Comparison between near-infrared fluorescence imaging with indocyanine green and infrared imaging: on-bench trial for kidney perfusion analysis. A project of the ESUT-YAUWP group.

BACKGROUND: Infrared thermography (IRT) imaging technology is able to measure surface temperatures in real-time. The aim of our study is to understand whether IRT imaging is a reliable technology for the assessment of kidney-parenchyma perfusion with warm fluids. METHODS: We used three porcine kidneys as a sample. IRT was compared to Near-infrared fluorescence (NIRF) technology with Indocyanine Green (ICG), X-rays with Contrast medium was used as a benchmark. Each kidney, placed inside an incubator, was perfused with contrast medium by a vascular 6-Fr catheter, to preview the perfusable parenchymal area. 100 mL of saline solution at 45 °C was then administered along a five-minutes time, followed by a second administration of 2/10 diluted ICG solution. A FLIR© C2 IR camera was used to acquire thermal data. During ICG administration, image acquisition was obtained with FireFly technology, with a 0° endoscopic camera. Quantitative variables are described using median and quartiles. RESULTS: Real-time evaluation by IRT showed that, after five minutes of perfusion, it was possible to highlight the same parenchymal areas as visualized by X-ray. The IR images showed that surface temperature rise was directly reflecting local perfusion with heated saline solution. Analysis of NIRF technology and ICG showed an overlap between the two technologies. In addition to the compared technology, IR provided separate temperature measurement for each pixel in real time. Our findings were replicable on all the three kidneys examined. Higher resolution IR-cameras could provide even more detailed information. CONCLUSIONS: Although NIRF technology with ICG is providing more image detail, we demonstrated that IRT is capable of detecting kidney parenchyma perfusion with warm fluids. Further studies will show its feasibility in graft re-perfusion assessment during kidney transplant or similar applications.

The enzymatic machinery for ADMA synthesis and degradation is fully expressed in human adipocytes.

BACKGROUND: The endogenous inhibitor of nitric oxide synthase (NOS), asymmetric dimethylarginine (ADMA), is implicated in endothelial dysfunction and is a marker of renal disease progression and cardiovascular (CV) complications. Various cell species exhibit the enzymatic system that generates and degrades this methylarginine, but it is unknown whether this machinery is expressed in adipocytes. The question is relevant because adipocyte-derived mediators are implicated both in renal and cardiovascular diseases. METHODS: We measured ADMA concentration in pure adipocytes in culture and measured mRNA levels of the enzymes involved in ADMA metabolism (real-time polymerase chain reaction) both in pure adipocytes in culture and in adipose tissue harvested in 9 healthy subjects. These enzymes included protein arginine N-methyltransferases type I (PRMTs) involved in ADMA synthesis, dimethylarginine dimethylaminohydrolases (DDAHs) responsible for ADMA degradation and constitutive and inducible forms of NOS (i.e., NOS1, NOS2A and NOS3 genes), the main functional target of ADMA. RESULTS: Human adipocytes express the whole gene set that codes for the enzymatic system responsible for the biosynthesis and the degradation of ADMA, and this methylarginine is actually released by adipocytes in culture. NOS gene isoforms have a low level of expression in human adipose tissue, indicating that putative functions of ADMA in fat cells may be in part mediated by mechanisms other than NOS inhibition. CONCLUSIONS: Human adipocytes produce ADMA and express the full enzymatic machinery responsible for ADMA metabolism. Studying the functional implication of these findings may be of relevance for clarifying the role of fat mass expansion in human disease.