Three-dimensional Matrices Research Articles

Chronic Optogenetic Pacing of Human-Induced Pluripotent Stem Cell-Derived Engineered Cardiac Tissues.

The delivery of cells into damaged myocardium induces limited cardiac regeneration due to extensive cell death. In an effort to limit cell death, our lab formulates three-dimensional matrices as a delivery system for cell therapy. Our primary work has been focused on the formation of engineered cardiac tissues (ECTs) from human-induced pluripotent stem cell-derived engineered cardiac cells. However, ECT immaturity hinders ability to fully recover damaged myocardium. Various conditioning regimens such as mechanical stretch and/or electric pacing have been used to activate maturation pathways. To improve ECT maturity, we use non-contacting chronic light stimulation using heterologously expressed light-sensitive channelrhodopsin ion channels. We transduce ECTs with an AAV packaged channelrhodopsin and chronically optically pace (C-OP) ECTs for 1week above the intrinsic beat rate, resulting in increased ECT electrophysiological properties.

Stepwise nanosphere lithography: an alternate way of fabricating nanostructures

This work demonstrates a new nanosphere lithography technique, termed stepwise nanosphere lithography, to create matrices of novel two- and three-dimensional nanostructures. Different sets of nanostructures are placed at desired locations through step-by-step deposition during thermal evaporation onto a substrate surface. Three deposition parameters: (1) number of deposition steps; (2) angle of deposition; and (3) nanosphere mask orientation angle were investigated. By changing these parameters, the ordering, shape, and size of nanostructures were modified accordingly. Two- and three-dimensional nanostructure matrices with different arrangements and symmetries were successfully simulated and fabricated experimentally through a combination of multiple stationary deposition stages with different parameters.

Calcium Carbonate/Gelatin Methacrylate Microspheres for 3D Cell Culture in Bone Tissue Engineering.

Hydrogel microspheres have been widely used as cell carriers and three-dimensional cell culture matrices. However, these microspheres are associated with several unfavorable properties for bone tissue engineering applications, for example, their surface is too smooth to attach cells and they do not contain inorganic materials. This article presents a new method to overcome these disadvantages by depositing CaCO3 crystals on the hydrogel microsphere surface. Specifically, we used a nonplanar flow-focusing microfluidic device to produce gelatin methacrylate (GelMA)-/Na2CO3-based microspheres. We subsequently obtained CaCO3 crystals by a chemical reaction between Na2CO3 and CaCl2. The efficacy of this method was demonstrated by in vitro experiments with human umbilical vein endothelial cells (HUVEC) and immortalized mouse embryonic fibroblasts (iMEF). Cell culture on GelMA/CaCO3 microspheres showed that cells can easily attach and adhere to GelMA/CaCO3 microspheres and maintain high viability. Alkaline phosphatase (ALP) expression was increased as well. These results suggest that this novel microsphere has a high potential for bone tissue engineering applications. Impact statement Microspheres as cell culture substrates have attracted a great deal of attention. The combination of organic and inorganic materials offers the unique merits in bone tissue engineering. In this study, there are two contributions. First, the organic and inorganic material of gelatin methacrylate (GelMA) and CaCO3 were successfully combined, especially, CaCO3 was formed as crystals to enhance cell attachment. Second, microspheres were successfully fabricated with one-step process: that is, the microfluidic technique was coupled with the CaCO3 precipitation in situ. Cell culture shows that the GelMA/CaCO3 microspheres proposed in this study have a high potential for bone tissue engineering applications.

Eigenvalues of Ising connection matrix with long-range interaction

We examine multidimensional Ising systems on hypercube lattices and calculate analytically the eigenvalues of their connection matrices. We express the eigenvalues in terms of spin–spin​ interaction constants and the eigenvalues of the one-dimensional Ising connection matrix (the latter are well known). To do this we present the eigenvectors as Kronecker products of the eigenvectors of the one-dimensional Ising connection matrix. For periodic boundary conditions, it is possible to obtain exact results for interactions with an arbitrary large number of neighboring spins. We present exact expressions for the eigenvalues for two- and three-dimensional Ising connection matrices accounting for the first five coordination spheres (that is interactions up to next-next-next-next nearest neighbors). In the case of free-boundary systems, we show that in the two and three dimensions the exact expressions could be obtained only if we account for interactions with spins of not more than first three coordination spheres.

