Single Cell Traction Force Measured by Foldable Microplates / 医用生物力学

Objective To fabricate a foldable microplate for single cell culture and establish finite element model of the folding microplate, so as to calculate traction force of single cells during contraction in three-dimensional (3D) state.Methods The folding angle of the microplate casued by cell traction force was calculated. Then the relation between bending moment and folding angle as well as the relation between traction force and bending moment were derived by using finite element simulation, so as to realize the characterization of traction force for singel cell in 3D state.Results The folding angles of the microplate with HSF and MC3T3-E1 cells in 3D state were 73°-173° and 49°-138°, respectively. The single cell traction forces of HSF and MC3T3-E1 cells were 55-210 nN and 52-161 nN, respectively.Conclusions The proposed method for measuring traction force of single cells in 3D state by fabricating the foldable microplate for single cell culture will provide some references for further development of calculating traction forces in 3D cell adhesion, spreading and migration.

Effect of sanguinarine on biomechanics of rat airway smooth muscle cells / 生物医学工程学杂志

This study aimed to evaluate the effect of sanguinarine on biomechanical properties of rat airway smooth muscle cells (rASMCs) including stiffness, traction force and cytoskeletal stress fiber organization. To do so, rASMCs cultured were treated with sanguinarine solution at different concentrations (0.005~5 μmol/L) for 12 h, 24 h, 36 h, and 48 h, respectively. Subsequently, the cells were tested for their viability, stiffness, traction force, migration and microfilament distribution by using methylthiazolyldiphenyl-tetrazolium bromide assay, optical magnetic twisting cytometry, Fourier transform traction microscopy, scratch wound healing method, and immunofluorescence microscopy, respectively. The results showed that at concentration below 0.5 μmol/L sanguinarine had no effect on cell viability, but caused dose and time dependent effect on cell biomechanics. Specifically, rASMCs treated with sanguinarine at 0.05 μmol/L and 0.5 μmol/L for 12 and 24 h exhibited significant reduction in stiffness, traction force and migration speed, together with disorganization of the cytoskeletal stress fibers. Considering the essential role of airway smooth muscle cells (ASMCs) biomechanics in the airway hyperresponsiveness (AHR) of asthma, these findings suggest that sanguinarine may ameliorate AHR via alteration of ASMCs biomechanical properties, thus providing a novel approach for asthma drug development.

Numeric reconstruction of 2D cellular actomyosin network from substrate displacement

Introduction: One of the fundamental structural elements of the cell is the cytoskeleton. Along with myosin, actin microfilaments are responsible for cellular contractions, and their organization may be related to pathological changes in myocardial tissue. Due to the complexity of factors involved, numerical modeling of the cytoskeleton has the potential to contribute to a better understanding of mechanical cues in cellular activities. In this work, a systematic method was developed for the reconstruction of an actomyosin topology based on the displacement exerted by the cell on a flexible substrate. It is an inverse problem which could be considered a phenomenological approach to traction force microscopy (TFM). Methods An actomyosin distribution was found with a topology optimization method (TOM), varying the material density and angle of contraction of each element of the actomyosin domain. The routine was implemented with a linear material model for the bidimensional actomyosin elements and tridimensional substrate. The topology generated minimizes the nodal displacement squared differences between the generated topology and experimental displacement fields obtained by TFM. The structure resulting from TOM was compared to the actin structures observed experimentally with a GFP-attached actin marker. Results The optimized topology reproduced the main features of the experimental actin and its squared displacement differences were 11.24 µm2, 27.5% of the sum of experimental squared nodal displacements (40.87 µm2). Conclusion This approach extends the literature with a model for the actomyosin structure capable of distributing anisotropic material freely, allowing heterogeneous contraction over the cell extension.

