Interferon regulatory factor 2 binding protein 2:a new player of the innate immune response for stroke recovery

Ischemic brain injury triggers an inflammatory response. tissue but can also exacerbate brain injury. Microglia are This response is necessary to clear damaged brain the innate immune cells of the brain that execute this critical function. In healthy brain, microglia perform a housekeeping function, pruning unused syn- apses between neurons. However, microglia become activated to an inflammatory phenotype upon brain injury. Interferon regulatory factors modulate microglial activation and their production of inflammatory cytokines. This review briefly discusses recent findings pertaining to these regulatory mechanisms in the context of stroke recovery.

Mutagenesis reveals that the rice OsMPT3 gene is an important osmotic regulatory factor

Plant mitochondrial phosphate transporters regulate phosphate transport and ATP synthesis. Determining whether they function in abiotic stress response process would shed light on their response to salt stress. We used the CRISPR/Cas9 gene-editing system to mutagenize two mitochondrial phosphate transporters, OsMPT3;1 and OsMPT3;2, to investigate their regulatory roles under salt stress. Two cas9(CRISPR-associated protein9)-free homozygous mutants, mpt33 and mpt30, were confirmed to be stable. Both OsMPT3;1 and OsMPT3;2 were markedly induced by salt stress, and their mutagenesis strongly inhibited growth and development, especially under salt stress. Mutagenesis sharply reduced the accumulation of ATP, phosphate, calcium, soluble sugar, and proline and increased osmotic potential, malondialdehyde, and Na^+ /K^+ ratio under salt stress. Both mutants demonstrate normal growth and development in the presence of ATP, revealing high sensitivity to exogenous ATP under salt stress. The mutants showed lowered rates of Na^+ efflux but also of K^+ and Ca^(2+) influx under salt stress. Mutagenesis of OsMPT3;2 altered the enrichment profiles of differentially expressed genes involved mainly in synthesis of secondary metabolites, metabolism of glycolysis, pyruvate, tricarboxylic acid cycle, in response to salt stress. The mutant displayed significant accumulation differences in 14 metabolites involved in 17 metabolic pathways, and strongly up-regulated the accumulation of glutamine, a precursor in proline synthesis, under salt stress. These findings suggest that the OsMPT3 gene modulates phosphate transport and energy supply for ATP synthesis and triggers changes in accumulation of ions and metabolites participating in osmotic regulation in rice under salt stress, thus increasing rice salt tolerance. This study demonstrates the effective application of CRISPR/Cas9 gene-editing to the investigation of plant functional genes.

Association of rs10954213 Polymorphisms and Haplotype Diversity in Interferon Regulatory Factor 5 with Systemic Lupus Erythematosus: A Meta-analysis

The rs10954213 polymorphism and the haplotype diversity in interferon regulatory factor 5 （1RF5） play a special role in systemic lupus erythematosus （SLE） but with inconclusive results. We conducted a meta-analysis integrating case-control and haplotype variant studies in multiple ethnic populations to clearly discern the effect of these two variants on SLE. Eleven studies on the relation between rs10954213 polymorpisms in IRF5 and SLE were included and we selected a random effect model to calculate the pooled odds ratios （ORs） and the corresponding 95% confidence interval （95% CI）. A total of 6982 cases and 8077 controls were involved in the meta-analysis. The pooled results in- dicated that A allele was significantly associated with increased risk of SLE as compared with the IRF5 rS10954213 G allele （A vs. G, P〈0.00001） in all subjects. The same pattern of the results was also ob- tained in the European, African American, and Latin American. Asian population had a much lower prevalence of the A allele （49.1%） than any other population studied, and Europeans had the highest frequency of the IRF5 rs10954213 A allele （62.1%）. The significant association of increased SLE risk and TCA haplotype was indicated in the contrast of TCA vs. TTA as the pooled OR was 2.14 （P=0.002）. The same result was also found in the contrast of TCA vs. TTG as the pooled OR was 1.45 （P=-0.004）. This meta-analysis suggests that the A allele of rs10954213 and TCA haplotype （rs2004640-rs2070197-rs10954213） in IRF5 is associated with the increased risk of SLE in different ethnic groups, and its prevalence is ethnicity dependent.