Increased Stiffness Inhibits Invadopodia Formation and Cell Migration in 3D

Cancer cells typically invade through basement membranes (BMs) at key points during metastasis, including primary tumor invasion, intravasation, and extravasation. Cells extend invadopodia protrusions to create channels in the nanoporous BM through which they can invade, either via proteolytic degradation or mechanical force. Increased matrix stiffness can promote cancer progression, and two-dimensional (2D) culture studies indicate that increased stiffness promotes invadopodia degradation activity. However, invadopodia can function mechanically, independent of their degradative activity, and cells do not form fully matured invadopodia or migrate in the direction of the invadopodia in 2D environments. Here, we elucidated the impact of matrix stiffness on the mechanical mode of invadopodia activity of cancer cells cultured in three-dimensional BM-like matrices. Invadopodia formation and cell migration assays were performed for invasive breast cancer cells cultured in mechanically plastic, nanoporous, and minimally degradable interpenetrating networks of reconstituted BM matrix and alginate, which presented a range of elastic moduli from 0.4 to 9.3 kPa. Across this entire range of stiffness, we find that cells form mature invadopodia that often precede migration in the direction of the protrusion. However, at higher stiffness, cells form shorter and more transient invadopodia and are less likely to extend invadopodia overall, contrasting with results from 2D studies. Subsequently, cell migration is diminished in stiff environments. Thus, although previous studies indicate that increased stiffness may promote malignant phenotypes and the degradative activity of invadopodia, our findings show that increased stiffness physically restricts invadopodia extension and cell migration in three-dimensional, BM-like environments.

Recovery of Tractions Exerted by Single Cells in Three-Dimensional Nonlinear Matrices.

Cell-generated tractions play an important role in various physiological and pathological processes such as stem-cell differentiation, cell migration, wound healing, and cancer metastasis. Traction force microscopy (TFM) is a technique for quantifying cellular tractions during cell-matrix interactions. Most applications of this technique have heretofore assumed that the matrix surrounding the cells is linear elastic and undergoes infinitesimal strains, but recent experiments have shown that the traction-induced strains can be large (e.g., more than 50%). In this paper, we propose a novel three-dimensional (3D) TFM approach that consistently accounts for both the geometric nonlinearity introduced by large strains in the matrix, and the material nonlinearity due to strain-stiffening of the matrix. In particular, we pose the TFM problem as a nonlinear inverse hyperelasticity problem in the stressed configuration of the matrix, with the objective of determining the cellular tractions that are consistent with the measured displacement field in the matrix. We formulate the inverse problem as a constrained minimization problem and develop an efficient adjoint-based minimization procedure to solve it. We first validate our approach using simulated data, and quantify its sensitivity to noise. We then employ the new approach to recover tractions exerted by NIH 3T3 cells fully encapsulated in hydrogel matrices of varying stiffness. We find that neglecting nonlinear effects can induce significant errors in traction reconstructions. We also find that cellular tractions roughly increase with gel stiffness, while the strain energy appears to saturate.

Eigenvectors of polarization coherency matrices.

Calculation of the eigenvectors of two- and three-dimensional coherency matrices, and the four-dimensional coherency matrix associated with a Mueller matrix, is considered, especially for algebraic cases, in the light of recently published algorithms. The preferred approach is based on a combination of an evaluation of the characteristic polynomial and an adjugate matrix. The diagonal terms of the coherency matrix are given in terms of the characteristic polynomial of reduced matrices as functions of the eigenvalues of the coherency matrix. The analogous polynomial form for the off-diagonal elements of the coherency matrix is also presented. Simple expressions are given for the pure component in the characteristic decomposition.

LRP-1 Promotes Colon Cancer Cell Proliferation in 3D Collagen Matrices by Mediating DDR1 Endocytosis.

