Alcohol based tissue fixation as an alternative for formaldehyde: influence on immunohistochemistry

The impact of different fixatives on immunostaining of lung adenocarcinomas in pleural effusion cell blocks

BACKGROUND

Cell blocks (CBs) are widely used for biomarker analyses such as immunostaining. Although immunohistochemistry on formalin-fixed paraffin-embedded tissues is standardized, there are multiple preparation methods and fixatives for cytology. Our objective was to investigate the effect of different common fixatives on the immunoreactivity of pleural effusion CBs with metastatic lung adenocarcinomas.

METHODS

This prospective study included 24 malignant pleural effusions from different patients with lung adenocarcinoma. From each case, four identical CBs were fixed in 10% neutral buffered formalin, PreservCyt, CytoLyt, and CytoRich Red (only 17 of the cases), respectively. Samples containing <100 malignant cells were excluded. All CBs were stained with thyroid transcription factor 1 (TTF-1; clones 8G7G3/1 and SPT24), napsin A, claudin 4, CEA, CK7, and epithelial cell adhesion molecule (EpCAM; clones BS14, Ber-Ep4, and MOC-31). The fraction and intensity of stained cells were evaluated.

RESULTS

Of the investigated markers, a significant difference in staining proportion was seen for TTF-1 clone 8G7G3/1 and EpCAM clone MOC-31, especially with cases being negative in CytoLyt (33.3% and 83.3% positive, respectively) and PreservCyt (62.5% and 83.3%) whereas being positive in CytoRich Red (76.5% and 94.1%) and formalin (both 95.8%). A significantly weaker intensity of staining was seen for all alcohol-based fixatives compared to formalin for TTF-1 clone 8G7G3/1, napsin A, and EpCAM clone MOC-31, whereas EpCAM clone Ber-Ep4 was significantly weaker only in PreservCyt compared with formalin.

CONCLUSIONS

Immunocytochemical expression and concordance with formalin-fixed CBs differ depending on the used fixative as well as the antibody and clone, warranting investigation of the reliability of each biomarker for non-formalin-fixed cytology.

Comparison of histological procedures and antigenicity of human post-mortem brains fixed with solutions used in gross anatomy laboratories

Background

Brain banks provide small tissue samples to researchers, while gross anatomy laboratories could provide larger samples, including complete brains to neuroscientists. However, they are preserved with solutions appropriate for gross-dissection, different from the classic neutral-buffered formalin (NBF) used in brain banks. Our previous work in mice showed that two gross-anatomy laboratory solutions, a saturated-salt-solution (SSS) and an alcohol-formaldehyde-solution (AFS), preserve antigenicity of the main cellular markers (neurons, astrocytes, microglia, and myelin). Our goal is now to compare the quality of histology and antigenicity preservation of human brains fixed with NBF by immersion (practice of brain banks) vs. those fixed with a SSS and an AFS by whole body perfusion, practice of gross-anatomy laboratories.

Methods

We used a convenience sample of 42 brains (31 males, 11 females; 25-90 years old) fixed with NBF (N = 12), SSS (N = 13), and AFS (N = 17). One cm3 tissue blocks were cut, cryoprotected, frozen and sliced into 40 μm sections. The four cell populations were labeled using immunohistochemistry (Neurons = neuronal-nuclei = NeuN, astrocytes = glial-fibrillary-acidic-protein = GFAP, microglia = ionized-calcium-binding-adaptor-molecule1 = Iba1 and oligodendrocytes = myelin-proteolipid-protein = PLP). We qualitatively assessed antigenicity and cell distribution, and compared the ease of manipulation of the sections, the microscopic tissue quality, and the quality of common histochemical stains (e.g., Cresyl violet, Luxol fast blue, etc.) across solutions.

