Quantitative assessment of liver steatosis on tissue section using infrared spectroscopy

Evaluation of Minimum-to-Severe Global and Macrovesicular Steatosis in Human Liver Specimens: A Portable Ambient Light-Compatible Spectroscopic Probe

BACKGROUND AND AIMS

Hepatic steatosis (HS), particularly macrovesicular steatosis (MaS), influences transplant outcomes. Accurate assessment of MaS is crucial for graft selection. While traditional assessment methods have limitations, non-invasive spectroscopic techniques like Raman and reflectance spectroscopy offer promise. This study aimed to evaluate the efficacy of a portable ambient light-compatible spectroscopic system in assessing global HS and MaS in human liver specimens.

METHODS

A two-stage approach was employed on thawed snap-frozen human liver specimens under ambient room light: biochemical validation involving a comparison of fat content from Raman and reflectance intensities with triglyceride (TG) quantifications and histopathological validation, contrasting Raman-derived fat content with evaluations by an expert pathologist and a "Positive Pixel Count" algorithm. Raman and reflectance intensities were combined to discern significant (≥ 10%) discrepancies in global HS and MaS.

RESULTS

The initial set of 16 specimens showed a positive correlation between Raman and reflectance-derived fat content and TG quantifications. The Raman system effectively differentiated minimum-to-severe global and macrovesicular steatosis in the subsequent 66 specimens. A dual-variable prediction algorithm was developed, effectively classifying significant discrepancies (> 10%) between algorithm-estimated global HS and pathologist-estimated MaS.

CONCLUSION

Our study established the viability and reliability of a portable spectroscopic system for non-invasive HS and MaS assessment in human liver specimens. The compatibility with ambient light conditions and the ability to address limitations of previous methods marks a significant advancement in this field. By offering promising differentiation between global HS and MaS, our system introduces an innovative approach to real-time and quantitative donor HS assessments. The proposed method holds the promise of refining donor liver assessment during liver recovery and ultimately enhancing transplantation outcomes.

Potential of Raman-Reflectance Combination in Quantifying Liver Steatosis and Fat Droplet Size: Evidence From Monte Carlo Simulations and Phantom Studies

This study explores a combined strategy of Raman and reflectance spectroscopy for quantifying liver fat content and fat droplet size, crucial in assessing donor livers. By using Monte Carlo simulations and experimental setups with oil-in-water phantoms, our findings indicate that Raman scattering can solely differentiate between varying fat contents. At the same time, reflectance intensity is influenced by both fat content and oil droplet size, with a more pronounced sensitivity to fat droplet size. This study demonstrates the efficacy of combined Raman and reflectance spectroscopy in assessing liver steatosis and fat droplet size, potentially aiding in assessing donor livers for transplantation.

Clinical Application of Infrared Spectroscopy in Liver Transplantation for Rapid Assessment of Lipid Content in Liver Graft

Liver transplantation (LT) is a major treatment for patients with end-stage liver diseases. Steatosis is a significant risk factor for primary graft nonfunction and associated with poor long-term graft outcomes. Traditionally, the evaluation of steatosis is based on frozen section examination to estimate the percentage of hepatocytes containing lipid vesicles. However, this visual evaluation correlates poorly with the true lipid content. This study aimed to address the potential of infrared (IR) microspectroscopy for rapidly estimating lipid content in the context of LT and assessing its impact on survival. Clinical data were collected for >20 months from 58 patients who underwent transplantation. For each liver graft, macrovacuolar steatosis and microvesicular steatosis were evaluated through histologic examination of frozen tissue section. Triglycerides (TG) were further quantified using gas phase chromatography coupled with a flame ionization detector (GC-FID) and estimated by IR microspectroscopy. A linear relationship and significant correlation were observed between the TG measured by GC-FID and those estimated using IR microspectroscopy (R2 = 0.86). In some cases, microvesicular steatosis was related to high lipid content despite low levels of macrovacuolar steatosis. Seven patients experienced posttransplantation liver failure, including 5 deceased patients. All patients underwent transplantation with grafts containing significantly high TG levels. A concentration of 250 nmol/mg was identified as the threshold above which the risk of failure after LT significantly increased, affecting 35% of patients. Our study established a strong correlation between LT outcomes and lipid content. IR microspectroscopy proved to be a rapid and reliable approach for assessing the lipid content in clinical settings.

