ABSTRACT
Mechanical stimulation widely exists in the body and participates in adjusting biological behavior of many kinds of cells. As a common stress pattern in the body, the tensile strain widely exists in many organs, such as bone and cartilage, muscle tendon, cardiac and pulmonary vessels, and so on. In recent years, with the development of the researches of biomechanics, a variety of mechanical loading devices, which are used to simulate the complex mechanical stimulation in the body to provide the tensile strain including the isometric, uniaxial and various types of mechanical waveform, came into being. This is a huge boost to biomechanical research. Many researchers have found that the tensile strain stimulation can lead to the transformation of proliferation, differentiation and apoptosis of cells and change of cell matrix. However, for the same kind of cells, different kinds of tensile strain stimulation can lead to different and even the contrary results. In this paper, the effects of the tensile strain on the proliferation, differentiation and matrix of cartilage were reviewed. Understanding these characteristics will have important implications for the mechanism of cell proliferation and differentiation under the biomechanic stimulation and the prevention and treatment of diseases.
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Objective To investigate the effect of frequency on osteoblast apoptosis induced by tensile strain. Methods MC3T3-E1 cells were applied with 1% biaxial tensile strain at the frequency of 1, 2, 3, 4, 5 Hz, respectively for 1 hour per day in 8 days. The survival rate of the cells was determined by activity of lactate dehydrogenase (LDH). Annexin V-FITC/ PI Flow cytometry was used to test cell apoptosis. Real-time RT-PCR was used to detect the gene level of apoptosis markers caspase-3, -9 as well as Bcl-2 and Bax, and Western blotting was used to test protein expressions of caspase-3, -9. Results Different loading frequencies had no effect on osteoblast activity of LDH. There was no significant difference in the total apoptosis rate of flow cytometry at different frequencies. However, the frequency of 2 Hz could induce early osteoblast apoptosis. Tensile strain at the frequency of 2 Hz could significantly increase the expression of caspase-3, -9 gene and protein, and induce cell apoptosis with the up-regulation of the Bax/Bcl-2. Conclusions Osteoblast apoptosis and death cannot be induced by 1% biaxial tensile strain at the frequency of 1-5 Hz, but the frequency of 2 Hz can induce the early apoptosis of osteoblasts by up-regulating the expression of Bax/BCl-2.
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Objective To investigate the effects of different cyclic tensile strains on the proliferation and expression of bone marrow stromal cells (BMSCs)-cocultured human degenerated anulus fibrosus (AF) cells. Methods AF cells were isolated from a patient with degenerated intervertebral disc degeneration (IVD), which were co-cultured with BMSCs. The solely cultured AF cells were used as control group. The two groups of cells were expanded in monolayer, and cyclically strained for 3 hours, which were applied 0, 5%, 10%, 15%and 20%strains at a frequency of 0.25 Hz using BioDynamic test instrument. A flow cytometry method was used to examine the AF cell proliferation at 24 hours followed the application of cyclic tensile strains. After the total RNA was extracted, real-time PCR technology was used to detect the gene expression of collagenⅠand aggrecan. Results Under the same appropriate stress, the proliferative index (PI), the proportion of cells in the period of DNA synthesis, the expression of collagenⅠand aggrecan were significantly higher in the co-cultured group than those of control group (P<0.05). However, the best mechanical stimulation was different in the two groups. For the AF cells, the peaks of PI, the proportion of cells in the period of S period, the expression of collagenⅠand aggrecan were found in the 10% strain group, while for the co-cultured cells, they were found in the 15% strain group. Conclusion Co-culturing with BMSCs has a positive effect on the proliferation and expression of human degenerative fibrous ring cells, which can protect AF cells from bad stress stimulation.