Low density lipoprotein receptor related protein-1 (LRP-1) is a large ubiquitous endocytic receptor mediating the clearance of various molecules from the extracellular matrix. Several studies have shown that LRP-1 plays crucial roles during tumorigenesis functioning as a main signal pathway regulator, especially by interacting with other cell-surface receptors. Discoïdin Domain Receptors (DDRs), type I collagen receptors with tyrosine kinase activity, have previously been associated with tumor invasion and aggressiveness in diverse tumor environments. Here, we addressed whether it could exist functional interplays between LRP-1 and DDR1 to control colon carcinoma cell behavior in three-dimensional (3D) collagen matrices. We found that LRP-1 established tight molecular connections with DDR1 at the plasma membrane in colon cancer cells. In this tumor context, we provide evidence that LRP-1 regulates by endocytosis the cell surface levels of DDR1 expression. The LRP-1 mediated endocytosis of DDR1 increased cell proliferation by promoting cell cycle progression into S phase and decreasing apoptosis. In this study, we identified a new molecular way that controls the cell-surface expression of DDR1 and consequently the colon carcinoma cell proliferation and apoptosis and highlighted an additional mechanism by which LRP-1 carries out its sensor activity of the tumor microenvironment.

Role of infill parameters on the mechanical performance and weight reduction of PEI Ultem processed by FFF

In comparison with conventional manufacturing technologies, Fused Filament Fabrication (FFF) offers countless benefits. It broadens the horizons of the design of structural components with high geometrical complexity, and lighter elements can be obtained by optimizing the infill of the part. The infill density stands as a manufacturing parameter that plays a significant part in weight reduction purposes. This fact provides FFF with an outstanding competitive advantage as compared to the rest of the additive manufacturing technologies. This work aims to investigate the role of infill parameters on the mechanical performance and weight reduction of ULTEMTM 9085 samples processed by FFF, under tensile, flexural, and shear loading conditions in six different orientations with several solid and sparse configurations. Regarding the effect of the part orientation and the infill settings, the experimental results permit to draw conclusions on stiffness, resilience, maximum stress, and type of failure of the printed parts. Three-dimensional compliance matrices for each infill configuration are provided. The analysis of the results correlates the infill configuration with the mechanical performance considering the intra-layer and inter-layer unions. Finally, this research provides experimental evidence to contribute to the definition of novel design-for-manufacturing strategies for obtaining functional structural elements by FFF.

Main-Chain Liquid Crystalline Hydrogels that Support 3D Stem Cell Culture.

Hydrogels are frequently utilized as three-dimensional matrices for the culture and regeneration of soft tissues, but one challenge with the existing hydrogels is that, though the natural extracellular matrix of tissues may be ordered, there are few biocompatible ways to incorporate anisotropy within hydrogels. Liquid crystalline (LC) polymers are well suited for this because of their combination of molecular ordering and polymer elasticity; however, the hydrophobic nature of LC monomers has hindered their polymerization into hydrogels under cytocompatible conditions. This work reports on the generation of main-chain LC hydrogels in aqueous media and the ability of LC phases to affect mesenchymal stem cell behavior. The synthesis results in high gel fraction materials, and calorimetry, thermomechanical analysis, and X-ray scattering show that the networks organize into LC phases in the dry and hydrogel states. Human mesenchymal stem cells (hMSCs) cultured within the hydrogels show excellent viability, and hMSC proliferation proceeds at a faster rate in LC hydrogels compared to non-LC hydrogels. TThe result is a new synthetic approach for calamitic liquid crystalline hydrogels, which support the encapsulation and culture of human stem cells and are expected to enable applications as anisotropic and responsive substrates for tissue engineering and regenerative medicine.

Dual Template, Three-Dimensional Hierarchical Porous Scaffolds Based on Graphene Oxide for Bone Tissue Engineering

