Effects Of Fibroblast Growth Factor-2 On Arteriogenesis Promoted By Isometric Exercise In Remote Ischemic Myocardium

Objective: To investigate the effects of fibroblast growth factor-2(FGF-2)on arteriogenesis promoted by isometric exercise(IE)in remote ischemic myocardium.Methods: Fifty-two male Sprague-Dawley rats weighing(200 ± 20)g were randomized into four groups: sham-operated group(SO),myocardial ischemia group(MI),isometirc exercise group(IE)and FGF inhibitor group(Inhi-FGF).Rats in SO gruop were injected saline subcutaneously for 2 weeks.Rats in MI group were injected isoproterenol of 10mg/kg/d subcutaneously for successive 2 weeks to induce myocardial ischemia.Rats in IE group accepted isometric exercise and myocardial ischemia.In addition to the treatment of IE group,rats in Inhi-FGF group were also given formononetin of 100mg/kg/d by intragastric administration.After 8 weeks,all rats were randomly divided into two groups based on the type of measurement: laboratory detection group and vascular imaging group.In the group of laboratory detection,the left ventricular myocardium was taken.Microspheres method was used to measure relative collateral blood flow(RCBF).Artery density(AD)and smooth muscle cells(SMCs)was measured by immunohistochemistry.The m RNA and protein expression of FGF-2 and its receptor FGFR-1 was measrured by real-time quantitative PCR and western blotting.In the vascular imaging group,the hearts were immediately excised and were prepared for micro-CT to detect the arteriogenesis.Results:(1)Relative collateral blood flow: RCBF in the IE group(43.62±1.21)increased significantly compared with that of the SO(28.49±1.21,P<0.001),MI(34.61±1.57,P<0.001)and Inhi-FGF group(32.76±1.14,P<0.001).RCBF in the SO group(28.49±1.21)was lower than that of the MI(34.61±1.57,P<0.001)and Inhi-FGF group(32.76±1.14,P < 0.001).There was no significant difference between MI and Inhi-FGF group(P>0.05).(2)Artery density: AD in the IE group(33.83±2.32)increased significantly compared with that of the SO(21.17±1.94,P<0.001),MI(24.67±1.21,P<0.001)and Inhi-FGF group(20.50±1.76,P<0.001).AD in the MI group(24.67±1.21)was higher than that of the SO(21.17±1.94,P<0.05)and Inhi-FGF group(20.50±1.76,P<0.05).There was no significant difference between SO and Inhi-FGF group(P>0.05).(3)Smooth muscle cells: The SMCs in the IE group(27.88±2.05)increased significantly compared with that of the SO(16.15±1.31,P < 0.001),MI(20.99±1.42,P < 0.001)and Inhi-FGF group(16.99±1.12,P<0.001).The SMCs in the MI group(20.99±1.42)was higher than that of the SO(16.15±1.31,P<0.001)and Inhi-FGF group(16.99±1.12,P=0.001).There was no significant difference between SO and Inhi-FGF group(P>0.05).(4)The m RNA expression of FGF-2 and FGFR-1: FGF-2: The m RNA expression of FGF-2 in the IE group(2.94±0.50)increased significantly compared with that of the SO(1.04±0.11,P=0.001),MI(1.62±0.12,P<0.05)and Inhi-FGF group(1.09±0.25,P<0.001).The m RNA expression of FGF-2 in the MI group(1.62±0.12)was higher than that of the SO(1.04±0.11,P<0.001)and Inhi-FGF group(1.09±0.25,P<0.05).There was no significant difference between SO and Inhi-FGF group(P>0.05).FGFR-1: The m RNA expression of FGFR-1 in the IE group(3.34±0.60)increased significantly compared with that of the SO(1.06±0.16,P=0.001),MI(1.78±0.11,P<0.05)and Inhi-FGF group(1.45±0.62,P<0.05).The m RNA expression of FGFR-1 in the MI group(1.78±0.11)was higher than that of the SO group(1.06±0.16,P<0.001).There were no significant difference between Inhi-FGF and SO,Inhi-FGF and MI group(P>0.05).(5)The protein expression of FGF-2 and FGFR-1: FGF-2: The protein expression of FGF-2 in the IE group(0.72±0.06)increased significantly compared with that of the SO(0.24±0.12,P<0.001),MI(0.48±0.11,P=0.001)and Inhi-FGF group(0.28±0.05,P < 0.001).The protein expression of FGF-2 in the MI group(0.48±0.11)was higher than that of the SO(0.24±0.12,P=0.001)and Inhi-FGF group(0.28±0.05,P<0.05).There was no significant difference between SO and Inhi-FGF group(P>0.05).FGFR-1: The protein expression of FGFR-1 in the IE group(0.82±0.08)increased significantly compared with that of the SO(0.25±0.06,P<0.001),MI(0.53±0.08,P<0.001)and Inhi-FGF group(0.40±0.12,P<0.001).The protein expression of FGFR-1 in the MI group(0.53±0.08)was higher than that of the SO group(0.25±0.06,P<0.001).There were no significant difference between Inhi-FGF and SO,Inhi-FGF and MI group(P>0.05).(6)The results of Micro CT: In the IE group,the original coronary vessels were well filled,and there was a significant increase in collateral artery formation compared with SO,MI and Inhi-FGF group.Compared with the SO group,the filling of original coronary vessels in MI group was worse,but there was more collateral artery formation.The original coronary vessels of Inhi-FGF group had filling defect and the collateral artery formation was significantly less than that of the IE group.(7)Correlation analysis: There significantly positive correlation between RCBF and AD(r=0.885,P<0.001),AD and SMCs(r=0.933,P<0.001),SMCs and the protein expression of FGF-2(r=0.843,P<0.001).Conclusion: IE can promote arteriogenesis and improve the blood perfusion of remote ischemic myocardium by promoting the expression of FGF-2 and its receptor.