Objective To observe the effects of mechanical stretch on cytokines release from alveolar macrophages( AMs) and the expression of macrophage inflammatory protein-2( MIP-2) induced by lipopolysaccharide( LPS) . Methods AMs were divided into the following groups: ①AMs were subjected to 20% elongation by Flexercell 4000T cell stress system for 24 hours and the supernatant was collected to detect the levels of TNF-α, IL-1β, IL-2, IL-4, IL-6, IL-10, IL-12, IFN-γ, macrophage inflammatory protein-1α( MIP-1α) , MIP-2, monocyte chemoattractant protein-1( MCP-1) , granulocyte /macrophage colony stimulating factors( GM-CSF) , interferon inducible protein-10( IP-10) , regulated on activation in normal T-cell expressed and secreted( Rantes) and keratinocyte chemoattractant( KC) , by using LiquiChip system. ② AMs were subjected to 5% , 10% , 15% and 20% elongation for 24 hours and the supernatant was collected to detect the levels of MIP-2. ③AMs were subjected to 20% elongation and MIP-2 in supernatant was detected 1, 3,6, 12, and 24 hours later. ④ AMs were subjected to 20% elongation and/ or LPS at a concentration of 10 ng/mL, and MIP-2 in supernatant was detected 24 hours later. Unstretched AMs were used as control in all kind of test. Results ①The levels of IL-1β, IL-6,MIP-2, MCP-1, IFN-γand IP-10 secreted by stretched AMs were 8. 7, 4. 3, 38. 6, 4. 8, 14. 2 and 5. 0 times those of the control group( all P lt; 0. 001) . ② The levels of MIP-2 secreted by AMs subjected to 10% , 15% and 20% elongation were ( 480. 5 ±93. 1) pg /mL,( 806. 3 ±225. 9) pg/mL and ( 1335. 7 ±18. 5) pg/mL respectively, all significantly higher than those oft he control group [ ( 34. 6 ±11. 4) pg/mL, all P lt;0. 001] . ③ Three hours after the stimulation of stretch the level of MIP-2 began to increase gradually. And 6, 12, and 24 hours after the stimulation the levels of MIP-2 secreted by the AMs were ( 819. 4 ±147. 5) pg/mL, ( 1287. 6 ±380 ±3 ) pg/mL and ( 1455. 9 ±436. 7) pg/mLrespectively, all significantly higher than those of the control group[ ( 33. 4 ±10. 2) pg/mL, all P lt; 0. 001] . ④When the AMs were stimulated individually by LPS( 10 ng /mL) or mechanical stretch ( 20% ) , the levels of MIP-2 increased to ( 1026. 3 ±339. 5 ) pg/mL and ( 1335. 7 ±318. 5 ) pg/mL respectively( both P lt; 0. 001) . When the AMs were costimulated by LPS and mechanical stretch, the level of MIP-2 increased to ( 2275. 3 ±492. 1) pg/mL, implicating a synergistic effect between mechanical stretch and LPS ( F = 121. 983, P lt; 0. 001) . Conclusions Mechanical stretch activates AMs to produce multiple inflammatory cytokines and induce AMs to secret MIP-2 in a strength- and time-dependent manner.Mechanical stretch also has synergistic effect with LPS in inducing MIP-2 release, which might play an important role in the development of ventilator-induced lung injury.
Idiopathic pulmonary fibrosis (IPF) is a progressive scar-forming disease with a high mortality rate that has received widespread attention. Epithelial mesenchymal transition (EMT) is an important part of the pulmonary fibrosis process, and changes in the biomechanical properties of lung tissue have an important impact on it. In this paper, we summarize the changes in the biomechanical microenvironment of lung tissue in IPF-EMT in recent years, and provide a systematic review on the effects of alterations in the mechanical microenvironment in pulmonary fibrosis on the process of EMT, the effects of mechanical factors on the behavior of alveolar epithelial cells in EMT and the biomechanical signaling in EMT, in order to provide new references for the research on the prevention and treatment of IPF.