Results

Sections of SSS-fixed brains were more difficult to manipulate and showed poorer tissue quality than those from brains fixed with the other solutions. The four antigens were preserved, and cell labeling was more often homogeneous in AFS-fixed specimens. NeuN and GFAP were not always present in NBF and SSS samples. Some antigens were heterogeneously distributed in some specimens, independently of the fixative, but an antigen retrieval protocol successfully recovered them. Finally, the histochemical stains were of sufficient quality regardless of the fixative, although neurons were more often paler in SSS-fixed specimens.

Conclusion

Antigenicity was preserved in human brains fixed with solutions used in human gross-anatomy (albeit the poorer quality of SSS-fixed specimens). For some specific variables, histology quality was superior in AFS-fixed brains. Furthermore, we show the feasibility of frequently used histochemical stains. These results are promising for neuroscientists interested in using brain specimens from anatomy laboratories.

Immunocytochemical markers, molecular testing and digital cytopathology for aspiration cytology of metastatic breast carcinoma

Fine-needle aspiration cytology (FNAC) is a versatile diagnostic procedure uniquely suited for tissue biopsy of breast carcinomas and axillary metastases and/or recurrences. With the expanding treatment options and accompanying theragnostic tests, it is crucial to recognize the developments on ancillary testing and digital cytopathology techniques related to aspiration cytology of metastatic breast carcinoma. In this review, we aim to summarize and update the evidence of immunocytochemistry, for the detection of carcinoma cells (epithelial markers), confirmation of breast primary (breast-specific markers), assessment of surrogate immunostains (hormone receptors, ki-67 proliferative index and HER2) and theragnostic biomarkers, with discussion on potential diagnostic pitfalls, followed by the application of molecular tests, and digital cytopathologic techniques for assessing metastatic breast carcinoma in cytology.

Antigenicity is preserved with fixative solutions used in human gross anatomy: A mice brain immunohistochemistry study

Background

Histology remains the gold-standard to assess human brain biology, so ex vivo studies using tissue from brain banks are standard practice in neuroscientific research. However, a larger number of specimens could be obtained from gross anatomy laboratories. These specimens are fixed with solutions appropriate for dissections, but whether they also preserve brain tissue antigenicity is unclear. Therefore, we perfused mice brains with solutions used for human body preservation to assess and compare the tissue quality and antigenicity of the main cell populations.

Materials and methods

Twenty-eight C57BL/6J mice were perfused with 4% formaldehyde (FAS, N = 9), salt-saturated solution (SSS, N = 9), and alcohol solution (AS, N = 10). The brains were cut into 40 μm sections for antigenicity analysis and were assessed by immunohistochemistry of four antigens: neuronal nuclei (NeuN), glial fibrillary acidic protein (GFAP astrocytes), ionized calcium-binding adaptor molecule 1 (Iba1-microglia), and myelin proteolipid protein (PLP). We compared the fixatives according to multiple variables: perfusion quality, ease of manipulation, tissue quality, immunohistochemistry quality, and antigenicity preservation.

Results

The perfusion quality was better using FAS and worse using AS. The manipulation was very poor in SSS brains. FAS- and AS-fixed brains showed higher tissue and immunohistochemistry quality than the SSS brains. All antigens were readily observed in every specimen, regardless of the fixative solution.

Conclusion

Solutions designed to preserve specimens for human gross anatomy dissections also preserve tissue antigenicity in different brain cells. This offers opportunities for the use of human brains fixed in gross anatomy laboratories to assess normal or pathological conditions.

Prenatal Hypoxia Affects Nicotine Consumption and Withdrawal in Adult Rats via Impairment of the Glutamate System in the Brain