Interferon Regulatory Factor 5 and Renin-Angiotensin-Aldosterone System Polymorphisms in Coronary Artery Disease: An Overview of Experimental and Clinical Studies

Heart diseases are the main cause of mortality in Mexico, being coronary heart disease the most frequent in the country. Its high prevalence makes important the study of the pathophysiology and the search for prognostic factors. Different genes and polymorphisms promote atherogenesis and coronary artery disease, they affect inflammatory and vascular pathological processes. Interferon regulatory factor 5 (IRF5) is associated with coronary heart disease, it promotes chronic inflammation and cytokines release;it could trigger immune reactions and its activating receptors express in the vascular endothelium. Besides, polymorphisms in the renin-angiotensin-aldosterone system (RAAS) are implied with coronary disease, they are found in angiotensinogen (AGT), angiotensin II type 1 receptor (AT1R), angiotensin II type 2 receptor (AT2R), and angiotensin-converting enzyme (ACE) genes. These genetic polymorphisms are associated with a prothrombotic state, endothelial dysfunction, and immune activation. Multiple experimental studies showed that chronic activation of RAAS and chronic expression of IRF5 generates an environment prone to the development of atherosclerosis, and autoimmune and cardiovascular diseases. Studying these specific genes and their relationship with coronary heart disease will allow a better understanding of the pathological process and possibly the quest for new treatments.

Interferon regulatory factor 3-CL,an isoform of IRF3,antagonizes activity of IRF3

Interferon regulatory factor 3(IRF3),one member of the IRF family,plays a central role in induction of type I interferon(IFN)and regulation of apoptosis.Controlled activity of IRF3 is essential for its functions.During reverse transcription(RT)-PCR to clone the full-length open reading frame(ORF)of IRF3,we cloned a full-length ORF encoding an isoform of IRF3,termed as IRF3-CL,and has a unique carboxyl-terminus of 125 amino acids.IRF3-CL is ubiquitously expressed in distinct cell lines.Overexpression of IRF3-CL inhibits Sendai virus(SeV)-triggered induction of IFN-β and SeV-induced and inhibitor of NF-kB kinase-e(IKKε)-mediated nuclear translocation of IRF3.When IKKε is overexpressed,IRF3-CL is associated with IRF3.These results suggest that IRF3-CL,the alternative splicing isoform of IRF-3,may function as a negative regulator of IRF3.

Variants of Interferon Regulatory Factor 5 are Associated with Neither Neuromyelitis Optica Nor Multiple Sclerosis in the Southeastern Han Chinese Population

Background： Neuromyelitis optica （NMO） and multiple sclerosis （MS） are demyelinating disorders of the central nervous system. Interferon regulatory factor 5 （IRF5） is a common susceptibility gene to different autoimmune disorders. However, the association of IRF5 variants with NMO and MS patients has not been well studied. Therefore, we aimed to evaluate whether IRF5 variants were associated with NMO and MS in the Southeastenl Han Chinese population. Methods： Four single nucleotide polymorphisnls （SNPs） were selected and genotyped by matrix-assisted laser desorption/ionization time of flight mass spectrometry in 111 NMO patients, 145 MS patients and 300 controls from Southeastern China. Results： None of these 4 SNPs was associated with NMO or MS patients. Conclusions： Our preliminary study indicates that genetic variants in IRI~ may affect neither NMO nor MS in the Southeastern Han Chinese population. Further studies with a large sample size and diverse ancestry populations are needed to clarify this isstie.

