Cyclic Stretch Promotes Migration of MC3T3-E1 Cells via Increasing Runx2 Expression / 医用生物力学

Objective To investigate the effects of cyclic stretch on migration of MC3T3-E1 cells and its related mechanism. Methods The strain loading system was used to stretch MC3T3-E1 cells cultured in vitro with 15% amplitude, to simulate the mechanical condition in vivo. The wound healing assay was used to detect the migration of MC3T3-E1 cells. Western blotting was used to test Runx2 expression. RNA interfering was used to decrease Runx2 expression. Results Cyclic mechanical stretch with 15% amplitude, 1.25 Hz frequency and lasting for 24 hours could promote the migration of MC3T3-E1 cells and increase the expression level of Runx2. Runx2 interference inhibited the migration of MC3T3-E1 cells in static culture condition. Interference with Runx2 expression in MC3T3-E1 cells could partially reduce the positive effect of cyclic mechanical stretch on cell migration. Conclusions Cyclic stretch can promote the migration of MC3T3-E1 cells, and Runx2 may play an important role in this process. This study provides experimental basis for finding innovative clinical treatment method to promote fracture healing.

Berberine Inhibits Mechanical Stretch Stress induced MAPK Phosphorylation，Proliferation and Migration of Vascular Smooth Muscle Cells / 中山大学学报(医学科学版)

@#【Objective】To observe whether berberine can inhibit vascular smooth muscle cells（VSMC）proliferation induced by mechanical strength stress and to investigate the role of MAPK pathway in it.【Methods】The cultured VSMC were divided into 4 groups：negative control group（NC group），stretch stress group（SS group），berberine pretreated and stretch stress stimulation group（BBR+SS group），and berberine group. In NC group，phosphate buffer saline was used as a negative control；in SS group，stretch stress was given to VSMC；in BBR+SS group，VSMC were pretreated with berberine for 1 hour and then exposed to stretch stress；in BBR group，VSMC were treated only with berberine for 1 hour and cultured in serum- free DMEM afterwards. We collected VSMC in each group ，detected and analyzed their MAPK phosphorylation，proliferation and migration by using Western blotting，immunofluorescence and wound-healing assay respectively. 【Results】 Compare with NC group，stretch stress markedly induced VSMC proliferation and migration ，which could be inhibited significantly by berberine. Stretch stress obviously increased phosphorylation of MAPK （ERK，JNK，p38），which could be inhibited by berberine in a concentration dependent manner. 【Conclusion】 Berberine inhibits hypertension-induced proliferation and migration of VSMC through MAPK pathway. The results revealed the new use and mechanism of berberine，and provided important data for further study on the prevention and treatment of vascular remodeling caused by abnormal increase of mechanical stress in hypertension.

In vivo Mechanical Niches of Vascular Cells / 医用生物力学

The elastic stress and viscous shear stress experienced by the vessel wall under pulse blood pressure and blood flow and the mechanical properties of the substrate constitute the in vivo mechanical niches of vascular cells, and these mechanical stimuli are involved in regulating the biological responses of vascular cells and inducing the remodeling and pathological changes of vascular tissues. Although many experimental studies on vascular mechanobiology have been reported, the quantitative correlation between the mechanical stimuli of in vitro experiments and the physiological and pathological conditions of blood vessels remains to be elucidated. This paper summarized the quantitative evaluation method of in vivo mechanical niches of vascular cells from the viewpoint of biomechanics, and then focused on effects of the physiological locations and aging on mechanical behaviors of the vessel wall. This paper also explored the physiological and pathological characteristics of the cellular mechanical niches and their implications for current vascular mechanobiological studies.

Policistina-1 protege a los cardiomiocitos de la necrosis inducida por estrés mecánico / Policystin-1 protects cardiomyocytes from mechanical stress induced necrosis

