytoskeleton plays a critical role in the axon steering mechanism. Our results demonstrate that axons follow geometrical patterns through a contact-guidance mechanism, in which high-curvature geometrical features impart high traction forces to the growth cone. These results have important implications for our fundamental understanding of axonal growth as well as for bioengineering novel substrates that promote neuronal growth and nerve repair.

Multiphysics Modeling and Simulation of Subcutaneous Injection and Absorption of Biotherapeutics: Sensitivity Analysis

PURPOSE

A multiphysics simulation model was recently developed to capture major physical and mechanical processes of local drug transport and absorption kinetics of subcutaneously injected monoclonal antibody (mAb) solutions. To further explore the impact of individual drug attributes and tissue characteristics on the tissue biomechanical response and drug mass transport upon injection, sensitivity analysis was conducted and reported.

METHOD

Various configurations of injection conditions, drug-associated attributes, and tissue properties were simulated with the developed multiphysics model. Simulation results were examined with regard to tissue deformation, porosity change, and spatiotemporal distributions of pressure, interstitial fluid flow, and drug concentration in the tissue.

RESULTS

Injection conditions and tissue properties were found influential on the mechanical response of tissue and interstitial fluid velocity to various extents, leading to distinct drug concentration profiles. Intrinsic tissue porosity, lymphatic vessel density, and drug permeability through the lymphatic membrane were particularly essential in determining the local absorption rate of an mAb injection.

CONCLUSION

The sensitivity analysis study may shed light on the product development of an mAb formulation, as well as on the future development of the simulation method.

Analysis of Biomechanical Parameters of Muscle Soleus Contraction and Blood Biochemical Parameters in Rat with Chronic Glyphosate Intoxication and Therapeutic Use of C60 Fullerene

The widespread use of glyphosate as a herbicide in agriculture can lead to the presence of its residues and metabolites in food for human consumption and thus pose a threat to human health. It has been found that glyphosate reduces energy metabolism in the brain, its amount increases in white muscle fibers. At the same time, the effect of chronic use of glyphosate on the dynamic properties of skeletal muscles remains practically unexplored. The selected biomechanical parameters (the integrated power of muscle contraction, the time of reaching the muscle contraction force its maximum value and the reduction of the force response by 50% and 25% of the initial values during stimulation) of muscle soleus contraction in rats, as well as blood biochemical parameters (the levels of creatinine, creatine phosphokinase, lactate, lactate dehydrogenase, thiobarbituric acid reactive substances, hydrogen peroxide, reduced glutathione and catalase) were analyzed after chronic glyphosate intoxication (oral administration at a dose of 10 μg/kg of animal weight) for 30 days. Water-soluble C60 fullerene, as a poweful antioxidant, was used as a therapeutic nanoagent throughout the entire period of intoxication with the above herbicide (oral administration at doses of 0.5 or 1 mg/kg). The data obtained show that the introduction of C60 fullerene at a dose of 0.5 mg/kg reduces the degree of pathological changes by 40-45%. Increasing the dose of C60 fullerene to 1 mg/kg increases the therapeutic effect by 55-65%, normalizing the studied biomechanical and biochemical parameters. Thus, C60 fullerenes can be effective nanotherapeutics in the treatment of glyphosate-based herbicide poisoning.

Teriparatide and exercise improve bone, skeletal muscle, and fat parameters in ovariectomized and tail-suspended rats

INTRODUCTION

Although teriparatide (TPTD) and exercise may improve osteoporosis, muscle atrophy, and fat metabolism during ageing, the effects of treatment with a combination of TPTD and exercise on these factors remain unclear. Therefore, this study examined the effects of TPTD and exercise on bone, skeletal muscle, and fat in ovariectomized and tail-suspended rats.

MATERIALS AND METHODS

Seven-month-old female Wistar rats were ovariectomized and subjected to tail suspension. The rats were then randomized into one of the following four groups (n = 20/group) after 4 weeks: control group, treated with TPTD vehicle and no exercise; TPTD group (30 µg/kg TPTD, 3 days/week); Exercise group (treadmill at 12 m/min, 60 min/day, 5 days/week); and Combined group treated with TPTD and treadmill exercise. After 1 and 8 weeks of treatment, bone, skeletal muscle, and fat tissue parameters were evaluated.

RESULTS

TPTD improved bone mineral density (BMD), bone structure, bone strength at the femoral metaphysis, and the percentage of skeletal muscle mass, and decreased the percentage of fat mass and the adipose volume in the bone marrow. Treadmill exercise increased BMD, bone strength of cancellous bone, and the percentage of skeletal muscle mass, and decreased the percentage of fat mass as seen on dual-energy X-ray absorptiometry. Furthermore, combined treatment significantly affected BMD, bone structure, and bone strength of cortical bone at the femoral diaphysis.

CONCLUSION

TPTD or treadmill exercise improved bone, skeletal muscle, and fat mass. Combination therapy with TPTD and exercise had synergistic effects on BMD, structure, and bone strength in ovariectomized, tail-suspended rats.

Teriparatide and Abaloparatide Have a Similar Effect on Bone in Mice

Three bone anabolic pharmaceuticals are currently approved for treatment of osteoporosis, teriparatide (PTH (1-34)), the parathyroid hormone-related protein analog abaloparatide (ABL), and romosozumab. The present study compared the effect of intermittent PTH (1-34) and ABL on bone tissue directly mole-to-mole in female mice. Forty-seven C57BL/6 mice were randomly allocated to the following groups: Baseline (n = 11), Control (Ctrl) (n = 12), PTH (n = 12), and ABL (n = 12). The mice were injected s.c. with PTH (100 µg/kg), ABL (96 µg/kg), or saline (Ctrl) five days a week for three weeks. To assess the effect of PTH and ABL, the hindlimb bones were analyzed with DXA, µCT, mechanical testing, dynamic bone histomorphometry, and histological quantification of bone cells. In addition, serum calcium concentration was determined. PTH and ABL significantly increased femoral areal bone mineral density (aBMD) (borderline significant p = 0.06 for PTH), femoral mid-diaphyseal bone strength, femoral metaphyseal and epiphyseal and vertebral bone volume fraction (BV/TV), connectivity density, volumetric bone mineral density (vBMD), and bone formation rate (BFR/BS) compared to Ctrl. In addition, ABL also significantly increased mid-diaphyseal cortical thickness and bone area compared to Ctrl. Neither PTH nor ABL significantly increased bone strength at the femoral neck. In conclusion, abaloparatide and PTH have similar bone anabolic properties when compared directly mole-to-mole in mice.

Cumulative Effects of Strontium Ranelate and Impact Exercise on Bone Mass in Ovariectomized Rats

OBJECTIVE

To explore the effect of physical exercise (EXE), strontium ranelate (SR), or their combination on bone status in ovariectomized (OVX) rats.

DESIGN

Sixty female Wistar rats were randomized to one of five groups: sham (Sh), OVX (O), OVX+EXE (OE), OVX+SR (OSR), and OVX+EXE+SR (OESR). Animals in EXE groups were subjected to 10 drops per day (45 cm in height); rats in SR groups received 625 mg/kg/day of SR, 5 days/week for 8 weeks. Bone mineral density (BMD) and bone mineral content (BMC, dual-energy X-ray absorptiometry (DXA)), mechanical strength of the left femur (three-point bending test), and femur microarchitecture of (micro-computed tomography imaging, microCT) analyses were performed to characterize biomechanical and trabecular/cortical structure. Bone remodeling, osteocyte apoptosis, and lipid content were evaluated by ELISA and immunofluorescence tests.

RESULTS

In OVX rats, whole-body BMD, trabecular parameters, and osteocalcin (OCN) levels decreased, while weight, lean/fat mass, osteocyte apoptosis, and lipid content all increased. EXE after ovariectomy improved BMD and BMC, trabecular parameters, cross-sectional area (CSA), moment of inertia, and OCN levels while decreasing osteocyte apoptosis and lipid content. SR treatment increased BMD and BMC, trabecular parameters, CSA, stiffness, OCN, and alkaline phosphatase (ALP) levels. Furthermore, fat mass, N-telopeptide (NTX) level, osteocyte apoptosis, and lipid content significantly decreased. The combination of both EXE and SR improved bone parameters compared with EXE or SR alone.

CONCLUSION

EXE and SR had positive and synergistic effects on bone formation and resorption.

