| Objective:To investigate the possible mechanism of human umbilical cord mesenchymal stem cells(hUCMSCs)intervention in the treatment of dilated cardiomyopathy(DCM).Methods:40 SD rats were randomly divided into the normal control group(10)and the DCM model group(30).DCM group rats were given intraperitoneal injection of doxorubicin 2 mg/kg once a week for 8 weeks,and cardiac ultrasound was performed to evaluate cardiac function after 1 week of drug withdrawal.The surviving DCM rats were divided into the hUCMSCs treatment group and the DCM model control group with the same number randomly.In the hUCMSCs treatment group,2 mL of hUCMSCs cell suspension(10×10~6 cells)was injected into the muscles of the four limbs of the rats.In the DCM model control group and the normal control group,2mL of DMEM medium was injected into the same sites.HUCMSCs were evaluated by echocardiography 2 weeks after the last intervention.Cardiac histopathological changes were observed under HE staining under light microscope.Expression of transforming growth factor-β1 and Smad3 in cardiac tissue were determined by rt-pcr.The experimental data were expressed as mean±standard deviation((?)±S).The pairwise comparison between groups was conducted by one-way anova and LSD-t test.The independent sample t test was used to compare the two groups of data.Results1.Comparison of echocardiographic results between the DCM model group and the normal control group:LVIDd and LVIDs of the DCM model group were(4.90±0.20)mm and(3.88±0.33)mm,respectively,which were significantly higher than that of the normal control group【(3.20±0.10)mm and(3.15±0.40)mm】respectively,with statistically significant differences(t=25.193、5.324,all P<0.01).Left ventricular ejection fraction(LVEF)and left ventricular shortening rate(LVFS)in DCM model group were(60.55±2.90)%and(38.7±2.80)%,respectively,which were significantly lower than those in the normal control group【(70.59±0.50)%and(50.10±0.90)%】respectively,with statistically significant differences(t=10.776、12.460,all P<0.01).2.Echocardiographic changes in DCM model rats before and after hUCMSCs intervention:there was no significant difference in LVEF and LVFS between the hUCMSCs treatment group and the DCM model control group before and after hUCMSCs intervention(t=0.303、0.051,P>0.05).LVEF in the hUCMSCs treatment group was(84.0±3.10)%2 weeks after the last injection,which was significantly higher than that before the intervention【(66.20±1.2)%】and in the DCM model control group【(66.10±1.0)%】,with statistically significant differences(t=16.933,17.378,all P<0.01).LVFS in the hUCMSCs treatment group was(45.00±4.40)%2weeks after the last injection,which was significantly higher than that before the intervention【(38.30±4.20)%】and in the DCM model control group【(38.20±3.30)%】,with statistically significant differences(t=3.483,3.910,P<0.01).3.Effect of hUCMSCs intervention on myocardial histopathology and expression of TGF-β1/Smad3 in DCM rats:HE staining showed that the myocardial fiber tissue in DCM model control group was not arranged in a regular manner,myocardial fiber fracture and necrosis were observed,myocardial cells and interstitial edema were observed,and a large number of inflammatory cells were observed,clustered in the myocardial tissue in a focal manner.In the hUCMSCs treated group,the cardiomyocytes and stroma of the rats presented limited mild edema,and the myocardial fiber tissue was basically arranged in an orderly manner.Irregular and necrotic myocardial fiber tissue was partly observed,and part of inflammatory cell infiltration was observed in some myocardial tissues.According to the results of RT-PCR,the expression levels of TGF-β1mRNA and Smad3 mRNA in the DCM model control group were(31.87±5.52)and(35.97±4.80)times than the internal reference gene,respectively,which were significantly higher than those in the normal control group【for(1.11±0.26)times and(1.30±0.25)times】.The differences were statistically significant(t=17.61,22.81;All P<0.01).After hUCMSCs intervention,the expression level of TGF-β1 in DCM model rats was(1.20±0.14)times than that in the internal reference gene,which was significantly lower than that of DCM model control rats,with statistically significant difference(t=17.56,P<0.01),but no significant difference(t=1.07,P>0.05).After intervention,the expression level of Smad3 mRNA in the myocardial tissue of the DCM model rats in the hUCMSCs treatment group was(1.84±0.30)times than that in the internal reference gene,which was significantly lower than that in the DCM model control group(t=22.44,P<0.01),but still higher than that in the normal control group(t=4.37,P<0.01).Conclusions1.The expression levels of TGF-β1 mRNA and Smad3 mRNA in DCM model rats were significantly increased,while both were significantly decreased after hUCMSCs intervention.2.After intramuscular administration of hUCMSCs intervention,significant reduction of myocardial pathological changes and significant improvement of cardiac function were observed in DCM model rats,which may be closely related to inhibition of expression of TGF-β1 and Smad3 in myocardial tissues. |
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