Real-time confocal laser endomicroscopic evaluation of primary liver cancer based on human liver autofluorescence

Probe-based confocal laser endomicroscopy for real-time evaluation of colorectal liver metastasis in resected surgical specimens

Probe-based confocal laser endomicroscopy (pCLE) enables real-time examination of tissue structure. This study investigated pCLE with or without fluorescein sodium for the intraoperative diagnosis of colorectal liver metastasis (CLM) and detection of surgical margins. Thirty-four specimens of CLM and adjacent noncancerous tissue were obtained from 21 patients and examined by pCLE between May 2017 and March 2018. Images were obtained both without and with fluorescein sodium applied to the cut surface and compared with hematoxylin and eosin-stained tissue. Fluorescence intensity (FI) was measured by luminance-analysis software. Without external fluorophores, pCLE visualized 91.2% of CLM tissues as an irregular structure with low autofluorescence and 90.5% of noncancerous liver tissues as a regular structure with high autofluorescence. The median FI was significantly lower in cancer than in benign tissue in patients without chemotherapy [70.4 (51.6-110) vs. 48.3 (39.0-59.4), p = 0.002] and with chemotherapy [67.9 (54.6-89.2) vs. 48.6 (28.8-82.1), p < 0.001]. The border was clearly visible; pCLE with fluorescein sodium clearly showed their morphologies. In summary, our study demonstrated real-time pCLE distinguished CLM and noncancerous tissue by differences in structure and FI regardless of prehepatectomy chemotherapy. Fluorescein spray facilitated clear visualization of differences in the morphology.

Simultaneous quantification of Gadoxetic acid and Cisplatin in hepatocellular carcinomas using laser ablation-inductively coupled plasma-mass spectrometry

The gadolinium-based contrast agent Gadoxetic acid and the platinum-based antitumor agent Cisplatin were quantitatively imaged in liver and liver cancer (hepatocellular carcinoma, HCC) tissue of rats by means of laser ablation-inductively coupled plasma-mass spectrometry. HCC bearing rats simultaneously received a tail vein injection of the hepatocyte-specific magnetic resonance imaging contrast agent Gadoxetic acid and a transarterial injection of Cisplatin 15 min before sacrifice and liver removal. Resecting HCC with adjacent liver tissue allows the comparison of Gd, Pt, and endogenous elements like Fe, Cu, and Zn in the various tissue types. Region of interest analysis reveals lower concentrations of Gd in HCC and higher Gd content in the adjacent liver, fitting the selective uptake of Gadoxetic acid into hepatocytes. Furthermore, two malignancy grades and their possible impact on the Gadoxetic acid and Cisplatin uptake are compared. For this, four high grade (G3) and two moderate grade (G2) HCCs were analysed, including a control sample each. Gd concentrations were lower in HCC irrespective of the grade of dedifferentiation (G2, G3) compared to adjacent liver. Despite local arterial Cisplatin injection, concentrations of Pt were similar or also reduced in HCC compared to liver tissue. In addition, endogenous Fe, Cu, and Zn were quantified. While Zn was homogenously distributed, higher Fe concentrations were determined in liver tissue compared to HCC. Hotspots of Cu suggest a deregulated copper homeostasis in certain liver lesions. The Gd and Fe distributions are compared in detail with cellular alterations examined by hematoxylin and eosin staining.

Fatty Acids and Bilirubin as Intrinsic Autofluorescence Serum Biomarkers of Drug Action in a Rat Model of Liver Ischemia and Reperfusion

The autofluorescence of specific fatty acids, retinoids, and bilirubin in crude serum can reflect changes in liver functional engagement in maintaining systemic metabolic homeostasis. The role of these fluorophores as intrinsic biomarkers of pharmacological actions has been investigated here in rats administered with obeticholic acid (OCA), a Farnesoid-X Receptor (FXR) agonist, proven to counteract the increase of serum bilirubin in hepatic ischemia/reperfusion (I/R) injury. Fluorescence spectroscopy has been applied to an assay serum collected from rats submitted to liver I/R (60/60 min ± OCA administration). The I/R group showed changes in the amplitude and profiles of emission spectra excited at 310 or 366 nm, indicating remarkable alterations in the retinoid and fluorescing fatty acid balance, with a particular increase in arachidonic acid. The I/R group also showed an increase in bilirubin AF, detected in the excitation spectra recorded at 570 nm. OCA greatly reversed the effects observed in the I/R group, confirmed by the biochemical analysis of bilirubin and fatty acids. These results are consistent with a relationship between OCA anti-inflammatory effects and the acknowledged roles of fatty acids as precursors of signaling agents mediating damaging responses to harmful stimuli, supporting serum autofluorescence analysis as a possible direct, real-time, cost-effective tool for pharmacological investigations.

Autofluorescence-Raman Spectroscopy for Ex Vivo Mapping Colorectal Liver Metastases and Liver Tissue

INTRODUCTION

Identifying colorectal liver metastases (CRLM) during liver resection could assist in achieving clear surgical margins, which is an important prognostic variable for both disease-free and overall survival. The aim of this study was to investigate the effect of auto-fluorescence (AF) and Raman spectroscopy for ex vivo label-free discrimination of CRLMs from normal liver tissue. Secondary aims include exploring options for multimodal AF-Raman integration with respect to diagnosis accuracy and imaging speed on human liver tissue and CRLM.

METHODS

Liver samples were obtained from patients undergoing liver surgery for CRLM who provided informed consent (15 patients were recruited). AF and Raman spectroscopy was performed on CRLM and normal liver tissue samples and then compared to histology.