Objectives Scaffolds for bone tissue engineering (BTE) are three-dimensional (3D) porous matrices that provide the necessary sites for cell adhesion and proliferation, where the architecture plays an important role. Ideally, BTE scaffolds should have an interconnected network of both large and small pores to facilitate the infiltration of cells and the diffusion of growth factors and nutrients1. Scaffolds for BTE should also enhance osteogenic differentiation to improve bone regeneration. Graphene oxide (GO) can promote osteogenic differentiation of mesenchymal stem cells (MSCs) because it can provide biophysical cues and adsorb biological factors2. However, due to the lack of fabrication strategies, it remains a challenge to develop GO and GO composite scaffolds with a hierarchical architecture for BTE. In this study, we aim to develop a dual-templating method to control the assembly of GO sheets, in order to design and achieve this architecture. Experimental Methods We modified the amphiphilicity of GO by adding different amounts of cetyltrimethylammonium bromide (CTAB), hydroxyapatite (HA), polyacrylic acid (PAA) and elastin from bovine neck ligament. Then we developed GO-CTAB, GO-CTAB-HA, GO-CTAB-PAA and GO-elastin stabilized oil in water emulsions. Afterwards, we froze the emulsions at different temperatures (-190 oC and -20 oC), and upon freeze-drying we produced free-standing scaffolds. We reduced GO-CTAB scaffolds in different conditions to obtain rGO scaffolds. We studied the formation of emulsions and the structural and chemical properties of scaffolds through optical microscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared, and compressive strength tests. We seeded mouse bone marrow MSCs on 2D GO substrates and 3D GO-based scaffolds. Then, we compared the cell proliferation after 10 days of incubation. We also analyzed the cells on GO-based scaffolds after 7 days of incubation using SEM and confocal microscopy, in order to study cell morphology, attachment and infiltration in the scaffolds. Results and Discussion The scaffolds based on GO, GO-HA, GO-GO-PAA, GO-elastin and rGO have interconnected primary pores of 150-300 µm in diameter (Figure 1 a-j), which matches the size of the hexane droplet templates. Freezing at -190 oC results in smaller secondary pores around 10 µm in diameter (Figure 1 a-e) while freezing at -20 oC results in larger secondary pores with diameters around 30-50 µm (Figure 1 f-j). This result shows that the secondary pore formation is controlled by ice nucleation and growth in the aqueous phase of the emulsions at different temperatures. Scaffolds based on GO-HA, GO-PAA and especially GO-elastin show an improved modulus of compression compared to GO-based scaffolds (Figure 1 k). The cell culture using MSCs reveals cell proliferation up to 10 days on 2D GO substrates and 3D GO-based scaffolds (Figure 1 l). Compared to 2D substrates, the large and interconnected pores in 3D scaffolds contribute to the higher cell proliferation result. The cells are well spread on the scaffolds with an elongated shape and filamentous extensions at day 7 (Figure 1m). They infiltrate all the way to the center of GO-based scaffolds through primary pores (Figure 1 m, n). These results indicate that primary pores can facilitate the cell infiltration. Conclusions The rapid development and broad application of graphene-based porous materials requires efficient and facile fabrication methods. We developed a novel strategy to control the assembly of GO sheets using emulsions and ice templates to fabricate GO-based scaffolds with an interconnected and hierarchical porous structure. The ability to fabricate rGO and GO composite scaffolds with similar architectures demonstrates the versatility of this strategy. The GO-based scaffolds show biocompatibility and allow cell infiltration. We expect that this strategy can lead to improvements in the fabrication of GO-type scaffolds for BTE.

Association of extracellular matrix microarchitecture and three-dimensional collective invasion of cancer cells

ABSTRACT As much as 90% of cancer associated mortality follows metastasis of a primary tumor. Circulating tumor cells (CTCs) and CTC clusters are important for metastasis. Compared to CTCs, CTC clusters formed by collective invasion exhibit a 23−50 fold increase in metastatic potential, but the factors that influence collective invasion are largely unknown. Using well defined three-dimensional matrices and different extracellular matrix (ECM) concentrations, we found that cancer cells were more prone to collective invasion at low ECM concentration. Moreover, despite variation of biological factors, changes in ECM microarchitecture, especially the pore size of the matrix, was correlated with the probability of collective invasion, which indicates that the physical microarchitecture of ECM plays an important role in collective invasion of cancer cells.

Collagen Fibril Density Modulates Macrophage Activation and Cellular Functions during Tissue Repair.

