Cell Mechanics

Detailed evaluation of all steps in tumor cell metastasis is critical for evaluating the cell mechanisms controlling metastasis. Using green fluo- rescent protein transfectants of metastatic (MTLn3) and nonmetastatic (MTC) cell lines derived from the rat mammary adenocarcinoma 13762 NF, we have measured tumor cell density in the blood, individual tumor cells in the lungs, and lung metastases. Correlation of

Biomechanics is gaining relevance as complementary discipline to structural and cellular biology. The response of cells to mechanical stimuli determines cell type and function, while the spatial distribution of mechanical forces within the cells is crucial to understand cell activity. The experimental methodologies to approach cell mechanics are diverse but either they are effective in few cases or they rule

In this paper, we describe the design and fabrication of a bio-hybrid tactile sensor and experimental platform. The system uses tissue engineered alginate encapsulated fibroblasts and a conductivity sensor as a transduction system to monitor applied normal and tangential loads in a manner comparable to mechanotransduction in the human haptic system in nonglabrous skin. The tissue is integrated into a microfluidic system interfaced with a nanoporous membrane capable of sustaining the viability of the cells for extended times. The efficacy of the bio-hybrid tactile sensor is validated using a 2 DoF Cartesian manipulator, capable of indenting and sliding textured stimuli over the device. Also, the platform includes a two-cell Peltier-based temperature controlled control module. This allows the evaluation of the effect of temperature variation on the bio-hybrid sensor response, and to decouple the effect of temperature from mechanical stimulation.

Although much progress has been made in the characterization and identification of CD4 functions, its role in mechanical properties of cell membrane remains largely unknown. Here an atomic force microscopy (AFM) was used to investigate the roles of CD4 in the elasticity of the leukemic human Jurkat (clone E6-1) cell membranes. Analysis of the approach force curves with Hertz model for a completely elastic soft sample measured on the selected CD41 and CD4-cells showed that CD41 cell membrane was softer than CD4-one. To confirm that CD4 plays a role in altering cell elasticity, human embryonic kidney 293T cells were transiently trans-fected with wild type (wt) CD4 plasmid before being used in AFM nanoindentation experiments. The results also demonstrated CD4-membrane was stiffer than CD41 one suggesting that CD4 integrated into plasma membrane and altered its mechanical properties. The study gives insights into the role of CD4 on cell membrane mechanical characteristics and might be helpful for development of cell biology and medicine. V C 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 239–244, 2016.

Optical tweezers have been successfully adopted as exceptionally sensitive transducers for microrheology studies of complex fluids. Despite the general trend, in this article I explain why a similar approach should not be adopted for microrheology studies of living cells. This conclusion is acheived on the basis of statistical mechanics principles that indicate the unsuitability of optical tweezers for such purpose.

Analysis of how cells sense and respond to mechanical stress has been limited by the availability of techniques that can apply controlled mechanical forces to living cells while simultaneously measuring changes in cell and molecular distortion, as well as alterations of intracellular biochemistry. We have confronted this challenge by developing new engineering methods to measure and manipulate the mechanical properties of cells and their internal cytoskeletal and nuclear frameworks, and by combining them with molecular cell biological techniques that rely on microscopic analysis and real-time optical readouts of biochemical signaling. In this chapter, we describe techniques like microcontact printing, magnetic twisting cytometry, and magnetic pulling cytometry that can be systematically used to study the molecular basis of cellular mechanotransduction.

Introduction:The relative contributions of CD4+ and CD8+ T cells to transplant rejection remain unknown. The authors integrated a previous model of CD4-mediated graft rejection with a complementary model of CD8-mediated rejection to directly compare the function of graft-reactive CD4+ and CD8+ lymphocytes in vivo in a model where rejection requires transgenic T cells. These studies allow direct comparison of CD4 and CD8 T cell responses to the same antigen without the confounding effects of T cell depletion or homeostatic proliferation.Materials and Methods:Clone 4 and TS1 mice possess MHC class I- and II-restricted CD8+ and CD4+ T cells, respectively, which express transgenic T cell receptors that recognize the influenza hemagglutinin antigen (HA). We compared the in vivo response of CFSE-labeled, HA-specific transgenic CD8+ and CD4+ T cells after adoptive transfer into syngeneic BALB/c mice grafted with HA-expressing skin.Results:As in the authors’ CD4+ model, HA104 skin was consistently rejected by both Clone 4 mice (n=9, MST: 14.2) and by 5×105 Clone 4 lymphocytes transferred to naive BALB/c hosts that do not otherwise reject HA+ grafts. Rejection correlated with extensive proliferation of either graft-reactive T cell subset in the draining lymph nodes, and antigen-specific CD4+ and CD8+ cells acquired effector function and proliferated with similar kinetics.Conclusions:These data extend the authors’ unique transgenic transplantation model to the investigation of CD8 T cell function. The initial results confirm fundamental functional similarity between the CD4 and CD8 T cell subsets and provide insight into the considerable redundancy underlying T cell mechanisms mediating allograft rejection.