Positive effect of Astragaloside IV on neurite outgrowth via talin-dependent integrin signaling and microfilament force

Integrin plays a prominent role in neurite outgrowth by transmitting both mechanical and chemical signals. Integrin expression is closely associated with Astragaloside IV (AS-IV), the main component extracted from Astragali radix, which has a positive effect on neural-protection. However, the relationship between AS-IV and neurite outgrowth has not been studied exhaustively to date. The present study investigated the underlying mechanism of AS-IV on neurite outgrowth. Longer neurites have been observed in SH-SY5Y cells or cortical neurons after AS-IV treatment. Furthermore, AS-IV not only increased the expression of integrin β but also activated it. The AS-IV-induced increased integrin activity was attributed to the integrin-activating protein talin. Application of the actin force probe showed that AS-IV led to an increase in intracellular microfilament force during neurite growth. Furthermore, in response to AS-IV, the microfilament force was regulated by talin and integrin activity during neurite growth. These results suggest that AS-IV has the ability to increase intracellular structural force and facilitate neurite elongation by integrin signaling, which highlights its therapeutic potential for neurite outgrowth.

Multiseriate cortical sclerenchyma enhance root penetration in compacted soils

Mechanical impedance limits soil exploration and resource capture by plant roots. We examine the role of root anatomy in regulating plant adaptation to mechanical impedance and identify a root anatomical phene in maize (Zea mays) and wheat (Triticum aestivum) associated with penetration of hard soil: Multiseriate cortical sclerenchyma (MCS). We characterize this trait and evaluate the utility of MCS for root penetration in compacted soils. Roots with MCS had a greater cell wall-to-lumen ratio and a distinct UV emission spectrum in outer cortical cells. Genome-wide association mapping revealed that MCS is heritable and genetically controlled. We identified a candidate gene associated with MCS. Across all root classes and nodal positions, maize genotypes with MCS had 13% greater root lignin concentration compared to genotypes without MCS. Genotypes without MCS formed MCS upon exogenous ethylene exposure. Genotypes with MCS had greater lignin concentration and bending strength at the root tip. In controlled environments, MCS in maize and wheat was associated improved root tensile strength and increased penetration ability in compacted soils. Maize genotypes with MCS had root systems with 22% greater depth and 49% greater shoot biomass in compacted soils in the field compared to lines without MCS. Of the lines we assessed, MCS was present in 30 to 50% of modern maize, wheat, and barley cultivars but was absent in teosinte and wild and landrace accessions of wheat and barley. MCS merits investigation as a trait for improving plant performance in maize, wheat, and other grasses under edaphic stress.

Oral administration of resveratrol or lactic acid bacterium improves lens elasticity

A decrease in the elasticity of the ocular lens during aging is associated with loss of the accommodative ability of the eye, leading to presbyopia. Although near vision impairment is a social issue affecting the length of healthy life expectancy and productivity of elderly people, an effective treatment to improve near vision has not yet become available. Here we examined the effect of Enterococcus faecium WB2000, Lactobacillus pentosus TJ515, and resveratrol on lens elasticity in rats, where the stiffness of the ocular lens increases exponentially during the aging process. A combination of WB2000 and resveratrol improved lens elasticity not only in the long term but also with just short-term treatment. In addition, TJ515 decreased stiffness in the eye lens with long-term treatment. Therefore, the oral administration of WB2000 and resveratrol or TJ515 may be a potential approach for managing the progression of near vision impairment.

Computational models of cardiac hypertrophy

Cardiac hypertrophy, defined as an increase in mass of the heart, is a complex process driven by simultaneous changes in hemodynamics, mechanical stimuli, and hormonal inputs. It occurs not only during pre- and post-natal development but also in adults in response to exercise, pregnancy, and a range of cardiovascular diseases. One of the most exciting recent developments in the field of cardiac biomechanics is the advent of computational models that are able to accurately predict patterns of heart growth in many of these settings, particularly in cases where changes in mechanical loading of the heart play an import role. These emerging models may soon be capable of making patient-specific growth predictions that can be used to guide clinical interventions. Here, we review the history and current state of cardiac growth models and highlight three main limitations of current approaches with regard to future clinical application: their inability to predict the regression of heart growth after removal of a mechanical overload, inability to account for evolving hemodynamics, and inability to incorporate known growth effects of drugs and hormones on heart growth. Next, we outline growth mechanics approaches used in other fields of biomechanics and highlight some potential lessons for cardiac growth modeling. Finally, we propose a multiscale modeling approach for future studies that blends tissue-level growth models with cell-level signaling models to incorporate the effects of hormones in the context of pregnancy-induced heart growth.

Diminishing effects of mechanical loading over time during rat Achilles tendon healing

Mechanical loading affects tendon healing and recovery. However, our understanding about how physical loading affects recovery of viscoelastic functions, collagen production and tissue organisation is limited. The objective of this study was to investigate how different magnitudes of loading affects biomechanical and collagen properties of healing Achilles tendons over time. Achilles tendon from female Sprague Dawley rats were cut transversely and divided into two groups; normal loading (control) and reduced loading by Botox (unloading). The rats were sacrificed at 1, 2- and 4-weeks post-injury and mechanical testing (creep test and load to failure), small angle x-ray scattering (SAXS) and histological analysis were performed. The effect of unloading was primarily seen at the early time points, with inferior mechanical and collagen properties (SAXS), and reduced histological maturation of the tissue in unloaded compared to loaded tendons. However, by 4 weeks no differences remained. SAXS and histology revealed heterogeneous tissue maturation with more mature tissue at the peripheral region compared to the center of the callus. Thus, mechanical loading advances Achilles tendon biomechanical and collagen properties earlier compared to unloaded tendons, and the spatial variation in tissue maturation and collagen organization across the callus suggests important regional (mechano-) biological activities that require more investigation.

Antibacterial Action of Nanoparticles by Lethal Stretching of Bacterial Cell Membranes

It is commonly accepted that nanoparticles (NPs) can kill bacteria; however, the mechanism of antimicrobial action remains obscure for large NPs that cannot translocate the bacterial cell wall. It is demonstrated that the increase in membrane tension caused by the adsorption of NPs is responsible for mechanical deformation, leading to cell rupture and death. A biophysical model of the NP-membrane interactions is presented which suggests that adsorbed NPs cause membrane stretching and squeezing. This general phenomenon is demonstrated experimentally using both model membranes and Pseudomonas aeruginosa and Staphylococcus aureus, representing Gram-positive and Gram-negative bacteria. Hydrophilic and hydrophobic quasi-spherical and star-shaped gold (Au)NPs are synthesized to explore the antibacterial mechanism of non-translocating AuNPs. Direct observation of nanoparticle-induced membrane tension and squeezing is demonstrated using a custom-designed microfluidic device, which relieves contraction of the model membrane surface area and eventual lipid bilayer collapse. Quasi-spherical nanoparticles exhibit a greater bactericidal action due to a higher interactive affinity, resulting in greater membrane stretching and rupturing, corroborating the theoretical model. Electron microscopy techniques are used to characterize the NP-bacterial-membrane interactions. This combination of experimental and theoretical results confirm the proposed mechanism of membrane-tension-induced (mechanical) killing of bacterial cells by non-translocating NPs.

How Osmoviscoelastic Coupling Affects Recovery of Cyclically Compressed Intervertebral Disc

STUDY DESIGN

Osmoviscoelastic behavior of cyclically loaded cervical intervertebral disc.

OBJECTIVE

The aim of this study was to evaluate in vitro the effects of physiologic compressive cyclic loading on the viscoelastic properties of cervical intervertebral disc and, examine how the osmoviscoelastic coupling affects time-dependent recovery of these properties following a long period of unloading.

SUMMARY OF BACKGROUND DATA

The human neck supports repetitive loadings during daily activities and recovery of disc mechanics is essential for normal mechanical function. However, the response of cervical intervertebral disc to cyclic loading is still not very well defined. Moreover, how loading history conditions could affect the time-dependent recovery is still unclear.

METHODS

Ten thousand cycles of compressive loading, with different magnitudes and saline concentrations of the surrounding fluid bath, are applied to 8 motion segments (composed by 2 adjacent vertebrae and the intervening disc) extracted from the cervical spines of mature sheep. Subsequently, specimens are hydrated during 18 hours of unloading. The viscoelastic disc responses, after cyclic loading and recovery phase, are characterized by relaxation tests.

RESULTS

Viscoelastic behaviors are significantly altered following large number of cyclic loads. Moreover, after 18-hour recovery period in saline solution at reference concentration (0.15 mol/L), relaxation behaviors were fully restored. Nonetheless, full recovery is not obtained whether the concentration of the surrounding fluid, that is, hypo-, iso-, or hyper-osmotic conditions.

CONCLUSION

Cyclic loading effects and full recovery of viscoelastic behavior after hydration at iso-osmotic condition (0.15 mol/L) are governed by osmotic attraction of fluid content in the disc due to imbalance between the external load and the swelling pressure of the disc. After removal of the load, the disc recovers its viscoelastic properties following period of rest. Nevertheless, the viscoelastic recovery is a chemically activated process and its dependency on saline concentration is governed by fluid flow due to imbalance of ions between the disc tissues and the surrounding fluid.