The role of damaging factors in the prenatal period as a basis for drug addiction in offspring is of great interest. In this study, we aim at deciphering the effects and possible mechanisms of prenatal severe hypoxia (PSH) on predisposition to nicotine addiction in adult rats. In PSH rats, we found an increasing tendency to nicotine consumption in the two-bottle choice test. After 2 weeks of chronic treatment with nicotine via osmotic minipump (9 mg/kg per day), we assessed the symptoms of withdrawal in the conditioned place aversion test after mecamylamine (an antagonist of nicotinic acetylcholine receptors, nAChR) treatment. We showed that the mecamylamine-precipitated withdrawal aversion was stronger in the PSH group than in the control group. This suggests that PSH acts as a predisposing factor for developing nicotine addiction in adulthood. PSH rats also demonstrated an increased level of phosphorylated DARPP-32 protein (known as the relay for dopamine and glutamate signaling) at 34 threonine (pThr34DARPP-32) in relation to its total amount in the nucleus accumbens of the striatum (NAc). Meanwhile, no changes in both the content of dopamine in the mesolimbic pathway and the first type of dopamine receptors (DAR1) in NAc were found. The increased rate of DARPP-32 phosphorylation in adult PSH rats might result from excessive glutamatergic stimulation of the dopaminergic (DA) neurons of the ventral tegmental area (VTA) caused by activation of presynaptic nAChR by nicotine. This hypothesis is supported by the observed increase in VGluT2-positive terminals to Nurr1-positive neuronal bodies in VTA in PSH animals. Thus, the altered glutamate signaling phenotype might play a significant role in the development of PSH-related nicotine addiction.

Oligoribonucleotide interference-PCR: principles and applications

Polymerase chain reaction (PCR) amplification of multiple templates using common primers is used widely for molecular biological research and clinical diagnosis. However, amplifying a specific DNA sequence harboring a mutation that is present in a small number of mutant cells within a large population of normal cells (e.g., as in cancer) in a tissue is difficult using the original PCR protocol. Thus, some measures are necessary to suppress amplification of background signals. To achieve this, we developed the oligoribonucleotide (ORN) interference-PCR (ORNi-PCR) technology in which an ORN (short RNA) hybridizes with a complementary DNA sequence to inhibit PCR amplification across the specific target sequence. ORNs can be prepared inexpensively, and ORNi-PCR can be carried out easily by adding ORNs to the PCR reaction mixture. Suppressing amplification of target sequences by ORNi-PCR is useful for detecting target sequence mutations. We showed that ORNi-PCR can discriminate single-nucleotide mutations in cancer cells and indel mutations introduced by genome editing. We also showed that ORNi-PCR can identify the CpG methylation status of a target sequence within bisulfite-treated DNA, and can enrich DNA sequences of interest from a DNA mixture by suppressing amplification of unwanted sequences. Thus, ORNi-PCR has many potential applications in various fields, including medical diagnosis and molecular biology. In this review, we outline the principles of the ORNi-PCR method and its use to detect nucleotide mutations in a variety of specimens.

Prenatal Hypoxia Induces Premature Aging Accompanied by Impaired Function of the Glutamatergic System in Rat Hippocampus

Prenatal hypoxia is among leading causes of progressive brain pathologies in postnatal life. This study aimed to analyze the characteristics of the hippocampal glutamatergic system and behavior of rats in early (2 weeks), adult (3 months) and advanced (18 months) postnatal ontogenesis after exposure to prenatal severe hypoxia (PSH, 180 Torr, 5% O2, 3 h) during the critical period in the formation of the hippocampus (days 14-16 of gestation). We have shown an age-dependent progressive decrease in the hippocampal glutamate levels, a decrease of the neuronal cell number in the CA1 hippocampal region, as well as impairment of spatial long-term memory in the Morris water navigation task. The gradual decrease of glutamate was accompanied by decreased expression of the genes that mediate glutamate metabolism and recycling in the hippocampus. That deficiency apparently correlated with an increase of the metabotropic glutamate receptor type 1 (mGluR1) and synaptophysin expression. Generation of the lipid peroxidation products in the hippocampus of adult rats subjected to prenatal severe hypoxia (PSH rats) was not increased compared to the control animals when tested in a model of glutamate excitotoxicity induced by severe hypoxia. This demonstrates that excessive glutamate sensitivity in PSH rats does not compensate for glutamate deficiency. Our results show a significant contribution of the glutamate system dysfunction to age-associated decrease of this mediator, cognitive decline, and early neuronal loss in PSH rats.