Factors influencing myogenic differentiation of adipose-derived stem cells and their application in muscle regeneration

Skeletal muscle regeneration mainly depends on muscle satellite cells;however,these cells are not sufficient for supporting repair and regeneration in volumetric muscle loss(VML),Duchenne muscular dystrophy,and other muscle injuries or muscle diseases.As such,much work has been conducted in recent years to search for myogenic stem cells.Adipose-derived stem cells(ADSCs)have a wide range of sources,rapid growth,and multi-directional differentiation potential,and have become vital candidates for muscle regeneration.Multiple factors influence the myogenic differentiation capacity of ADSCs.This paper reviews the regulatory aspects and possible factors that have been identified in recent years to affect myogenic differentiation of ADSCs.Based on these factors,gene editing,and perfusion concepts,a method was proposed to achieve maximal differentiation efficiency of ADSCs.This study focused on the application of ADSCs in muscle regeneration and disease.Based on the importance of myogenic differentiation of ADSCs for the repair and regeneration of muscle damage,this study provides a basis for future research surrounding the efficient induction of myogenic differentiation of ADSCs in vitro.

Comprehensive multi-omics analysis identified core molecular processes in esophageal cancer and revealed GNGT2 as a potential prognostic marker

BACKGROUND Esophageal cancer is one of the most poorly diagnosed and fatal cancers in the world.Although a series of studies on esophageal cancer have been reported,the molecular pathogenesis of the disease remains elusive.AIM To investigate comprehensively the molecular process of esophageal cancer.METHODS Differential expression analysis was performed to identify differentially expressed genes(DEGs)in different stages of esophageal cancer from The Cancer Genome Atlas data.Exacting gene interaction modules were generated,and hub genes in the module interaction network were found.Further,through survival analysis,methylation analysis,pivot analysis,and enrichment analysis,some important molecules and related functions/pathways were identified to elucidate potential mechanisms in esophageal cancer.RESULTS A total of 7457 DEGs and 14 gene interaction modules were identified.These module genes were significantly involved in the positive regulation of protein transport,gastric acid secretion,insulin-like growth factor receptor binding,and other biological processes as well as p53 signaling pathway,epidermal growth factor signaling pathway,and epidermal growth factor receptor signaling pathway.Transcription factors(including hypoxia inducible factor 1A)and noncoding RNAs(including colorectal differentially expressed and hsa-miR-330-3p)that significantly regulate dysfunction modules were identified.Survival analysis showed that G protein subunit gamma transducin 2(GNGT2)was closely related to survival of esophageal cancer.DEGs with strong methylation regulation ability were identified,including SST and SH3GL2.Furthermore,the expression of GNGT2 was evaluated by quantitative real time polymerase chain reaction,and the results showed that GNGT2 expression was significantly upregulated in esophageal cancer patient samples and cell lines.Moreover,cell counting kit-8 assay revealed that GNGT2 could promote the proliferation of esophageal cancer cell lines.CONCLUSION This study not only revealed the potential regulatory factors involved in the development of esophageal cancer but also deepens our understanding of its underlying mechanism.

Cell cycle-related genes p57kip2, Cdk5 and Spin in the pathogenesis of neural tube defects

In the field of developmental neurobiology, accurate and ordered regulation of the cell cycle and apoptosis are crucial factors contributing to the normal formation of the neural tube. Preliminary studies identified several genes involved in the development of neural tube defects. In this study, we established a model of developmental neural tube defects by administration of retinoic acid to pregnant rats. Gene chip hybridization analysis showed that genes related to the cell cycle and apoptosis, signal transduction, transcription and translation regulation, energy and metabolism, heat shock, and matrix and cytoskeletal proteins were all involved in the formation of developmental neural tube defects. Among these, cell cycle-related genes were predominant. Retinoic acid treat-ment caused differential expression of three cell cycle-related genes p57kip2, Cdk5 and Spin, the expression levels of which were downregulated by retinoic acid and upregulated during normal neural tube formation. The results of this study indicate that cell cycle-related genes play an im-portant role in the formation of neural tube defects. P57kip2, Cdk5 and Spin may be critical genes in the pathogenesis of neural tube defects.

