An in silico study on the influence of extracellular matrix mechanics on vasculogenesis.

BACKGROUND AND OBJECTIVES: Blood vessels form a network of capillaries throughout the body that perform essential functions for life. Vasculogenesis, i.e. the formation of new blood vessels, is regulated by many factors, biochemical ones being among the most important. However, others such as the biomechanical influence on shape, organization and structure of vessel networks require further investigation. In this paper, we develop a 3D agent-based mechanobiological model of vasculogenesis with the aim of analyzing how the mechanics of the extracellular matrix (ECM) affects vasculogenesis. METHODS: For this purpose, we consider a growing domain composed of different cells: tip cells, which are the driving cells located at the end of the vessels and stalk cells, which are found in the interior of the vascular network. ECM is considered as particles (agents) that surround the growth of the vascular network. Depending on the cell type, different sets of forces are considered, such as chemotactic, mechanical, random and viscoelastic forces among others. RESULTS: The growth of the network is iteratively analyzed and updated at each time step based on a mechanically-driven proliferation rule. The influence of different biomechanical factors, such as ECM stiffness or viscoelasticity are explored through in silico simulations. A number of indicators are defined along the algorithm, like number of cells, branches, tortuosity and anisotropy, in order to compare topological differences of the vascular network during vasculogenesis under different ECM conditions. The obtained results are qualitatively compared with other related works in the literature. CONCLUSIONS: The present study sheds some light and partially explain, from an in silico perspective, the role of ECM mechanics on vasculogenesis. The main conclusions of this work are: (i) increased stiffness increases proliferation, (ii) the network tends to migrate towards stiffer areas, and (iii) increased viscoelasticity decreases proliferation.

Advanced in silico validation framework for three-dimensional traction force microscopy and application to an in vitro model of sprouting angiogenesis.

In the last decade, cellular forces in three-dimensional hydrogels that mimic the extracellular matrix have been calculated by means of Traction Force Microscopy (TFM). However, characterizing the accuracy limits of a traction recovery method is critical to avoid obscuring physiological information due to traction recovery errors. So far, 3D TFM algorithms have only been validated using simplified cell geometries, bypassing image processing steps or arbitrarily simulating focal adhesions. Moreover, it is still uncertain which of the two common traction recovery methods, i.e., forward and inverse, is more robust against the inherent challenges of 3D TFM. In this work, we established an advanced in silico validation framework that is applicable to any 3D TFM experimental setup and that can be used to correctly couple the experimental and computational aspects of 3D TFM. Advancements relate to the simultaneous incorporation of complex cell geometries, simulation of microscopy images of varying bead densities and different focal adhesion sizes and distributions. By measuring the traction recovery error with respect to ground truth solutions, we found that while highest traction recovery errors occur for cases with sparse and small focal adhesions, our implementation of the inverse method improves two-fold the accuracy with respect to the forward method (average error of 23% vs. 50%). This advantage was further supported by recovering cellular tractions around angiogenic sprouts in an in vitro model of angiogenesis. The inverse method recovered higher traction peaks and a clearer pulling pattern at the sprout protrusion tips than the forward method. STATEMENT OF SIGNIFICANCE: Biomaterial performance is often studied by quantifying cell-matrix mechanical interactions by means of Traction Force Microscopy (TFM). However, 3D TFM algorithms are often validated in simplified scenarios, which do not allow to fully assess errors that could obscure physiological information. Here, we established an advanced in silico validation framework that mimics real TFM experimental conditions and that characterizes the expected errors of a 3D TFM workflow. We apply this framework to demonstrate the enhanced accuracy of a novel inverse traction recovery method that is illustrated in the context of an in vitro model of sprouting angiogenesis. Together, our study shows the importance of a proper traction recovery method to minimise errors and the need for an advanced framework to assess those errors.

Data-Driven Computational Simulation in Bone Mechanics.