Histomorphological Assessment of Formalin versus Nonformalin Fixatives in Diagnostic Surgical Pathology

Introduction  Fixation is the critical step in the preservation of tissues in diagnostic pathology. The formalin is an economical and excellent fixative with the inherent property of adequate fixation. The well-established side effects of formalin include mucosal irritation, upper respiratory diseases, and corrosive injury to the gastrointestinal tract. In addition, substantial evidence exists regarding the potential role of formaldehyde as a human carcinogen. The carcinogenic and toxic effects of formalin encourage searching for alternative fixatives for tissue fixation. However, “the formalin dogma” has severely hampered the search for alternative fixatives for many years.

Material and Methods  Ninety tissues of liver and skeletal muscle obtained during autopsies were immersed in adequate amounts of the following fixatives: formalin (10%), methyl alcohol (70%), and acetone (100%). The comparison among the three was made based on time for fixation, preservation of tissue architecture, cell borders, cytoplasm, nuclear contours, chromatin texture, and uniformity of staining.

Results  The tissue preserved in formalin undergoes rapid fixation compared with alcohol and acetone. The tissue architecture, cell border characteristics of alcohol and acetone was found satisfactory compared with formalin. The cytoplasm and nuclear contour were superior with the formalin. The chromatin texture and uniformity of staining were similar with all the three fixatives.

Conclusion  The formalin is considered superior to most of the parameters, whereas both methyl alcohol and acetone showed nearly equivalent scores. Hence, owing to the potential human health hazards and carcinogenicity of formalin, no rational reasons hamper the complete substitution of formalin with alternative fixatives such as alcohol and acetone in diagnostic pathology and medical research.

Beneficial Effect of Heat-induced Antigen Retrieval in Immunocytochemical Detection of Intracellular Antigens in Alcohol-fixed Cell Samples

Immunohistochemistry and immunocytochemistry (ICC) play an irreplaceable role in research and diagnostics. It is well known that antigen retrieval (AR) can, as a technique, have beneficial outcomes on immunohistochemistry results when using formalin-fixed, paraffin-embedded tissue samples. The main purpose of AR is to break protein crosslinks which are formed during formalin fixation. Although AR was originally designed for formalin-fixed, paraffin-embedded samples, the usefulness of AR in ICC has been described in previous studies. Cytologic samples are often fixed in alcohol-based fixatives which does not lead to the formation of crosslinks. Therefore, alcohol-fixed samples can be successfully immunostained without AR. We investigated the effect of heat-induced antigen retrieval (HIAR) on alcohol-fixed HEK293 cell line samples and patient cytologic samples from thyroid gland obtained by fine needle aspiration technique. We compared indirect 2-step ICC staining results performed according to the protocol with or without HIAR in citrate buffer pH 6 for several antibodies. Utilizing HIAR against intracellular antigens has beneficial effects. Therefore, more diluted antibodies can be used for satisfactory results. However, surface antigens were probably damaged by HIAR treatment. We demonstrated evident changes in cell surface topography after HIAR treatment by atomic force microscopy. Staining specificity of patient samples improves and background staining is reduced, allowing higher dilutions of primary antibody. Improving staining specificity is necessary for accurate diagnostics. Although we have shown the beneficial effect of HIAR for immunostaining intracellular antigens, proper staining protocol should be tested on appropriate controls for individual antibodies.