Recent Insights into Signaling Responses to Cope Drought Stress in Rice

Drought is one of the hot topics needing urgent attention in the current era of climate change.It massively disturbs the rice growth and productivity and is becoming a serious threat.The drought avoidance strategies in rice include stomatal closure,cellular adaptation and changes in root development.Moreover,the endogenous plant hormones(abscisic acid and jasmonic acid)and reactive oxygen species have paramount importance in drought tolerance in rice.The drought tolerance induces modification in biochemical,molecular and physiological properties of plants.At the molecular level,expression of several transcription-factors is modulated which further determine the activation of drought responsive gene families.Mitogen activated protein kinases and Ca signaling pathways initiate an array of signaling cascade for mediating the gene expression in rice.Approaches,conventional breeding methods combined with modern emerging techniques such as genetic engineering,to improve rice drought tolerance were discussed.This review provided recent insights into major regulatory factors against drought stress,signaling mechanisms and molecular engineering strategies(including conventional transgenic and recent genome editing approaches)to induce drought tolerance in rice.

Increased cGAS/STING signaling components in patients with Mooren's ulcer

AIM:To explore the expression of cGAS/STING signaling components in Mooren’s ulcer(MU).METHODS:Samples were obtained from ten MU patients,and eight residual corneal-scleral rings of healthy donor corneas for controls.Human corneal epithelial cells(HCECs)were used to evaluate the effect of cGAS/STING signaling pathway.Immunohistochemistr y(IHC)and Western blot were used to examine the expression of cGAS,STING,and phosphorylated interferon regulatory factor 3(p-IRF3)in MU tissues.The expression of interferon-β(IFN-β)and interferon-stimulated genes(ISGs)was quantified by real-time polymerase chain reaction(PCR)and enzymelinked immunosorbent assay(ELISA).RESULTS:The protein levels of cGAS and STING in MU samples were significantly elevated when compared with the healthy controls by Western blot and IHC.After stimulation with cGAMP,real-time PCR and ELISA showed a dramatic increase of IFN-βand ISGs(containing CXCL10,IFIT1,and IL-6)in HCECs.Moreover,HCECs treated with cGAMP was characterized by increased phosphorylation and more nuclear translocation of IRF3.Meanwhile,increased p-IRF3 was observed in MU samples via IHC and Western blot.CONCLUSION:The pronounced expression of cGAS/STING signaling components in the patients with MU and probably contribute to the onset and development of MU.

Molecular Cloning,Characterization and Expression Profile of Myf5 and Myf6 During Growth and Development in the Seriola lalandi

Myogenic Regulatory Factors(MRFs)is involved in the muscle growth and differentiation.In this study,the cDNA sequence of yellowtail kingfish MRFs genes were cloned by rapid amplification of cDNA ends(RACE)method;then,the character-istics of these genes and the predicted protein sequences were analyzed by bioinformatics methods,the tissue and embryonic stages differential expression pattern were detected by the quantitative real-time PCR.Our results showed that the yellowtail kingfish(YTK)Myf5 cDNA has a full length of 951 bp,encoding 266 amino acids.The yellowtail kingfish Myf6 cDNA has a full length of 1105bp,encoding 250 amino acids.The proteins containα-helix,β-strand,and loops.The Neighbour-joining tree revealed that YTK Myf5 and Myf6 are closely related to Seriola dumerili.The yellowtail kingfish Myf5 and Myf6 gene expressed significantly higher in mus-cle than in other tissues(P<0.05).In addition,Myf5 and Myf6 in muscle was significantly expressed in 400g and 500 g fish but not in 50 g,suggesting that myogenic regulatory factors expression had a great relationship with the fish size.Our results also indicated that Myf5 and Myf6 have different functions during embryonic development,because Myf5 showed highest expression level at the neuroembryo period,but Myf6 had the highest expression level at embryo coverage yolk 70%stage.Myf5 gene showed highest ex-pression at 30 d of age,suggesting it played key roles in myogenic period.However,the Myf6 gene was significantly highly ex-pressed at 60 d,revealing this gene functioned in the later muscle formation period.

