Callus Stimulation Through the Dynamic Mechanical Environment Imposed by Unilateral External Fixation

Cells in the body exist in a dynamic mechanical environment where they are subject to mechanical stretch as well as changes in composition and stiffness of the underlying extracellular matrix (ECM). However, the underlying mechanisms by which cells sense and adapt to their dynamic mechanical environment, in particular to stretch, are not well understood. In this study, we hypothesized that emergent phenomena at the level of the actin network arising from active structural rearrangements driven by nonmuscle myosin II molecular motors play a major role in the cellular response to both stretch and changes in ECM stiffness. To test this hypothesis, we introduce a simple network model of actin-myosin interactions that links active self-organization of the actin network to the stiffness of the network and the traction forces generated by the network. We demonstrate that such a network replicates not only the effect of changes in substrate stiffness on cellular traction and stiffness and the dependence of rate of force development by a cell on the stiffness of its substrate, but also explains the physical response of adherent cells to transient and cyclic stretch. Our results provide strong indication that network phenomena governed by the active reorganization of the actin-myosin structure plays an important role in cellular mechanosensing and response to both changes in ECM stiffness and externally applied mechanical stretch.

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An in Silico Axisymmetric Multistage Model of Linear Biphasic Mesenchymal Stem Cell and Chondrocyte Protein Secreted-Matrix Interactions for the Reconstruction of the Dynamic Mechanical Environment of a Time Varying Magnetic Field Expanded Chondrocyte Biphasic Finite Elemental Model in Articular Cartilage

Cytotherapy ◽

10.1016/j.jcyt.2016.03.288 ◽

2016 ◽

Vol 18 (6) ◽

pp. S154

Author(s):

I. Grigoriadis

Keyword(s):

Magnetic Field ◽

Stem Cell ◽

Articular Cartilage ◽

Mesenchymal Stem Cell ◽

In Silico ◽

Time Varying ◽

Mechanical Environment ◽

Multistage Model ◽

Dynamic Mechanical ◽

Matrix Interactions

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Quantitative Evaluation of Cardiac Cell Interactions and Responses to Cyclic Strain

Cells ◽

10.3390/cells10113199 ◽

2021 ◽

Vol 10 (11) ◽

pp. 3199

Author(s):

Richard Duc Hien Tran ◽

Tessa Altair Morris ◽

Daniela Gonzalez ◽

Ali Hatem Salaheldin Hassan Ahmed Hetta ◽

Anna Grosberg

Keyword(s):

Mechanical Strain ◽

Heart Tissue ◽

Cell Interactions ◽

Cell Phenotype ◽

Cardiac Cell ◽

Cell Type ◽

Mechanical Environment ◽

Dynamic Mechanical ◽

Tissue Organization ◽

Cell Type Specific

The heart has a dynamic mechanical environment contributed by its unique cellular composition and the resultant complex tissue structure. In pathological heart tissue, both the mechanics and cell composition can change and influence each other. As a result, the interplay between the cell phenotype and mechanical stimulation needs to be considered to understand the biophysical cell interactions and organization in healthy and diseased myocardium. In this work, we hypothesized that the overall tissue organization is controlled by varying densities of cardiomyocytes and fibroblasts in the heart. In order to test this hypothesis, we utilized a combination of mechanical strain, co-cultures of different cell types, and inhibitory drugs that block intercellular junction formation. To accomplish this, an image analysis pipeline was developed to automatically measure cell type-specific organization relative to the stretch direction. The results indicated that cardiac cell type-specific densities influence the overall organization of heart tissue such that it is possible to model healthy and fibrotic heart tissue in vitro. This study provides insight into how to mimic the dynamic mechanical environment of the heart in engineered tissue as well as providing valuable information about the process of cardiac remodeling and repair in diseased hearts.

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Nonbridging External Fixation for Fractures of the Distal Radius

Yearbook of Hand and Upper Limb Surgery ◽

10.1016/s1551-7977(08)70094-3 ◽

2006 ◽

Vol 2006 ◽

pp. 126-127

Author(s):

K. Azari

Keyword(s):

External Fixation ◽

Distal Radius

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Surgical treatment of fractures of the distal radius – ORIF vs external fixation with ligamentotaxis

Perspectives in Surgery ◽

10.33699/pis.2020.99.8.343-349 ◽

2020 ◽

Vol 99 (8) ◽

Keyword(s):

External Fixation ◽

Distal Radius ◽

Locking Plates ◽

X Rays ◽

Ao Classification ◽

Radial Inclination ◽

First Choice ◽

Sagittal Tilt ◽

Radial Length ◽

The Mean

Introduction: The study compares the results of open reduction using volar locking plates with ligamentotaxis by external fixation in fractures of distal radius type 2R3C according to AO classification. Methods: A retrospective study evaluating the results of osteosynthesis in patients with distal radius fractures type 2R3C according to AO classification, operated until December 2018. The ORIF method with volar locking plates (LCP) was used in 54 patients, and closed reduction with ligamentotaxis using external fixation (EF) was used in 33 patients. The mean age of the patients was 46.7 years in the LCP group and 59.6 years in the EF group. All were evaluated for their X-ray and functional outcomes and according to the Green and O’Brien score at 6 and 12 months after surgery. Results: According to X-rays at 12 months in the LCP group, the mean sagittal tilt was 10.13°, the mean radial inclination was 23.89°, and the mean radial length was 11.84 mm. In the EF group, the mean sagittal tilt was 6.32°, the mean radial inclination was 24.78°, and the mean radial length was 9.89 mm. According to the Green and O’Brien score, we recorded a mean score of 84.44 points in the LCP group at 12 month; we achieved good and excellent results in 83.33% of the patients and no poor result was observed. In the EF group the final mean score was 77.27; good and excellent results were achieved in 45.46% of the patients and a poor result in one patient. Conclusion: Based on the results in our group of patients, the internal type osteosynthesis using LCP implants can be recommended as a first-choice technique in the treatment of 2R3C fractures according to AO classification.

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