Monocytes circulate in the bloodstream, extravasate into the tissue and differentiate into specific macrophage phenotypes to fulfill the immunological needs of tissues. During the tissue repair process, tissue density transits from loose to dense tissue. However, little is known on how changes in tissue density affects macrophage activation and their cellular functions. In this work, monocytic cell line THP-1 cells were embedded in three-dimensional (3D) collagen matrices with different fibril density and were then differentiated into uncommitted macrophages (MPMA) using phorbol-12-myristate-13-acetate (PMA). MPMA macrophages were subsequently activated into pro-inflammatory macrophages (MLPS/IFNγ) and anti-inflammatory macrophages (MIL-4/IL-13) using lipopolysaccharide and interferon-gamma (IFNγ), and interleukin 4 (IL-4) and IL-13, respectively. Although analysis of cell surface markers, on both gene and protein levels, was inconclusive, cytokine secretion profiles, however, demonstrated differences in macrophage phenotype. In the presence of differentiation activators, MLPS/IFNγ secreted high amounts of IL-1β and tumor necrosis factor alpha (TNFα), while M0PMA secreted similar cytokines to MIL-4/IL-13, but low IL-8. After removing the activators and further culture for 3 days in fresh cell culture media, the secretion of IL-6 was found in high concentrations by MIL-4/IL-13, followed by MLPS/IFNγ and MPMA. Interestingly, the secretion of cytokines is enhanced with an increase of fibril density. Through the investigation of macrophage-associated functions during tissue repair, we demonstrated that M1LPS/IFNγ has the potential to enhance monocyte infiltration into tissue, while MIL-4/IL-13 supported fibroblast differentiation into myofibroblasts via transforming growth factor beta 1 (TGF-β1) in dependence of fibril density, suggesting a M2a-like phenotype. Overall, our results suggest that collagen fibril density can modulate macrophage response to favor tissue functions. Understanding of immune response in such complex 3D microenvironments will contribute to the novel therapeutic strategies for improving tissue repair, as well as guidance of the design of immune-modulated materials.

Prediction of transient tumor enlargement using MRI tumor texture after radiosurgery on vestibular schwannoma.

PurposeVestibular schwannomas (VSs) are uncommon benign brain tumors, generally treated using Gamma Knife radiosurgery (GKRS). However, due to the possible adverse effect of transient tumor enlargement (TTE), large VS tumors are often surgically removed instead of treated radiosurgically. Since microsurgery is highly invasive and results in a significant increased risk of complications, GKRS is generally preferred. Therefore, prediction of TTE for large VS tumors can improve overall VS treatment and enable physicians to select the most optimal treatment strategy on an individual basis. Currently, there are no clinical factors known to be predictive for TTE. In this research, we aim at predicting TTE following GKRS using texture features extracted from MRI scans.MethodsWe analyzed clinical data of patients with VSs treated at our Gamma Knife center. The data was collected prospectively and included patient‐ and treatment‐related characteristics and MRI scans obtained at day of treatment and at follow‐up visits, 6, 12, 24 and 36 months after treatment. The correlations of the patient‐ and treatment‐related characteristics to TTE were investigated using statistical tests. From the treatment scans, we extracted the following MRI image features: first‐order statistics, Minkowski functionals (MFs), and three‐dimensional gray‐level co‐occurrence matrices (GLCMs). These features were applied in a machine learning environment for classification of TTE, using support vector machines.ResultsIn a clinical data set, containing 61 patients presenting obvious non‐TTE and 38 patients presenting obvious TTE, we determined that patient‐ and treatment‐related characteristics do not show any correlation to TTE. Furthermore, first‐order statistical MRI features and MFs did not significantly show prognostic values using support vector machine classification. However, utilizing a set of 4 GLCM features, we achieved a sensitivity of 0.82 and a specificity of 0.69, showing their prognostic value of TTE. Moreover, these results increased for larger tumor volumes obtaining a sensitivity of 0.77 and a specificity of 0.89 for tumors larger than 6 cm3.ConclusionsThe results found in this research clearly show that MRI tumor texture provides information that can be employed for predicting TTE. This can form a basis for individual VS treatment selection, further improving overall treatment results. Particularly in patients with large VSs, where the phenomenon of TTE is most relevant and our predictive model performs best, these findings can be implemented in a clinical workflow such that for each patient, the most optimal treatment strategy can be determined.