Retinoic acid induction of genes associated with neural tube developmental defects

To date, little information has been available regarding genes involved in the regulation of embryonic cell development, which participate in retinoic acid-induced neural tube defects in mice. Previous studies have revealed seven differentially expressed genes involved in neural tube developmental defects. However, gene expression and regulation is a complex process. Therefore, gene expression differences between normal and defective neural tubes at 9.5 and 10.5 days were compared. A total of eight differentially expressed genes exhibited coincident alterations at embryonic 9.5 and 10.5 days. In mice with retinoic acid-induced neural tube defects, NeK7, IGFBP5 ZW10, Csf3r, PSMC6, Cdk5, and Rbl expressions were downregulated, but Apoa-4 expression was upregulated. These results were confirmed by Northern blot hybridization. Results suggested that NeK7, IGFBP5, ZW10, Csf3r, PSMC6, Cdk5, Rb1, and Apoa-4 are important regulatory factors involved in neural tube defects.

COMBINED DETECTION OF CYCLIN D1,P27 AND DNA CONTENT IN ESOPHAGEAL CANCER

Objective： To investigate the expressions of cyclin D1 and p27 and DNA content in esophageal cancer and adjacent normal tissues, and to discuss the relationship between them. Methods： The cyclinD1 and p27 were detected by immunohistochernical staining; DNA content was measured by flow cytometry. Results： The positive expression rates of cyclinD1 and p27 in cancer were 45.8% and 33.3% respectively, the DNA content in the positive group of cyclinD1 was higher than that in the negative group of cyclinDl（1.54±0.21 versus 1.08i-0.43, P〈0.05）, while the DNA content and SPF （S-phase fraction） in the positive group of p27 were lower than those in the negative group （1.10±0.19 and 5.56%±5.18% versus 1.66±0.28 and 19.78%±6.12%, P〈0.05）. Conclusion： The data show that the expression of cyclinD1 and p27 are related to the ontogenesis and progression of esophageal cancer. The combined detection of cyclinD1, p27 and DNA content may be indicators of diagnosis and assessment of esophageal cancer.

Expression and clinical significance of miRNA-146a and IRF-3 in children with infectious mononucleosis

Objective:To investigate the expression levels of interferon regulatory factor 3(IRF-3)and miRNA146a in peripheral blood of children with infectious mononucleosis and the effect of miRNA146a on IRF-3 expression.Methods:In an in vivo experiment,the expression levels of IRF-3 and miRNA146a in peripheral blood of 45 children with infectious mononucleosis and 34 healthy controls were detected by real-time PCR.The in vitro experiment was performed to examine the effect of miRNA146a on IRF-3 expression levels by transfecting miRNA146a mimics and their inhibitors.Results:There was significant difference in IRF-3 gene expression in peripheral blood between healthy controls and children with infectious mononucleosis(t=30.340,P<0.001)while miRNA146a expression was significantly increased compared with healthy controls(t=34.659,P<0.001),and there was a negative correlation between the two groups(r=-0.960,P<0.05).In HeLa cells,transfection with miRNA146a mimics significantly decreased the expression of IRF-3 mRNA(t=8.270,P<0.001)and protein(t=46.170,P<0.001),while miRNA146a inhibitor significantly up-regulated the expression of IRF-3 mRNA(t=8.582,P<0.001)and protein(t=25.891,P<0.001).Conclusion:miRNA146a may be involved in the down-regulation of IRF-3 gene expression by Epstein-Barr virus in children with infectious mononucleosis and then involved in the pathogenesis of infectious mononucleosis.

