Greater Traction Forces Research Articles

Dynamic nanomechanical characterization of cells in exosome therapy

Exosomes derived from mesenchymal stem cells (MSCs) have been confirmed to enhance cell proliferation and improve tissue repair. Exosomes release their contents into the cytoplasmic solution of the recipient cell to mediate cell expression, which is the main pathway through which exosomes exert therapeutic effects. The corresponding process of exosome internalization mainly occurs in the early stage of treatment. However, the therapeutic effect of exosomes in the early stage remains to be further studied. We report that the three-dimensional cell traction force can intuitively reflect the ability of exosomes to enhance the cytoskeleton and cell contractility of recipient cells, serving as an effective method to characterize the therapeutic effect of exosomes. Compared with traditional biochemical methods, we can visualize the early therapeutic effect of exosomes in real time without damage by quantifying the cell traction force. Through quantitative analysis of traction forces, we found that endometrial stromal cells exhibit short-term cell roundness accompanied by greater traction force during the early stage of exosome therapy. Further experiments revealed that exosomes enhance the traction force and cytoskeleton by regulating the Rac1/RhoA signaling pathway, thereby promoting cell proliferation. This work provides an effective method for rapidly quantifying the therapeutic effects of exosomes and studying the underlying mechanisms involved.

Assessment of the efficiency of the skidding portage on the slopes with incomplete information on the technological properties of thawing soils of the cryolithozone

In the Russian Federation, a significant part of the territory of the forest fund is located on permafrost. Many regions of Russia have large reserves of ripe and over-mature operational forests, and a significant part of these reserves are located in hard-to-reach places, not vehicles and skidding systems based on them not only remains relevant, but becomes even more acute, since the ecosystems of mountain forests, forests on the slopes of hills, etc., are among the most vulnerable, subject to water and wind erosion. To reduce the negative impact of forest machinery movers on soils, semi-tracked vehicles are often used, which, due to a significantly larger contact spot with the surface of the movement, and a greater traction force in difficult conditions, show better performance characteristics. The article shows that when drawing up a plan for the development of cryolithozone cutting areas on slopes, it is necessary, among other things, to take into account the geotechnical conditions of the cutting area, namely, its relief, hydrogeology, technological properties of composing soils — their stability, strength, bearing capacity, elastic-plastic and deformation characteristics. The results of the performed studies contribute to the solution of the task and allow for a more reliable assessment of the operability of the skidding portage (technological corridor) on the slopes with incomplete information about the parameters of the strength passport (technological properties) of the thawing soil. only in relation to the development of the road network, but also in terms of terrain. Currently, the overwhelming volume of wood harvesting in Russia is produced with the help of modern machine complexes, mainly including wheeled forestry machines of various layouts and purposes. At the same time, the problem of the negative impact of wheeled forest vehicles and skidding systems based on them not only remains relevant, but becomes even more acute, since the ecosystems of mountain forests, forests on the slopes of hills, etc., are among the most vulnerable, subject to water and wind erosion. To reduce the negative impact of forest machinery movers on soils, semi-tracked vehicles are often used, which, due to a significantly larger contact spot with the surface of the movement, and a greater traction force in difficult conditions, show better performance characteristics. The article shows that when drawing up a plan for the development of cryolithozone cutting areas on slopes, it is necessary, among other things, to take into account the geotechnical conditions of the cutting area, namely, its relief, hydrogeology, technological properties of composing soils — their stability, strength, bearing capacity, elastic-plastic and deformation characteristics. The results of the performed studies contribute to the solution of the task and allow for a more reliable assessment of the operability of the skidding portage (technological corridor) on the slopes with incomplete information about the parameters of the strength passport (technological properties) of the thawing soil.

A New Proposal for Calibrated Gauges for Removable Partial Dentures: A Finite Element Analysis.