ObjectiveTo evaluate the clinical value of skin stretching device in repair of diabetic foot wound.MethodsA retrospective analysis was made on the clinical data of 48 cases with diabetic foot wound who were treated with skin stretching device (trial group, n=24) and with the vacuum sealing drainage combined with skin graft (control group, n=24) respectively between October 2015 and July 2016. There was no significant difference in gender, age, side, course of disease, TEXAS stage between 2 groups (P>0.05). Both patients in 2 groups were treated with sensitive antibiotics according to the results of bacterial culture.ResultsOne case in control group was infected and the skin graft failed, and 1 case in trial group was infected after the treatment, and the two wounds healed after symptomatic treatment. The wounds of the other patients healed successfully, and the healing time of the trial group was significantly shorter than that of the control group [(12.8±11.6) days vs. (22.3±10.4) days; t=2.987, P=0.005). All patients were followed up 3-12 months after operation, and no wound dehiscence or recurrence occurred during follow-up.ConclusionCompared with the vacuum sealing drainage combined with skin graft, the application of skin stretching device in the repair of diabetic foot wound has advantages, such as easy to operate, shorten the wound healing time, and the appearance of wound was similar with the adjacent skin.
In order to investigate the effects of mechanical stretching combined with prostaglandin E2 (PGE2) on the gene expression of lysyl oxidases (LOXs) in keratoconus, we treated cultured corneal fibroblasts from healthy human cornea and keratoconus patient cornea with PGE2 and/or cyclic stretch (12% elongation, 0.1 Hz, 12 h). Real-time fluorescent quantitative polymerase chain reaction was used to detect the gene expression of LOXs. The results showed that the gene expression of LOXs in keratoconus group was significantly lower than that in the healthy one. Compared to the static control group, 12% stretching alone up-regulated gene expression of LOXL-2, LOXL-4 in the healthy group, whereas it down-regulated LOXL-3, LOXL-4 in the keratoconus group. Combination of 12% stretching and PEG2 induced LOXL-4 down-regulation in in healthy group, and all LOXs except LOXL-1 in keratoconus group. The results suggested that combination of mechanical stretching and PGE2 down-regulate the gene expression of LOXs in keratoconus. Lower LOXs expression may lead to impaired cross-linking, and thus to a loss of cohesion between collagen fibrils, affecting corneal structural stability by collagen lamellae slippage. This may facilitate the development of keratoconus. Exploring the effects of mechanical stretching and inflammatory factor on the expression LOXs in this paper will help us to understand the possible mechanism of how the keratoconus occurs and develops well, and provide the reference for the prevention and treatment of keratoconus.
Objective To investigate whether mechanical stretch stimulation affects the expression of the immediate early gene c-fos mRNA in rat Achilles-derived tendon stem cells (TSCs)in vitro. Methods TSCs were isolated from the Achilles tendons of 8 weeks old male Sprague Dawley rats by enzymatic digestion method and cultured for 3 passages. The TSCs were stimulated by a uniaxial cyclic stretching loading system under the condition of 1 Hz, respectively with 4% or 8% stretch intensity for 0, 5, 15, 30, 60, and 120 minutes. At each time point, TSCs were collected to detect c-fos mRNA expressions and to find the best time-point Tmax by real-time fluorescence quantitative PCR. Then, TSCs were simulated with 2%, 4%, 6%, 8%, or 12% stretch intensity for Tmax to observe the relative expressions of c-fos mRNA under different stretch intensities. Next, TSCs were stretched for 0, 5, or 15 minutes respectively and followed by incubation at relax status up to Tmax to observe the changes of c-fos mRNA expressions after short period stimulation. Finally, TSCs were stimulated with 4% or 8% stretch intensity respectively for 0, Tmax, or 120 minutes to detect the expressions of the tenogenic differentiation related genes [collagen type I, tenomodulin (TNMD)], the osteogenic differentiation related genes [runt related transcription factor 2 (Runx2), distal-less homeobox 5 (Dlx5)], and the adipogenic differentiation related gene [fatty acid binding protein 4 (FABP4)]. Results Under 4% or 8% stretch intensity, the relative expressions of c-fos mRNA significantly increased at 15 minutes (P<0.05), reached the maximum at 30 minutes (P<0.05), and returned to baseline at 60 minutes (P>0.05) when compared with expression at 0 minute. Therefore, Tmax was 30 minutes. The stretch intensity of 2% was enough to cause the expression of c-fos mRNA at 30 minutes, and the expression was significantly higher under the stretch intensity of 6%, 8%, and 12% than 2% and 4% (P<0.05). Even for a short period stimulation of 5 minutes, c-fos mRNA expression could still significantly increase at 30 minutes (P<0.05). The relative expressions of differentiation related genes at 30 and 120 minutes showed no significant difference when compared with the expression at 0 minute under 4% stretch intensity (P>0.05); but the relative expression of Runx2 gene significantly increased at 30 minutes, and the relative expressions of collagen type I, TNMD, Dlx5, and Runx2 increased at 120 minutes under 8% stretch intensity (P<0.05). Conclusion Mechanical stretch stimulation can affect the relative expression of the immediate early gene c-fos mRNA of rat Achilles-derived tendon stem cellsin vitro, and there is time- and intensity-dependence. It is suggested that the mechanical stimulation with different time or intensity may affect the differentiation of TSCs at early stage. This study is meaningful for the further study on TSCs intracellular mechanical signal transfer mechanism.