Association of Single Nucleotide Polymorphisms in IRF6 and TGFA Genes With Nonsyndromic Cleft Lip With Or Without Cleft Palate in Chinese Patients

Objective： Nonsyndromic cleft lip with or without cleft palate（NSCL/P） is a common birth defect with unclear etiology. Both genetic and environmental factors may contribute to NSCL/P. Many genes have been identified as candidate genes associated with this disease. Interferon regulatory factor 6（IRF6） gene and transforming growth factor-a（TGFA） gene seem to be crucial in the predisposition of NSCL/ P. Here we evaluated some single nucleotide polymorphisms（SNPs） loci of TGFA and IRF6 genes in Chinese nuclear families consisting of fathers, mothers and affected offspring with NSCL/P. Methods：Fifty patients of NSCL/P were confirmed by the plastic surgeons. They and their parents were included in the study, all with the informed consents. SNPs loci of TGFA and IRF6 genes were analyzed by microarray technology. Some PCR products were randomly chosen and sequenced to check microarray results. The distribution of gene type and allele frequency between patient group and parents group were compared. Then a Haplotype Relative Risk（HRR） and Transmission Disequilibrium Test（TDT） were performed. Results：The sequences of randomly selected PCR products were all consistent with the microarray results. All loci were in Hardy-Weinberg equilibrium. There were no significant differences in the distribution of genotypes and alleles between patients and their parents. Using HRR and TDT analyses the V274I of IRF6 was associated with NSCL/P, while another SNP locus oflRF6 was not. Strong evidence of linkage disequilibrium was found between the 2 SNP loci of TGFA and disease with the HRR analysis, but not with the TDT analysis. Conclusion：Our study confirms the contribution of IRF6 in the etiology of NSCL/P in populations of Asian ancestry. The association of TGFA with NSCL/P requires further research.

Research status of E3 ubiquitin ligase Smurf2 and related signaling pathways in glioma

Glioma is the tumor with the highest incidence in the brain,and it is eager to seek new and efiective treatment.The interaction of ubiquitination and deubiquitination regulates many cell activities in organisms,and participates in tumor occurrence,development,migration,invasion and other processes.This article summarized the progress of E3 ubiquitination ligase smad ubiquitination regulatory factor 2(Smurf2)and glioma-related signaling pathways to assist clinical diagnosis and treatment of glioma.

Co-expression network analysis predicts a key role of microRNAs in the adaptation of the porcine skeletal muscle to nutrient supply

Background:The role of non-coding RNAs in the porcine muscle metabolism is poorly understood,with few studies investigating their expression patterns in response to nutrient supply.Therefore,we aimed to investigate the changes in microRNAs(miRNAs),long intergenic non-coding RNAs(lincRNAs)and mRNAs muscle expression before and after food intake.Results:We measured the miRNA,lincRNA and mRNA expression levels in the gluteus medius muscle of 12 gilts in a fasting condition(AL-T0)and 24 gilts fed ad libitum during either 5 h.(AL-T1,N=12)or 7 h.(AL-T2,N=12)prior to slaughter.The small RNA fraction was extracted from muscle samples retrieved from the 36 gilts and sequenced,whereas lincRNA and mRNA expression data were already available.In terms of mean and variance,the expression profiles of miRNAs and lincRNAs in the porcine muscle were quite different than those of mRNAs.Food intake induced the differential expression of 149(AL-T0/AL-T1)and 435(AL-T0/AL-T2)mRNAs,6(AL-T0/AL-T1)and 28(AL-T0/AL-T2)miRNAs and none lincRNAs,while the number of differentially dispersed genes was much lower.Among the set of differentially expressed miRNAs,we identified ssc-miR-148a-3p,ssc-miR-22-3p and ssc-miR-1,which play key roles in the regulation of glucose and lipid metabolism.Besides,co-expression network analyses revealed several miRNAs that putatively interact with mRNAs playing key metabolic roles and that also showed differential expression before and after feeding.One case example was represented by seven miRNAs(ssc-miR-148a-3p,ssc-miR-151-3p,ssc-miR-30a-3p,ssc-miR-30e-3p,ssc-miR-421-5p,ssc-miR-493-5p and ssc-miR-503)which putatively interact with the PDK4 mRNA,one of the master regulators of glucose utilization and fatty acid oxidation.Conclusions:As a whole,our results evidence that microRNAs are likely to play an important role in the porcine skeletal muscle metabolic adaptation to nutrient availability.