High-energy density LixSi-S full cell based on 3D current collector of few-wall carbon nanotube sponge

For the practical use of innovative, high-energy-density batteries, loading of high-capacity active materials at high gravimetric and volumetric fractions is required. In this work, a flexible self-supporting paper of few-wall carbon nanotubes (FWCNTs) was used as three-dimensional conductive matrices to capture Si and S at ∼70 mass% without metal foils nor polymeric binders. The full cell comprised of the LixSi-CNT and S-CNT electrodes with a negative to positive (N/P) capacity ratio of ∼1 realized high initial energy densities of 810 W h kg−1 and 680 W h L−1 based on the total mass and volume of the electrodes, respectively. However, the cell showed a poor cycle performance due to the depletion of active Li. The increased N/P capacity ratio of 2.7 drastically improved the cycle performance, realizing an energy density of 610 W h kg−1 at first discharge and 360 W h kg−1 after 100 cycles based on the total mass of the electrodes. The full cell architecture based on 3D current collector of FWCNTs is a promising solution for loading active materials at high fractions and achieving high energy densities at the total electrode level.

Study of polylactide matrices using x-ray microtomography

Three-dimensional matrices of biodegradable polymers are promising materials for regenerative medicine. They are widely used in restoring the integrity and functions of tissues and organs using bio-artificial tissue engineering structures. We present the results of studying the structure of porous bioresorbable polymer matrices for tissue engineering using X-ray microtomography. Samples were obtained by supercritical fluid plasticization of D,L-polylactide with subsequent foaming in cylindrical molds. The tomographic method makes it possible to construct a three-dimensional voxel model of the object under study and gain apart from the estimate on the integral matrix porosity (characteristic data obtained by traditional sorption procedures) additional information about the size and spatial distribution of pores thus providing a possibility of optimization of the process parameters for production of polylactide matrices required for specific biomedical applications of architectonics, as well as forecasting the processes of their bioresorption in enzymatic media. The experiments were carried out on a laboratory microtomograph (Mo anode, the scan time of the sample is 120 min, the detector pixel size is 9 μm). Tomographic reconstruction was performed by algebraic method. The binarization procedure required for calculation of the structural characteristics of studied matrices was implemented by the method with the choice of a global threshold. Calculations of the porosity and homogeneity of the porosity distribution in the bulk, as well as estimation of the specific surface area of pores revealed the isotropy of the spatial structure of polylactide matrices.

Granulosa cells in three-dimensional culture: A follicle-like structure for domestic cat vitrified oocytes.

Follicle-like structures are three-dimensional matrices joint with living cells that allow the in vitro development of female gametes in more physiological conditions. They have been shown to be beneficial to fresh oocytes in different species, and in this study, domestic cat (Felis silvestris catus) granulosa cells were used to create a functional follicle-like structure aimed at supporting the in vitro maturation of conspecific vitrified oocytes, key players of fertility preservation programmes that usually struggle to acquire their full developmental competence after warming. Cat granulosa cells were cultured for up to 6days in three-dimensional barium alginate microcapsules (i.e. follicle-like structures) or in two-dimensional monolayers, and their steroidogenic ability (estradiol and progesterone secretion) was assessed to confirm their functionality. The same systems were used (on day 2 or 6 of granulosa cells culture) for the in vitro maturation (IVM) of Cryotop® vitrified immature cat oocytes and compared with microdrops of IVM medium without cells (control). Granulosa cells were able to maintain their functionality in vitro in both the conditions, even if with a different extent of hormonal secretion along culture (p=.02). Vitrified oocytes resumed meiosis at higher rates when cultured with 2days old granulosa cells (p=.03), but full maturation rates slightly raised when granulosa cells were cultured longer, albeit without differences with the control group. This study paved the road for the creation of enriched culture systems in the domestic cat, but innovations are strongly needed for vitrified oocytes that deserve better chances to develop in vitro.

Electrospun nanofiber-reinforced three-dimensional chitosan matrices: Architectural, mechanical and biological properties