Resumen: Antecedentes: La muerte de los cardiomiocitos es determinante en el desarrollo de patologías cardiacas posteriores al infarto del miocardio y la insuficiencia cardiaca. Las variaciones en la expresión de la familia de proteínas BCL-2 regulan vías, tanto de muerte, como de sobrevida celular. Así, BCL-2 es una proteína anti- apoptótica y NIX una proteína que induce la necrosis y/o la apoptosis celular. La Policistina-1 (PC1) es un mecanosensor vital para la función contráctil cardiaca; sin embargo, se desconoce su papel en la sobrevida de los cardiomiocitos durante el estrés mecánico. Objetivo: Determinar si PC-1 previene la muerte de los cardiomiocitos inducida por estrés mecánico y las proteínas BCL-2 y NIX. Métodos: Se utilizó cultivo de cardiomiocitos de ratas neonatas controles o deficientes en la expresión de PC1, estimulados con solución hiposmótica (HS), como modelo de estrés mecánico. Se midió la muerte por necrosis y apoptosis y los niveles de BCL-2 y NIX. Resultados: La deficiencia de la PC1 en los cardiomiocitos induce un aumento de la necrosis y los niveles proteicos de NIX en las células estimuladas con HS. El estrés mecánico induce la apoptosis basal relacionada a una disminución de BCL- 2, independiente de la expresión de la PC1. Conclusiones: La PC1 protege a los cardiomiocitos de la necrosis por estrés mecánico, lo que podría deberse en parte a su papel en la regulación de los niveles de las proteínas NIX.

Abstracts: Background: Cardiomyocytes death is a determining factor in the development of cardiac dysfunction after myocardial infarction and heart failure. The change in BCL-2 family protein expression regulates both cell death and survival pathways, whereas BCL-2 is an anti-apoptotic protein and NIX induces necrosis and/or apoptosis. Polycystin-1 (PC1) is a crucial mechanosensor for cardiac contractile function. However, its role in cardiomyocyte survival during mechanical stress is unknown. Aim: To study the relationship of PC1 with mechanical stretch-death in cardiomyocytes and the BCL-2, and NIX proteins. Methods. Controls or deficient expression of PC1 neonatal rat ventricular myocytes were stimulated with hypoosmotic solution (HS) and used as a model of mechanical stress. Necrosis or apoptosis cell death, BCL-2 and NIX protein levels were measured. Results: Deficient expression of PC1 increases cardiomyocyte necrosis and NIX protein levels in cells stimulated with HS. Mechanical stress induces basal apoptosis related to a decrease in BCL-2, independent of PC1 expression. Conclusion: PC1 protects cardiomyocytes from mechanical stress necrosis, at least in part, by regulating NIX protein levels.

Effects of silencing the HIF-1α gene on the expression of BSP and osterix in rat BMMSCs under tension / 口腔疾病防治

Objective@#To explore the effect of hypoxia inducible factor 1α (HIF-1α) gene silencing in rat bone marrow mesenchymal stem cells (BMMSCs) under mechanical distraction on the expression of bone sialoprotein (BSP) and osterix and to provide a new idea for repairing bone defects with BMMSCs.@*Methods @#The shRNA sequence was designed according to the rat HIF-1α gene, and the pGMLV-SC1RNAi lentiviral vector was cloned after PCR amplification. After screening positive clones and identifying competent transformed cells by sequencing, 293T cells were packaged and titered, rat BMMSCs were transfected and cultured in vitro. Clones with stably silenced HIF-1α expression were screened by inverted fluorescence microscopy. The RNAi response experiment was divided into four groups: the blank control group, the HIF-1α shRNA group, the negative control group, and the response group. Western blot was used to detect the expression of HIF-1α protein in the four groups to verify the response of the target genes and exclude off-target effects. A Flexcell FX-5000T cell stress loading system was used to intervene in the mechanical stretch of the cells. qRT-PCR and Western blot were used to detect the expression of BSP and osterix in the blank control group, HIF-1α shRNA group, and negative control group.@*Results@#The HIF-1α shRNA lentiviral vector was successfully constructed. The results of the RNAi response showed no significant difference in the expression of HIF-1α between the response and the blank control group (P > 0.05). The recombinant lentivirus could effectively silence HIF-1α in BMMSCs. After mechanical distraction of the BMMSCs, compared with the blank and negative control groups, the HIF-1α shRNA group showed significantly increased mRNA and protein expression of the bone-related factors BSP and osterix (P < 0.05); there was no significant difference in the mRNA and protein expression of BSP or osterix between the blank and negative control groups (P > 0.05).@*Conclusion @#Silencing HIF-1α in BMMSCs under mechanical distraction can promote the expression of BSP and osterix.