The data-driven approach was formally introduced in the field of computational mechanics just a few years ago, but it has gained increasing interest and application as disruptive technology in many other fields of physics and engineering. Although the fundamental bases of the method have been already settled, there are still many challenges to solve, which are often inherently linked to the problem at hand. In this paper, the data-driven methodology is applied to a particular problem in tissue biomechanics, a context where this approach is particularly suitable due to the difficulty in establishing accurate and general constitutive models, due to the intrinsic intra and inter-individual variability of the microstructure and associated mechanical properties of biological tissues. The problem addressed here corresponds to the characterization and mechanical simulation of a piece of cortical bone tissue. Cortical horse bone tissue was mechanically tested using a biaxial machine. The displacement field was obtained by means of digital image correlation and then transformed into strains by approximating the displacement derivatives in the bone virtual geometric image. These results, together with the approximated stress state, assumed as uniform in the small pieces tested, were used as input in the flowchart of the data-driven methodology to solve several numerical examples, which were compared with the corresponding classical model-based fitted solution. From these results, we conclude that the data-driven methodology is a useful tool to directly simulate problems of biomechanical interest without the imposition (model-free) of complex spatial and individually-varying constitutive laws. The presented data-driven approach recovers the natural spatial variation of the solution, resulting from the complex structure of bone tissue, i.e. heterogeneity, microstructural hierarchy and multifactorial architecture, making it possible to add the intrinsic stochasticity of biological tissues into the data set and into the numerical approach.

Inverse method based on 3D nonlinear physically constrained minimisation in the framework of traction force microscopy.

Traction force microscopy is a methodology that enables to estimate cellular forces from the measurement of the displacement field of an extracellular matrix (ECM)-mimicking hydrogel that a cell is mechanically interacting with. In this paper, a new inverse and physically-consistent methodology is developed and implemented in the context of 3D nonlinear elasticity. The proposed method searches for a displacement field that approximates the measured one, through the imposition of fulfillment of equilibrium with real and known forces acting in the hydrogel. The overall mathematical formulation leads to a constrained optimisation problem that is treated through a Lagrange operator and that is solved numerically by means of a nonlinear finite element framework. In order to illustrate the potential and enhanced accuracy of the proposed inverse method, it is applied to a total of 5 different real cases of cells cultured in a 3D hydrogel that is considered to behave as a nonlinear elastic material. Different error indicators are defined in order to compare ground truth simulated displacements and tractions to the ones recovered by the new inverse as well as by the forward method. Results indicate that the evaluation of displacement gradients leads to errors, in terms of recovered tractions, that are more than three times lower (on average) for the inverse method compared to the forward method. They highlight the enhanced accuracy of the developed methodology and the importance of appropriate inverse methods that impose physical constraints to traction and stress recovery in the context of traction force microscopy.

Mercury speciation in mine tailings amended with biochar: Effects on mercury bioavailability, methylation potential and mobility.

Biochar is a low-cost and environmentally friendly amendment with strong ability for adsorption of mercury (Hg) from aqueous solutions, contaminated soils, and sediments. In the present study, six biochars were prepared from the pyrolysis of cocoa pod husk, sugarcane bagasse and banana pseudostem at 400 and 600 °C in order to use them as an organic amendment and to evaluate their capacities to reduce the bioavailability, methylation potential, and mobility of Hg present in mine tailings without environmental treatment. To quantify the effects of each variety of biochar, incubation experiments of soil were established by mixing mine tailings with 5% by weight of biochar for 90 days. Once the incubation time concluded, sequential extraction procedures were carried out to determine the fractionation of the Hg species. Speciation analysis results indicated that the remedial effects of biochar depended on the source of organic matter and pyrolysis temperature. The bioavailable and organic Hg fractions decreased respectively by up to 75 and 79%, indicating a methylation potential reduction. Immobile Hg fraction increased to 76% with respect to the control. Adsorption and stabilization to HgS from the soluble forms of Hg reduce the percentage of bioavailable Hg. The organic Hg fraction reduction was correlated with the decrease of the bioavailable Hg fraction and with direct adsorption processes in the biochar structure. Highly porous biochars developed at high temperature, with large contents of superficial polar functional groups (H/C), and high pH, electrical conductivity, ash percentage and cation exchange capacity values favor the stabilization and adsorption of Hg in mine tailings. In summary, the application of biochar could be an effective method for the remediation of Hg-contaminated mine tailings, transforming the Hg species into less toxic, soluble, reactive, and bioavailable forms.