Effects of various fixatives and temperature on the quality of glycogen demonstration in the brain and liver tissues

The visualization of glycogen deposits in cells and tissues is important for studying glycogen metabolism as well as diagnosis of glycogen storage diseases. Evidence suggests that the demonstration of glycogen can better be enhanced by factors such the choice of fixative and temperature during fixation. Here, we assessed efficacy of neutral buffered formalin (NBF), alcoholic formalin (AF) and paraformaldehyde (PFA) at 4 °C, 37 °C and 40 °C using Periodic Acid Schiff's staining method. Each liver specimen was fixed in NBF and AF while the brain tissues were fixed in NBF, AF and PFA. We found that there was a better PAS staining intensity with the liver tissues fixed in AF compared with NBF. Also, there was no difference in the quality of the staining for tissues fixed in AF at 37 °C, 4 °C and 40 °C, but fixation with NBF at 4 °C gave the best staining quality when compared with 40 °C and 37 °C. Furthermore, hippocampal tissues fixed in AF showed better quality of PAS staining compared with NBF and PFA. A significant increase in staining intensity was observed for PFA when compared with NBF. Superior staining intensity for PAS was observed at 4 °C for hippocampal tissues fixed with NBF, AF and PFA. Taken together our results show that AF at a temperature of 4 °C gave the best result. Hence, glycogen demonstration can better be enhanced by the choice of fixative and temperature during fixation.

Discrimination of CpG Methylation Status and Nucleotide Differences in Tissue Specimen DNA by Oligoribonucleotide Interference-PCR

Oligoribonucleotide (ORN) interference-PCR (ORNi-PCR) is a method in which PCR amplification of a target sequence is inhibited in a sequence-specific manner by the hybridization of an ORN with the target sequence. Previously, we reported that ORNi-PCR could detect nucleotide mutations in DNA purified from cultured cancer cell lines or genome-edited cells. In this study, we investigated whether ORNi-PCR can discriminate nucleotide differences and CpG methylation status in damaged DNA, such as tissue specimen DNA and bisulfite-treated DNA. First, we showed that ORNi-PCR could discriminate nucleotide differences in DNA extracted from acetone-fixed paraffin-embedded rat liver specimens or formalin-fixed paraffin-embedded human specimens. Rat whole blood specimens were compatible with ORNi-PCR for the same purpose. Next, we showed that ORNi-PCR could discriminate CpG methylation status in bisulfite-treated DNA. These results demonstrate that ORNi-PCR can discriminate nucleotide differences and CpG methylation status in multiple types of DNA samples. Thus, ORNi-PCR is potentially useful in a wide range of fields, including molecular biology and medical diagnosis.

Pharmacological HIF1 Inhibition Eliminates Downregulation of the Pentose Phosphate Pathway and Prevents Neuronal Apoptosis in Rat Hippocampus Caused by Severe Hypoxia

The pentose phosphate pathway (PPP) of glucose metabolism in the brain serves as a primary source of NADPH which in turn plays a crucial role in multiple cellular processes, including maintenance of redox homeostasis and antioxidant defense. In our model of protective mild hypobaric hypoxia in rats (3MHH), an inverse correlation between hypoxia-inducible factor-1 (HIF1) activity and mRNA levels of glucose-6-phosphate dehydrogenase (G6PD), the key enzyme of PPP, was observed. In the present study, it was demonstrated that severe hypobaric hypoxia (SH) induced short-term upregulation of HIF1 alpha-subunit (HIF1α) in the hippocampal CA1 subfield and decreased the activity of G6PD. The levels of NADPH were also reduced, promoting oxidative stress, triggering apoptosis, and neuronal loss. Injection of a HIF1 inhibitor (HIF1i), topotecan hydrochloride (5 mg/kg, i.p.), before SH prevented the upregulation of HIF1α and normalized G6PD activity. In addition, HIF1i injection caused an increase in NADPH levels, normalization of total glutathione levels and of the cellular redox status as well as suppression of free-radical and apoptotic processes. These results demonstrate a new molecular mechanism of post-hypoxic cerebral pathology development which involves HIF1-dependent PPP depletion and support a recently suggested injurious role of HIF1 activation in the acute phase of cerebral hypoxia/ischemia. Application of PPP stimulators in early post-hypoxic/ischemic period might represent a promising neuroprotective strategy. Graphical abstract HIF1-dependent down-regulation of the pentose phosphate pathway contributes to the hypoxia-induced oxidative stress and neuronal apoptosis in the rat hippocampus.