Expression characteristics of Piezo1 protein in stress models of human degenerative chondrocytes / 中国骨伤

<p><b>OBJECTIVE</b>To explore the expression characteristics of new mechanosensitive ion channel Piezo1 protein in stress models of human degenerative chondrocytes.</p><p><b>METHODS</b>The stress stimulation model of human degenerative chondrocytes in vitro was constructed. Multi-channel cell stretch stress loading system FX-4000T was used to treat chondrocytes. According to the results of pre-test, the loading frequency of 0.5 Hz and the cell elongation of 20% were loaded. According to cell processing time, it was divided into 0 h, 2 h, 12 h, 24 h and 48 h mechanical stress group. The RT-PCR and Western-blot were used to test the expression of the Piezo1, also the Laser scanning confocal microscope (LSCM) was used to test the intensity of the fluorescence of the Piezo1.</p><p><b>RESULTS</b>(1)The result of the RT-PCR showed that the expression of the Piezo1 in the 2 h group was higher than the 0 h group(13.917, 0.037 1, <0.05). The expression of the piezo1 in the 24 h group was the highest. While the expression of the piezo1 in the 48 h group was lower than the expression of the piezo1 in the 24 h group(13.917, 0.049 5, <0.05). (2)The result of the Western-blot showed that the 2 h group was higher than the 0 h group(19.341, 0.037 1, <0.05). The expression of the 24 h had the highest expression which was higher than the 48 h group(19.341, 0.017 7, <0.05). (3)The Piezo1 protein was extensively expressed in the cytoplasm and nucleus of the nucleus pulposus cells. And with the increase of stress processing time, the fluorescence intensity of the protein also increased.</p><p><b>CONCLUSIONS</b>In human degeneration cartilage cells, the new mechanio sensitive ion channel Piezo1 protein has a trace expression. After loading periodic mechanical tensile force, the expression of Piezo1 protein increases with time dependence.</p>

Effects of mechanical stretch stress on the proliferation and differentiation of human stem cells from the ap-ical papilla / 医学研究生学报

Objective SCAP are seen as seed cells of peri-apical tissue regeneration and used in periapical tissue regeneration project based on stem cells .In this study, we aim to explore the ef-fectdifferent mechanical stretch stress on the proliferation and differen-tiation potential of human stem cells from the apical papilla ( SCAP ) ,and to clarify the mechanism of how mechanical stretch stress regulate human SCAP ,which will provide theoretical guidance for ortho-dontic treatment . Methods Human SCAP was isolated , cultured and identified by combined explants method and enzymatic separa-tion method and limited dilution .MTT assay was used to detect the effect different static mechanical stretch stress stimulation have on the proliferation of SCAP .Western blot was used to detect the expression changes of SCAP osteogenesis /odontoblast differentiation-re-lated protein (ALP, OSX,DSP) under mechanical stretch stressand to detect the expression of SCAP endoplasmic reticulum stress mo -lecular chaperone GRP 78 under different static mechanical stretch stress . Results SCAP were successfully isolated and cultured , and we induced SCAP to differentiate into osteoblasts and adipocytes successfully by osteogenic medium and adipogenic medium .Flow cytometry was performed in accordance with SCAP immunophenotype .Compared with the control group , 150g mechanical stretch stress stimulation promoted SCAP proliferation first and then inhibited SCAP proliferation [(0.481±0.226),(1.375±0.104),(1.425± 0.136),(1.556±0.268),(0.589±0.29),P<0.05].It was same in the 200g group.250g mechanical stretch stress stimulation signifi-cantly inhibited SCAP proliferation [(0.373±0.146),(0.545±0.069),(0.745±0.273),(0.967±0.278),(1.060±0.362),P<0.05]. The expression levels of ALP , OSX and DSP protein in each group were higher than those in the control group (P<0.05).Compared with the control group, the expression of GRP78 protein was up-regulated (P<0.05). Conclusion Mechanical stretch stress could regulate the SCAP proliferation and osteogenesis/odontoblast differentiation .What′s more,endoplasmic reticulum stress played a role in osteogenesis/odontoblast differentiation under mechanical stretch stress and promoted SCAP osteogenesis /odontoblast differentiation .

Effects of mechanical stretch stress on the proliferation and differentiation of human stem cells from the ap-ical papilla / 医学研究生学报