Comparing the direct assessment of steatosis in liver explants with mid- and near-infrared vibrational spectroscopy, prior to organ transplantation

A fast and accurate assessment of liver steatosis is crucial during liver transplantation surgery as it can negatively impact its success. Recent research has shown that near-infrared (NIR) and attenuated total reflectance-Fourier transform mid-infrared (ATR-FTIR) spectroscopy could be used as real-time quantitative tools to assess steatosis during abdominal surgery. Here, in the frame of a clinical study, we explore the performance of NIR and ATR-FTIR spectroscopy for the direct assessment of steatosis in liver tissues. Results show that both NIR and ATR-FTIR spectroscopy are able to quantify the % of steatosis with cross-validation errors of 1.4 and 1.6%, respectively. Furthermore, the two portable instruments used both provided results within seconds and can be placed inside an operating room evidencing the potential of IR spectroscopy for initial characterization of grafts in liver transplantation surgery. We also evaluated the complementarity of the spectral ranges through correlation spectroscopy.

Diffuse Reflectance Spectroscopy for The Assessment of Steatosis in Liver Phantom and Liver Donors - A Pilot Study

This paper reports the application of a low-cost diagnostic modality for fat analysis in a liver phantom as well as human liver donors. The device works on the principle of diffuse reflectance spectroscopy, which absorbs and/or scatters depending upon the molecules that compose a tissue. Here, we describe the development of liver phantom of varying fat concentration using saturated fat mimicking liver steatosis. Followed by a pilot study in the human liver donor setting. Later, handheld device based on Infrared-LED and Photodetector for real-time time assessment of live donor liver and fat assessment. Clinical Relevance- This device can be used in the development of an accurate and non-invasive for quantification of liver fat in the deceased donor selection process. It has an error margin of 10% in the quantification of fat which is comparable to a standard biopsy technique.

Non-invasive real-time assessment of hepatic macrovesicular steatosis in liver donors: Hypothesis, design and proof-of-concept study

Macrovesicular Steatosis (MS) is an independent risk factor for adverse post-liver transplant (LT) outcomes. The degree of MS is intimately related to the viability of the liver graft, which in turn is crucial to the success of the operation. An ideal liver graft should have no MS and most centres would find it unacceptable to use a donor liver with severe MS for LT. While a formal liver biopsy is the gold-standard diagnostic test for MS, given the logistical and time constraints it is not universally feasible. Other tests like a frozen section biopsy are plagued by issues of fallibility with reporting and sampling bias making them inferior to a liver biopsy. Hence, the development of an accurate, non-invasive, easy-to-use, handheld, real-time device for quantification of MS would fill this lacuna in the deceased donor selection process. We present the hypothesis, design and proof-of-concept of a study, which aims to standardise and determine the feasibility and accuracy of a novel handheld device applying the principle of diffuse reflectance spectroscopy for real-time quantification of MS.

Surface color spectrophotometry in a murine model of steatosis: an accurate technique with potential applicability in liver procurement

