Showing papers by "Juan C. del Álamo published in 2014"
TL;DR: The diastolic vortex is responsible for entering a significant fraction of LV filling volume at no energetic or pressure cost, and intraventricular fluid mechanics are an important determinant of global chamber LV operative stiffness.
103 citations
TL;DR: A reference-free quantitative assay for measuring three-dimensional traction stresses generated by cells during the initial stages of invasion into matrices exerting varying levels of mechanical resistance shows that as cells encounter higher mechanical resistance, a larger fraction of them shift to protease-mediated invasion, and this process begins at lower values of cell invasion depth.
80 citations
TL;DR: Vortices may have a role in optimizing the mechanical efficiency and blood mixing of the left ventricle (LV) and enlarged vortices are helpful for ameliorating convective pressure losses and facilitating transport.
Abstract: Vortices may have a role in optimizing the mechanical efficiency and blood mixing of the left ventricle (LV). We aimed to characterize the size, position, circulation, and kinetic energy (KE) of LV...
75 citations
TL;DR: During chemotactic movement, D. discoideum exhibits step-wise amoeboid motility driven by both contractile axial forces and lateral forces.
Abstract: Chemotaxing Dictyostelium discoideum cells adapt their morphology and migration speed in response to intrinsic and extrinsic cues. Using Fourier traction force microscopy, we measured the spatiotemporal evolution of shape and traction stresses and constructed traction tension kymographs to analyze cell motility as a function of the dynamics of the cell’s mechanically active traction adhesions. We show that wild-type cells migrate in a step-wise fashion, mainly forming stationary traction adhesions along their anterior–posterior axes and exerting strong contractile axial forces. We demonstrate that lateral forces are also important for motility, especially for migration on highly adhesive substrates. Analysis of two mutant strains lacking distinct actin cross-linkers (mhcA− and abp120− cells) on normal and highly adhesive substrates supports a key role for lateral contractions in amoeboid cell motility, whereas the differences in their traction adhesion dynamics suggest that these two strains use distinct mechanisms to achieve migration. Finally, we provide evidence that the above patterns of migration may be conserved in mammalian amoeboid cells.
62 citations
TL;DR: In this article, the authors examined how cyclic mechanical stretch modulates embryonic cardiomyocytes to improve understanding of normal and pathologic ventricular development, and they observed that cyclic stretch promotes cardiocyte proliferation, growth, and gene expression.
Abstract: Rationale: Perturbed biomechanical stimuli are critical for the pathogenesis of a number of congenital heart defects, including Hypoplastic Left Heart Syndrome (HLHS). While ventricular cardiomyocytes experience biomechanical stretch every heart beat, the molecular responses of embryonic cardiomyocytes to biomechanical stimuli are poorly understood. In this study, we examined how cyclic mechanical stretch modulates embryonic cardiomyocytes to improve understanding of normal and pathologic ventricular development. We hypothesize that biomechanical stimuli activates specific signaling pathways that impact proliferation, gene expression and myocyte contraction.
Objective: The objective for this study was to examine key molecular and phenotypic responses of embryonic cardiomyocytes to cyclic stretch that will provide a deeper understanding of HLHS.
Methods and Results: Embryonic mouse cardiomyocytes were exposed to cyclic stretch. Analysis of RNA-Sequencing data demonstrated that gene ontology (GO) groups associated with myofibril and cardiac development were significantly modulated. Stretch increased cardiomyocyte proliferation, size, and cardiac gene expression. Since the Tgf-β GO term was modulated by stretch, the role of Tgf-β in the cardiomyocyte response to stretch was examined. Stretched Cardiomyocytes had decreased Tgf-β expression, protein, and signaling. Functionally, Tgf-β signaling repressed cardiomyocyte proliferation, and both inotropic and chronotropic contractile function, which was assayed for confluent cell cultures by dynamic monolayer force microscopy (DMFM). Tgf-β inhibitor treatment resulted in increased cardiomyocyte size.
Conclusions: Herein, we observed that cyclic stretch promotes cardiomyocyte proliferation, growth, and gene expression. Stretch-mediated repression of Tgf-β appears to play a key role. Together these findings advance the understanding of how the biomechanical/molecular axis modulates ventricular development.
33 citations
TL;DR: It is demonstrated that, upon dexamethasone (osteogenic induction) treatment, guanine nucleotide exchange factor H1 (GEF-H1) is significantly enriched in FAs, and a role for FA signaling in specifying MSC commitment is demonstrated.
Abstract: Focal adhesions (FAs) undergo maturation that culminates in size and composition changes that modulate adhesion, cytoskeleton remodeling and differentiation. Although it is well recognized that stimuli for osteogenesis of mesenchymal stem cells (MSCs) drive FA maturation, actin organization and stress fiber polarization, the extent to which FA-mediated signals regulated by the FA protein composition specifies MSC commitment remains largely unknown. Here, we demonstrate that, upon dexamethasone (osteogenic induction) treatment, guanine nucleotide exchange factor H1 (GEF-H1, also known as Rho guanine nucleotide exchange factor 2, encoded by ARHGEF2) is significantly enriched in FAs. Perturbation of GEF-H1 inhibits FA formation, anisotropic stress fiber orientation and MSC osteogenesis in an actomyosin-contractility-independent manner. To determine the role of GEF-H1 in MSC osteogenesis, we explore the GEF-H1-modulated FA proteome that reveals non-muscle myosin-II heavy chain-B (NMIIB, also known as myosin-10, encoded by MYH10) as a target of GEF-H1 in FAs. Inhibition of targeting NMIIB into FAs suppresses FA formation, stress fiber polarization, cell stiffness and osteogenic commitments in MSCs. Our data demonstrate a role for FA signaling in specifying MSC commitment.