Objective SCAP are seen as seed cells of peri-apical tissue regeneration and used in periapical tissue regeneration project based on stem cells .In this study, we aim to explore the ef-fectdifferent mechanical stretch stress on the proliferation and differen-tiation potential of human stem cells from the apical papilla ( SCAP ) ,and to clarify the mechanism of how mechanical stretch stress regulate human SCAP ,which will provide theoretical guidance for ortho-dontic treatment . Methods Human SCAP was isolated , cultured and identified by combined explants method and enzymatic separa-tion method and limited dilution .MTT assay was used to detect the effect different static mechanical stretch stress stimulation have on the proliferation of SCAP .Western blot was used to detect the expression changes of SCAP osteogenesis /odontoblast differentiation-re-lated protein (ALP, OSX,DSP) under mechanical stretch stressand to detect the expression of SCAP endoplasmic reticulum stress mo -lecular chaperone GRP 78 under different static mechanical stretch stress . Results SCAP were successfully isolated and cultured , and we induced SCAP to differentiate into osteoblasts and adipocytes successfully by osteogenic medium and adipogenic medium .Flow cytometry was performed in accordance with SCAP immunophenotype .Compared with the control group , 150g mechanical stretch stress stimulation promoted SCAP proliferation first and then inhibited SCAP proliferation [(0.481±0.226),(1.375±0.104),(1.425± 0.136),(1.556±0.268),(0.589±0.29),P<0.05].It was same in the 200g group.250g mechanical stretch stress stimulation signifi-cantly inhibited SCAP proliferation [(0.373±0.146),(0.545±0.069),(0.745±0.273),(0.967±0.278),(1.060±0.362),P<0.05]. The expression levels of ALP , OSX and DSP protein in each group were higher than those in the control group (P<0.05).Compared with the control group, the expression of GRP78 protein was up-regulated (P<0.05). Conclusion Mechanical stretch stress could regulate the SCAP proliferation and osteogenesis/odontoblast differentiation .What′s more,endoplasmic reticulum stress played a role in osteogenesis/odontoblast differentiation under mechanical stretch stress and promoted SCAP osteogenesis /odontoblast differentiation .

Effect of mechanical stretch preconditioning on pathological stretch-induced activation ofγ-aminobutyric acid signaling pathway in human typeⅡ alveolar epithelial cells / 中华危重病急救医学

Objective To evaluate the effect of mechanical stretch preconditioning on pathological stretch-induced activation of γ-aminobutyric acid (GABA) signaling pathway in human type Ⅱ alveolar epithelial cells (AEC Ⅱ).Methods AEC Ⅱ cell line (A549 cells) culturedin vitro were divided into control group (group C), pathological stretch group (group P1) and mechanical stretch preconditioning group (group P2). In group C, A549 cells were cultured routinely. In group P1, A549 cells were exposed to 20% cyclic stretch for 6 hours. In group P2, A549 cells were exposed to 5% cyclic stretch for 60 minutes, and then exposed to 20% cyclic stretch for 6 hours. The cells were harvested for determination of the cell viability by methyl thiazolyl tetrazolium assay, lactate dehydrogeuase (LDH) release was determined by colorimetric method, the levels of interleukin (IL-1β and IL-6) and tumor necrosis factor-α (TNF-α) were determined by enzyme linked immunosorbent assay (ELISA), the mRNA expressions of IL-1β, IL-6 and TNF-α were determined by reverse transcription-polymerase chain reaction (RT-PCR), and the protein expressions of glutamic acid decarboxylase (GAD) and γ-aminobutyric acid A receptor (GABAAR) were determined by Western Blot.Results Compared with group C, the cell viability of group P1 was significantlydecreased (A value: 0.196± 0.071 vs. 0.886±0.107), the release rate of LDH was significantly increased [(12.3±2.4)% vs. (1.9±0.5)%]; the contents and mRNA expressions of IL-1β, IL-6 and TNF-α in cell culture medium were significantly increased [IL-1β (ng/L): 138.6±19.7 vs. 32.7±7.4, IL-6 (ng/L): 196.5±31.7 vs. 55.4±13.8, TNF-α (ng/L): 111.3±21.8 vs. 20.8±7.6; IL-1β mRNA (2-ΔΔCT): 2.79±0.44 vs. 0.83±0.12, IL-6 mRNA (2-ΔΔCT): 1.99±0.25 vs. 0.56±0.11, TNF-α mRNA (2-ΔΔCT): 2.54±0.37 vs. 0.72±0.09]; the protein expressions of GAD and GABAAR were significantly decreased [GAD (gray value): 0.38±0.12 vs. 1.75±0.45, GABAAR (gray value): 0.29±0.09 vs. 1.68±0.39; allP < 0.05]. Compared with group P1, the cell viability of group P2 was significantly increased (A value: 0.523±0.132 vs. 0.196±0.071),the release rate of LDH was significantly decreased [(6.9±1.7)% vs. (12.3±2.4)%]; the contents and mRNA expressions of IL-1β, IL-6 and TNF-α in cell culture medium were significantly decreased [IL-1β (ng/L): 79.2±11.6 vs. 138.6±19.7, IL-6 (ng/L): 89.6±15.6 vs. 196.5±31.7, TNF-α (ng/L): 55.9±11.4 vs. 111.3±21.8; IL-1β mRNA (2-ΔΔCT): 1.92±0.36 vs. 2.79±0.44, IL-6 mRNA (2-ΔΔCT): 1.09±0.18 vs. 1.99±0.25, TNF-α mRNA (2-ΔΔCT): 1.77±0.25 vs. 2.54±0.37]; the protein expressions of GAD and GABAAR were significantly increased [GAD (gray value): 1.26±0.33 vs. 0.38±0.12, GABAAR (gray value): 1.04±0.15 vs. 0.29±0.09; allP < 0.05]. Conclusion The mechanism by which mechanical stretch preconditioning attenuates pathological stretch-induced injury in human AECⅡ is related to the activation of GABA signaling pathway.

