RESUMEN
Objective To investigate the utility of diffusion weighted imaging (DWI) and blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) in the assessment of renal hypoxia in an experimental model of mice with lupus nephritis (LN).Methods MRL/lpr mice (n=13) were studied and C57BL/6 mice (n=10) served as controls.Urinary albumin to creatinine ratio (ACR),serum creatinine (Scr),anti-ds-DNA antibody,and complement C3 levels were measured.The mice underwent coronal echo-planar DWI and BOLD MRI of the kidneys when they were 14-16 weeks old.Hypoxyprobe was administered intraperitoneally to the mice 1 hour before they were sacrificed.The distribution of HypoxyprobeTM-1,hypoxia-inducible factor 1 α (HIF-1 o) and heme oxygenase-1 (HO-1) in renal tissues was detected by immunohistochemical analysis and Western blotting.Results Urinary ACR,Scr and anti-ds-DNA antibody levels in MRL/lpr mice were significantly higher than that in C57BL/6 mice.It was found that HypoxyprobeTM-1,HIF-1o and HO-1 distributed widely in the renal tissue of MRL/lpr mice,and closely associated with the renal tubulointerstitial lesion.The mean apparent diffusion coefficient (ADC) value of kidneys in MRL/lpr mice was (1.52±0.27) × 10-3 mm2/s,and the mean R2* values of the renal cortex and medulla were (30.95 ±4.59)/s and (23.43± 3.06)/s respectively,all significantly lower than that in C57BL/6 mice (P=0.037,P=0.030 and P=0.043,respectively).The ADC of medulla was negatively correlated with urinary albumin to creatinine ratio (r=-0.364,P=0.032;r=-0.329,P=0.050),the ADC of cortex was negatively correlated with the level of serum creatinine (r=-0.814,P=0.014;r=-0.755,P=0.031) when b value was 500 s/mm2 and 800 s/mm2,and the mean R2* value was negatively correlated with the degree of tubulointerstitial lesions and the expression of hypoxia parameters (all P ＜ 0.05).Conclusions Renal hypoxia may play an important role in renal tubulointerstitial lesion.Functional MRI may be used to monitor renal function changes,pathological injuries and renal hypoxia in LN.