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Objective To investigate the effect of frequency on osteoblast apoptosis induced by tensile strain.Methods MC3T3-E1 cells were applied with 1％ biaxial tensile strain at the frequency of 1,2,3,4,5 Hz,re spectively for 1 hour per day in 8 days.The survival rate of the cells was determined by activity of lactate dehydrogenase (LDH).Annexin V-FITC/ PI Flow cytometry was used to test cell apoptosis.Real-time RT-PCR was used to detect the gene level of apoptosis markers caspase-3,-9 as well as Bcl-2 and Bax,and Western blotting was used to test protein expressions of caspase-3,-9.Results Different loading frequencies had no effect on osteoblast activity of LDH.There was no significant difference in the total apoptosis rate of flow cytometry at different frequencies.However,the frequency of 2 Hz could induce early osteoblast apoptosis.Tensile strain at the frequency of 2 Hz could significantly increase the expression of caspase-3,-9 gene and protein,and induce cell apoptosis with the up-regulation of the Bax/Bcl-2.Conclusions Osteoblast apoptosis and death cannot be induced by 1％ biaxial tensile strain at the frequency of 1-5 Hz,but the frequency of 2 Hz can induce the early apoptosis of osteoblasts by up-regulating the expression of Bax/BCI-2.
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Objective To study the roles of icariin and cyclic tensile strain (CTS) in promoting the osteogenic differentiation of adipose-derived stem cells (ASCs) and the molecular mechanisms involved.Methods ASCs were isolated from Sprague-Dawley rats and treated either with icariin (10-7 mol/L) or with 1000 μ,2000 μ or 3000 μ of CTS for 7 days,or with icariin plus CTS at 2000 μ for three days.Alkaline phosphatase (ALP) activity was detected after 3 and 7 days of intervention.Western blotting was performed to detect the expression of Runt-related transcriptional factor 2 (Runx2),Yes-associated protein (YAP) and connective tissue growth factor (CTGF) after the third day of the intervention.A reverse transcription polymerase chain reaction was performed at 7 days to detect the expression of osteopontin (OPN) and collagen la and after 3 days to detect the expression of the YAP target gene,CTGF and ankyrin repeating domain 1 (Ankrd1).Results Icariin and CTS at 1000 μ,2000 μ or 3000 μ could all significantly promote the expression of ALP protein.CTS at 2000 μ was the nost effective.The co-treatment with icariin and CTS significantly promoted ALP protein expression compared with icariin or CTS treatment alone.It also significantly promoted the expression of Runx2 and CTGF protein.Icariin or CTS (2000 μ) alone could not promote the expression of YAP protein,but icariin combined with CTS (2000 μ) promoted it significantly.Either icariin or CTS (2000 μ) could significantly promote ALP activity after 3 and 7 days,but icariin combined with CTS had the most obvious effect.Both icariin and CTS (2000 μ) could also significantly promote the expression of the osteogenesis-related genes OPN and collagen la,as well as the YAP targeted genes CTGF and Ankrdl.However,the combination of icariin and CTS had the greatest effect in promoting the expression of OPN mRNA,collagen la mRNA,CTGF mRNA and ankrdl mRNA.Conclusion Icariin and CTS co-treatment may promote osteogenic differentiation of ASCs via activating YAP expression.
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BACKGROUND: Mechanical strain plays a great role in growth and differentiation of osteoblast. A previous study indicated that integrin-ß (ß1, ß5) mediated osteoblast proliferation promoted by mechanical tensile strain. However, the involvement of integrin-ß; in osteoblastic differentiation and extracellular matrix (ECM) formation induced by mechanical tensile strain, remains unclear. RESULTS: After transfection with integrin-ß1 siRNA or integrin-ß5 siRNA, mouse MC3T3-E1 preosteoblasts were cultured in cell culture dishes and stimulated with mechanical tensile strain of 2500 microstrain (µÎµ) at 0.5 Hz applied once a day for 1 h over 3 or 5 consecutive days. The cyclic tensile strain promoted osteoblastic differentiation of MC3T3-E1 cells. Transfection with integrin-ß1 siRNA attenuated the osteoblastic diffenentiation induced by the tensile strain. By contrast, transfection with integrin-ß5 siRNA had little effect on the osteoblastic differentiation induced by thestrain. At thesametime, theresultofECM formation promoted by the strain, was similar to the osteoblastic differentiation. CONCLUSION: Integrin-ß1 mediates osteoblast differentiation and osteoblastic ECM formation promoted by cyclic tensile strain, and integrin-ß5 is not involved in the osteoblasts response to the tensile strain.