Improved transdermal delivery of cetirizine hydrochloride using polymeric microneedles

PURPOSE

The aim of this study was to design and characterize microneedle patch formulation containing cetirizine hydrochloride.

METHODS

Chitosan was co-formulated with cetirizine hydrochloride. Transdermal patches were prepared by casting this solution to microneedle molds. Control patches were formulated by casting this solution to a plain cuvet of same area as mold but lacking microneedles. An array of methods namely; differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were employed for the characterization of the films and the microneedles accordingly whereas in vitro permeation studies were conducted across rat skin. Light microscopy was performed to assess any histological changes upon microneedles application onto the rat skin.

RESULTS

The patches had a reproducible thickness (0.86 ± 0.06 mm) and folding endurance. Both the blank and drug loaded patches had 100 microneedles each of 300 micrometre length. In addition, the microneedle patches were ascribed with a two-fold increase in drug permeation across rat skin in the presence of microneedles as compared to the control formulations. Histological examination confirms a minimal invasion of the skin conferred by the microneedles.

CONCLUSION

The microneedle patches serve as an alternate route of drug administration in patients with nausea and swelling difficulties. Graphical abstract Microneedle patch manifest a two-fold increase in the skin permeation of Cetirizine Hydrochloride as compared to the control that is drug loaded patch without microneedles.

Comparison of Fixation Methods for Preservation Cytology Specimens of Cell Block Preparation Using 10% Neutral Buffer Formalin and 96% Alcohol Fixation in E-cadherin and Ki-67 Immunohistochemical Examination

BACKGROUND:

Cytological and molecular examinations are among the most important examinations in cancer diagnosis. 96% alcohol is a fixative solution commonly used by clinicians for cytological samples because of its accessibility and affordability. Cellblock preparation from cytology specimen may increase morphology detail and may be used for further biomarker analysis. E-cadherin is an adhesion protein expressed in the cell membrane of most carcinoma. Ki67 is a protein expressed in nuclei of malignant cells that used as a proliferation marker.

AIM:

This study was designed to investigate the effect of fixation duration in 96% alcohol on protein preservation for immunohistochemistry (IHC) evaluation compared to 10% neutral buffered formalin (NBF) as the gold standard.

METHODS:

Twenty-five fine-needle aspiration biopsy (FNAB) specimen diagnosed as carcinoma were fixed in 10% NBF and 96% alcohol for 1 hour, 6 hours, 24 hours, 48 hours and 72 hours. Cell blocks preparation were made from those 6 groups of specimens. E-cadherin and Ki67 IHC were done to cell blocks section and evaluated. The data were statistically analysed using the Friedman test with p-value < 0.05 of a significant level.

RESULTS:

There were significant differences between E-cadherin and Ki67 expression in cell block preparation from 96% alcohol-fixed cytology specimen for 1 hour, 6 hours, 24 hours, 48 hours and 72 hours to 10% NBF (p = 0.0001).

CONCLUSION:

The result indicated that 96% alcohol is not suitable as a fixative solution for cell block preparation in E-cadherin and Ki-67 IHC examination.

Effects of short and long-term alcohol-based fixation on Sprague-Dawley rat tissue morphology, protein and nucleic acid preservation

Safety concerns on the toxic and carcinogenic effects of formalin exposure have drawn increasing attention to the search for alternative low risk fixatives for processing tissue specimens in laboratories worldwide. Alcohol-based fixatives are considered some of the most promising alternatives. We evaluated the performance of alcohol-fixed paraffin-embedded (AFPE) samples from Sprague-Dawley (SD) rats analyzing tissue morphology, protein and nucleic acid preservation after short and extremely long fixation times (up to 7 years), using formalin-fixed paraffin-embedded (FFPE) samples as a comparator fixative. Following short and long-term alcohol fixation, tissue morphology and cellular details in tissues, evaluated by scoring stained sections (Hematoxylin-Eosin and Mallory's trichrome), were optimally preserved if compared to formalin fixation. Immunoreactivity of proteins (Ki67, CD3, PAX5, CD68), evaluated by immunohistochemistry, showed satisfactory results when the fixation period did not exceed 1 year. Finally, we confirm the superiority of alcohol fixation compared to formalin, in terms of quantity of nucleic acid extracted from paraffin blocks, even after an extremely long time of alcohol fixation. Our results confirm that alcohol fixation is a suitable and safe alternative to formalin for pathological evaluations. There is a need for standardization of formalin-free methods and harmonization of diagnosis in pathology department worldwide.

