Predictive assessment of kidney functional recovery following ischemic injury using optical spectroscopy

Abstract

"Predictive assessment of kidney functional recovery following ischemic injury using optical spectroscopy," J. Biomed. Opt. 22(5), 056001 (2017), doi: 10.1117/1.JBO.22.5.056001. Abstract. Functional changes in rat kidneys during the induced ischemic injury and recovery phases were explored using multimodal autofluorescence and light scattering imaging. The aim is to evaluate the use of noncontact optical signatures for rapid assessment of tissue function and viability. Specifically, autofluorescence images were acquired in vivo under 355, 325, and 266 nm illumination while light scattering images were collected at the excitation wavelengths as well as using relatively narrowband light centered at 500 nm. The images were simultaneously recorded using a multimodal optical imaging system. The signals were analyzed to obtain time constants, which were correlated to kidney dysfunction as determined by a subsequent survival study and histopathological analysis. Analysis of both the light scattering and autofluorescence images suggests that changes in tissue microstructure, fluorophore emission, and blood absorption spectral characteristics, coupled with vascular response, contribute to the behavior of the observed signal, which may be used to obtain tissue functional information and offer the ability to predict posttransplant kidney function. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Label-Free Metabolic Imaging In Vivo by Two-Photon Fluorescence Lifetime Endomicroscopy

“…65,68,74 Commonly adopted metabolic biomarkers are quantitative NAD fluorescence measurement (or NADH fluorimetry) or phasor-based NADH lifetime analysis. 64,74,75 Multiexponential decay analysis, albeit computationally intensive, unveiled on the acute renal ischemia−reperfusion model that the elevated postischemia free NADH fraction (or equivalently, free-to-bound NADH ratio) is attributed to the extent of increase in C free outweighing that in C bound (see Figure 5c−e). To the best of our knowledge, this observation has not been reported in previous bench-top two-photon experiments of mouse kidney models and the underlying biochemical reactions are worthy of further investigation.…”

“…Multiphoton microscopy has been well received as a valuable tool for imaging functioning kidney, interrogating cellular structures, and metabolic dynamics in rodent models under physiological or psychological conditions. , Endogenous fluorescence from NADH and FAD has been widely used to study mitochondrial structures and function during acute kidney injury. ,, Commonly adopted metabolic biomarkers are quantitative NAD fluorescence measurement (or NADH fluorimetry) or phasor-based NADH lifetime analysis. ,, Multiexponential decay analysis, albeit computationally intensive, unveiled on the acute renal ischemia–reperfusion model that the elevated postischemia free NADH fraction (or equivalently, free-to-bound NADH ratio) is attributed to the extent of increase in C free outweighing that in C bound (see Figure c–e). To the best of our knowledge, this observation has not been reported in previous bench-top two-photon experiments of mouse kidney models and the underlying biochemical reactions are worthy of further investigation.…”

Enhancing in vivo renal ischemia assessment by high-dynamic-range fluorescence molecular imaging

“…Previous works on enhancing renal ischemia assessment include spectroscopic imaging 17,[36][37][38][39] and autofluorescence imaging. [40][41][42][43][44][45] These approaches have improved the assessment of ischemic physiology; however, they have limitations such as interference with imaging process due to hypothermic preservation, 36 altered fluorophore quantum efficiency, 39 phototoxicity, 43 and limited application in clinical settings.…”

“…[6][7][8] Therefore, NIR fluorescence imaging serves as a valuable tool 9 for research fields including tumor pharmacokinetics, [10][11][12] vascular function, 13,14 and tissue ischemia. [15][16][17] Kidneys receive ∼20% of the cardiac output, 18 and the renal anatomy is vascular-rich. Clinically, renal ischemia could be caused by various reasons, including arterial and venous occlusion, thrombosis, and vasculitis.…”

“…Modifying CCD hardware could help to solve this limitation, [33][34][35] but hardware modification could be costly and time-consuming. Another strategy adopted multiwavelength approaches including optical spectroscopic imaging 17,[36][37][38][39] and autofluorescence imaging [40][41][42][43][44][45] to investigate the renal ischemia physiology. However, these approaches have limitations, including altered fluorophore quantum efficiency, 39 weak or absent correlation between fluorescence and ischemia, 41 phototoxicity under short-wavelength, 43 and restricted clinical application.…”