The Effects of Epigallocatechin-3-Gallate and Mechanical Stimulation on Osteogenic Differentiation of Human Mesenchymal Stem Cells: Individual or Synergistic Effects

This study aims to investigate the roles and effects of EGCG (epigallocatechin-3-gallate) during the osteogenic differentiation of human mesenchymal stem cells (hMSCs) in vitro. Recent studies have shown that proper mechanical stimuli can induce osteogenic differentiation of hMSCs apart from biochemical factors. In this study, the hMSC cultures were subjected to: (1) 25 uM EGCG alone or (2) 3% mechanical stretching (0.2 Hz for 4 h/day for 4 days) or (3) in combination with 3% mechanical stretching (0.2 Hz for 4 h/day for 4 days). The two factors were applied to the cell cultures separately and in combination to investigate the individual and synergistic effect of both mechanical stimulation and ECGC in the osteogenic differentiation of hMSCs. Utilizing real time PCR, we measured various osteogenic markers and even those related to intracellular signalings. Further investigation of mitochondria was performed that mitochondria biogenesis, antioxidant capacity, and morphological related markers were measured. hMSCs were to be osteogenic or myogenic differentiated when they were under 3% stretching only. However, when EGCG was applied along with stretching they were to be osteogenic differentiated rather than to be myogenic differentiated. This was supported by evaluating intracellular signalings: BMP-2 and VEGF. Therefore, the synergistical effects of simultaneous employment of stretching and EGCG on osteogenic differentiation were confirmed. Moreover, simultaneous employment was found positive in mitochondria biogenesis, antioxidant capacity, and morphological changes. Through this study, we came into the conclusion that the combination of proper mechanical stretching, 3% in this study, and EGCG promote osteogenic differentiation. Reflecting that EGCG can be obtained from plants not from the chemical syntheses, it is worth to be studied further either by animal tests or long-term experiments for clinical applications.

The influence of mechanical stretch on expression of NLRP3 inflammasome related factors in human periodontal ligament cells / 医用生物力学

Objective To study the effect of mechanical stretch on expression of inflammasome related factors in human periodontal ligament cells (HPDLCs). Methods HPDLCs were subjected to mechanical stretch with a 20% elongation magnitude for 6 h or 24 h, respectively. The mRNA and protein expression levels of IL-1β, Caspase-1 and NLRP3 were detected by real-time quantitative PCR and Western blot. The levels of IL-1β in the cell-culture medium of HPLCs in response to mechanical stretch for 1, 2, 4, 6 h were detected by ELISA, respectively. In control group, HPDLCs were cultured in similar conditions but not subjected with stretch. Results The mRNA and protein expression levels of IL-1β, Caspase-1 and NLRP3 were up-regulated with mechanical stretch for 6 h (P<0.05). The protein expression level of NLRP3 was up-regulated with mechanical stretch for 24 h (P<0.05). Compared with control group, the content of IL-1β in the cell-culture medium of HPLCs was increased significantly in response to mechanical stretch for 4 h and 6 h(P<0.05). Conclusions The expression of NLRP3/Caspase-1/IL-1β related factors in HPDLCs can be induced by 20% mechanical stretch for 6 h.