Neuroprotective Mechanism of Hypoxic Post-conditioning Involves HIF1-Associated Regulation of the Pentose Phosphate Pathway in Rat Brain

Post-conditioning is exposure of an injured organism to the same harmful factors but of milder intensity which mobilizes endogenous protective mechanisms. Recently, we have developed a novel noninvasive post-conditioning (PostC) protocol involving three sequential episodes of mild hypobaric hypoxia which exerts pronounced neuroprotective action. In particular, it prevents development of pathological cascades caused by severe hypobaric hypoxia (SH) such as cellular loss, lipid peroxidation, abnormal neuroendocrine responses and behavioural deficit in experimental animals. Development of these post-hypoxic pathological effects has been associated with the delayed reduction of hypoxia-inducible factor 1 (HIF1) regulatory α-subunit levels in rat hippocampus, whereas PostC up-regulated it. The present study has been aimed at experimental examination of the hypothesis that intrinsic mechanisms underlying the neuroprotective and antioxidant effects of PostC involves HIF1-dependent stimulation of the pentose phosphate pathway (PPP). We have observed that SH leads to a decrease of glucose-6-phosphate dehydrogenase (G6PD) activity in the hippocampus and neocortex of rats as well as to a reduction in NADPH and total glutathione levels. This depletion of the antioxidant defense system together with excessive lipid peroxidation during the reoxygenation phase resulted in increased oxidative stress and massive cellular death observed after SH. In contrast, PostC led to normalization of G6PD activity, stabilization of the NADPH and total glutathione levels and thereby resulted in recovery of the cellular redox state and prevention of neuronal death. Our data suggest that stabilization of the antioxidant system via HIF1-associated PPP regulation represents an important neuroprotective mechanism enabled by PostC.

Optimization and validation of PD-L1 immunohistochemistry staining protocols using the antibody clone 28-8 on different staining platforms

Several immunohistochemistry (IHC) assays have been developed to assess tumor programmed death-ligand 1 (PD-L1) expression levels in patients who are candidates for programmed death-1 (PD-1)/PD-L1 inhibitor therapy. The PD-L1 IHC 28-8 pharmDx kit is FDA-approved as a complementary diagnostic and CE-marked as an in vitro diagnostic device for nivolumab therapy in melanoma and specific lung cancer subtypes (and for squamous cell carcinoma of the head and neck/urothelial carcinoma in Europe only). Kit availability is limited outside the United States, and its use requires the Dako Autostainer Link 48 platform, which is unavailable in many laboratories. Validated laboratory-developed tests based on 28-8 concentrated antibody outside the kit are needed. This study compared the results from PD-L1 expression level analysis across four immunohistochemistry platforms (Dako Autostainer Link 48, Dako Omnis, Leica Bond-III, and Ventana BenchMark ULTRA) with the 28-8 pharmDx kit in lung cancer (multiple histologies), melanoma, and head and neck cancer (multiple histologies). Samples were prepared per protocol for each platform and stained using PD-L1 IHC 28-8 pharmDx kit on Dako Autostainer Link 48, and per protocol for each platform. The control samples (tonsil and placenta tissue; cell lines with prespecified PD-L1 expression levels) were tested to evaluate the specificity and the sensitivity of test assays. An agreement level of 0.90 with the pharmDx kit was set for each platform. Inter- and intra-assay reliability were assessed. Evaluable samples were lung cancer = 29; melanoma = 31; head and neck cancer = 30. Mean agreement was calculated for PD-L1 expression levels of ≥1%, ≥5%, ≥10%, and ≥50%. Mean overall agreement for all indications was 0.87-0.99. Inter- and intra-assay of scoring/classification repeatability was 100%. Analysis of PD-L1 expression levels using laboratory-developed immunohistochemistry assays with 28-8 antibody may be permissible if the platform is validated using reference samples with defined expression levels.