Effect of Chronic Consumption of Sweeteners on Microbiota and Immunity in the Small Intestine of Young Mice.

The consumption of sweeteners has increased as a measure to reduce the consumption of calories and thus combat obesity and diabetes. Sweeteners are found in a large number of products, so chronic consumption has been little explored. The objective of the study was to evaluate the effect of chronic sweetener consumption on the microbiota and immunity of the small intestine in young mice. We used 72 CD1 mice of 21 days old, divided into 3 groups: (i) No treatment, (ii) Group A (6 weeks of treatment), and (iii) Group B (12 weeks of treatment). Groups A and B were divided into 4 subgroups: Control (CL), Sucrose (Suc), Splenda® (Spl), and Svetia® (Sv). The following were determined: anthropometric parameters, percentage of lymphocytes of Peyer's patches and lamina propria, IL-6, IL-17, leptin, resistin, C-peptide, and TNF-α. From feces, the microbiota of the small intestine was identified. The BMI was not modified; the mice preferred the consumption of Splenda® and Svetia®. The percentage of CD3+ lymphocytes in Peyer's patches was increased. In the lamina propria, Svetia® increased the percentage of CD3+ lymphocytes, but Splenda® decreases it. The Splenda® and Svetia® subgroups elevate leptin, C-peptide, IL-6, and IL-17, with reduction of resistin. The predominant genus in all groups was Bacillus. The chronic consumption of sweeteners increases the population of lymphocytes in the mucosa of the small intestine. Maybe, Bacillus have the ability to adapt to sweeteners regardless of the origin or nutritional contribution of the same.

Contaminating viral sequences in high-throughput sequencing viromics: a linkage study of 700 sequencing libraries.

OBJECTIVES: Sample preparation for high-throughput sequencing (HTS) includes treatment with various laboratory components, potentially carrying viral nucleic acids, the extent of which has not been thoroughly investigated. Our aim was to systematically examine a diverse repertoire of laboratory components used to prepare samples for HTS in order to identify contaminating viral sequences. METHODS: A total of 322 samples of mainly human origin were analysed using eight protocols, applying a wide variety of laboratory components. Several samples (60% of human specimens) were processed using different protocols. In total, 712 sequencing libraries were investigated for viral sequence contamination. RESULTS: Among sequences showing similarity to viruses, 493 were significantly associated with the use of laboratory components. Each of these viral sequences had sporadic appearance, only being identified in a subset of the samples treated with the linked laboratory component, and some were not identified in the non-template control samples. Remarkably, more than 65% of all viral sequences identified were within viral clusters linked to the use of laboratory components. CONCLUSIONS: We show that high prevalence of contaminating viral sequences can be expected in HTS-based virome data and provide an extensive list of novel contaminating viral sequences that can be used for evaluation of viral findings in future virome and metagenome studies. Moreover, we show that detection can be problematic due to stochastic appearance and limited non-template controls. Although the exact origin of these viral sequences requires further research, our results support laboratory-component-linked viral sequence contamination of both biological and synthetic origin.

Oviductal Proteins Effect in Rooster Spermatic Cryopreservation.

BACKGROUND: Cryopreservation induces spermatic cryo capacitation, which can decrease thawed sperm fertilizing capability. OBJECTIVE: To evaluate the effect of uterus-vaginal union protein factors to inhibit sperm cryo capacitation and maintain viability and fertilizing capability of rooster spermatozoa. MATERIALS AND METHODS: Rooster spermatozoa was cryopreserved using Lake extender supplemented with different hen's uterus-vaginal junction protein concentrations, to determine spermatic viability, sperm physiological condition and fertilizing capability in vivo. RESULTS: It was possible to induce spermatic decapacitation in vitro, inhibiting cryo capacitation and allowing fertility results comparable to those obtained with fresh semen. CONCLUSION: Uterus-vaginal protein extracts induce spermatic decapacitation in vitro.

In silico dynamic characterization of the femur: Physiological versus mechanical boundary conditions.