LEVEL OF EVIDENCE

3.

Success Criteria and Preclinical Testing of Multifunctional Hydrogels for Tendon Regeneration

Tendon injuries are difficult to heal, in part, because intrinsic tendon healing, which is dominated by scar tissue formation, does not effectively regenerate the native structure and function of healthy tendon. Further, many current treatment strategies also fall short of producing regenerated tendon with the native properties of healthy tendon. There is increasing interest in the use of cell-instructive strategies to limit the intrinsic fibrotic response following injury and improve the regenerative capacity of tendon in vivo. We have established multifunctional, cell-instructive hydrogels for treating injured tendon that afford tunable control over the biomechanical, biochemical, and structural properties of the cell microenvironment. Specifically, we incorporated integrin-binding domains (RGDS) and assembled multifunctional collagen mimetic peptides that enable cell adhesion and elongation of stem cells within synthetic hydrogels of designed biomechanical properties and evaluated these materials using targeted success criteria developed for testing in mechanically demanding environments such as tendon healing. The in vitro and in situ success criteria were determined based on systematic reviews of the most commonly reported outcome measures of hydrogels for tendon repair and established standards for testing of biomaterials. We then showed, using validation experiments, that multifunctional and synthetic hydrogels meet these criteria. Specifically, these hydrogels have mechanical properties comparable to developing tendon; are noncytotoxic both in two-dimensional bolus exposure (hydrogel components) and three-dimensional encapsulation (full hydrogel); are formed, retained, and visualized within tendon defects over time (2-weeks); and provide mechanical support to tendon defects at the time of in situ gel crosslinking. Ultimately, the in vitro and in situ success criteria evaluated in this study were designed for preclinical research to rigorously test the potential to achieve successful tendon repair before in vivo testing and indicate the promise of multifunctional and synthetic hydrogels for continued translation. Impact statement Tendon healing results in a weak scar that forms due to poor cell-mediated repair of the injured tissue. Treatments that tailor the instructions experienced by cells during healing afford opportunities to regenerate the healthy tendon. Engineered cell-instructive cues, including the biomechanical, biochemical, and structural properties of the cell microenvironment, within multifunctional synthetic hydrogels are promising therapeutic strategies for tissue regeneration. In this article, the preclinical efficacy of multifunctional synthetic hydrogels for tendon repair is tested against rigorous in vitro and in situ success criteria. This study indicates the promise for continued preclinical translation of synthetic hydrogels for tissue regeneration.

Effect of silver diamine fluoride and proanthocyanidin on resistance of carious dentin to acid challenges

The aim of this study was to evaluate the effect of silver diamine fluoride and grape seed extract on the microstructure and mechanical properties of carious dentin following exposure to acidic challenge. Ninety-eight molars with occlusal caries were used. In the control group the specimens were kept in distilled water. In the GSE group, the specimens were immersed in 6.5% grape seed extract solution for 30 minutes. In the SDF group, the specimens were immersed in 30% SDF solution for 4 minutes. In the GSE+SDF group, the specimens were immersed in 6.5% grape seed extract solution for 30 minutes and then exposed to 30% SDF solution for 4 minutes. All the groups underwent pH cycling model for 8 days. Microhardness measurements were taken at the baseline before surface treatments and after pH cycling. Elastic modulus was measured, after pH cycling. In the control group, the final hardness was significantly lower than the initial hardness (P = 0.001). In the SDF group, the final hardness was significantly higher than the initial hardness (P < 0.001). There was no significant difference between the initial and final hardness values in the GSE and GSE + SDF groups (p = 0.92, p = 0.07). The H₁-H₀ in the SDF group was significantly higher than the other groups (P<0.05). Moreover, elastic modulus of the experimental groups except GSE+SDF group was significantly higher than control. The highest mean elastic modulus was detected in the SDF group (P<0.001). The use of SDF and GSE prior to the acid challenge improved mechanical properties. Microstructural investigation, using scanning electron microscope showed dentin structure protection against acid challenges with SDF treatment and collagen matrix stabilization with GSE treatment. However combined use of these agents was not beneficious.

Oral administration of bovine lactoferrin accelerates the healing of fracture in ovariectomized rats

INTRODUCTION

Lactoferrin has recently been reported for its potent bone growth effects. However, the effects of lactoferrin on the healing process of fragility fracture have not yet been studied, so the purpose of this study is to investigate whether oral administration of lactoferrin can promote the fracture healing in an OVX animal model.

MATERIALS AND METHODS

Three months after bilateral ovariectomy, all rats underwent unilateral tibial osteotomy and were then randomly divided into control group and bovine lactoferrin (bLF) group. At 4 and 8 weeks post-fracture, animals were sacrificed, and the fractured tibiae and serum samples were collected for evaluation.

RESULTS

Our results showed that bLF treatment not only accelerated the bone growth at an early stage of OPF healing but also shortened the remolding process of OPF healing. When compared to control group, bLF treatment induced a significant rise in callus BMD (by 35.0% at 4 weeks and by 39.7% at 8 weeks; both p < 0.05) consistent with enhanced biomechanical strength of the callus, with ultimate force increased by 3.39-fold at 4 weeks (p < 0.05) and 1.95-fold at 8 weeks (p < 0.05). Besides, bLF administration resulted in a substantial increase in serum levels of BALP and a significant decrease in serum levels of TRAP 5b and TNF-α. Moreover, both the RANKL/OPG mRNA ratio and the expression of TNF-α in the callus of bLF-treated group were markedly lower than those in the control group.

CONCLUSIONS

At a dose of 85mg/kg/day orally administrated bLF potently promoted the bone healing following tibial fracture in OVX rats.

Rotary-jet spun polycaprolactone/nano-hydroxyapatite scaffolds modified by simulated body fluid influenced the flexural mode of the neoformed bone

Polycaprolactone (PCL) is a biocompatible, biodegradable synthetic polymer which in combination with nanohydroxyapatite (nHAp) can give rise to a low cost, nontoxic bioactive product with excellent mechanical properties and slow degradation. Here we produced, characterized and evaluated in vivo the bone formation of PCL/nHAp scaffolds produced by the rotary jet spinning technique. The scaffolds produced were firstly soaked into simulated body fluid for 21 days to also obtain nHAp onto PCL/nHAp scaffolds. Afterwards, the scaffolds were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy and Raman spectroscopy. For in vivo experiments, 20 male Wistar rats were used and randomly divided in 4 experimental groups (n = 5). A critical defect of 3 mm in diameter was made in the tibia of the animals, which were filled with G1 control (clot); G2-PCL scaffold; G3-PCL/nHAp (5%) scaffold; G4-PCL/nHAp (20%) scaffold. All animals were euthanized 60 days after surgery, and the bone repair in the right tibiae were evaluated by radiographic analysis, histological analysis and histomorphometric analysis. While in the left tibias, the areas of bone repair were submitted to the flexural strength test. Radiographic and histomorphometric analyses no showed statistical difference in new bone formation between the groups, but in the three-point flexural tests, the PCL/nHAp (20%) scaffold positively influenced the flexural mode of the neoformed bone. These findings indicate that PCL/nHAp (20%) scaffold improve biomechanical properties of neoformed bone and could be used for bone medicine regenerative.

Model lipid systems and their use to evaluate the phase state of biomembranes, their mechanical properties and the effect of non-conventional antibiotics: the case of daptomycin

The lipid bilayer is the basis of the structure and function of the cell membrane. The study of the molecular phenomena that affect biological membranes has a great impact on the understanding of cellular physiology. To understand these phenomena, it has become increasingly necessary to develop simple synthetic models that allow the most basic details of such processes to be reproduced. In this short communication, we took advantage of the properties of two well-established lipid model systems, GUVs and SLBs, with compositions mimicking the cell membrane present in mammals and bacteria, to study the thermotropic phase behavior of lipids as well as the effect of daptomycin, a cyclic lipopeptide used as an antibiotic. The study of mechanical and thermodynamical properties of these model systems could contribute to establish a theoretical framework to develop more efficient strategies for biological control.