ObjectiveTo investigate the utility of stretched exponential model diffusion-weighted imaging (DWI) for diagnosing of advanced liver fibrosis.MethodsThe patients with chronic liver disease complicated with vary degrees of fibrosis confirmed by pathological examination underwent DWI using different b-values (0, 50, 600 s/mm2) at the First Affiliated Hospital of Chengdu Medical College from June 2015 to February 2020 were collected. In addition, patients who underwent upper abdominal MRI examination in the same hospital at the same time and had no liver disease or disease affecting liver function were collected as a control group. The apparent diffusion coefficient (ADC) was calculated by using a mono-exponential model. The distributed diffusion coefficient (DDC) and water molecular diffusion heterogeneity index (α) were calculated by using a stretched exponential model. The fibrosis stage was evaluated by using the Metavir scoring system. The ADC, DDC, and α among different fibrosis groups were compared. The receiver operating characteristic (ROC) curve was used to analyze the diagnostic efficacy of these three quantitative parameters for advanced liver fibrosis.ResultsA total of 42 patients with chronic liver disease were collected in this study, including mild liver fibrosis (S1–S2, n=16) and advanced liver fibrosi (≥S3, n=24); 15 patients in the control group. The values of ADC, DDC, and α of the patients with mild liver fibrosis and advanced liver fibrosis were significantly lower than those of the control patients (P<0.05). The area under the ROC curve of ADC, DCC, and α in diagnosing liver fibrosis (≥S1) was 0.915, 0.974, and 0.835, respectively, which in diagnosing advanced liver fibrosis (≥S3) was 0.744, 0.869, and 0.758, respectively. However, further the area under ROC curve among these three metrics had no statistical differences (P>0.05).ConclusionDDC based on stretched exponential model is valuable for diagnosis of advanced liver fibrosis.
ObjectiveTo explore the reaction of normal skin fibroblasts from different sites of human body to cyclic stretch.
MethodsThe normal skin tissues from scapular upper back and medial side of upper arm of 3 patients were cultured in vitro. Fibroblasts of experimental group were loaded by cyclic stretch with 10% amplitude for 24, 36, and 48 hours respectively. Fibroblasts of control group were cultured without cyclic stretch. The morphologic changes were observed using inverted microscope. CCK-8 method was used to detect the proliferation of the fibroblasts. The expressions of integrin β1 mRNA, p130Crk-associated substance (P130Cas) mRNA, transform growth factor β1 (TGF-β1) mRNA, and collagen type Ⅰ α1 chain (COL1A1) mRNA were detected by real-time quantitative PCR. The protein levels of collagen type Ⅰ and TGF-β1 were detected by ELISA.
ResultsThe cultured cells showed a significantly increased cell proliferation ability, and apparent orientation after the applied strain. The proliferation activity, mRNA expression levels of integrin β1, P130Cas, and TGF-β1, protein levels of TGF-β1 in back skin were significantly higher than those in arm skin (P<0.05) when the fibroblasts were loaded for 36 and 48 hours, but no significant difference between back skin and arm skin at 24 hours (P>0.05). There was no significant difference in mRNA expression level of COL1A1 and protein level of collagen type Ⅰ between back skin and arm skin at 24, 36, and 48 hours (P>0.05). There was no significant difference in all above indexes between back skin and arm skin in control group (P>0.05).
ConclusionFibroblasts from scapular upper back and medial side of upper arm display different reactions to cyclic stretch, which indicates that there exists site difference in the reactions of fibroblasts to cyclic stretch. It might be related with the incidence of hypertrophic scar in different sites of the body.