It is established that bone tissue adapts and responds to mechanical loading. Several studies have suggested an existence of positive influence of vibration on the bone mass maintenance. Thus, some bone regeneration therapies are based on vibration of bone tissue under circumstances of disease to stimulate its formation. Frequency of loading should be properly selected and therefore a correct characterization of the dynamic properties of this tissue may be critical for the success of such orthopedic techniques. On the other hand, many studies implement vibration techniques with in silico models. Numerical results are exclusively dependent on properties of bone tissue, i.e. geometry, density distribution and stiffness, as well as boundary conditions. In the present study, the influence of boundary conditions and material properties on the dynamic characteristics of bone tissue was explored in a human femur. Bone shape and density were directly reconstructed from computer tomographies, whereas natural frequencies and modes of vibration were obtained for different boundary conditions including physiological and mechanical ones. Results of this study show the moderate effect of material properties compared to the much substantial effect of boundary conditions. A factor of 2 in the natural frequency was obtained depending on imposed boundary conditions, highlighting the importance in the selection of appropriate conditions in the analysis of the bone organ.

Model of dissolution in the framework of tissue engineering and drug delivery.

Dissolution phenomena are ubiquitously present in biomaterials in many different fields. Despite the advantages of simulation-based design of biomaterials in medical applications, additional efforts are needed to derive reliable models which describe the process of dissolution. A phenomenologically based model, available for simulation of dissolution in biomaterials, is introduced in this paper. The model turns into a set of reaction-diffusion equations implemented in a finite element numerical framework. First, a parametric analysis is conducted in order to explore the role of model parameters on the overall dissolution process. Then, the model is calibrated and validated versus a straightforward but rigorous experimental setup. Results show that the mathematical model macroscopically reproduces the main physicochemical phenomena that take place in the tests, corroborating its usefulness for design of biomaterials in the tissue engineering and drug delivery research areas.

Effect of Supplementation with n-3 Fatty Acids Extracted from Microalgae on Inflammation Biomarkers from Two Different Strains of Mice.

BACKGROUND: Diabetes mellitus is considered a chronic noncommunicable disease in which inflammation plays a main role in the progression of the disease and it is known that n-3 fatty acids have anti-inflammatory properties. One of the most recent approaches is the study of the fatty acids of microalgae as a substitute for fish oil and a source rich in fatty acids EPA and DHA. OBJECTIVE: To analyze the effect of supplementation with n-3 fatty acids extracted from microalgae on the inflammatory markers from two different strains of mice. METHODS: Mice of two strains, db/db and CD1, were supplemented with n-3 fatty acids extracted from microalgae in lyophilized form and added to food; the experiment was carried out from week 8 to 16 of life. Flow cytometry was performed to determine the percentage of TCD4+ cells producing Th1 and Th2 cytokines. RESULTS: Supplementation with microalgae fatty acids decreased the percentage of TCD4+ cells producing IFN-γ and TNF-α and increased the ones producing IL-17A and IL-12 in both strains; on the other hand, supplementation decreased percentage of TCD4+ cells producing IL-4 and increased the ones producing TGF-ß. CONCLUSIONS: Microalgae n-3 fatty acids could be a useful tool in the treatment of diabetes as well as in the prevention of the appearance of health complications caused by inflammatory states.

In silico design of magnesium implants: Macroscopic modeling.

Magnesium-based biomedical implants offer many advantages versus traditional ones although some challenges are still present. In this context, mathematical modeling and computational simulation may be a useful and complementary tool to evaluate in silico the performance of magnesium biomaterials under different conditions. In this paper, a phenomenologically-based model to simulate magnesium corrosion is developed. The model describes the physico-chemical interactions and evolution of species present in this phenomenon. A set of 7 species is considered in the model, which allows to simulate hydrogen release, pH evolution, corrosion products formation as well as degradation of magnesium. The model is developed under the continuum media theory and is implemented in a finite element framework. In the results section, the effect of model parameters on outcomes is firstly explored. Second, model results are qualitative validated versus two examples of application found in the literature. Two main conclusions are derived from this work: (i) the model captures well the experimental trends and allows to analyze the main variables present in magnesium corrosion, (ii) even though further validation is needed the model may be a useful standard in the design of degradable metal implants.

