Use of ultrasound to assess renal reperfusion and P-selectin expression following unilateral renal ischemia

Renal ischemia-reperfusion injury is a major cause of acute kidney injury that carries a high mortality rate and increases the risk of later development of hypertension and chronic kidney disease. Although mouse models have contributed much to our understanding of the mechanisms involved, studying aspects of the injury process in vivo remains technically challenging. This study validates the use of noninvasive ultrasound imaging to assess both renal perfusion and vascular adhesion molecule expression following 1-h unilateral renal ischemia in male and female mice. Pulsed-wave Doppler measurements of renal arterial blood velocity revealed renal perfusion recoveries of 56 ± 9% in male and 69 ± 10% in female mice 1 h after the commencing of reperfusion, which is similar to what we have previously published using conventional invasive methodology. At 24 h postischemia, renal perfusion was 40 ± 8% in male and 46 ± 7% in female mice, representing a further significant reduction of perfusion (P_Time < 0.001). Using ultrasound imaging of a P-selectin-targeted contrast agent, a significant increase in vascular P-selectin protein expression was observed after 1-h reperfusion in the cortex of the postischemic compared with contralateral kidney in both male and female mice (18 ± 5 vs. 3 ± 3 intensity units in male and 30 ± 6 vs. 0 ± 4 in female mice, P_Ischemia < 0.01). An approximately sixfold increase in P-selectin mRNA was observed ex vivo in the renal vasculature of male and female mice at this time point (P < 0.01). In conclusion, ultrasound represents an effective and noninvasive method for the measurement of both renal perfusion and vascular adhesion molecule expression in mice.