Steatosis is the most important prognostic histologic feature in the setting of liver procurement. The currently utilized diagnostic methods, including gross evaluation and frozen section examination, have important shortcomings. Novel techniques that offer advantages over the current tools could be of significant practical utility. The aim of this study is to evaluate the accuracy of surface color spectrophotometry in the quantitative assessment of steatosis in a murine model of fatty liver. C57BL/6 mice were divided into a control group receiving normal chow (n = 19), and two steatosis groups receiving high-fat diets for up to 20 weeks-mild steatosis (n = 10) and moderate-to-severe steatosis (n = 19). Mouse liver surfaces were scanned with a hand-held spectrophotometer (CM-600D; Konica-Minolta, Osaka, Japan). Spectral reflectance data and color space values (L*a*b*, XYZ, L*c*h*, RBG, and CMYK) were correlated with histopathologic steatosis evaluation by visual estimate, digital image analysis (DIA), as well as biochemical tissue triglyceride measurement. Spectral reflectance and most color space values were very strongly correlated with histologic assessment of total steatosis, with the best predictor being % reflectance at 700 nm (r = 0.91 [0.88-0.94] for visual assessment, r = 0.92 [0.88-0.95] for DIA of H&E slides, r = 0.92 [0.87-0.95] for DIA of oil-red-O stains, and r = 0.78 [0.63-0.87] for biochemical tissue triglyceride measurement, p < 0.0001 for all). Several spectrophotometric parameters were also independently predictive of large droplet steatosis. In conclusion, hepatic steatosis can accurately be assessed using a portable, commercially available hand-held spectrophotometer device. If similarly accurate in human livers, this technique could be utilized as a point-of-care tool for the quantitation of steatosis, which may be especially valuable in assessing livers during deceased donor organ procurement.

Changing Trends in Liver Transplantation: Challenges and Solutions

Despite improvements in postliver transplant outcomes through refinements in perioperative management and surgical techniques, several changing trends in liver transplantation have presented challenges. Mortality on the waitlist remains high. In the United States, Europe, and the United Kingdom, there is an increasing need for liver transplantation, primarily as a result of increased incidence of nonalcoholic steatohepatitis-related cirrhosis and cancer indications. Meanwhile, donor suitability has decreased, as donors are often older and have more comorbidities. Despite a mismatch between organ need and availability, many organs are discarded. Notwithstanding this, many solutions have been developed to overcome these challenges. Innovative techniques in allograft preservation, viability assessment, and reconditioning have allowed the use of suboptimal organs with adequate results. Refinements in surgical procedures, including live donor liver transplantations, have increased the organ pool and are decreasing the time and mortality on the waitlist. Despite many challenges, a similar number of solutions and prospects are on the horizon. This review seeks to explore the changing trends and challenges in liver transplantation and highlight possible solutions and future directions.

Toward Rapid Screening of Liver Grafts at the Operating Room Using Mid-infrared Spectroscopy

The estimation of steatosis in a liver graft is mandatory prior to liver transplantation, as the risk of graft failure increases with the level of infiltrated fat. However, the assessment of liver steatosis before transplantation is typically based on a qualitative or semiquantitative characterization by visual inspection and palpation and histological analysis. Thus, there is an unmet need for transplantation surgeons to have access to a diagnostic tool enabling an in situ fast classification of grafts prior to extraction. In this study, we have assessed an attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic method compatible with the requirements of an operation room for the evaluation of the lipid contents in human livers. A set of 20 human liver biopsies obtained from organs intended for transplantation were analyzed by expert pathologists, ATR-FTIR spectroscopy, lipid biochemical analysis, and UPLC-ESI(+/-)TOFMS for lipidomic profiling. Comparative analysis of multisource data showed strong correlations between ATR-FTIR, clinical, and lipidomic information. Results show that ATR-FTIR captures a global picture of the lipid composition of the liver, along with information for the quantification of the triradylglycerol content in liver biopsies. Although the methodology performance needs to be further validated, results support the applicability of ATR-FTIR for the in situ determination of the grade of liver steatosis at the operation room as a fast, quantitative method, as an alternative to the qualitative and subjective pathological examination.