Changes in the membrane carbohydrates from sperm cryopreserved with dimethylsulfoxide or polyvinylpyrrolidone of red-tailed hawk (Buteo jamaicencis).

BACKGROUND: That cryopreservation can induce alterations in sperm. OBJECTIVE: The goal of this study was to evaluate sperm quality and distribution of N-acetylglucosamine, sialic acid and mannose residues in sperm cryopreserved of red-tailed hawk (Buteo jamaicensis). MATERIALS AND METHODS: We studied twenty samples of ejaculated semen for each cryoprotectant dimethylsulfoxide or polyvinylpyrrolidone. Carbohydrate identification was carried out with lectins Triticum vulgaris agglutinin to N-acetylglucosamine and sialic acid and Concanavalia ensiformis for mannose residues. Sperm viability was not altered but motility decreased significantly with both crioprotectants compared with fresh sperm. RESULTS: Neither the number of WGA positive sperm nor the distribution of N-acetylglucosamine and/or sialic acid residues were affected by the cryopreservation procedure. The sperm proportion with fluorescence associated with the presence of mannose residues was higher in thawed sperm. CONCLUSION: Values obtained with the cryopreservation technique proposed in this study by freezing drops in liquid nitrogen, were within normal parameters established for good quality fresh semen. We can say that it can be used for assisted reproduction of Buteo jamaicensis.

REPRODUCTIVE ACTIVITY AFTER INDUCED ANESTRUS USING ALTRENOGEST IN Tursiops truncatus FEMALES IN CAPTIVITY IN MARINE ENVIRONMENT / ACTIVIDAD REPRODUCTIVA DESPUÉS DEL ANESTRO INDUCIDO CON ALTRENOGEST EN HEMBRAS DE Tursiops truncatus EN CAUTIVERIO EN AMBIENTE MARINO

Interest to reproduce Bottlenose dolphin (Tursiops truncatus) in captivity has increased due to the international restrictions for its commercialization and the risks and logistical difficulties for transporting specimens. Therefore, it has become important to study its reproductive biology in captivity. The objective of the present study was to determine altrenogest (Regumate ®) post-treatment indicators of vaginal cytology, estradiol levels and restarting of reproductive activity of T truncatus females in captivity in marine environment. Twelve females received altrenogest at a daily dose of 0.07mg kg-1 for a year. A total 420 slides of vaginal cytology of each female were performed to determine the percentage of cornified cells. Also, 60 blood samples of each animal were analyzed to determine estradiol levels. Regarding the vaginal cytology; percentage of cornified cells increased between 60 and 70% from day 4 to day 9 after removing the altrenogest treatment and between 70 and 80% from day 12 to day 19. Estradiol levels were in the range of 16 to 1l4pg ml-1 during the entire monitoring period. A positive correlation (r = 0.7062; P<0.05) was found between these indicators. Therefore, we conclude that treatment with altrenogest and monitoring the estrous cycle with simple techniques such as vaginal cytology might be used for designing protocols for assisted reproduction for groups of T truncatus in captivity.

La necesidad de reproducir delfín nariz de botella (Tursiops truncatus) en cautiverio se ha incrementado debido a las restricciones internacionales para su comercialización y por el riesgo y dificultad logística para el traslado de ejemplares. Por lo anterior, se hace importante conocer su biología reproductiva en cautiverio. El objetivo de este trabajo, fue conocer los indicadores post tratamiento con altrenogest (Regumate®), de citología vaginal, niveles de estradiol y reinicio de la actividad reproductiva en cautiverio de hembras de T truncatus en ambiente marino. Por un año, 12 hembras recibieron diariamente una dosis de 0,07mg kg-1 de altrenogest. Se realizaron un total 420 citologías vaginales, una diaria de cada hembra, para determinar el porcentaje de células cornificadas. También se obtuvieron de la red vascular, 60 muestras sanguíneas, en las que se determinó los niveles de estradiol. En cuanto a la citología vaginal, al cuarto día de retirar la administración de altrenogest, el porcentaje total de células cornificadas incrementó del 60% a 70% hasta el día nueve y continuó ascendiendo al 80% entre los días 12 al 19. Los niveles de estradiol, presentaron un rango de 16 a 114pg ml-1. Se encontró una correlación (r = 0,7062 P<0.05) positiva entre estos indicadores. Se concluye que es posible la manipulación con altrenogest y el monitoreo del ciclo estral de las hembras mediante técnicas simples como la citología vaginal para el diseño de protocolos de reproducción asistida específicos para grupos en cautiverio de T truncatus.