Effects of utterance rate and length on the spatiotemporal index in Parkinson's disease

Purpose: To characterise labial articulatory pattern variability using the spatiotemporal index (STI) in speakers with idiopathic Parkinson's disease (PD) across different speaking rates and syllable-sentence conditions compared to age- and sex-matched healthy controls.Method: Ten speakers with mild-severe idiopathic PD and 10 controls produced "pa" and the Rainbow Passage at slow, typical and fast speech rates. Upper lip and lower lip kinematics were digitised during a motion capture system. Data were analysed using linear mixed modelling.Result: Regardless of the participant group, a high STI value was observed in the fast speech rate for the "pa" syllable condition, particularly for movements of the lower lip. As utterance rate increased, the control group showed the highest variability, followed by PD OFF and PD ON conditions. Syllable "pa" showed a greater STI value compared to both the first and second utterance of Rainbow Passage.Conclusion: PD manifests sufficient residual capacity to achieve near-normal motor compensation to preserve the consistency of lower lip movements during speech production. The lack of a significant difference in lip STI values between ON-OFF medication states suggests that dopaminergic treatment does not influence stability of speech for individuals with mild-moderate stage PD.

TGF-β3 Loaded Electrospun Polycaprolacton Fibre Scaffolds for Rotator Cuff Tear Repair: An in Vivo Study in Rats

Biological factors such as TGF-β3 are possible supporters of the healing process in chronic rotator cuff tears. In the present study, electrospun chitosan coated polycaprolacton (CS-g-PCL) fibre scaffolds were loaded with TGF-β3 and their effect on tendon healing was compared biomechanically and histologically to unloaded fibre scaffolds in a chronic tendon defect rat model. The biomechanical analysis revealed that tendon-bone constructs with unloaded scaffolds had significantly lower values for maximum force compared to native tendons. Tendon-bone constructs with TGF-β3-loaded fibre scaffolds showed only slightly lower values. In histological evaluation minor differences could be observed. Both groups showed advanced fibre scaffold degradation driven partly by foreign body giant cell accumulation and high cellular numbers in the reconstructed area. Normal levels of neutrophils indicate that present mast cells mediated rather phagocytosis than inflammation. Fibrosis as sign of foreign body encapsulation and scar formation was only minorly present. In conclusion, TGF-β3-loading of electrospun PCL fibre scaffolds resulted in more robust constructs without causing significant advantages on a cellular level. A deeper investigation with special focus on macrophages and foreign body giant cells interactions is one of the major foci in further investigations.

Elucidating the Role of K+ Channels during In Vitro Capacitation of Boar Spermatozoa: Do SLO1 Channels Play a Crucial Role?

This study sought to identify and localize SLO1 channels in boar spermatozoa by immunoblotting and immunofluorescence, and to determine their physiological role during in vitro sperm capacitation. Sperm samples from 14 boars were incubated in a capacitation medium for 300 min in the presence of paxilline (PAX), a specific SLO1-channel blocker, added either at 0 min or after 240 min of incubation. Negative controls were incubated in capacitation medium, and positive controls in capacitation medium plus tetraethyl ammonium (TEA), a general K+-channel blocker, also added at 0 min or after 240 min of incubation. In all samples, acrosome exocytosis was triggered with progesterone after 240 min of incubation. Sperm motility and kinematics, integrity of plasma and acrosome membranes, membrane lipid disorder, intracellular calcium levels and acrosin activity were evaluated after 0, 60, 120, 180, 240, 250, 270 and 300 min of incubation. In boar spermatozoa, SLO1 channels were found to have 80 kDa and be localized in the anterior postacrosomal region and the mid and principal piece of the tail; their specific blockage through PAX resulted in altered calcium levels and acrosome exocytosis. As expected, TEA blocker impaired in vitro sperm capacitation, by altering sperm motility and kinematics and calcium levels. In conclusion, SLO1 channels are crucial for the acrosome exocytosis induced by progesterone in in vitro capacitated boar spermatozoa.

Substrate Strain Mitigates Effects of β-Aminopropionitrile-Induced Reduction in Enzymatic Crosslinking

Enzymatic crosslinks stabilize type I collagen and are catalyzed by lysyl oxidase (LOX), a step interrupted through β-aminopropionitrile (BAPN) exposure. This study evaluated dose-dependent effects of BAPN on osteoblast gene expression of type I collagen, LOX, and genes associated with crosslink formation. The second objective was to characterize collagen produced in vitro after exposure to BAPN, and to explore changes to collagen properties under continuous cyclical substrate strain. To evaluate dose-dependent effects, osteoblasts were exposed to a range of BAPN dosages (0-10 mM) for gene expression analysis and cell proliferation. Results showed significant upregulation of BMP-1, POST, and COL1A1 and change in cell proliferation. Results also showed that while the gene encoding LOX was unaffected by BAPN treatment, other genes related to LOX activation and matrix production were upregulated. For the loading study, the combined effects of BAPN and mechanical loading were assessed. Gene expression was quantified, atomic force microscopy was used to extract elastic properties of the collagen matrix, and Fourier Transform infrared spectroscopy was used to assess collagen secondary structure for enzymatic crosslinking analysis. BAPN upregulated BMP-1 in static samples and BAPN combined with mechanical loading downregulated LOX when compared to control-static samples. Results showed a higher indentation modulus in BAPN-loaded samples compared to control-loaded samples. Loading increased the mature-to-immature crosslink ratios in control samples, and BAPN increased the height ratio in static samples. In summary, effects of BAPN (upregulation of genes involved in crosslinking, mature/immature crosslinking ratios, upward trend in collagen elasticity) were mitigated by mechanical loading.

The effect of gabapentin and pregabalin on bone turnover and bone strength: A prospective study in Wistar rats

BACKGROUND

There are limited data on the effects of GBP on bone and no data for PGB. Some data suggest that there is a significant influence of sex hormone balance on the susceptibility of bone to antiepileptic drug-induced bone loss.

METHODS

Forty-eight male Wistar rats were divided into six groups that were subjected to two surgeries, sham (noORX) or real orchidectomy (ORX), and were fed three diets, a SLD, a SLD enriched with GBP or a SLD enriched with PGB. Dual energy X-ray absorptiometry was used to measure the bone mineral density. The concentrations of bone turnover markers were assayed. The femurs were biomechanically tested.

RESULTS

Significant reductions in bone mineral density, weight and biomechanical strength were observed in ORX animals. GBP or PGB exposure did not cause significant alterations in bone mineral density or biomechanical strength. No changes in bone turnover markers were observed, except for RANKL. A significant increase was found in the ORX GBP and ORX PGB groups. Within the orchidectomized animal group, RANKL levels were significantly higher in the ORX PGB group than in the ORX GBP group.

CONCLUSIONS

Because neither GBP nor PGB affected bone mineral density or mechanical bone strength, both of these antiepileptic drugs could be considered drugs with lower risks to bone health. A shift in RANKL levels indicates that the effects of GBP and PGB on osteoclast activity may be dependent on the hormonal status of animals.

Prostaglandin D2 signaling is not involved in the recovery of rat hind limb tendons from injury

Injured tendons heal through the formation of a fibrovascular scar that has inferior mechanical properties compared to native tendon tissue. Reducing inflammation that occurs as a result of the injury could limit scar formation and improve functional recovery of tendons. Prostaglandin D2 (PGD2 ) plays an important role in promoting inflammation in some injury responses and chronic disease processes, and the inhibition of PGD2 has improved healing and reduced disease burden in animal models and early clinical trials. Based on these findings, we sought to determine the role of PGD2 signaling in the healing of injured tendon tissue. We tested the hypothesis that a potent and specific inhibitor of hematopoietic PGD synthase (HPGDS), GSK2894631A, would improve the recovery of tendons of adult male rats following an acute tenotomy and repair. To test this hypothesis, we performed a full-thickness plantaris tendon tenotomy followed by immediate repair and treated rats twice daily with either 0, 2, or 6 mg/kg of GSK2894631A. Tendons were collected either 7 or 21 days after surgical repair, and mechanical properties of tendons were assessed along with RNA sequencing and histology. While there were some differences in gene expression across groups, the targeted inhibition of HPGDS did not impact the functional repair of tendons after injury, as HPGDS expression was surprisingly low in injured tendons. These results indicate that PGD2 signaling does not appear to be important in modulating the repair of injured tendon tissue.

