The fuss over lipo"fuss"cin: not all autofluorescence is the same

The Use of 5-Aminolevulinic Acid in Low-Grade Glioma Resection: A Systematic Review

BACKGROUND

For optimizing high-grade glioma resection, 5-aminolevulinic acid is a reliable tool. However, its efficacy in low-grade glioma resection remains unclear.

OBJECTIVE

To study the role of 5-aminolevulinic acid in low-grade glioma resection and assess positive fluorescence rates and the effect on the extent of resection.

METHODS

A systematic review of PubMed, Google Scholar, and Cochrane was performed from the date of inception to February 1, 2019. Studies that correlated 5-aminolevulinic acid fluorescence with low-grade glioma in the setting of operative resection were selected. Studies with biopsy only were excluded. Positive fluorescence rates were calculated. The quality index of the selected papers was provided. No patient information was used, so Institutional Review Board approval and patient consent were not required.

RESULTS

A total of 12 articles met the selection criteria with 244 histologically confirmed low-grade glioma patients who underwent microsurgical resection. All patients received 20 mg/kg body weight of 5-aminolevulinic acid. Only 60 patients (n = 60/244; 24.5%) demonstrated visual intraoperative 5-aminolevulinic acid fluorescence. The extent of resection was reported in 4 studies; however, the data combined low- and high-grade tumors. Only 2 studies reported on tumor location. Only 3 studies reported on clinical outcomes. The Zeiss OPMI Pentero microscope was most commonly used across all studies. The average quality index was 14.58 (range: 10-17), which correlated with an overall good quality.

CONCLUSION

There is an overall low correlation between 5-aminolevulinic acid fluorescence and low-grade glioma. Advances in visualization technology and using standardized fluorescence quantification methods may further improve the visualization and reliability of 5-aminolevulinic acid fluorescence in low-grade glioma resection.

In Vivo Real-Time Discrimination Among Glioma, Infiltration Zone, and Normal Brain Tissue via Autofluorescence Technology

BACKGROUND

Surgery is the first-line therapy for glioblastoma. There is evidence that extent of resection is significantly associated with patient survival. Unfortunately, optimal surgical resection is usually limited because of the difficulty in discriminating tumor-infiltrated region and normal brain tissue. This study aimed to develop a tool to distinguish between infiltration zone and normal tissue in real time during glioma surgery.

METHODS

In an in vivo study, C6 glioma cells were implanted into the left cerebral hemispheres of 6 rats to mimic tumorigenesis. A newly designed optical fiber-embedded needle probe was used to measure the autofluorescence of both cerebral hemispheres at various depths 5 days after the implantation. These rats were then sacrificed, and both cerebral hemispheres were removed for histopathologic analysis.

RESULTS

Comparative analyses of corresponding areas by histopathology and autofluorescence revealed highly significant (P < 0.001) differences among the normal tissue, infiltration zone, tumors, and the contralateral cerebral hemispheres. The area of the receiver operating characteristic curve was 0.978, and the sensitivity and specificity of tumor delineation were 93.9% and 94.4%, respectively.

CONCLUSIONS

The newly designed in vivo fiber-optic probe can distinguish tumor-infiltration zones from normal brain tissue in this in vivo study. Therefore, it may help neurosurgeons to increase extent of resection without damaging normal brain tissue and thus potentially improve the patients' survival and quality of life.

Cigarette Smoke Induces Stem Cell Features of Pancreatic Cancer Cells via PAF1

BACKGROUND & AIMS

Cigarette smoking is a major risk factor for pancreatic cancer. Aggressive pancreatic tumors contain cancer cells with stem cell features. We investigated whether cigarette smoke induces stem cell features in pancreatic cancer cells.

METHODS

Kras^G12D; Pdx1-Cre mice were exposed to cigarette smoke or clean air (controls) for up to 20 weeks; pancreata were collected and analyzed by histology, quantitative reverse transcription polymerase chain reaction, and confocal immunofluorescence microscopy. HPNE and Capan1 cells were exposed to cigarette smoke extract (CSE), nicotine and nicotine-derived carcinogens (NNN or NNK), or clean air (controls) for 80 days and evaluated for stem cell markers and features using flow cytometry-based autofluorescence, sphere formation, and immunoblot assays. Proteins were knocked down in cells with small interfering RNAs. We performed RNA sequencing analyses of CSE-exposed cells. We used chromatin immunoprecipitation assays to confirm the binding of FOS-like 1, AP-1 transcription factor subunit (FOSL1) to RNA polymerase II-associated factor (PAF1) promoter. We obtained pancreatic ductal adenocarcinoma (PDAC) and matched nontumor tissues (n = 15) and performed immunohistochemical analyses.

RESULTS

Chronic exposure of HPNE and Capan1 cells to CSE caused them to increase markers of stem cells, including autofluorescence and sphere formation, compared with control cells. These cells increased expression of ABCG2, SOX9, and PAF1, via cholinergic receptor nicotinic alpha 7 subunit (CHRNA7) signaling to mitogen-activated protein kinase 1 and FOSL1. CSE-exposed pancreatic cells with knockdown of PAF1 did not show stem cell features. Exposure of cells to NNN and NNK led to increased expression of CHRNA7, FOSL1, and PAF1 along with stem cell features. Pancreata from Kras^G12D; Pdx1-Cre mice exposed to cigarette smoke had increased levels of PAF1 mRNA and protein, compared with control mice, as well as increased expression of SOX9. Levels of PAF1 and FOSL1 were increased in PDAC tissues, especially those from smokers, compared with nontumor pancreatic tissue. CSE exposure increased expression of PHD-finger protein 5A, a pluripotent transcription factor and its interaction with PAF1.