Parámetros hemaoológicos en polluelos de psitácidos en cautiverio de origen silvestre / Hematologial parrameters of wild parrot chicks kept in captivity

El objetivo de este estudio fue describir los parámetros hematológicos en 69 polluelos en cautiverio de origen silvestre, clínicamente sanos, menores de tres meses de edad, en cuatro especies de psitácidos: Pionus senilis (n = 18), Amazona albifrons (n = 15), Amazona autumnalis (n = 25) y Amazona oratrix (n = 11), procedentes de la región central de México. Para determinar dichos parámetros, de cada ejemplar se obtuvieron 500 µl de sangre por punción de la vena braquial. En las cuatro especies citadas, el porcentaje del hematocrito fue de 56,4 ± 3,36; 51 ± 6,52; 47,6 ± 6,47 y 53,8 ± 9,26; el VCM en fl fue de 184,6 ± 13,4; 142,0 ± 25,4; 106,3 ± 11,7 y 162,3 ± 71,9; la cuenta eritrocítica fue de 4,7 ± 2,1 x10(6)/µl; 6,1 ± 8,2 x10(6)/µl; 6,9 ± 1,2 x10(6)/µl y 5,4 ± 1,1 x10(6)/µl; y la cuenta leucocitaria de 3,06 ± 0,15 x10³/µl; 3,62 ± 0,24 x10³/µl; 4,48 ± 0,36 x10³/µl y 3,56 ± 0,71 x10³/µl respectivamente para P. senilis, A. albifrons, A. autumnalis y A. oratrix. Se constató tendencia a la heterofilia en A. albifrons y A. oratrix, lo cual puede ser de gran utilidad para un diagnóstico cada vez más preciso en la clínica de aves en cautiverio.

The aim of this study, conducted in central Mexico, was to describe the hematological parameters in 69 wild chicks of psittacine kept in captivity, younger than three months of age of four different species: Pionus senilis (n = 18), Amazona albifrons (n = 15), Amazona autumnalis (n = 25) and Amazona oratrix (n = 11). All parrots were sampled to obtaind 500 µl of blood for quantifying hematological parameters. Hematocrit percentage was 56.4 ± 3.36, 51 ± 6.52, 47.6 ± 6.47 and 53.8 ± 9.26; the MCV (fl) was 184.6 ± 13.4, 142.0 ± 25.4, 106.3 ± 11.7 and 162.3 ± 71.9; the erythrocyte count was, 4.7 ± 2.1x10(6)/μl, 6.1 ± 8.2 x10(6)/μl, 6.9 ± 1.2 x10(6)/μl and 5.4 ± 1.1 x10(6)/μl, and leukocyte count was of 3.06 ± 0.15 x10³/µl, 3.62 ± 0.24 x10³/µl, 4.48 ± 0.36 x10³/µl y 3.56 ± 0.71 x10³/µl respectively for P. senilis, A. albifrons, A. autumnalis y A. oratrix. There was a trend to heterophilia in A. oratrix and A. albifrons, which represents a contribution that may be useful for more precise diagnosis in avian clinical practice.

A novel method for visualising and quantifying through-plane skin layer deformations.

