Effects Of BRCA1/p21 Gene Knockout On Radiation-induced Heart Disease In Mice

Objective:The radiation-induced heart disease?RIHD?models of endothelial cells-specific BRCA1 homozygous knockout(EC-BRCA1^-/-)mice and p21knockout(p21^-/-)mice were constructed,and the primary cardiac microvascular endothelial cells of EC-BRCA1^-/-mice(CMEC-BRCA1^-/-)were extracted to explore the effect of BRCA1/p21 gene knockout on RIHD in mice.Method:To prepare and breed p21^-/-mice and EC-BRCA1^-/-mice,identify and screen p21^-/-mice and EC-BRCA1^-/-mice as experimental groups,p21^+/-mice and EC-BRCA1^+/-mice as respective control groups.To establish the model of RIHD,small animal radiation research platform was used to irradiate the hearts of p21^-/-,p21^+/-and EC-BRCA1^-/-,EC-BRCA1^+/-mice with a single dose of 10Gy and 16Gy,respectively.Six weeks after radiation in the hearts of p21^-/-and p21^+/-mice and eight weeks after radiation in the hearts of EC-BRCA1^-/-and EC-BRCA1^+/-mice,the survival curve was drawn by Kaplan-Meier method,the heart was detected by Vevo2100 ultrasound imaging system,the microvessel density of heart was detected by immunofluorescence,the hypoxia of cardiac tissue was detected by hypoxia probe method,and the apoptosis of cardiac cells was detected by TUNEL method.Primary cardiac microvascular endothelial cells of EC-BRCA1^-/-mice(CMEC-BRCA1^-/-)and CMEC-BRCA1^+/-were extracted and the expression level of P21 protein was detected by western blot.Results:Compared with p21^+/-mice,after heart irradiation with 10Gy for six weeks,the lifetime of p21^-/-mice was shortened?P=0.0039?,left ventricular ejection fraction?LVEF?decreased?P<0.0001?,interventricular septum?IVS?decreased(P_?IVS-s?=0.0057),left ventricular posterior wall?LVPW?thickened(P_?LVPW-d?<0.0001),cardiac microvessel density decreased,cardiac hypoxia aggravated and cardiac cell apoptosis increased.Compared with EC-BRCA1^+/-mice,after heart irradiation with16Gy for eight weeks,LVEF of EC-BRCA1^-/-mice decreased?P=0.0485?,LVPW thinned(P_?LVPW-d?=0.0292,P_?LVPW-s?=0.0423),cardiac microvessel density decreased,cardiac hypoxia aggravated and cardiac cell apoptosis increased.Compared with the primary CMEC-BRCA1^+/-,the expression of P21 protein in the primary CMEC-BRCA1^-/-decreased?P=0.0278?.Conclusions:The RIHD in P21 gene knockout mice and endothelial cell BRCA1 knockout mice was more severe than that in control group,and the expression of P21 protein in primary vascular endothelial cells of endothelial cell BRCA1 knockout mice also decreased.It is inferred that the existence of BRCA1/p21 gene has a certain protective effect on RIHD of mouse.