CONCLUSIONS

Exposure to cigarette smoke activates stem cell features of pancreatic cells, via CHRNA7 signaling and FOSL1 activation of PAF1 expression. Levels of PAF1 are increased in pancreatic tumors of humans and mice with chronic cigarette smoke exposure.

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.

Non-labeling multiphoton excitation microscopy as a novel diagnostic tool for discriminating normal tissue and colorectal cancer lesions

Multiphoton excitation microscopy (MPM) is regarded as an effective tool that enables the visualization of deep regions within living tissues and organs, with little damage. Here, we report novel non-labeling MPM (NL-MPM) imaging of fresh human colorectal mucosa, which is useful for discriminating cancer lesions from normal tissues quantitatively without any need for resection, fixation, or staining. Using NL-MPM, we visualized three components in human colorectal mucosa, epithelial cells, immune cells, and basement membranes, based on their characteristic patterns of fluorescence. These patterns are characterized by the different auto-fluorescence properties of nicotinamide adenine dinucleotide, nicotinamide adenine dinucleotide phosphate, and flavin adenine dinucleotide and from second harmonic generation (SHG). NL-MPM images were at least as informative to pathologists as were ‘conventional’ images of fixed tissue sections stained with hematoxylin and eosin. Additionally, two quantitative parameters extracted from NL-MPM images – the nucleus diameter (index N) and the intensity of SHG in the basement membrane (index S) – rendered it possible to diagnose cancer regions effectively. In conclusion, NL-MPM is a novel, promising method for real-time clinical diagnosis of colorectal cancers, and is associated with minimal invasiveness.

Is there still room for novelty, in histochemical papers?

Histochemistry continues to be widely applied in biomedical research, being nowadays mostly addressed to detect and locate single molecules or molecular complexes inside cells and tissues, and to relate structural organization and function at the high resolution of the more advanced microscopical techniques. In the attempt to see whether histochemical novelties may be found in the recent literature, the articles published in the European Journal of Histochemistry in the period 2014-2016 have been reviewed. In the majority of the published papers, standardized methods have been preferred by scientists to make their results reliably comparable with the data in the literature, but several papers (approximately one fourth of the published articles) described novel histochemical methods and procedures. It is worth noting that there is a growing interest for minimally-invasive in vivo techniques (magnetic resonance imaging, autofluorescence spectroscopy), which may parallel conventional histochemical analyses to acquire evidence not only on the morphological features of living organs and tissues, but also on their functional, biophysical and molecular characteristics. Thanks to this unceasing methodological refinement, histochemistry will continue to provide innovative applications in the biomedical field.

Histochemistry in biology and medicine: a message from the citing journals

Especially in recent years, biomedical research has taken advantage of the progress in several disciplines, among which microscopy and histochemistry. To assess the influence of histochemistry in the biomedical field, the articles published during the period 2011-2015 have been selected from different databases and grouped by subject categories: as expected, biological and biomedical studies where histochemistry has been used as a major experimental approach include a wide of basic and applied researches on both humans and other animal or plant organisms. To better understand the impact of histochemical publications onto the different biological and medical disciplines, it was useful to look at the journals where the articles published in a multidisciplinary journal of histochemistry have been cited: it was observed that, in the five-years period considered, 20% only of the citations were in histochemical periodicals, the remaining ones being in journals of Cell &amp; Tissue biology,  general and experimental Medicine, Oncology, Biochemistry &amp; Molecular biology, Neurobiology, Anatomy &amp; Morphology, Pharmacology &amp; Toxicology, Reproductive biology, Veterinary sciences, Physiology, Endocrinology, Tissue engineering &amp; Biomaterials,  as well as in multidisciplinary journals.It is easy to foresee that also in the future the histochemical journals will be an attended forum for basic and applied scientists in the biomedical field. It will be crucial that these journals be open to an audience as varied as possible, publishing articles on the application of refined techniques to very different experimental models: this will stimulate non-histochemist scientists to approach histochemistry whose application horizon could expand to novel and possibly exclusive subjects.

New light in flavin autofluorescence

Our attention was captured by the interesting debate on the identification of lipofuscins, lipofuscin-like lipopigments, or flavins as the responsible for intracellular autofluorescence (AF) detected in epithelial cancer stem cells when exciting at 480-490 nm. Evidence was provided leading to ascribe AF emission to flavins accumulating in cytoplasmic structures, bounded to membranes and bearing ATP-dependent ABCG2 transporters. Flavins were then proposed as an intrinsic AF biomarker of cancer stem cells, with advantageous implications on cell invasiveness and chemoresistance investigations. It is however worth recalling the huge amount of literature on flavins and NAD(P)H as AF biomarkers of cell energetic metabolism and redox state, an aspect that should not be overlooked in the renewed course to extend the potential of flavins as AF biomarkers, entailing also a recent proposal of Flavin-based fluorescent proteins as substitutes of Green fluorescent proteins.