RESULTS

AF emission spectra demonstrated that the 671 nm and 775/785 nm excitation wavelengths provided the highest contrast, as normal liver tissue elicited on average around eight-fold higher AF intensity compared to CRLM. The use of the 785 nm wavelength had the advantage of enabling Raman spectroscopy measurements from CRLM regions, allowing discrimination of CRLM from regions of normal liver tissue eliciting unusual low AF intensity, preventing misclassification. Proof-of-concept experiments using small pieces of CRLM samples covered by large normal liver tissue demonstrated the feasibility of a dual-modality AF-Raman for detection of positive margins within few minutes.

CONCLUSIONS

AF imaging and Raman spectroscopy can discriminate CRLM from normal liver tissue in an ex vivo setting. These results suggest the potential for developing integrated multimodal AF-Raman imaging techniques for intraoperative assessment of surgical margins.

Autofluorescence imaging within the liver: a promising tool for the detection and characterization of primary liver tumors

OBJECTIVES

To assess the performance of 405 nm-induced autofluorescence for the characterization of primary liver nodules on ex vivo resected specimens.

MATERIALS AND METHODS

Forty resected liver specimens bearing 53 primary liver nodules were included in this IRB-approved prospective study. Intratissular spectroscopic measurements were performed using a 25-G fibered-needle on all ex vivo specimens: 5 autofluorescence measurements were performed in both nodules and adjacent parenchyma. The spectra derivatives of the 635 and 670 nm autofluorescence peaks observed in nodules and in adjacent liver parenchyma were compared (Kruskal-Wallis and Mann-Whitney when appropriate).

RESULTS

A total of 42 potentially evolutive primary liver nodules-34 hepatocellular carcinomas, 4 intrahepatic cholangiocarcinomas, 4 hepatocellular adenomas-and 11 benign nodules-5 focal nodular hyperplasias, 6 regenerative nodules-were included. Both 635 and 670 nm Δderivatives were significantly higher in benign as compared to potentially evolutive (PEV) nodules (respectively 32.9 ± 4.5 vs 15.3 ± 1.4; p < 0.0001 and 5.7 ± 0.6 vs 2.5 ± 0.1; p < 0.0001) with respective sensitivity and specificity of 78% and 91% for distinguishing PEV from benign nodules.

CONCLUSION

405 nm-induced autofluorescence enables the discrimination of benign from PEV primary liver nodules, suggesting that autofluorescence imaging could be used to optimize US targeted liver biopsies.

KEY POINTS

• 405 nm-induced autofluorescence can distinguish liver tumors from the adjacent liver parenchyma. • The analysis of autofluorescence imaging observed within primary liver tumors can discriminate benign tumors from those requiring follow-up or targeted liver biopsy. • In current practice, autofluorescence imaging could be embedded within biopsy needle, to enable, in addition to ultrasound guidance, optimal targeting of liver nodules which could optimize tissue sampling.

Fluorescence imaging in the surgical management of liver cancers: Current status and future perspectives

Over the last decades, imaging technologies have got significant developments and become indispensable in the surgical management of liver cancers. Real-time navigation afforded by intraoperative images has a significant impact on the success of liver surgeries. Fluorescence imaging in the near-infrared spectrum has shown potential for tumor detection and image-guided surgery in clinics. While predominantly focused on indocyanine green (ICG) imaging, there is also accelerated development of more specific molecular tracers. Compared to passive targeting contrast agents ICG, active targeting and activatable probes both shed new light for intraoperative navigation owing to the higher degree of specificity for the tumor target. A variety of fluorescence imaging probes have been developed to target biomarkers unique to cancer cells or tumor microenvironment and demonstrated promising results. In this review, we provide a comprehensive update on preclinical development and clinical applications of fluorescence imaging in the surgical management of liver cancers. By highlighting the current status, we aim to offer insight into the challenges and opportunities for further investigation.

Autofluorescence-based optical biopsy: An effective diagnostic tool in hepatology

Autofluorescence emission of liver tissue depends on the presence of endogenous biomolecules able to fluoresce under suitable light excitation. Overall autofluorescence emission contains much information of diagnostic value because it is the sum of individual autofluorescence contributions from fluorophores involved in metabolism, for example, NAD(P)H, flavins, lipofuscins, retinoids, porphyrins, bilirubin and lipids, or in structural architecture, for example, fibrous proteins, in close relationship with normal, altered or diseased conditions of the liver. Since the 1950s, hepatocytes and liver have been historical models to study NAD(P)H and flavins as in situ, real-time autofluorescence biomarkers of energy metabolism and redox state. Later investigations designed to monitor organ responses to ischaemia/reperfusion were able to predict the risk of dysfunction in surgery and transplantation or support the development of procedures to ameliorate the liver outcome. Subsequently, fluorescent fatty acids, lipofuscin-like lipopigments and collagen were characterized as optical biomarkers of liver steatosis, oxidative stress damage, fibrosis and disease progression. Currently, serum AF is being investigated to improve non-invasive optical diagnosis of liver disease. Validation of endogenous fluorophores and in situ discrimination of cancerous from non-cancerous tissue belong to the few studies on liver in human subjects. These reports along with other optical techniques and the huge work performed on animal models suggest many optically based applications in hepatology. Optical diagnosis is currently offering beneficial outcomes in clinical fields ranging from the respiratory and gastrointestinal tracts, to dermatology and ophthalmology. Accordingly, this review aims to promote an effective bench to bedside transfer in hepatology.