Contrast-enhanced ultrasound and photoacoustic imaging to assess early and late renal ischemia-reperfusion injuries in male mice.

Tissue perfusion and oxygenation, key factors of renal ischemia-reperfusion injury (RIR), can be assessed using contrast-enhanced ultrasound (CEUS) and photoacoustic (PA) imaging. We hypothesized that early changes in renal perfusion and oxygenation caused by IRI, or protection by mild therapeutic hypothermia (mTH), could be detected and correlate with fibrosis. C57BL6 mice underwent 15-min unilateral renal ischemia, with or without mTH, followed by 1-month reperfusion. They were assigned to sham (n = 5), normothermic renal ischemia (IR-37°C, n = 7), mTH renal ischemia (IR-34°C, n = 7). The IR-37°C and IR-34°C groups had body temperature maintained at 37°C or 34°C during surgery. CEUS and PA were conducted at baseline, 20 min, and 1 month after reperfusion. Histological analysis was performed at 1 month. IRI induced renal atrophy and fibrosis at 1 month, prevented by mTH. CEUS revealed altered perfusion in IR-37°C at 20 min, sustained at 1 month, compared to Sham, while perfusion was preserved with mTH in IR-34°C. Oxygenation assessed by PA was not modified. However, oxygenation measured 20 min after IRI correlated with fibrosis at 1 month. CEUS and PA are promising tools for non-invasive assessment of renal IRI. IRI induced early and sustained perfusion alterations, while early assessment of oxygenation correlated with fibrosis. mTH prevented these alterations.