Objective To study the effect of mechanical stretch on the microenvironment of BEAS-2B on macrophage polarization and the role of polarized macrophages in the epithelial-mesenchymal transition (EMT) of BEAS-2B. Methods Using enzyme linked immunosorbent assay to detect the changes in the levels of cytokines such as interferon-γ, granulocyte-macrophage colony stimulating factor, tumor necrosis factor-α, interleukin (IL)-4, IL-6, IL-10 in the supernatant of lung epithelial cells cultured statically and mechanically stretched. The M0 macrophages (derived from THP-1) were stimulated by stretch/static conditioned medium of BEAS-2B. The surface markers of M1 (CD197) /M2 (CD206) macrophages were detected by flow cytometer. Stretch/static conditioned medium were used to stimulate the co-culture system of macrophages and BEAS-2B in the presence or absence of platelet-derived growth factor receptor inhibitor (PDGFRi), then the protein expression level of EMT makers was examined by Western blot. Results Exposure of BEAS-2B to mechanical stretch resulted in significantly higher production of the pro-M1/M2 polarized factor. The EMT of the co-culture system of M0 and BEAS-2B could be induced by stretch conditioned medium, epithelial marker cytokeratin (CK)-8 and E-cadherin were decreased, while mesenchymal marker α-smooth muscle actin, N-cadherin and vimentin were increased in stretch conditioned medium group. The expression of platelet-derived growth factor (PDGF) was significantly higher in stretch conditioned medium group. The PDGFRi can block the EMT in stretch conditioned medium group. Conclusions The lung epithelial cell supernatant induced by mechanical stretch can promote the polarization of macrophages to M1 and M2. Polarized macrophages promote EMT in human lung epithelial cells via PDGF, and blocking PDGF might attenuate the VILI-associated lung fibrosis.
Objective To investigate the guiding value of bedside lung ultrasound and lung stretch index for optimal positive end-expiratory pressure (PEEP) in lung recruitment of patients with acute respiratory distress syndrome (ARDS). Methods From February 2020 to October 2023, 90 patients with ARDS requiring invasive mechanical ventilation were selected from the Department of Critical Care Medicine, the Second Affiliated Hospital of Zhengzhou University. According to the setting method of PEEP after lung recruitment, they were randomly divided into an ultrasound group (45 cases) and a stretch group (45 cases). Both groups were treated with PEEP incremental method for lung recruitment, and the ultrasound group was treated with bedside ultrasound-guided method to set PEEP after lung recruitment. PEEP was set by lung stretch index method in the stretch group. The dynamic changes of oxygenation index (PaO2/FiO2), dynamic compliance (Cdyn), mean airway pressure and peak airway pressure were monitored before lung recruitment and 15 min, 1 h, 6 h and 24 h after lung recruitment. Heart rate, mean arterial pressure and central venous pressure were monitored before and 24 h after lung recruitment in the two groups. The optimal PEEP value and the corresponding volume at the end of recruitment were explored. The mechanical ventilation time, ICU hospitalization time, incidence of barotrauma, incidence of extrapulmonary organ failure, and 28-day mortality were recorded as well. Results After lung recruitment, the oxygenation index, Cdyn, mean airway pressure, and peak airway pressure in the ultrasound group were higher than those in the stretch group at 15 min, 1 h, 6 h, and 24 h after recruitment (all P<0.05). There was no significant difference in heart rate, mean arterial pressure or central venous pressure between the two groups at 24 h after lung recruitment (all P>0.05). After lung recruitment, the optimal PEEP value and the corresponding volume at the end of recruitment in the ultrasound group were higher than those in the distraction group (both P<0.05). The mechanical ventilation time and ICU stay in the ultrasound group were shorter than those in the stretch group (both P<0.05). There was no significant difference in the incidence of barotrauma, extrapulmonary organ failure rate or 28-day mortality between the two groups (all P>0.05). Conclusions Both bedside lung ultrasound-guided PEEP and lung stretch index-guided PEEP can improve oxygenation and respiratory compliance, and have no adverse effects on hemodynamics. Bedside lung ultrasound-guided PEEP can make the alveoli fully expand, which is more conducive to improving patients’ oxygenation and respiratory compliance, and the guiding value is higher than the lung stretch index.
OBJECTIVE: To investigate the availability and effect of skin stretch in closing the firearm injured soft tissue defect. METHODS: Eight white pigs with firearm injured soft tissue defect were divided into 3 groups. Each group I and group II had 3 pigs which were performed skin stretch. The control group had 2 pigs without stretch. The average diameter of the defect in three groups was (7.3 +/- 0.2) cm, (9.1 +/- 0.3) cm, (7.3 +/- 0.2) cm respectively, and the site of defect was on the lateral thigh and buttock. RESULTS: Skin stretch could make a visible reduction of the wound. It was possible to close the wound by direct traction when the diameter of the buttock wound was less than 7 cm, and when the diameter of the lateral thigh wound was less than the radius of thigh. The skin stretch should not last more than 7 days and the best effect appeared in 4 to 5 days after performing the skin stretch. CONCLUSION: The skin stretch can be applied in the repair of the firearm injured soft tissue defect. It has many advantage compared with the tradtional treatment.