Zoledronate and Raloxifene combination therapy enhances material and mechanical properties of diseased mouse bone

Current interventions to reduce skeletal fragility are insufficient at enhancing both the quantity and quality of bone when attempting to improve overall mechanical integrity. Bisphosphonates, such as Zoledronate (ZOL), are used to treat a variety of bone disorders by increasing bone mass to decrease fracture risk, but long-term use has been shown in some settings to compromise bone quality. Alternatively, Raloxifene (RAL) has recently been demonstrated to improve tissue quality and overall mechanical properties in a cell-independent manner by binding to collagen and increasing tissue hydration. We hypothesized that a combination of RAL and ZOL would improve mechanical and material properties of bone more than either monotherapy alone by enhancing both quantity and quality. In this study, wildtype (WT) and heterozygous (OIM+/-) male mice from the Osteogenesis Imperfecta (OI) murine model were treated with either RAL, ZOL, or both from 8 weeks to 16 weeks of age. Using the OIM model allows for investigation of therapeutic effects on a quality-based bone disease. Combination treatment resulted in higher trabecular architecture, cortical mechanical properties, and cortical fracture toughness in diseased mouse bone. Two fracture toughness properties, which are direct measures of the tissue's ability to resist the initiation and propagation of a crack, were significantly improved with combination treatment in OIM+/- compared to control. There was no significant effect on fracture toughness with either monotherapy alone in either genotype. Following the mass-based effects of ZOL, trabecular bone volume fraction was significantly higher with combination treatment in both genotypes. Combination treatment resulted in higher ultimate stress in both genotypes. RAL and combination treatment in OIM+/- also increased resilience compared to the control. In conclusion, this study demonstrates the beneficial effects of using combination drug treatments to increase bone mass while simultaneously improving tissue quality, especially to enhance the mechanical integrity of diseased bone. Combination therapies could be a potential method to improve bone health and combat skeletal fragility on both the microscopic and macroscopic levels.

High dose vitamin D supplementation does not rescue bone loss following Roux-en-Y gastric bypass in female rats

Postoperative bone loss and increased fracture risk associated with Roux-en-Y gastric bypass (RYGB) have been attributed to vitamin D/calcium malabsorption and resultant secondary hyperparathyroidism (HPT). Adequate vitamin D supplementation (VDS), particularly in an older female population, reduces incidence of secondary HPT but the effect on bone loss and fracture risk remains unclear. To investigate whether VDS corrects the RYGB bone phenotype, 41 obese adult female rats were randomized to RYGB with 1000 IU (R1000) or 5000 IU (R5000) vitamin D/kg food or a sham surgical procedure with either paired (PF) or ad libitum (AL) feeding. Bone turnover markers, urinary calcium/creatinine ratio (CCR), and serum calciotropic and gut hormones were assessed throughout a 14-week postoperative period. Femurs were analyzed by micro-computed tomography (μCT), three-point bending test, and histomorphometry. 1000 IU animals had low 25‑hydroxyvitamin D (25(OH)D), high serum parathyroid hormone (PTH), and very low urine CCR levels. 5000 IU corrected the 25(OH)D and secondary HPT but did not increase urine CCR or serum levels of 1,25‑dihydroxyvitamin D (1,25(OH)D) significantly between RYGB groups. Compared to sham animals at 14 weeks, RYGB animals had significantly higher serum osteocalcin (OCN) and C-terminal telopeptide (CTX) levels. The gut hormone peptide tyrosine tyrosine hormone (PYY) was higher in the RYGB groups, and leptin was lower. μCT and biomechanical testing revealed RYGB females had decreased cortical and trabecular bone volume and weaker, stiffer bone than controls. Histomorphometry showed decreased bone volume and increased osteoid volume with increased mineral apposition rate in RYGB compared to controls. No differences in bone phenotype were identified between 1000 IU and 5000 IU groups, and osteoclast numbers were comparable across all four groups. Thus, in our model, 5000 IU VDS corrected vitamin D deficiency and secondary HPT but did not rescue RYGB mineralization rate nor the osteomalacia phenotype. Longer studies in this model are required to evaluate durability of these detrimental effects. Our findings not only underscore the importance of lifelong repletion of both calcium and vitamin D but also suggest that additional factors affect skeletal health in this population.

Glucocorticoid aggravates bone micro-architecture deterioration and skeletal muscle atrophy in mice fed on high-fat diet

High fat diet (HFD) induced obesity has deleterious effect on bone micro-architecture and is associated with low-grade chronic inflammation. Exogenous glucocorticoids (GC) are used to treat inflammatory conditions but with concomitant adverse effect on musculoskeletal system. This study aims to highlight the effect of exogenous GCs on musculoskeletal system in mice fed on HFD. Adult BALB/c mice were fed either normal chow or high fat diet and were exogenously administered with GC for 10 weeks. At the end of the study, animals were autopsied and bone, muscle, serum samples were collected for micro-CT, gene expression and histological study. HFD induced obesity resulted in deterioration in bone micro-architecture predominant in trabecular region of long bones and was significantly amplified with GC administration. Approximately, 37% and 25% loss in femoral and tibial bone volume was observed in obese animals with exogenous GC. Further, deteriorating bone pathology was apparent from reduced bone mineral density (BMD) and bone strength parameter which was correlated to alteration in osteoblast and adipocytes pool of cells in bone marrow. Transcriptional analysis of osteoblast marker genes, bone morphogenetic protein 2 (BMP-2), osteocalcin (OCN) exhibited decreased formation. Moreover, similar degeneration was observed in skeletal muscle physiology with stimulation in muscle atrophy genes atrogin-1, muscle ring finger motif-1 (MuRF-1) and inflammatory markers accompanied with intra-myocellular lipid accumulation. Thus, our results showed that detrimental effect of GC on bone and skeletal muscle is aggravated with HFD, attributed to alteration in bone marrow cell population and skeletal muscle atrophy.

Multi-laminate annulus fibrosus repair scaffold with an interlamellar matrix enhances impact resistance, prevents herniation and assists in restoring spinal kinematics

Focal defects in the annulus fibrosus (AF) of the intervertebral disc (IVD) arising from herniation have detrimental impacts on the IVD's mechanical function. Thus, biomimetic-based repair strategies must restore the mechanical integrity of the AF to help support and restore native spinal loading and motion. Accordingly, an annulus fibrosus repair patch (AFRP); a collagen-based multi-laminate scaffold with an angle-ply architecture has been previously developed, which demonstrates similar mechanical properties to native outer AF (oAF). To further enhance the mimetic nature of the AFRP, interlamellar (ILM) glycosaminoglycan (GAG) was incorporated into the scaffolds. The ability of the scaffolds to withstand simulated impact loading and resist herniation of native IVD tissue while contributing to the restoration of spinal kinematics were assessed separately. The results demonstrate that incorporation of a GAG-based ILM significantly increased (p < 0.001) the impact strength of the AFRP (2.57 ± 0.04 MPa) compared to scaffolds without (1.51 ± 0.13 MPa). Additionally, repair of injured functional spinal units (FSUs) with an AFRP in combination with sequestering native NP tissue and a full-thickness AF tissue plug enabled the restoration of creep displacement (p = 0.134), short-term viscous damping coefficient (p = 0.538), the long-term viscous (p = 0.058) and elastic (p = 0.751) damping coefficients, axial neutral zone (p = 0.908), and axial range of motion (p = 0.476) to an intact state. Lastly, the AFRP scaffolds were able to prevent native IVD tissue herniation upon application of supraphysiologic loads (5.28 ± 1.24 MPa). Together, these results suggest that the AFRP has the strength to sequester native NP and AF tissue and/or implants, and thus, can be used in a composite repair strategy for IVDs with focal annular defects thereby assisting in the restoration of spinal kinematics.

Abaloparatide improves cortical geometry and trabecular microarchitecture and increases vertebral and femoral neck strength in a rat model of male osteoporosis

Androgen deficiency is a leading cause of male osteoporosis, with bone loss driven by an inadequate level of bone formation relative to the extent of bone resorption. Abaloparatide, an osteoanabolic PTH receptor agonist used to treat women with postmenopausal osteoporosis at high risk for fracture, increases bone formation and bone strength in estrogen-deficient animals without increasing bone resorption. This study examined the effects of abaloparatide on bone formation, bone mass, and bone strength in androgen-deficient orchiectomized (ORX) rats, a male osteoporosis model. Four-month-old Sprague-Dawley rats underwent ORX or sham surgery. Eight weeks later, sham-operated rats received vehicle (saline; n = 10) while ORX rats (n = 10/group) received vehicle (Veh) or abaloparatide at 5 or 25 μg/kg (ABL5 or ABL25) by daily s.c. injection for 8 weeks, followed by sacrifice. Dynamic bone histomorphometry indicated that the tibial diaphysis of one or both abaloparatide groups had higher periosteal mineralizing surface, intracortical bone formation rate (BFR), endocortical BFR, and cortical thickness vs Veh controls. Vertebral trabecular BFR was also higher in both abaloparatide groups vs Veh, and the ABL25 group had higher trabecular osteoblast surface without increased osteoclast surface. By micro-CT, the vertebra and distal femur of both abaloparatide-groups had improved trabecular bone volume and micro-architecture, and the femur diaphysis of the ABL25 group had greater cortical thickness with no increase in porosity vs Veh. Biomechanical testing indicated that both abaloparatide-groups had stronger vertebrae and femoral necks vs Veh controls. These findings provide preclinical support for evaluating abaloparatide as an investigational treatment for male osteoporosis.

