The potential role of circulating exosomes in protecting myocardial injury in acute myocardial infarction via regulating miR-190a-3p/CXCR4/CXCL12 pathway.

Exosomes of different origins have been found to be protective against ischemic-induced myocardial injury. This study examined the protective effects of circulating exosomes in the mice model of acute myocardial infarction (AMI) and explored the underlying molecular mechanisms. The effects of exosomes on myocardial injury were assessed in the AMI mice model. The in vivo studies showed that circulating exosomes reduced the infarcted size, improved the morphology of heart tissues and also reduced apoptosis of the heart tissues. In addition, the model mice showed an increase in the CD34 + /VEGFR2 + cell population and CD31, CXCR4 and CXCL12 expression after exosomes treatment. MiR-190a-3p was significantly down-regulated in the exosomes derived from the culture medium of hypoxia-treated human cardiomyocytes (HCMs). Further analysis revealed that miR-190a-3p could physically interact with CXCR4/CXCL12 by targeting the respective 3'UTRs. These exosomes could up-regulated CXCR4 and CXCL12 expression in the EPCs; in addition, miR-190a-3p mimics repressed CXCR4/CXCL12 expression in EPCs, while its inhibitor had opposite effects. The in vitro functional assays showed that miR-190a-3p overexpression suppressed the cell viability, proliferation, migration, adhesion and tube formation of EPCs; while miR-190a-3p inhibitor had the opposite effects; exosomes derived from the culture medium of hypoxia-treated HCMs exhibited similar actions of miR-190a-3p inhibitor. Moreover, miR-190a-3p was down-regulated in exosomes from serum in the AMI group when compared to that from sham group. Treatment with exosomes from serum in the AMI group promoted cell proliferation, migration, adhesion and tube formation of EPCs when compared to that in the sham group. More importantly, IT1t attenuated the enhanced effects of miR-190a-3p inhibition on EPC proliferation, migration, adhesion and tube formation. In conclusion, circulating exosomes exerted protective effects on myocardial injury in the AMI mice model, and down-regulation of miR-190a-3p in the circulating exosomes may exert protective effects against myocardial injury. Hypoxia induced the downregulation of miR-190a-3p in the culture medium of HCMs, and the mechanistic investigations indicated that exosomes of hypoxia-conditioned HCM culture medium promoted the cell viability, proliferation, migration, adhesion and tube formation of EPCs via regulating miR-190a-3p/CXCR4/CXCL12 pathway.

[Urotensin II induces hypertrophy of in vitro cultured neonatal rat cardiac myocytes].

OBJECTIVE: To examine whether urotensinII (UII) induces hypertrophy of neonatal rat cardiomyocytes cultured in vitro. METHODS: The primary cardiac myocytes cultured for 40 h followed by further culture in serum-free media for another 24 h were subjected to exposure to UII of varied concentrations for 24 h, after which the changes in the size of the cells were analyzed by flow cytometry with (3)H-leucine incorporation also measured. RESULTS: At the concentration of 1x10(-7) mol/L, UIIcould increase the size of the cultured cardiac myocardial cells (P=0.021) and 3H-Leucine incorporation (P=0.015). CONCLUSION: UII may induce hypertrophy of neonatal rat cardiac myocytes cultured in vitro.

[Effects of urotensin II on cultured cardiac fibroblast proliferation and collagen type I mRNA expression].

OBJECTIVE: To observe the effect of urotensin II on cultured cardiac fibroblast collagen type I mRNA expression and proliferation, thereby to explore the role of urotensin II in myocardial remodeling in the event of cardiac failure. METHODS: Cardiac fibroblasts of neonatal Sprague-Dawley rats isolated by trypsin digestion method were stimulated by urotensin II at varied concentrations when the cells reached growth arrest. MTT assay was employed to measure the proliferation and determine the number of the cells, and reverse transcriptional (RT)-PCR used to detect the collagen mRNA expression. RESULTS: With the increase of urotensin II concentration, the optical density at 570 nm of the fibroblasts as shown by MTT assay first increased but then decreased, and remained at a significantly higher level in the cells treated with 1x10(-8) or 1x10(-9) mol/L urotensin II as compared with the control (P<0.05). The collagen type I mRNA levels of the cells treated with 1x10(-7), 1x10(-8) or 1x10(-9) mol/L urotensin II were significantly higher than that of the control cells (P<0.01). CONCLUSION: Urotensin II can directly induce cardiac fibroblast proliferation and significantly increase collagen type I mRNA expression, suggesting the crucial role of urotensin II in myocardial remodeling.