A Novel Imaging Technique for The On-site Assessment of Renal Biopsy Specimens

Background

Renal biopsy is one of the most important procedures for the assessment of kidney diseases. Upon performing renal biopsy, it is necessary to obtain a sufficient number of glomeruli, which are exclusively distributed in the renal cortex. A stereomicroscope or magnifying lens are usually used for this purpose; however, it is often difficult to clearly identify the cortex. Therefore, novel methods for the on-site assessment of renal biopsy specimens need to be established.

Gamma-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG) is a recently developed activatable fluorescent probe (Urano et al., 2011). This probe is characterized by immediate fluorescence emission upon enzymatic catalysis by gamma-glutamyl transpeptidase (GGTP). gGlu-HMRG was originally developed for the detection of several types of cancer that express high levels of GGTP (Mitsunaga et al., 2013), and has not been applied to renal biopsy specimens.

Our recent work has focused on investigating the feasibility of gGlu-HMRG for the on-site assessment of renal biopsy specimens (Iyama et al., 2020). Renal cortex, in which most of the glomeruli are contained, showed rapid induction of fluorescence upon the incubation of gGlu-HMRG and could be clearly distinguished from renal medulla. We herein present a protocol for the induction of fluorescence by gGlu-HMRG with some modifications for better clarity of the images.