The aim of this study was to evaluate the stress distribution of a planned removable partial denture (RPD) using new proposals for calibrated gauges of 0.3 mm and 0.35 mm undercuts through the three-dimensional (3D) finite element methodology, and compare them with 0.25 mm and 0.5 mm gauges that are already existing in clinical practice. Kennedy class-I edentulous 3D models and their respective RPDs (InVesalius software; Rhinoceros and SolidWorks CAD) were created and exported to the finite element program HyperMesh 2019 for mesh configuration. In the following steps, axial loading (0º) of 40 N per point was performed, with 3 points on the molars and 2 points on the premolars, totaling 280 N unilaterally. The model was processed by the OptiStruct 2019 software and imported into the HyperView 2019 software to obtain the stress maps (MPa). The use of 0.30 and 0.35 mm calibrated gauges presented tensions similar to those with the 0.25 mm gauge (gold standard) and caused no significant damage to biological structures. The use of a 0.5 mm undercut caused greater traction force in the periodontal ligament of the abutments. The 0.35 mm undercut seems promising as it presented more favorable results in this simulation, on the other hand, a 0.5 mm undercut is greater than that necessary for retainers made of CoCr. This study aims to measure a new undercut gauge (0.35 mm) to increase the retention area in abutment teeth of removable partial dentures.

The transcription factor PREP1(PKNOX1) regulates nuclear stiffness, the expression of LINC complex proteins and mechanotransduction

Mechanosignaling, initiated by extracellular forces and propagated through the intracellular cytoskeletal network, triggers signaling cascades employed in processes as embryogenesis, tissue maintenance and disease development. While signal transduction by transcription factors occurs downstream of cellular mechanosensing, little is known about the cell intrinsic mechanisms that can regulate mechanosignaling. Here we show that transcription factor PREP1 (PKNOX1) regulates the stiffness of the nucleus, the expression of LINC complex proteins and mechanotransduction of YAP-TAZ. PREP1 depletion upsets the nuclear membrane protein stoichiometry and renders nuclei soft. Intriguingly, these cells display fortified actomyosin network with bigger focal adhesion complexes resulting in greater traction forces at the substratum. Despite the high traction, YAP-TAZ translocation is impaired indicating disrupted mechanotransduction. Our data demonstrate mechanosignaling upstream of YAP-TAZ and suggest the existence of a transcriptional mechanism actively regulating nuclear membrane homeostasis and signal transduction through the active engagement/disengagement of the cell from the extracellular matrix.

Venting the Central Compartment of the Hip Prior to Distraction Minimizes Overall Hip Distraction Forces

Objectives:Arthroscopic hip surgery requires application of ipsilateral lower extremity traction to achieve adequate joint distraction and hip central compartment access. Higher traction forces applied to the lower extremity allow greater hip joint distraction, improving the working space, in order minimize iatrogenic chondral and labral injury. However, greater traction forces have demonstrated a higher potential for iatrogenic traction related injuries. Controversy exists about the clinical relevance of procedural modifications, such as venting the hip, as a means of reducing the amount of traction force required to safely distract the hip joint. This study was designed to evaluate the difference between no venting versus venting the hip prior to application of traction on the overall amount of traction needed to distract the hip joint during hip arthroscopy.Methods:A total of 55 hips in 54 consecutive patients undergoing primary arthroscopic hip surgery were retrospectively reviewed. Prior to any instrumentation, interval fluoroscopic images of the operative hip joint were taken at 0, 25, 50, 75, and 100 pound-force (lb-f) (0, 11.3, 22.7, 34.0, and 45.4 kilogram-force (kg-f)) of applied traction. The hip was then taken off traction and the joint was vented using a standard hip access 14-gauge spinal needle and injected with 20 milliliters of air. Before any additional intervention, traction was again applied to the operative extremity and fluoroscopic images were obtained at the same traction force intervals. Joint displacement was measured at each traction force interval both before and after venting. Fluoroscopic images were scaled based on AP pelvis radiographs in order to obtain millimeteric joint space measurements.Results:The mean difference in hip joint displacement without venting and with venting was 0.29, 2.24, 4.06, 4.13, and 3.80mm at 25, 50, 75, and 100 lbs-f of traction, respectively. Paired samples t-testing demonstrated statistically significant increases in distraction distance (p<0.01) at all levels of traction (Table 1). Prior to venting, 0%, 7.3%, 27.8%, 44.0% of hips distracted at least 10 mm at 25, 50, 75, and 100 lbs-f of traction, respectively. After venting, 14.6%, 45.0%, 74.0%, 86% of hips distracted at least 10 mm at 25, 50, 75, and 100 lbs-f of traction, respectively (Figure 1).Conclusion:This study demonstrates that venting the hip prior to the application of traction significantly increases the amount of distraction distance achieved for a given traction force at multiple levels of traction. With venting of the hip, the percentage of hips achieving at least 10mm of distraction for 100lbsf almost doubled. These findings suggest venting the hip prior to application of traction could serve to reduce the maximal amount of traction required to safely instrument the hip arthroscopically.Table 1.Pre and post-venting distraction distances by amount of traction force Amount of Traction Pre-venting Mean Distraction Distance (mm)Post-venting Mean Distraction Distance (mm)Mean Pre- versus Post-venting Difference (mm)p-value0 lb-f (0 kg-f)4.614.900.290.00325 lb-f (11.3 kg-f)4.877.112.24<0.00150 lb-f (22.7 kg-f)5.829.884.06<0.00175 lb-f (34.0 kg-f)7.6611.784.13<0.001100 lb-f (45.4 kg-f)9.2213.023.80<0.001Figure 1.