Use of Artificial Intelligence as an Innovative Method for Liver Graft Macrosteatosis Assessment

The worldwide implementation of a liver graft pool using marginal livers (ie, grafts with a high risk of technical complications and impaired function or with a risk of transmitting infection or malignancy to the recipient) has led to a growing interest in developing methods for accurate evaluation of graft quality. Liver steatosis is associated with a higher risk of primary nonfunction, early graft dysfunction, and poor graft survival rate. The present study aimed to analyze the value of artificial intelligence (AI) in the assessment of liver steatosis during procurement compared with liver biopsy evaluation. A total of 117 consecutive liver grafts from brain-dead donors were included and classified into 2 cohorts: ≥30 versus <30% hepatic steatosis. AI analysis required the presence of an intraoperative smartphone liver picture as well as a graft biopsy and donor data. First, a new algorithm arising from current visual recognition methods was developed, trained, and validated to obtain automatic liver graft segmentation from smartphone images. Second, a fully automated texture analysis and classification of the liver graft was performed by machine-learning algorithms. Automatic liver graft segmentation from smartphone images achieved an accuracy (Acc) of 98%, whereas the analysis of the liver graft features (cropped picture and donor data) showed an Acc of 89% in graft classification (≥30 versus <30%). This study demonstrates that AI has the potential to assess steatosis in a handy and noninvasive way to reliably identify potential nontransplantable liver grafts and to avoid improper graft utilization.

Evaluation of a micro-spectrometer for the real-time assessment of liver graft with mild-to-moderate macrosteatosis: A proof of concept study

BACKGROUND & AIMS

Liver macrosteatosis (MS) is a major predictor of graft dysfunction after transplantation. However, frozen section techniques to quantify steatosis are often unavailable in the context of procurements, and the findings of preoperative imaging techniques correlate poorly with those of permanent sections, so that the surgeon is ultimately responsible for the decision. Our aim was to assess the accuracy of a non-invasive pocket-sized micro-spectrometer (PSM) for the real-time estimation of MS.

METHODS

We prospectively evaluated a commercial PSM by scanning the liver capsule. A double pathological quantification of MS was performed on permanent sections. Initial calibration (training cohort) was performed on 35 livers (MS ≤60%) and an algorithm was created to correlate the estimated (PSM) and known (pathological) MS values. A second assessment (validation cohort) was then performed on 154 grafts.

RESULTS

Our algorithm achieved a coefficient of determination R2 = 0.81. Its validation on the second cohort demonstrated a Lin's concordance coefficient of 0.78. Accuracy reached 0.91%, with reproducibility of 86.3%. The sensitivity, specificity, positive and negative predictive values for MS ≥30% were 66.7%, 100%, 100% and 98%, respectively. The PSM could predict the absence (<30%)/presence (≥30%) of MS with a kappa coefficient of 0.79. Neither graft weight nor height, donor body mass index nor the CT-scan liver-to-spleen attenuation ratio could accurately predict MS.

CONCLUSION

We demonstrated that a PSM can reliably and reproducibly assess mild-to-moderate MS. Its low cost and the immediacy of results may offer considerable added-value decision support for surgeons. This tool could avoid the detrimental and prolonged ischaemia caused by the pathological examination of (potentially) marginal grafts. This device now needs to be assessed in the context of a large-scale multicentre study.

LAY SUMMARY

Macro-vacuolar liver steatosis is a major prognostic factor for outcomes after liver transplantation. However, it is often difficult for logistical reasons to get this estimation during procurement. Therefore, we developed an algorithm for a commercial, portable and affordable spectrometer to accurately estimate this content in a real-time fashion. This device could be of great interest for clinical decision-making to accept or discard a potential human liver graft.

Assessment of Liver Graft Steatosis: Where Do We Stand?

The growing number of patients on waiting lists for liver transplantation and the shortage of organs have forced many centers to adopt extended criteria for graft selection, moving the limit of acceptance for marginal livers. Steatotic grafts that were, in the past, considered strictly unacceptable for transplantation because of the high risk of early nonfunction are now considered as a potential resource for organ implementation. Several methods to diagnose, measure, classify, and stage steatosis exist, but none can be considered qualitatively and quantitatively "the ideal method" to date. Clinical, biological, and imaging data can be very helpful to estimate graft steatosis, but histology still remains the gold standard. There is an increasing need for rapid and reliable tools to assess graft steatosis. Herein, we present a comprehensive review of the approaches that are currently used to quantify steatosis in liver grafts.