Biomechanical test in vivo on reduction fixator for treating distal radius fractures / 医用生物力学

Objective To investigate the regular pattern of traction forces during the treatment of distal radius fracture by reduction fixator with pins. Methods A self-designed pin-lock style force transducer instead of two original pin locks in the distal of reduction fixator was adopted to conduct continuous testing on six cases of unstable distal radius fracture of forearms treated by reduction fixator in vivo. The value of static traction force and the added value of traction force in fist clenching at the postoperative 1st, 5th, 14th, 21st, 28th, 35th, 42nd, 49th day, was recorded respectively. Results The maximum and minimum static traction force was 9.93 kg and 2.26 kg, respectively, with mean value of (4.93±1.79) kg. The maximum and minimum traction force increment in fist clenching was 10.40 kg and 0.13 kg, respectively, with mean value of (3.17±2.42) kg. Conclusions Larger axial forces can be generated in muscles of the forearm, by both static tension and dynamic contraction, which might be a serious negative factor in healing unstable distal radius fractures.

High-resolution cellular traction force recovery in two dimensional Fourier domain / 医用生物力学

Objective To develop a new set of algorithms for high-resolution cellular traction force recovery based on two-dimensional Fourier domain by addressing the ill-posed nature of classic cellular force traction recovery. Methods By exploring the inherent characteristics and rules of displacement data on the substrates and Green’s function in the Fourier domain, the phenomenon of ill-posed deconvolution arising in cellular force traction recovery was investigated and a set of self-adaptive filtering algorithms was consequently developed to remarkably restrain the high frequency noise amplification. Results The ill-posed nature of classical Fourier transform traction cytometry (FTTC) made cellular traction force recovery extremely unstable, especially for relatively dense displacement data sampling. In contrast, the proposed self-adaptive filtering algorithms based on FTTC could make cellular traction force distribution more stable and reliable, as the effect of high frequency noise in displacement field on recovery results was weakened significantly. Conclusions This new technique for cellular traction force recovery can effectively suppress the noise and therefore improve the stability of force recovery procedure and spatial resolution, which is expected to find wider application in the study of cell substrate interactions.

Validação de teorias de simulação para operações com escarificadores em solo argiloso no planalto do Estado do Rio Grande do Sul, Brasil / Validation of prediction theories to chisel plow in soils of Rio Grande do Sul State, Brazil

O objetivo deste trabalho foi estudar teorias, utilizadas especialmente para simular situações reais de campo, contrastada por dados empíricos obtidos em condições reais de trabalho agrícola mecanizado em solo de textura argilosa com os resultados obtidos em trabalhos semelhantes realizados em outros países. Avaliou-se as demandas de tração de diferentes combinações entre velocidade e profundidade de trabalho de um escarificador. Buscou-se a representação gráfica da demanda requerida de força de tração e patinagem através da utilização do software Predição versão 1.0, contrastadas com resultados obtidos pela aplicação das teorias de predição Cn, Bn e Mn. As teorias preditivas Cn, Bn e Mn apresentam correlação boa com os valores experimentais, no entanto, existe uma superestimativa por parte das teorias comparadas aos valores medidos experimentalmente, para força de tração e patinagem, causando um dimensionamento do trator inadequado.

The objective of this research was studied theories used specially to simulate real field situations contrasted by empiric data obtained in real real working conditions in mechanized agricultural clay soil with the results obtained in similar studies conducted in other countries. We tried to the graphical representation of the demand required traction force and slippage through the use of Prediction software version 1.0, contrasted with results obtained by applying the theories of prediction Cn, Bn and Mn. Predictive theories Cn, Bn and Mn have good correlation with experimental values, however, there is an overestimation by the theory compared to the values measured experimentally, for traction force and slippage, causing a tractor design inadequate.

Retinal Detachment Associated with Probable Zonular Traction Tufts

Zonular traction tufts, which exist in 15% of normal population, do not cause retinal detachment by themselves but they can cause traction retinal detaehment when there is traction force added. It is thought that the possibility of development of retinal detaehment increases especially when zonular traetion tufts originate posterior to the vitreous base No case of traction retinal detachment caused by zonular traction tufts has been reported. Here, we report one suspected case of traction retinal detachment induced by zonular traction tufts and lens subluxation.