Quasi-3D morphology and modulation of focal adhesions of human adult stem cells through combinatorial concave elastomeric surfaces with varied stiffness

In vivo cell niches are complex architectures that provide a wide range of biochemical and mechanical stimuli to control cell behavior and fate. With the aim to provide in vitro microenvironments mimicking physiological niches, microstructured substrates have been exploited to support cell adhesion and to control cell shape as well as three dimensional morphology. At variance with previous methods, we propose a simple and rapid protein subtractive soft lithographic method to obtain microstructured polydimethylsiloxane substrates for studying stem cell adhesion and growth. The shape of adult renal stem cells and nuclei is found to depend predominantly on micropatterning of elastomeric surfaces and only weakly on the substrate mechanical properties. Differently, focal adhesions in their shape and density but not in their alignment mainly depend on the elastomer stiffness almost regardless of microscale topography. Local surface topography with concave microgeometry enhancing adhesion drives stem cells in a quasi-three dimensional configuration where stiffness might significantly steer mechanosensing as highlighted by focal adhesion properties.

Low-diluted Phenacetinum disrupted the melanoma cancer cell migration

Dynamic and reciprocal interactions generated by the communication between tumor cells and their matrix microenvironment, play a major role in the progression of a tumor. Indeed, the adhesion of specific sites to matrix components, associated with the repeated and coordinated formation of membrane protrusions, allow tumor cells to move along a determined pathway. Our study analyzed the mechanism of action of low-diluted Phenacetinum on murine cutaneous melanoma process in a fibronectin matrix environment. We demonstrated a reduction of dispersed cell migration, early and for as long as 24 h, by altering the formation of cell protrusions. Moreover, low-diluted Phenacetinum decreased cell stiffness highly on peripheral areas, due to a disruption of actin filaments located just under the plasma membrane. Finally, it modified the structure of the plasma membrane by accumulating large ordered lipid domains and disrupted B16 cell migration by a likely shift in the balance between ordered and disordered lipid phases. Whereas the correlation between the excess of lipid raft and cytoskeleton disrupting is not as yet established, it is clear that low-diluted Phenacetinum acts on the actin cytoskeleton organization, as confirmed by a decrease of cell stiffness affecting ultimately the establishment of an effective migration process.

Effect of cyclic deformation on xenogeneic heart valve biomaterials

Glutaraldehyde-fixed bovine pericardium is currently the most popular biomaterial utilized in the creation of bioprosthetic heart valves. However, recent studies indicate that glutaraldehyde fixation results in calcification and structural valve deterioration, limiting the longevity of bioprosthetic heart valves. Additionally, glutaraldehyde fixation renders the tissue incompatible with constructive recipient cellular repopulation, remodeling and growth. Use of unfixed xenogeneic biomaterials devoid of antigenic burden has potential to overcome the limitations of current glutaraldehyde-fixed biomaterials. Heart valves undergo billion cycles of opening and closing throughout the patient’s lifetime. Therefore, understanding the response of unfixed tissues to cyclic loading is crucial to these in a heart valve leaflet configuration. In this manuscript we quantify the effect of cyclic deformation on cycle dependent strain, structural, compositional and mechanical properties of fixed and unfixed tissues. Glutaraldehyde-fixed bovine pericardium underwent marked cyclic dependent strain, resulting from significant changes in structure, composition and mechanical function of the material. Conversely, unfixed bovine pericardium underwent minimal strain and maintained its structure, composition and mechanical integrity. This manuscript demonstrates that unfixed bovine pericardium can withstand cyclic deformations equivalent to 6 months of in vivo heart valve leaflet performance.

Mechanoregulation of Cancer-Associated Fibroblast Phenotype in Three-Dimensional Interpenetrating Hydrogel Networks

Tumor stromal residing cancer-associated fibroblasts (CAFs) are significant accomplices in the growth and development of malignant neoplasms. As cancer progresses, the stroma undergoes a dramatic remodeling and stiffening of its extracellular matrix (ECM). However, exactly how these biomechanical changes influence the CAF behavior and the functional paracrine crosstalk with the neighboring tumor cells in a 3-dimensional (3D) microenvironment remains elusive. Herein, a collagen and alginate interpenetrating network (CoAl-IPN) hydrogel system was employed as a 3D in vitro surrogate of the cancerous breast tissue stromal niche. In this study, the mechanical properties of CoAl-IPN were precisely fine-tuned with Young's modulus ( E) values of ∼108 and 898 Pa. The results revealed that the 3D polymeric network mechanics and microstructure are critical biophysical determinants of the human breast CAF (b-CAF) morphology, phenotype, and paracrine dialogue with MDA-MB-231 tumoroids. A compliant hydrogel network favors b-CAF spreading, nuclear translocation of the YAP/TAZ mechanosignaling protein, and upregulation of CAF hallmark transcripts. Conversely, a rigid and highly cross-linked hydrogel network imposed a physical entrapment effect on the b-CAFs that limited their spreading and phenotype in a manner that effectively muted their pro-tumorigenic paracrine activity. Collectively, the CoAl-IPN 3D culture system has proven to be a versatile platform in defining the 3D biophysical parameters that could either promote or restrain the protumorigenic activity of b-CAFs and sheds critical mechano-mediated light onto the phenotypic plasticity and corresponding specific bioactivity of b-CAFs in the 3D microenvironment.

Photoactivatable Hydrogel Interfaces for Resolving the Interplay of Chemical, Mechanical, and Geometrical Regulation of Collective Cell Migration

Collective migration is the mechanobiological interplay within migrating cell clusters and against extracellular matrixes (ECMs) underneath, mediating various physiological and pathological processes. Therefore, it is crucial to develop a robust platform on which collective migration can be studied under standardized conditions to understand how cells migrate differently between normal and disease states. We herein demonstrated phtotoactivatable hydrogel interfaces as suitable candidates for such applications. The substrate was composed of a poly(acrylamide) (PAAm) hydrogel whose surface was sequentially functionalized with poly-d-lysine (PDL) and photocleavable poly(ethylene glycol) (PEG). On the surface of the gel substrates, cell clusters with any given geometries can be prepared by controlling the irradiation patterns (geometrical cue), and their collective migration can be induced by the subsequent irradiation of the surrounding regions. Moreover, the substrate mechanical properties can be controlled by changing the composition of the PAAm hydrogel (mechanical cue), and the chemical properties were controlled by changing the amount of immobilized PDL, thereby altering the adsorbed amount of ECM proteins (chemical cue). The photoactivatable gel substrates were characterized by fluorescence microscopy, ζ-potential measurements, and the protein adsorption test. Through the study of the interplay of chemical, mechanical, and geometrical cues in the regulation of collective characteristics, we found additive effects of chemical and mechanical cues on the suppression of circular expansion by up-regulating the epithelial morphology. Also, the impact of geometrical cues became more significant by decreasing the chemical cue. We believe the present platform will be a useful research tool for the comprehensive mechanobiological analysis of collective cell migration.

Impact of vitamin C on teriparatide treatment in the improvement of bone mineral density, strength, and quality in vitamin C-deficient rats

Age-related decreases in serum levels of vitamin C (VC) may negatively affect the efficacy of anti-osteoporotic pharmacotherapy. The purpose of this study was to evaluate the effects of VC and teriparatide (TPTD) on bone mineral density (BMD), strength, and quality in VC-deficient osteogenic disorder Shionogi (ODS) rats. Six-month-old female ODS rats were divided into an untreated ODS control group, a VC group, a TPTD group, and a VC + TPTD group, based on the administration of VC and TPTD (n = 10 each). VC was given as 2.0 mg/ml supplemented water. TPTD was administered subcutaneously once a week at 30 µg/kg body weight. After 12 weeks of treatment, BMDs of the femur and lumbar spine, bone strengths of the femoral diaphysis and metaphysis, and cancellous bone quality of proximal tibiae as estimated by Fourier transform infrared spectroscopy (FTIR) were compared between groups. Compared to the ODS control group, the VC group showed significantly higher total femoral BMD, but the TPTD group showed significantly higher femoral and lumbar spinal BMD, maximum load of femoral metaphysis, and hydroxyapatite (HA) crystallinity by FTIR (p < 0.05). In addition to the increases shown in the TPTD group, the VC + TPTD group also showed significantly higher stiffness of the femoral diaphysis and breaking energy of the femoral metaphysis compared to the ODS control group (p < 0.05). These results indicated that TPTD alone increased cancellous/cortical BMD and cancellous bone strength with improvement of HA crystallinity in ODS rats, but addition of VC supplementation further improved cortical bone strength.