The poor intrinsic mechanical properties of chitosan hydrogels have greatly hindered their practical applications. Inspired by nature, we proposed a strategy to enhance the mechanical properties of chitosan hydrogels by construction of a nanofibrous and cellular architecture in the hydrogel without toxic chemical crosslinking. To this end, electrospun nanofibers including cellulose acetate, polyacrylonitrile, and SiO2 nanofibers were introduced into chitosan hydrogels by homogenous dispersion and lyophilization. With the addition of 30% cellulose acetate nanofibers, the cellular structure could be maintained even in water without crosslinking, and integration of 60% of the nanofibers could guarantee the free-standing structure of the chitosan hydrogel with a low solid content of 1%. Moreover, the SiO2 nanofiber-reinforced chitosan (SiO2 NF/CS) three-dimensional (3D) matrices exhibit complete shape recovery from 80% compressive strain and excellent injectability. The cellular architecture and nanofibrous structure in the SiO2 NF/CS matrices are beneficial for human mesenchymal stem cell adhesion and stretching. Furthermore, the SiO2 NF/CS matrices can also act as powerful vehicles for drug delivery. As an example, bone morphogenetic protein 2 could be immobilized on SiO2 NF/CS matrices to induce osteogenic differentiation. Together, the electrospun nanofiber-reinforced 3D chitosan matrices exhibited improved mechanical properties and enhanced biofunctionality, showing great potential in tissue engineering.

Association of bone mineral density with bone texture attributes extracted using routine magnetic resonance imaging

OBJECTIVE:Dual-energy X-ray absorptiometry (DXA)-derived bone mineral density (BMD) often fails to predict fragility fractures. Quantitative textural analysis using magnetic resonance imaging (MRI) may potentially yield useful radiomic features to predict fractures. We aimed to investigate the correlation between BMD and texture attributes (TAs) extracted from MRI scans and the interobserver reproducibility of the analysis.METHODS:Forty-nine volunteers underwent lumbar spine 1.5-T MRI and DXA. Three-dimensional (3-D) gray-level co-occurrence matrices were measured from routine sagittal T2 fast spin-echo images using the IBEX software. Twenty-two TAs were extracted from 3-D segmented L3 vertebrae. The estimated concordance coefficient was calculated using linear regression analysis. A Pearson correlation coefficient analysis was performed to evaluate the correlation between BMD and the TAs. Interobserver reproducibility was assessed with the concordance coefficient described by Lin.RESULTS:The results revealed a fair-to-moderate significant correlation between BMD and 13 TAs (r=−0.20 to 0.39; p<0.05). Eight TAs (autocorrelation, energy, homogeneity 1, homogeneity 1.1, maximum probability, sum average, sum variance, and inverse difference normalized) negatively correlated with BMD (r=−0.20 to −0.38; p<0.05), whereas five TAs (dissimilarity, difference entropy, entropy, sum entropy, and information measure corr 1) positively correlated with BMD (r=0.29-0.39; p<0.05). The interobserver agreement was almost perfect for all significant TAs (95% confidence interval, 0.92-1.00; p<0.05).CONCLUSION:Specific TAs could be reliably extracted from routine MRI and correlated with BMD. Our results encourage future evaluation of the potential usefulness of quantitative texture measurements from MRI scans for predicting fragility fractures.

Engineering cell-derived matrices with controlled 3D architectures for pathophysiological studies.

The composition and architecture of the extracellular matrix (ECM) and their dynamic alterations, play an important regulatory role on numerous cellular processes. Cells embedded in 3D scaffolds show phenotypes and morphodynamics reminiscent of the native scenario. This is in contrast to flat environments, where cells display artificial phenotypes. The structural and biomolecular properties of the ECM are critical in regulating cell behavior via mechanical, chemical and topological cues, which induce cytoskeleton rearrangement and gene expression. Indeed, distinct ECM architectures are encountered in the native stroma, which depend on tissue type and function. For instance, anisotropic geometries are associated with ECM degradation and remodeling during tumor progression, favoring tumor cell invasion. Overall, the development of innovative in vitro ECM models of the ECM that reproduce the structural and physicochemical properties of the native scenario is of upmost importance to investigate the mechanistic determinants of tumor dissemination. In this chapter, we describe an extremely versatile technique to engineer three-dimensional (3D) matrices with controlled architectures for the study of pathophysiological processes in vitro. To this aim, a confluent culture of "sacrificial" fibroblasts was seeded on top of microfabricated guiding templates to induce the 3D ECM growth with specific isotropic or anisotropic architectures. The resulting matrices, and cells seeded on them, recapitulated the structure, composition, phenotypes and morphodynamics typically found in the native scenario. Overall, this method paves the way for the development of in vitro ECMs for pathophysiological studies with potential clinical relevance.