Objective To investigate the expression and significance of microRNA - 21(miR - 21)in acute kidney injury mice model at the different time points following ischemic/ reperfusion. Methods C57BL/ 6J mice were divided into 3 major groups:the control group(C group),sham operation group(S group)and ischemia - reperfusion group(IR group). Later 2 groups were divided into 9 sub - groups respectively according to the time following reperfu-sion. Automatic biochemical analyzer detected serum creatinine(Scr),blood urea nitrogen(BUN)level. HE staining detected renal pathological damage. Renal tubulointerstitial pathological score accessed pathological damage. Real time - PCR tested the expression of miR - 21 and mitogen - activated protein kinase kinase 3(MKK3)mRNA in renal respectively. Immunohistochemistry staining tested expression of MKK3. Results IR group's Scr,BUN levels gradually increased following reperfusion,24 h reached its peak,then gradually declined. The Scr,BUN level had statistically sig-nificant difference between IR group and S group at the same time subgroup from 3 h to 168 h following reperfusion(all P ﹤ 0. 01). The change of kidney damage and pathological changes of interstitial and tubular injury score consensus with renal function. miR - 21 increased gradually in renal ischemia after reperfusion,24 h peaked and then stabilized at this high level. miR - 21 was positively correlated with pathological tubulointerstitial injury from 0 h to 168 h after reperfu-sion(r = 0. 969,P ﹤ 0. 05). IR group's MKK3 mRNA and protein expression rose sharply following ischemia/ reperfu-sion,24 h peaked,and then gradually decreased. From 3 h to 168 h,the expression of MKK3 mRNA and proteins had significant difference at each same time points subgroups between IR group and S group(all P ﹤ 0. 01). Conclusions miR - 21 increases gradually in renal ischemia after reperfusion,24 h peaked and then stabilized at this high level. miR - 21 is positively correlated with pathological tubulointerstitial injury,which may be associated with the negative regulated relationship between miR - 21 and MKK3.

Objective To investigate the protective effect of ischemia preconditioning(IPC)on apoptosis in-duced by renal ischemia - reperfusion(IR)and relations to the changing expressions of Bcl - 2,Bax in rat kidney. Methods Ischemia models were induced by clipping bilateral renal pedicles for 30 min by using the artery clamp;IPC group was induced by clipping bilateral renal pedicles for 15 min,4 days later IR was performed again by clipping bila-teral renal pedicle for 30 min. Rats were randomly divided into 5 groups with 5 animals in each group:control group(C group),sham - operation group(S group),IR group,IPC group(IPC ﹢ IR group),sham IPC group(S ﹢ IR group),all groups were randomly divided into 9 sub groups(0 h,3 h,6 h,12 h,24 h,48 h,3 d,5 d,7 d)except C group according to the time points after reperfusion. Occurrence of apoptosis was detected by terminal deoxynuleotidyl transferase media-ted dUTP nick end and labeling(TUNEL)method;the mRNA expression and protein levels of Bax and Bcl - 2 were de-tected by reverse transcriptase - polymerase chain reaction and quantitave immunohistochemisty. Results (1)Com-pared with S group and S ﹢ IR group,serum creatinine,blood urea nitrogen,kidney pathological damage scores in IR group gradually increased after IR,and peak point was 24 h after reperfusion;among all the subgroups there was a sig-nificant difference(all P ﹤ 0. 01). The expression of Bax,Bcl - 2 mRNA raised sharply in IR group after reperfusion, peaking at 6 h,24 h of reperfusion respectively,2. 66 ± 0. 12,2. 70 ± 0. 10,and among all the subgroups there was a sig-nificant difference(all P ﹤ 0. 01);the expression of Bax,Bcl - 2 protein had significant difference(all P ﹤ 0. 05). TUNEL immunofluorescence staining showed C group and S group had no obvious apoptosis cells in renal tubular epi-thelium;epithelial cell apoptosis after IR gradually increased in IR group,peaking at 24 h of reperfusion[(25. 07 ± 2. 29)% ].(2)Compared with IR group and S ﹢ IR group,pathological injury was significantly decreased in IPC ﹢ IR group;the expression of Bax,Bcl - 2 mRNA and protein,apoptosis cells were significantly decreased in IPC ﹢ IR group (all P ﹤ 0. 05). Conclusions Bax,Bcl - 2 are closely associated with kidney injury induced by IR. IPC may regulate acute kidney injuries by regulating Bax/ Bcl - 2.