Subject(s)
Animals , Mice , Osteoblasts/physiology , Tensile Strength/physiology , Cell Differentiation/physiology , Integrin beta1/physiology , Integrin beta Chains/physiology , Extracellular Matrix/physiology , Stress, Mechanical , Transfection , Cell Line , Blotting, Western , RNA, Small Interfering , Cell Proliferation/physiology , Real-Time Polymerase Chain ReactionABSTRACT
Objective To investigate the effect of mechanical loading with different magnitudes on the proliferation, differentiation and activity of preosteoclasts and osteoclasts. Methods One group of RAW264.7 preosteoclastic cells cultured in osteoclast inductive medium were subjected to the cyclic tensile strain for three days, and then cultured for four days; the other group of RAW264.7 cells were induced in osteoclast inductive medium for four days to be osteoclasts, then subjected to the cyclic tensile strain for three days. Results Under the tensile strain at different magnitudes, the proliferation variations in two groups of RAW264.7 cells were approximately identical, but changes in the activities of tartrate-resistant acid phosphatage (TRAP) and numbers of TRAP-positive multinucleated cells (osteoclasts) in the two groups were significantly different. Under the moderate tensile strain (2 500 με), the reduction of TRAP activity and osteoclasts number were both the highest in the first group, and both the lowest in the second group. Conclusions The influence of different tensile strain on osteoclast differentiation and osteoclastic activity of preosteoclasts in early differentiation is different to that of the preosteoclasts already differentiated into osteoclasts.
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Objective To investigate the effects of different cyclic tensile strain on the proliferation of human anulus fibrosus cells from degenerated discs.Methods Anulus fibrosus(AF) cells were isolated from a degenerated human IVD,expanded in monolayer,and cyclically strained for 3 hours,applying 0,5％,10％,15％ and 20％ strains at a frequency of 0.25 Hz with the use of the DioDynamic test instrument.The flow cytometry method was used to examine the Af cells proliferation at 24 hours following application of the cyclic tensile strains.Results The proliferative index (PI) increased with the magnitude value of cyclic tensile strain except 20％ group.The most significant increase of proliferation index were found in 15％ group.Conclusion There might be some corelationships between magnitude of cyclic tensile strain and the proliferation of the degenerative AF cells.
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Objective: To study the effects of static tensile strai n on the secretion of prostaglandin E 2 (PGE 2) of human periodontal ligament fibroblasts (PLFs). Methods: Human PLFs were treated by tensile strain values of 0%,8%,12%,16% and 20% for 24, 48 and 72 h respecti vely with a self-devised loading apparatus in vitro. All samples were rando mly allocated into 15 groups and there were 3 in each group. After treatment cu lture media of the samples were collected and the content of PGE 2 in each medi um sample was determined using RIA ELISA. The data analysis was carried out with SPSS using Dunnett test. Results: In group of 0% the sec retion of PGE 2 by PLFs per day had no relation with loading time; E 2 secre tion increased with the increace of loading time and with the tensile strain va lue in the group of 8%,12% and 16%(P
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Objective: To study the effects of static tensile strain on the cytoskeleton of human periodontal ligament fibroblasts (HPLFs). Methods: Tensile strain with the strain variate of 8%,12%,16% and 20% was applied in the culture of HPLFs for 1,2 and 3 d respectively with a self-devised loading apparatus. With the aid of laser scanning confocal microscope, the projected areas of each observed cell and its nuclear were calculated and the cell cytosketeton was observed. The data analysis was carried out with SPSS using Dunnett test. Results:The projected areas of the cells and nucleus incereased with the increace of loading time and tensile strain value in trial groups of 8%,12% and 16%(P