Effects of cyclic mechanical stretch stimulation on proliferation and aerobic capacity of C2C12 myoblasts / 医用生物力学

Objective To investigate the influence of mechanical stretch at different frequencies on proliferation and aerobic capacity of mice myoblast cells C2C12. Methods C2C12 cells cultured in vivo were exposed to mechanical strain with the magnitude of 15% at the frequency of 1 and 2 Hz, respectively, for 2 hours per day over a period of 4 days by using Flexercell Cell Tension System, while in control group C2C12 cells were cultured statically. The C2C12 cells were observed by inverted phase contrast microscope. CCK-8 Cell Counting Kit was used to estimate the proliferation of cells. After the experiment, the cells were obtained by trypsin digestion. MitoXpress-Xtra system with oxygen sensitive probe was induced to detect the extracellular oxygen consumption level. Results The morphology of C2C12 cells presented a typical long spindle under the microscope following the mechanical stretch stimulation. The cells were arranged in a certain direction, parallel to the direction of tension stimulation and growing in good condition. Compare with the control group, the cell numbers in 1 Hz group and 2 Hz group were significantly increased (P0.05). Conclusions Cyclic mechanical stretch stimulation can effectively induce proliferation of C2C12 cells, which is related to the frequency of mechanical stretch, with the frequency of 1 Hz being optimum. But stretch stimulation has no significant impact on the aerobic ability of C2C12 cells.

The effect of hydrochloric acid stimulation and mechanical stretch on epithelial-mesenchymal transition in ;human lung epithelial cells / 中华危重病急救医学

Objective To investigate the effect of hydrochloric acid (HCl) stimulation and mechanical stretch on epithelial-mesenchymal transition (EMT) and hyaluronan (HA) production in human lung epithelial cells. Methods Human lung epithelial cell line BEAS-2B was cultured in vitro, which was divided into phosphate-buffer saline (PBS) + static group, HCl + static group, PBS + stretch group, and HCl + stretch group respectively in the logarithmic phase. The BEAS-2B cells in two stretching groups were challenged by cyclic stretch with 20% amplitude, frequency of 0.33 Hz, sine wave of the FX-5000T system for 48 hours. The morphology changes in cells before and after stretch were observed with inverted microscope. The protein expressions of epithelial markers E-cadherin and cytokeratin-8 (CK-8) as well as mesenchymal markers vimentin and α-smooth muscle actin (α-SMA) were determined by Western Blot. The secretion of HA was determined by enzyme linked immunosorbent assay (ELISA). Results ① It was shown by microscopic observation that BEAS-2B cells displayed cobblestone morphology, linked closely and cell polarity in PBS + static group, which did not change obviously after HCl stimulation alone. Given purely mechanical stretch after 48 hours, the cells morphology changed from cobblestone shape into long spindle, and increased intercellular space obviously. Double hit of HCl and stretch changed the cells morphology more significantly. ② It was shown by Western Blot that compared with the PBS + static group, HCl alone or combined with purely mechanical stretch after 48 hours, the expressions of E-cadherin and CK-8 were decreased, while those of vimentin and α-SMA were increased, and it was more pronounced in HCl + stretch group [the expression quantity (gray value) as base 1 in PBS + static group, E-cadherin: 0.16±0.08 vs. 1, CK-8: 0.10±0.03 vs. 1, vimentin: 3.35±0.38 vs. 1, α-SMA: 3.10±0.45 vs. 1, all P < 0.01]. ③ It was shown by ELISA that both HCl stimulation and stretch could induce BEAS-2B cells secreting HA as compared with PBS + static group (μg/L: 55.763±0.687, 63.005±0.493 vs. 49.876±1.867), and the production of HA increased more remarkably after double hit (μg/L: 78.220±1.085 vs. 49.876±1.867, P < 0.01). Conclusions Both HCl and mechanical stretch could induce EMT and increase HA secretion in human lung epithelial cells in vitro. Double hit of HCl stimulation and mechanical stretch induced EMT apparently, and further increased the production of HA.

Research progress of tenascin-C in acute aortic dissection / 第二军医大学学报

Acute aortic dissection(AAD) is a medical emergency caused by the destruction of the aortic tunica media and is always fatal. Genetic disorders are known to be responsible for AAD, but little is known about the etiology of other non-genetic cases. Tenascin-C(TnC) is a large extracellular matrix glycoprotein and mechanical stretching can up-regulate TnC expression. TnC knockout (TnC-KO) mice have higher blood pressure in the aortic artery and are liable to develop AAD; and mice with AAD have more inflammatory cells in the aortic tissue. TnC prevents aorta from AAD by regulating ECM structure, regulating vascular smooth muscle cell function and inhibiting inflammatory response in the aorta. In this paper we reviewed the role of TnC in the development and progression of AAD.