BPA Directly Decreases GnRH Neuronal Activity via Noncanonical Pathway

Peripheral feedback of gonadal estrogen to the hypothalamus is critical for reproduction. Bisphenol A (BPA), an environmental pollutant with estrogenic actions, can disrupt this feedback and lead to infertility in both humans and animals. GnRH neurons are essential for reproduction, serving as an important link between brain, pituitary, and gonads. Because GnRH neurons express several receptors that bind estrogen, they are potential targets for endocrine disruptors. However, to date, direct effects of BPA on GnRH neurons have not been shown. This study investigated the effects of BPA on GnRH neuronal activity using an explant model in which large numbers of primary GnRH neurons are maintained and express many of the receptors found in vivo. Because oscillations in intracellular calcium have been shown to correlate with electrical activity in GnRH neurons, calcium imaging was used to assay the effects of BPA. Exposure to 50μM BPA significantly decreased GnRH calcium activity. Blockage of γ-aminobutyric acid ergic and glutamatergic input did not abrogate the inhibitory BPA effect, suggesting direct regulation of GnRH neurons by BPA. In addition to estrogen receptor-β, single-cell RT-PCR analysis confirmed that GnRH neurons express G protein-coupled receptor 30 (G protein-coupled estrogen receptor 1) and estrogen-related receptor-γ, all potential targets for BPA. Perturbation studies of the signaling pathway revealed that the BPA-mediated inhibition of GnRH neuronal activity occurred independent of estrogen receptors, GPER, or estrogen-related receptor-γ, via a noncanonical pathway. These results provide the first evidence of a direct effect of BPA on GnRH neurons.

Discrimination of cirrhotic nodules, dysplastic lesions and hepatocellular carcinoma by their vibrational signature

Background

Hepatocarcinogenesis is a multistep process characterized in patients with chronic liver diseases by a spectrum of hepatic nodules that mark the progression from regenerative nodules to dysplastic lesions followed by hepatocellular carcinoma (HCC). The differential diagnosis between precancerous dysplastic nodules and early HCC still represents a challenge for both radiologists and pathologists. We addressed the potential of Fourier transform-infrared (FTIR) microspectroscopy for grading cirrhotic nodules on frozen tissue sections.

Methods

The study was focused on 39 surgical specimens including normal livers (n = 11), dysplastic nodules (n = 6), early HCC (n = 1), progressed HCC on alcoholic cirrhosis (n = 10) or hepatitis C virus cirrhosis (n = 11). The use of the bright infrared source emitted by the synchrotron radiation allowed investigating the biochemical composition at the cellular level. Chemical mapping on whole tissue sections was further performed using a FTIR microscope equipped with a laboratory-based infrared source. The variance was addressed by principal component analysis.

Results

Profound alterations of the biochemical composition of the pathological liver were demonstrated by FTIR microspectroscopy. Indeed, dramatic changes were observed in lipids, proteins and sugars highlighting the metabolic reprogramming in carcinogenesis. Quantifiable spectral markers were characterized by calculating ratios of areas under specific bands along the infrared spectrum. These markers allowed the discrimination of cirrhotic nodules, dysplastic lesions and HCC. Finally, the spectral markers can be measured using a laboratory FTIR microscope that may be easily implemented at the hospital.

Conclusion

Metabolic reprogramming in liver carcinogenesis can constitute a signature easily detectable using FTIR microspectroscopy for the diagnosis of precancerous and cancerous lesions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0763-6) contains supplementary material, which is available to authorized users.

Mid-infrared fibre evanescent wave spectroscopy of serum allows fingerprinting of the hepatic metabolic status in mice

Infrared spectroscopy from mice unveils a transition in the time course of steatosis.