H2-calponin Gene Knockout Increases Traction Force of Mouse Fibroblasts in vitro

Cell traction force (CTF) plays a critical role in controlling cell shape, enabling cell motility, and maintaining cellular homeostasis during various biological processes such as wound healing, angiogenesis, and cancer metastasis. It has been demonstrated that h2-calponin, an actin binding protein found in smooth muscle and non-muscle cells including epithelial cells, endothelial cells, macrophages and fibroblasts, plays a role in regulating the actin cytoskeleton activities in cell adhesion, migration and cytokinesis. We recently found that knockout (KO) of h2-calponin gene increased cell motility when compared to wild-type (WT) cells. This finding indicated a potential involvement of h2-calponin in producing CTF. The present study investigated the role of h2-calponin in mouse fibroblast traction force. Primary fibroblasts were isolated from leg muscles of h2-calponin KO and WT mice and analyzed using CTF-microscopy. CTF-microscopy is the current state-of-the-art method to determine CTF in a cell spread on a two-dimensional substrate. Using CTF-microscopy, we determined the root-mean square traction force, the total strain energy, net contractile movement produced by mouse fibroblasts cultured on a thin layer of 8-kPa polyacrylamide gel containing fluorescent beads of 0.2 µm in diameter. The results showed that h2-calponin KO fibroblasts had greater traction force than WT control. In comparison to WT cells expressing abundant tropomyosin-2, h2-calponin KO fibroblasts lost tropomyosin-2, a phenotype mimicking that of metastatic cancer cells. H2-calponin KO fibroblasts also adhered to cultural substrate slower than WT control, had smaller cell spreading area, and rounded up faster during trypsin treatment, supporting the role of h2-calponin in stabilizing the actin cytoskeleton. Our findings indicate that h2-calponin has an inhibitory role in the production of CTF, consistent with the increased motility of h2-calponin-null cells. Further studies on the mechanisms of h2-calponin-mediated CTF regulation and cell motility are underway.

An experimental study on spinal cord traction effect.

An experimental study was carried out on the pathophysiology of spinal cord traction injury. In 50 dogs, spinal cord traction impairment was created by gradual lumbosacral cord traction. Physiologic integrity of the spinal cord was monitored and recorded by the spinal evoked potentials. With greater traction force, the potentials gradually lessened in amplitude. The vulnerability of the spinal cord to compression force was increased by spinal cord traction. Under 200 g traction, the vulnerability of the lower thoracic cord was most increased. The authors conclude that tethered cord syndrome is caused by the impairment of the spinal cord and lumbosacral roots due to traction, and that spinal cord traction not only causes spinal cord impairment but increases the spinal cord vulnerability to compression.