Effects from cyclic mechanical stretch on proliferation of rheumatoid arthritis fibroblast-like synoviocytes / 医用生物力学

Objective To investigate the effects from cyclic mechanical stretch on proliferation of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLSs). Methods In the experimental groups, cyclic mechanical stretch, with frequency of 1.0 Hz and magnitude of 3%, 6% and 9%, respectively, was applied to RA-FLSs for 2 h, 6 h, and 12 h. The control group remained in the same culture condition as the experimental groups, but without any mechanical stretch. After mechanical loading, the cell viability was analyzed by MTS, and its proliferation was assayed by flow cytometry. RT-PCR was used to measure the gene expression of the cell cycle regulatory factors, including CDK2, cyclinD1, cyclinE1, and P27. Results Cyclic mechanical stretch with magnitude of 6% and 9% for 6 h or 12 h significantly decreased the cell proliferation and viability in RA-FLSs (P0.05). Conclusions The effects from cyclic mechanical stretch on proliferation of RA-FLSs depend on the stretch magnitude and duration. Mechanical stretch with magnitude of 6% and 9% can inhibit RA-FLSs proliferation, which may be achieved by regulating the expression of Cyclin E1, CDK2 and P27. This study provides references for investigating the role of mechanical stimulation in pathogenesis of rheumatoid arthritis, as well as its prevention and treatment.

Effects of mechanical stimulus on mesenchymal stem cells differentiation toward cardiomyocytes.

Background: Mesenchymal stem cells (MSCs) known to be sensitive to mechanical stimulus. This type of stimulus plays a role in cellular differentiation, so that it might affect MSCs differentiation toward cardiomyocytes. Objectives: Investigate the effect of mechanical stimulus on MSCs differentiation toward cardiomyocytes. Methods: The adipose tissue-derived MSCs were induced to differentiate with 5-azacytidine, and stimulated by one Hz mechanical stretching up to 8%. After 10 days, the cell’s cardiac markers and cardiogenesis-related genes were detected by immumohistochemistrical staining and reverse transcriptase-polymerase chain reaction, and the cell’s ATPase activity was detected. Results: The cyclic mechanical stretching enhanced the expression of cardiogenesis-related genes and cardiac markers, and stimulated the activity of Na+-K+-ATPase and Ca2+-ATPase in the MSCs treated with 5-azacytidine. Without 5-azacytidine pre-treatment, cyclic mechanical stretch alone has little effect. Conclusion: Mechanical stretch combined with 5-azacytidine treatment could accelerate MSCs differentiation toward cardiomyocytes.

Study on the correlation of integrin distribution changes with directional migration of hepatoma cells / 医用生物力学

Objective To explore the influence of integrin redistribution on hepatoma cell alignment and migration and the influence of cytoskeleton reassembly on integrin redistribution by the method of mechanical loading unloading and fibronection(FN) coating. Method By using immuneofluescence staining, cofocal laser scanning microscopy and quantitative morphological analysis, integrin distribution change and crtoskeleton assembly adjustment were observed and the deformation of cell movement was tested and analyzed quantitatively. Results (1) cells with different forms have different integrin expressions and distribution features. The β1 integrin expression for spreading cells was higher than that for round (nonspreading) cells. For spreading cells, the strongest staining was found towards the attachment surface. While for round (nonspreading) cells, the integrin staining on the free surface towards medium was stronger than that towards the attachment surface. (2) After 5 hours of mechanical stretch, the β1 integrin expression for both spreading and round cells increased, and distribution peaks towards the attachment surface broadened. At 1 hour after unloading, the β1 integrin expression decreased and the distribution of integrin staining showed the tendency of dispersion, especially for round cells. (3) After coating the substrates with FN, the β1 integrin expression increased. The integrin staining for either spreading or round cells was more towards the attachment surface to reduce the migration of hepatoma cells. 4) After 5 hours of mechanical stretch, 60% of cells showed their orientation of major axes distributed between 70°～110° towards the stretching direction, and the cytoskeleton aligned vertically to the stretching direction. Cytoskeletons were found significantly depolymerized at 1 hour of unloading. Conclusions The change of integrin distribution is affected by cytoskeleton aligned and the number of ligand. The distribution feature of the whole integrin expression on the surface of individual round cells is related to their stronger invasion and metastasis capability.

