Photoacoustic imaging of kidney fibrosis for assessing pretransplant organ quality

Roughly 10% of the world's population has chronic kidney disease (CKD). In its advanced stages, CKD greatly increases the risk of hospitalization and death. Although kidney transplantation has revolutionized the care of advanced CKD, clinicians have limited ways of assessing donor kidney quality. Thus, optimal donor kidney-recipient matching can not be performed, meaning that some patients receive damaged kidneys that function poorly. Fibrosis is a form of chronic damage often present in donor kidneys that is an important predictor of future renal function. Currently, no safe, easy to perform technique exists that accurately quantifies renal fibrosis. We describe a novel photoacoustic (PA) imaging technique that directly images collagen, the principal component of fibrotic tissue. PA imaging non-invasively quantifies whole kidney fibrotic burden in mice, and cortical fibrosis in pig and human kidneys, with outstanding accuracy and speed. Remarkably, three-dimensional PA imaging exhibited sufficiently high resolution to capture intra-renal variations in collagen content. We further show that PA imaging can be performed in a setting that mimics human kidney transplantation, suggesting the potential for rapid clinical translation. Taken together, our data suggests that PA collagen imaging is a major advance in fibrosis quantification that could have widespread pre-clinical and clinical impact.