Traction microscopy with integrated microfluidics: responses of the multi-cellular island to gradients of HGF

Collective cellular migration plays a central role in development, regeneration, and metastasis. In these processes, mechanical interactions between cells are fundamental but measurement of these interactions is often hampered by technical limitations. To overcome some of these limitations, here we describe a system that integrates microfluidics with traction microscopy (TM). Using this system we can measure simultaneously, and in real time, migration speeds, tractions, and intercellular tension throughout an island of confluent Madin-Darby canine kidney (MDCK) cells. The cell island is exposed to hepatocyte growth factor (HGF) at a controlled gradient of concentrations; HGF is known to elicit epithelial-to-mesenchymal transition (EMT) and cell scattering. As expected, the rate of expansion of the cell island was dependent on the concentration of HGF. Higher concentrations of HGF reduced intercellular tensions, as expected during EMT. A novel finding, however, is that the effects of HGF concentration and its gradient were seen within an island. This integrated experimental system thus provides an integrated tool to better understand cellular forces during collective cellular migration under chemical gradients.

Cryopreservation of tendon tissue using dimethyl sulfoxide combines conserved cell vitality with maintained biomechanical features

Biomechanical research on tendon tissue evaluating new treatment strategies to frequently occurring clinical problems regarding tendon degeneration or trauma is of expanding scientific interest. In this context, storing tendon tissue deep-frozen is common practice to collect tissue and analyze it under equal conditions. The commonly used freezing medium, phosphate buffered saline, is known to damage cells and extracellular matrix in frozen state. Dimethyl sulfoxide, however, which is used for deep-frozen storage of cells in cell culture preserves cell vitality and reduces damage to the extracellular matrix during freezing. In our study, Achilles tendons of 26 male C57/Bl6 mice were randomized in five groups. Tendons were deep frozen in dimethyl sulfoxide or saline undergoing one or four freeze-thaw-cycles and compared to an unfrozen control group analyzing biomechanical properties, cell viability and collagenous structure. In electron microscopy, collagen fibrils of tendons frozen in saline appeared more irregular in shape, while dimethyl sulfoxide preserved the collagenous structure during freezing. In addition, treatment with dimethyl sulfoxide preserved cell viability visualized with an MTT-Assay, while tendons frozen in saline showed no remaining metabolic activity, indicating total destruction of cells during freezing. The biomechanical results revealed no differences between tendons frozen once in saline or dimethyl sulfoxide. However, tendons frozen four times in saline showed a significantly higher Young’s modulus over all strain rates compared to unfrozen tendons. In conclusion, dimethyl sulfoxide preserves the vitality of tendon resident cells and protects the collagenous superstructure during the freezing process resulting in maintained biomechanical properties of the tendon.

Sequential Treatment with Eldecalcitol After PTH Improves Bone Mechanical Properties of Lumbar Spine and Femur in Aged Ovariectomized Rats

Parathyroid hormone (PTH) analogs have a powerful anabolic effect on bone and are used in the treatment of patients with severe osteoporosis. However, there are limitations to how long they can be safely administered. Withdrawal of PTH results in the cancelation of its effects, necessitating subsequent treatment to maintain the bone quantity and quality. This study assessed the effects of Eldecalcitol (ELD), an active vitamin D3 derivative, after PTH in estrogen-deficient osteoporotic rats. Six-month-old female rats were ovariectomized, and PTH administration was started 7 weeks later. After 4 weeks of PTH treatment, the animals were divided into three groups and either continued to receive PTH (PTH-PTH), or were switched to ELD (PTH-ELD) or vehicle (PTH-Veh) for an additional 4 weeks. In the femur, increased BMD by 4 weeks treatment of PTH was significantly reduced in PTH-Veh but not in PTH-PTH and PTH-ELD. The same tendency was observed in the lumbar vertebrae. MicroCT imaging and histomorphometry analysis revealed that the favorable bone structure changes by PTH administration were also maintained in the femurs and tibias of the PTH-PTH and PTH-ELD groups. Increased bone strength by 4-week treatment of PTH in lumber also maintained in PTH-ELD. Furthermore, minimodeling was observed in the PTH-ELD group. These results demonstrate that treatment with ELD sequentially following PTH prevented the bone quantity and strength reduction that accompanies PTH withdrawal in estrogen-deficient rats.

Effect of Long-Term Green Tea Polyphenol Supplementation on Bone Architecture, Turnover, and Mechanical Properties in Middle-Aged Ovariectomized Rats

We investigated the effects of 6-month green tea polyphenols (GTP) supplementation on bone architecture, turnover, and mechanical properties in middle-aged ovariectomized (OVX) rats. Female rats were sham-operated (n = 39, 13/group) or OVX (n = 143, 13/group). Sham-control and OVX-control rats (n = 39) receiving no GTP were assigned for sample collection at baseline, 3, or 6 months. The remaining OVX rats (n = 104) were randomized to 0.15%, 0.5%, 1%, and 1.5% (g/dL) GTP for 3 or 6 months. Blood and bone samples were collected. Relative to the OVX-control group, GTP (1% and 1.5%) lowered serum procollagen type 1 N-terminal propeptide at 3 and 6 months, C-terminal telopeptides of type I collagen at 3 months, and insulin-like growth factor-I at 6 months. GTP did not affect bone mineral content and density. At 6 months, no dose of GTP positively affected trabecular bone volume based on microCT, but a higher cortical thickness and improved biomechanical properties of the femur mid-diaphysis was observed in the 1.5% GTP-treated group. At 3 and 6 months, GTP (0.5%, 1%, and 1.5%) had lower rates of trabecular bone formation and resorption than the OVX-control group, but the inhibitory effects of GTP on periosteal and endocortical bone mineralization and formation at the tibial midshaft were only evident at 3 months. GTP at higher doses suppressed bone turnover in the trabecular and cortical bone of OVX rats and resulted in improved cortical bone structural and biomechanical properties, although it was not effective in preventing the ovariectomy-induced dramatic cancellous bone loss.

Rehmanniae Radix Preparata suppresses bone loss and increases bone strength through interfering with canonical Wnt/β-catenin signaling pathway in OVX rats

Rehmanniae Radix Preparata (RRP) improves bone quality in OVX rats through the regulation of bone homeostasis via increasing osteoblastogenesis and decreasing osteoclastogenesis, suggesting it has a potential for the development of new anti-osteoporotic drugs.

INTRODUCTION

Determine the anti-osteoporotic effect of RRP in ovariectomized (OVX) rats and identify the signaling pathway involved in this process.

METHODS

OVX rats were treated with RRP aqueous extract for 14 weeks. The serum levels of tartrate-resistant acid phosphatase (TRAP), receptor activator of nuclear factor kappa-Β ligand (RANKL), alkaline phosphatase (ALP), and osteoprotegerin (OPG) were determined by ELISA. Bone histopathological alterations were evaluated by H&E, Alizarin red S, and Safranin O staining. Bone mineral density (BMD) and bone microstructure in rat femurs and lumbar bones were determined by dual-energy X-ray absorptiometry and micro-computed tomography. Femoral bone strength was detected by a three-point bending assay. The expression of Phospho-glycogen synthase kinase 3 beta (p-GSK-3β), GSK-3β, Dickkopf-related protein 1 (DKK1), cathepsin K, OPG, RANKL, IGF-1, Runx2, β-catenin, and p-β-catenin was determined by western blot and/or immunohistochemical staining.

RESULTS

Treatment of OVX rats with RRP aqueous extract rebuilt bone homeostasis demonstrated by increasing the levels of OPG as well as decreasing the levels of TRAP, RANKL, and ALP in serum. Furthermore, RRP treatment preserved BMD and mechanical strength by increasing cortical bone thickness and epiphyseal thickness as well as improving trabecular distribution in the femurs of OVX rats. In addition, RRP downregulated the expression of DKK1, sclerostin, RANKL, cathepsin K, and the ratio of p-β-catenin to β-catenin, along with upregulating the expression of IGF-1, β-catenin, and Runx2 and the ratio of p-GSK-3β to GSK-3β in the tibias and femurs of OVX rats. Echinacoside, jionoside A1/A2, acetoside, isoacetoside, jionoside B1, and jionoside B2 were identified in the RRP aqueous extract.

CONCLUSION

RRP attenuates bone loss and improves bone quality in OVX rats partly through its regulation of the canonical Wnt/β-catenin signaling pathway, suggesting that RRP has the potential to provide a new source of anti-osteoporotic drugs.