ERK signal is pathway involved in mechanical stretch induced HMGB1 expression in alveolar epithelial cells / 解剖学报

Objective To investigate the role of extracellular regulated protein kinase (ERK) signal pathway in mechanical stretch induced high mobility group box 1 protein (HMGB1) expression on alveolar epithelial cells (A549). MethodsA549 cells were cultured and seeded at 1×10~5 cells/ml in 6-well Bioflex cell culture plates. Subsequently, the cells were exposed to cyclic mechanical stretch at 14% (group B) elongation for 4 hours using Flexercell 4000T cell stretching unit. In group C, cells were pretreated with PD98059 for 2 hours before mechanical stretch. Cells in group A without stretch were served as control. The expression of HMGB1 protein and mRNA in A549 cells were detected by immunocytochemisty staining and RT-PCR, respectively. ERK activity was measured by Western blotting method. Results Immunocytochemisty staining indicated that the expression of HMGB1 protein in A549 cells was increased obviously in group B (P<0.05) and decreased in group C (P<0.05). Polymerase chain reaction (RT-PCR) showed that the expression of HMGB1 mRNA was also significantly increased in group B (P<0.05) and decreased in group C (P<0.05). Western blotting analysis confirmed the activation of ERK in A549 cells by mechanical stretch (P<0.05). PD98059, an inhibitor of ERK, might significantly inhibit mechanical stretch induced HMGB1 protein and mRNA expression in A549 cells (P<0.05). Conclusion Mechanical stretch could regulate the expression of HMGB1 gene and protein in A549 cells through ERK signal pathway.

Effects of mechanical stretch on the expression of human beta-defensin-3 in alveolar epithelial cells elicited by interferon- gamma / 中华急诊医学杂志

Objective To study the effect of mechanical stretch on the expression of human beta-defensin-3 (HBD-3) in alveolar epithelial cells(A549 cells) elicited by interferon-gamma(IFN-γ) and to investigate the role of HBD-3 in the pathogenesis of ventilator-associated pneumonia (VAP) . Method A549 cells cultured in vitro were treated with mechanical stretch (group S), 10 ng/ml IFN-γ (group I) ,and 10 ng/ml IFN-γ with mechanical stretch (group IS), respectively. Cells without treatment served as controls (group C). Cells were stretched by 20% amplitude of stretch at 30 cycles/mm by Flexercell-4000[TM]Unit for 2 h, 4 h, and 6 hours. The HBD-3 mRNA expression was determined by real-time RT-PCR after treatment. After 6 hours, treatment, cells were cultured for 24 hours and the expression of HBD-3 was examined by laser scanning confocal microscope. The experimental data were statistically analyzed by using one-way ANOVA analysis and q-test. Results The expression of HBD-3 mRNA in A549 cells could not significantly be changed by mechanical stretch alone. Compared with group C,the HBD-3 mRNA expression after treatment with 10 ng/ml IFN-γ for 2 hours,4 hours and 6 hours increased significantly by (2.63 C,the HBD-3 mRNA expression after treatment with 10 ng/ml IFN-γ and mechanical stretch for 2 hours,4 hours and 6 hours increased by (1.54 were significantly lower than those in group I (P < 0.01). The HBD-3 expression in group IS after mechanical stretch for 6 significantly different from than in group C. Conclusions Mechanical stretch can significantly suppress the up-regulation of HBD-3 in alveolar epithelial cells elicited by IFN-γ, and this may be one of the explaina-tions that patients under mechanical ventilatiori(MV) have a higher risk of VAP.

Effects of Acute Mechanical Stretch on the Expression of Mechanosensitive Potassium Channel TREK-1 in Rat Left Ventricle / 华中科技大学学报（医学）（英德文版）

To explore the role of mechanosensitive potassium channel TREK-1, Western blot analysis was used to investigate the expression changes of TREK-1 in left ventricle in acute mechanically stretched heart. Forty Wistar rats were randomly divided into 8 groups (n=5 in each group),subject to single Langendorff perfusion for 0, 30, 60, 120 min and acute mechanical stretch for 0, 30,60, 120 min respectively. With Langendorff apparatus, an acute mechanically stretched heart model was established. There was no significant difference in the expression of TREK-1 among single Langendorff perfusion groups (P＞0.05). As compared to non-stretched Langendorff-perfused heart, only the expression of TREK-1 in acute mechanically stretched heart (120 min) was greatly increased (P＜0.05). This result suggested that some course of mechanical stretch could up-regulate the expression of TREK-1 in left ventricle. TREK-1 might play an important role in mechanoelectric feedback,so it could reduce the occurrence of arrhythmia that was induced by extra mechanical stretch.