Illuminating necrosis: From mechanistic exploration to preclinical application using fluorescence molecular imaging with indocyanine green

Abstract

Tissue necrosis commonly accompanies the development of a wide range of serious diseases. Therefore, highly sensitive detection and precise boundary delineation of necrotic tissue via effective imaging techniques are crucial for clinical treatments; however, no imaging modalities have achieved satisfactory results to date. Although fluorescence molecular imaging (FMI) shows potential in this regard, no effective necrosis-avid fluorescent probe has been developed for clinical applications. Here, we demonstrate that indocyanine green (ICG) can achieve high avidity of necrotic tissue owing to its interaction with lipoprotein (LP) and phospholipids. The mechanism was explored at the cellular and molecular levels through a series of in vitro studies. Detection of necrotic tissue and real-time image-guided surgery were successfully achieved in different organs of different animal models with the help of FMI using in house-designed imaging devices. The results indicated that necrotic tissue with a 0.6 mm diameter could be effectively detected with precise boundary definition. We believe that the new discovery and the associated imaging techniques will improve personalized and precise surgery in the near future.

In vivo visualization and ex vivo quantification of experimental myocardial infarction by indocyanine green fluorescence imaging

“…The present study is also the first report on ICG fluoroscopy for in vivo evaluation of irreversible ischemia-reperfusion injury in the heart. ICG accumulation at the site of injury has been described for different injuries such as ischemic tissue damage, inflammation, and tumors [13][14][15][16] and observed in various organs, but the accumulation of ICG in the myocardium to date has not yet been described. ICG choroidal angiography allows the observation of injury caused by ischemia or inflammatory processes that are detected by leakage of ICG [16,21].…”

“…Return of the ~10% of fluid/ICG that will not enter the venous capillaries, but instead enters the lymphatic capillaries may be deferred, because the inflammation caused by ischemia could induce production of inflammatory cytokines and other molecular mediators of lymphatic flow arrest [22,23]. Fang et al (2016) detected necrosis in the rat skeletal muscle using fluorescence molecular imaging with ICG [13]. The authors suggest that increased vascular permeability is an insufficient explanation for indocyanine staining of necrosis, and proposed a mechanism by which ICG selectively binds to necrotic tissue.…”

“…The detection sensitivity of this approach is high and comparable with TTC assay. The smallest necrosis that is successfully detected is 0.6 mm [13]. However, maybe most important is the ability to visualize the infarcted area in vivo.…”

“…The loss of functional integrity of the vessel wall was evident after 90 minutes of ischemia by extravasation of fluorescein isothiocyanate-conjugated albumin-fluorescein (FITC-albumin). Recently Fang et al (2016) demonstrated that ischemia-induced necrosis in skeletal muscle may be demonstrated by another fluorescent dye -indocyanine green (ICG) [13].…”

Lasing in blood

“…In cancer surgery, one of the main prognostic factors for survival rate is complete tumor resection and imaging modalities that allow the specific differentiation and identification of vital structures, which would be of huge benefit during image guided surgery. However, in clinical applications, due to background fluorescence and omnipresent tissue scattering, it remains challenging to obtain high contrast in ICG emission between the tumor and normal tissue for precise tumor detection and margins of excision [12,14–16]. In in vitro applications, ICG emission is often not sensitive enough to detect or monitor subtle changes in concentrations or structures in biomolecules, cells, and tissues.…”