Pre-treatment with Pamidronate Improves Bone Mechanical Properties in Mdx Mice Treated with Glucocorticoids

Duchenne muscular dystrophy (DMD) is an X-linked disease of progressive muscle deterioration and weakness. Patients with DMD have poor bone health which is partly due to treatment with glucocorticoids, a standard therapy to prolong muscle function that also induces bone loss. Bisphosphonates are used to treat adults at risk of glucocorticoid-induced osteoporosis but are not currently used in DMD patients until after they sustain fractures. In this study, C57BL/10ScSn-mdx mice, a commonly used DMD animal model, received continuous glucocorticoid, prednisone treatment (0.083 mg/day) from 5 to 10 weeks of age. Pre-treatment with the bisphosphonate pamidronate started at 4 weeks of age over a period of 2 weeks or 6 weeks (cumulative dose 8 mg/kg for both) to assess the effectiveness of the two dosing regimens in ameliorating glucocorticoid-induced bone loss. Mdx mice treated with prednisone had improved muscle function that was not changed by pamidronate treatment. Glucocorticoid treatment caused cortical bone loss and decreased cortical bone strength. Both 2 and 6 week pamidronate treatment increased cortical thickness and bone area compared to prednisone-treated Mdx mice, however, only 2 week pamidronate treatment improved the strength of cortical bone compared to that of glucocorticoid-treated Mdx mice. In the trabecular bone, both pamidronate treatments significantly increased the amount of bone, and increased the ultimate load but not the energy to fail. These results highlight the importance of when and how much bisphosphonate is administered prior to glucocorticoid exposure.

On-chip refractive index cytometry for whole-cell deformability discrimination

On-chip high-throughput phenotyping of single cells has gained a lot of interest recently due to the discrimination capability of label-free biomarkers such as whole-cell deformability and refractive index. Here we present on-chip refractive index cytometry (RIC) for whole-cell deformability at a high measurement rate. We have further exploited a previously published on-chip optical characterization method which enhances cellular discrimination through the refractive index measurement of single cells. The proposed on-chip RIC can simultaneously probe the cellular refractive index, effective volume and whole-cell deformability while reaching a measurement rate up to 5000 cells per second. Additionally, the relative position of the nucleus inside the cell is reflected by the asymmetry of the measured curve. This particular finding is confirmed by our numerical simulation model and emphasized by a modified cytoskeleton HL-60 cells model. Furthermore, the proposed device discriminated HL-60 derived myeloid cells such as neutrophils, basophils and promyelocytes, which are indistinguishable using flow cytometry. To our knowledge, this is the first integrated device to simultaneously characterize the cellular refractive index and whole-cell deformability, yielding enhanced discrimination of large myeloid cell populations.

Single-dose local administration of parathyroid hormone (1-34, PTH) with β-tricalcium phosphate/collagen (β-TCP/COL) enhances bone defect healing in ovariectomized rats

Parathyroid hormone (1-34, PTH) combined β-tricalcium phosphate (β-TCP) achieves stable bone regeneration without cell transplantation in previous studies. Recently, with the development of tissue engineering slow release technology, PTH used locally to promote bone defect healing become possible. This study by virtue of collagen with a combination of drugs and has a slow release properties, and investigated bone regeneration by β-TCP/collagen (β-TCP/COL) with the single local administration of PTH. After the creation of a rodent critical-sized femoral metaphyseal bone defect, β-TCP/COL was prepared by mixing sieved granules of β-TCP and atelocollagen for medical use, then β-TCP/COL with dripped PTH solution (1.0 µg) was implanted into the defect of OVX rats until death at 4 and 8 weeks. The defected area in distal femurs of rats was harvested for evaluation by histology, micro-CT, and biomechanics. The results of our study show that single-dose local administration of PTH combined local usage of β-TCP/COL can increase the healing of defects in OVX rats. Furthermore, treatments with single-dose local administration of PTH and β-TCP/COL showed a stronger effect on accelerating the local bone formation than β-TCP/COL used alone. The results from our study demonstrate that combination of single-dose local administration of PTH and β-TCP/COL had an additive effect on local bone formation in osteoporosis rats.

3D Spatiotemporal Mechanical Microenvironment: A Hydrogel-Based Platform for Guiding Stem Cell Fate

Stem cells hold great promise for widespread biomedical applications, for which stem cell fate needs to be well tailored. Besides biochemical cues, accumulating evidence has demonstrated that spatiotemporal biophysical cues (especially mechanical cues) imposed by cell microenvironments also critically impact on the stem cell fate. As such, various biomaterials, especially hydrogels due to their tunable physicochemical properties and advanced fabrication approaches, are developed to spatiotemporally manipulate biophysical cues in vitro so as to recapitulate the 3D mechanical microenvironment where stem cells reside in vivo. Here, the main mechanical cues that stem cells experience in their native microenvironment are summarized. Then, recent advances in the design of hydrogel materials with spatiotemporally tunable mechanical properties for engineering 3D the spatiotemporal mechanical microenvironment of stem cells are highlighted. These in vitro engineered spatiotemporal mechanical microenvironments are crucial for guiding stem cell fate and their potential biomedical applications are subsequently discussed. Finally, the challenges and future perspectives are presented.

Examining the influence of PTH(1-34) on tissue strength and composition

The lacunar-canaliculi system is a network of channels that is created and maintained by osteocytes as they are embedded throughout cortical bone. As osteocytes modify their lacuna space, the local tissue composition and tissue strength are subject to change. Although continual exposure to parathyroid hormone (PTH) can induce adaptation at the lacunar wall, the impact of intermittent PTH treatment on perilacunar adaptation remains unclear. Therefore, the primary objective of this study was to establish how intermittent PTH(1-34) treatment influences perilacunar adaptation with respect to changes in tissue composition. We hypothesized that local changes in tissue composition following PTH(1-34) are associated with corresponding gains in tissue strength and resistance to microdamage at the whole bone level. Adult male C57BL/6J mice were treated daily with PTH(1-34) or vehicle for 3 weeks. In response to PTH(1-34), Raman spectroscopy revealed a significant decrease in the carbonate-to-phosphate ratio and crystallinity across the entire tissue, while the mineral-to-matrix ratio demonstrated a significant decrease in just the perilacunar region. The shift in perilacunar composition largely explained the corresponding increase in tissue strength, while the degree of new tissue added at the endosteum and periosteum did not produce any significant changes in cortical area or moment of inertia that would explain the increase in tissue strength. Furthermore, fatigue testing revealed a greater resistance to crack formation within the existing tissue following PTH(1-34) treatment. As a result, the shift in perilacunar composition presents a unique mechanism by which PTH(1-34) produces localized differences in tissue quality that allow more energy to be dissipated under loading, thereby increasing tissue strength and resistance to microdamage. In addition, our findings demonstrate the potential for PTH(1-34) to amplify osteocytes' mechanotransduction by producing a more compliant tissue. Overall, the present study demonstrates that changes in tissue composition localized at the lacuna wall contribute to the strength and fatigue resistance of cortical bone gained in response to intermittent PTH(1-34) treatment.

Siglec-15-targeting therapy increases bone mass in rats without impairing skeletal growth

The treatment of juvenile osteoporosis has not been established due to a lack of data regarding the efficacy and adverse effects of therapeutic agents. The possible adverse effects of the long-term use of antiresorptive therapies on skeletal growth in children is of particular concern. Sialic acid-binding immunoglobulin-like lectin 15 (Siglec-15) is an immunoreceptor that regulates osteoclast development and bone resorption, and its deficiency suppresses bone remodeling in the secondary spongiosa, but not in the primary spongiosa, due to a compensatory mechanism of osteoclastogenesis. This prompted us to develop an anti-Siglec-15 therapy for juvenile osteoporosis because most anti-resorptive drugs have potential adverse effects on skeletal growth. Using growing rats, we investigated the effects of an anti-Siglec-15 neutralizing antibody (Ab) on systemic bone metabolism and skeletal growth, comparing this drug to bisphosphonate, a first-line treatment for osteoporosis. Male 6-week-old F344/Jcl rats were randomized into six groups: control (PBS twice per week), anti-Siglec-15 Ab (0.25, 1, or 4 mg/kg every 3 weeks), and alendronate (ALN) (0.028 or 0.14 mg/kg twice per week). Treatment commenced at 6 weeks of age and continued for the next 6 weeks. Changes in bone mass, bone metabolism, bone strength, and skeletal growth during treatment were analyzed. Both anti-Siglec-15 therapy and ALN increased bone mass and the mechanical strength of both the femora and lumbar spines in a dose-dependent manner. Anti-Siglec-15 therapy did not have a significant effect on skeletal growth as evidenced by micro-CT-based measurements of femoral length and histology, whereas high-dose ALN resulted in growth retardation with histological abnormalities in the growth plates of femurs. This unique property of the anti-Siglec-15 Ab can probably be attributed to compensatory signaling for Siglec-15 inhibition in the primary spongiosa, but not in the secondary spongiosa. Thus, anti-Siglec-15 therapy could be a safe and effective for juvenile osteoporosis.