Skin is a multilayer composite and exhibits highly non-linear, viscoelastic, anisotropic material properties. In many consumer product and medical applications (e.g. during shaving, needle insertion, patient re-positioning), large tissue displacements and deformations are involved; consequently large local strains in the skin tissue can occur. Here, we present a novel imaging-based method to study skin deformations and the mechanics of interacting skin layers of full-thickness skin. Shear experiments and real-time video recording were combined with digital image correlation and strain field analysis to visualise and quantify skin layer deformations during dynamic mechanical testing. A global shear strain of 10% was applied to airbrush-patterned porcine skin (thickness: 1.2-1.6mm) using a rotational rheometer. The recordings were analysed with ARAMIS image correlation software, and local skin displacement, strain and stiffness profiles through the skin layers determined. The results of this pilot study revealed inhomogeneous skin deformation, characterised by a gradual transition from a low (2.0-5.0%; epidermis) to high (10-22%; dermis) shear strain regime. Shear moduli ranged from 20 to 130kPa. The herein presented method will be used for more extended studies on viable human skin, and is considered a valuable foundation for further development of constitutive models which can be used in advanced finite element analyses of skin.

Evaluation of genotoxicity and DNA protective effects of mangiferin, a glucosylxanthone isolated from Mangifera indica L. stem bark extract.

Mangiferin is a glucosylxantone isolated from Mangifera indica L. stem bark. Several studies have shown its pharmacological properties which make it a promising candidate for putative therapeutic use. This study was focused to investigate the in vitro genotoxic effects of mangiferin in the Ames test, SOS Chromotest and Comet assay. The genotoxic effects in bone marrow erythrocytes from NMRI mice orally treated with mangiferin (2000 mg/kg) were also evaluated. Additionally, its potential antimutagenic activity against several mutagens in the Ames test and its effects on CYP1A1 activity were assessed. Mangiferin (50-5000 µg/plate) did not increased the frequency of reverse mutations in the Ames test, nor induced primary DNA damage (5-1000 µg/mL) to Escherichia coli PQ37 cells under the SOS Chromotest. It was observed neither single strand breaks nor alkali-labile sites in blood peripheral lymphocytes or hepatocytes after 1h exposition to 10-500 µg/mL of mangiferin under the Comet assay. Furthermore, micronucleus studies showed mangiferin neither induced cytotoxic activity nor increased the frequency of micronucleated/binucleated cells in mice bone marrow. In short, mangiferin did not induce cytotoxic or genotoxic effects but it protect against DNA damage which would be associated with its antioxidant properties and its capacity to inhibit CYP enzymes.

Scaffold microarchitecture determines internal bone directional growth structure: a numerical study.

A number of successful results have been reported in bone tissue engineering, although the routine clinical practice has not been reached so far. One of the reasons is the poor understanding of the role of each scaffold design parameter in its functional performance, which yields an uncertain outcome of each clinical application. Specifically, the role of internal scaffold microarchitectural shape on the regeneration rate and distribution of newly formed bone is still unknown. This work is focused on the in-silico determination of the role of scaffold microstructural anisotropy in bone tissue regeneration. A multiscale approach of the problem is established distinguishing between macroscopic region domain (bone organ and scaffold) and microscopic domain (scaffold microstructure). Results show that, once the scaffold microstructure is properly interconnected and the porosity is sufficiently high, similar rates of bone regeneration are found. However, the main conclusion of the work is that initial scaffold microstructural anisotropy has important consequences since it determines the spatial distribution of the newly formed tissue.

A mathematical approach to bone tissue engineering.

Tissue engineering is becoming consolidated in the biomedical field as one of the most promising strategies in tissue repair and regenerative medicine. Within this discipline, bone tissue engineering involves the use of cell-loaded porous biomaterials, i.e. bioscaffolds, to promote bone tissue regeneration in bone defects or diseases such as osteoporosis, although it has not yet been incorporated into daily clinical practice. The overall success of a particular bone tissue engineering application depends strongly on scaffold design parameters, which do away with long and expensive clinical protocols. Computer simulation is a useful tool that may reduce animal experiments and help to identify optimal patient-specific designs after concise model validation. In this paper, we present a novel mathematical approach to bone regeneration within scaffolds, based on a multiscale framework. Results are presented over an actual scaffold microstructure, showing the potential of computer simulation, and how it can aid in the task of making bone tissue engineering a reality in clinical practice.