33 citations
TL;DR: The role that specific cytoskeletal components play in the regulation of the cell migration mechanics is reviewed and the ability of the cells to perform the motility cycle effectively and the generation of traction forces is investigated.
Abstract: Migrating cells exert traction forces when moving. Amoeboid cell migration is a common type of cell migration that appears in many physiological and pathological processes and is performed by a wide variety of cell types. Understanding the coupling of the biochemistry and mechanics underlying the process of migration has the potential to guide the development of pharmacological treatment or genetic manipulations to treat a wide range of diseases. The measurement of the spatiotemporal evolution of the traction forces that produce the movement is an important aspect for the characterization of the locomotion mechanics. There are several methods to calculate the traction forces exerted by the cells. Currently the most commonly used ones are traction force microscopy methods based on the measurement of the deformation induced by the cells on elastic substrate on which they are moving. Amoeboid cells migrate by implementing a motility cycle based on the sequential repetition of four phases. In this paper, we review the role that specific cytoskeletal components play in the regulation of the cell migration mechanics. We investigate the role of specific cytoskeletal components regarding the ability of the cells to perform the motility cycle effectively and the generation of traction forces. The actin nucleation in the leading edge of the cell, carried by the ARP2/3 complex activated through the SCAR/WAVE complex, has shown to be fundamental to the execution of the cyclic movement and to the generation of the traction forces. The protein PIR121, a member of the SCAR/WAVE complex, is essential to the proper regulation of the periodic movement and the protein SCAR, also included in the SCAR/WAVE complex, is necessary for the generation of the traction forces during migration. The protein Myosin II, an important F-actin cross-linker and motor protein, is essential to cytoskeletal contractility and to the generation and proper organization of the traction forces during migration.
14 citations
TL;DR: The cytoskeletal reorganization induced by EHEC infection mediated a dramatic increase in the cytoplasmic elastic shear modulus of the infected cells, and a transition in the viscoelastic behavior of the cells from viscous-like to elastic-like.
Abstract: Enterohaemorrhagic E. coli (EHEC) is a type of human pathogenic bacteria. The main virulence characteristics of EHEC include the formation of attaching and effacing lesions (A/E lesions) and the production of one or more Shiga-like toxins, which may induce human uremic complications. When EHEC infects host cells, it releases translocated intimin receptor (Tir) and effector proteins inside the host cells, inducing the rearrangement and accumulation of the F-actin cytoskeleton, a phenotype leading to the formation of pedestals in the apical cell surface, and the growth of stress fibers at the base of the cells. To examine the effect of EHEC infection on cell mechanics, we carried out a series of experiments to examine HeLa cells with and without EHEC infection to quantify the changes in (1) focal adhesion area, visualized by anti-vinculin staining; (2) the distribution and orientation of stress fibers; and (3) the intracellular viscoelasticity, via directional video particle tracking microrheology. Our results indicated that in EHEC-infected HeLa cells, the focal adhesion area increased and the actin stress fibers became thicker and more aligned. The cytoskeletal reorganization induced by EHEC infection mediated a dramatic increase in the cytoplasmic elastic shear modulus of the infected cells, and a transition in the viscoelastic behavior of the cells from viscous-like to elastic-like. These changes in mechanobiological characteristics might modulate the attachments between EHEC and the host cell to withstand exfoliation, and between the host cell and the extracellular matrix, and might also alter epithelial integrity.
12 citations
TL;DR: In this article, the role of GEF-H1 in mesenchymal stem cell (MSC) osteogenesis was investigated. But, the extent to which FA-mediated signals regulated by the FA protein composition specifies MSC commitment remains largely unknown.
Abstract: Focal adhesions (FAs) undergo maturation that culminates in size and composition changes that modulate adhesion, cytoskeleton remodeling and differentiation. Although it is well recognized that stimuli for osteogenesis of mesenchymal stem cells (MSCs) drive FA maturation, actin organization and stress fiber polarization, the extent to which FA-mediated signals regulated by the FA protein composition specifies MSC commitment remains largely unknown. Here, we demonstrate that, upon dexamethasone (osteogenic induction) treatment, guanine nucleotide exchange factor H1 (GEF-H1, also known as Rho guanine nucleotide exchange factor 2, encoded by ARHGEF2) is significantly enriched in FAs. Perturbation of GEF-H1 inhibits FA formation, anisotropic stress fiber orientation and MSC osteogenesis in an actomyosin-contractility-independent manner. To determine the role of GEF-H1 in MSC osteogenesis, we explore the GEF-H1-modulated FA proteome that reveals non-muscle myosin-II heavy chain-B (NMIIB, also known as myosin-10, encoded by MYH10) as a target of GEF-H1 in FAs. Inhibition of targeting NMIIB into FAs suppresses FA formation, stress fiber polarization, cell stiffness and osteogenic commitments in MSCs. Our data demonstrate a role for FA signaling in specifying MSC commitment.
8 citations
TL;DR: 3-D traction measurements indicate that the vertical and horizontal traction forces are regulated by the cortical and cytoskeletal crosslinking, which are interconnected since the time evolution of the Vertical and horizontal forces is well correlated.