Targeting the Warburg effect:A revisited perspective from molecular mechanisms to traditional and innovative therapeutic strategies in cancer

Cancer reprogramming is an important facilitator of cancer development and survival,with tumor cells exhibiting a preference for aerobic glycolysis beyond oxidative phosphorylation,even under sufficient oxygen supply condition.This metabolic alteration,known as the Warburg effect,serves as a significant indicator of malignant tumor transformation.The Warburg effect primarily impacts cancer occurrence by influencing the aerobic glycolysis pathway in cancer cells.Key enzymes involved in this process include glucose transporters(GLUTs),HKs,PFKs,LDHs,and PKM2.Moreover,the expression of transcriptional regulatory factors and proteins,such as FOXM1,p53,NF-κB,HIF1a,and c-Myc,can also influence cancer progression.Furthermore,lncRNAs,miRNAs,and circular RNAs play a vital role in directly regulating the Warburg effect.Additionally,gene mutations,tumor microenvironment remodeling,and immune system interactions are closely associated with the Warburg effect.Notably,the development of drugs targeting the Warburg effect has exhibited promising potential in tumor treatment.This comprehensive review presents novel directions and approaches for the early diagnosis and treatment of cancer patients by conducting in-depth research and summarizing the bright prospects of targeting the Warburg effect in cancer.

Effect of constant compressive stress induced by imitating tuina stimulation with various durations on the cell cycle,cellular secretion,apoptosis,and expression of myogenic differentiation and myogenic factor 5 of rat skeletal muscle cells in vitro

OBJECTIVE:To investigate the effect of constant compressive stress induced by imitating Tuina stimulation with various durations on the cell cycle,cellular secretion,apoptosis,and expression of myogenic regulatory factors(MRFs),myogenic factor 5(Myf5)and myogenic differentiation(MyoD)of rat skeletal muscle cells(RSkMCs)in vitro.METHODS:Third passage RSkMCs were subjected to constant compressive stresses with various durations at 2000μstrain for 15,30,60,90,and 120 min via a four-point bending system.The control group(CG)was cultured in the absence of mechanical loading.Alterations of the cell cycle and apoptosis rate were detected by flow cytometry(FCM).The concentrations of interleukin 6(IL-6)/prostaglandin E2(PGE2)and nitric oxide(NO)in supernatants were determined by enzyme-linked immunosorbent assays and the nitrate reductase method,respectively.Expression of Myf5 and MyoD was detected by immunohistochemistry.RESULTS:Compared with the CG,a significant alteration was observed in the synthesis phase fraction(SPF)(P<0.01).The SPF and proliferation index(PI)were reduced from 15 to 90 min,but reached levels similar to those at 120 min.Apoptosis was increased significantly at 30 min(P<0.05)and especially at 90 and 120 min(P<0.01).Expression of MyoD and Myf5 was increased significantly at 15,30,and 90 min(P<0.01).Compared with 15 and 30 min,MyoD and Myf5 expression at 60 and 120 min was decreased significantly(P<0.01).Compared with 60 min,M yoD expression at 90 min was increased significantly(P<0.05),whereas MyoD and Myf5 expression at 120 min was significantly lower(P<0.05).The IL-6 concentration was increased at 60 min compared with the CG and 15 min(P<0.05),whereas the concentrations of PGE2 and NO were the highest at 15 and 30 min,respectively,compared with the CG and other time points(P<0.05).CONCLUSION:The cell cycle,secretion,apoptosis,and Myf5 and MyoD expression of RSkMCs were regulated by compressive stress in a time-dependent manner.SPF and PI were inhibited at short durations(<90 min),but NO and PGE2 secretion was the highest at shorter durations(<30 min).With the prolongation of stimulation time,SPF,PI,and apoptosis were increased,but Myf5 and MyoD expression was decreased gradually at 15-30 min.