Evaluation of cardiovascular responses to silver nanoparticles (AgNPs) in spontaneously hypertensive rats

Silver nanoparticles (AgNPs) are used in the medical, pharmaceutical and food industry. Adverse effects and toxicity induced by AgNPs upon cardiac function related to nitric oxide (NO) and oxidative stress (OS) are described. AgNPs-toxicity may be influenced by cardiovascular pathologies such as hypertension. However, the molecules involved under pathophysiological conditions are not well studied. The aim of this work was to evaluate perfusion pressure (PP) and left ventricle pressure (LVP) as physiological parameters of cardiovascular function in response to AgNPs, using isolated perfused hearts from spontaneously hypertensive rats (SHR), and identify the role of NO and OS. The results suggest that AgNPs reduced NO derived from endothelial/inducible NO-synthase and increased OS, leading to increased and sustained vasoconstriction and myocardial contractility. Additionally, the hypertension condition alters phenylephrine (Phe) and acetylcholine (ACh) classic effects. These data suggest that hypertension intensified AgNPs-cardiotoxicity. Nevertheless, the precise mechanism of action is still under elucidation.

KINFix--A formalin-free non-commercial fixative optimized for histological, immunohistochemical and molecular analyses of neurosurgical tissue specimens

An optimal fixative should ideally combine the advantages of formalin fixation and freezing, allowing for good preservation of histology and molecular components, easy handling and storage, lack of toxicity, and low costs. Most of these criteria are fulfilled by ethanol-based solutions, and due to our good experience with the commercial RCL2 fixative, reflected by our published single-center trial, we initiated a multicenter ring trial. However, during its course, RCL2 was discontinued on the market. Therefore, we created our own agent, KINFix, composed of the same main constituents as RCL2, and employed it in our laboratory with similar results. Here we present our evaluation of the three fixatives formalin, RCL2, and KINFix from the perspective of histopathology as well as nucleic acid and protein analyses in comparison to fresh frozen tissues together with the multicenter ring trial data for RCL2. We observe that RCL2 and KINFix offer comparable histomorphology and superior template for molecular analyses than formalin. Moreover, KINFix as freely available fixative might overcome some of the difficulties related to the commercial agents. Therefore, we conclude that KINFix might be an attractive complement to formalin in tissue processing and advocate its use in neuropathological practice.

Evaluation of whole cell fixation methods for the analysis of nanoscale surface features of Yersinia pestis KIM

Manipulation of viable Yersinia pestis (etiologic agent of plague) in the laboratory usually necessitates elevated biosafety and biocontainment procedures, even with avirulent or vaccine strains. To facilitate downstream biochemical or physical analyses in a Biosafety Level 1 laboratory environment, effective inactivation without affecting its intrinsic properties is critical. Here, we report on the morphological and biochemical changes to Y. pestis surfaces following four different fixation methods that render the cells nonviable. The results, obtained at the single cell level, demonstrate that methanol inactivation is best able to preserve bacterial morphology and bioactivity, enabling subsequent analysis. This nanoscale evaluation of the effects of inactivation on cell morphology and surface bioactivity may provide a crucial preparatory approach to study virulent pathogens in the lab setting using high-resolution microscopic techniques such as atomic force microscopy.

Isolation, Cryosection and Immunostaining of Skeletal Muscle

Adult skeletal muscle is maintained and repaired by resident stem cells called satellite cells, located between the plasmalemma of a muscle fiber, and the surrounding basal lamina. When needed, satellite cells are activated to form proliferative myoblasts, that then differentiate and fuse to existing muscle fibers, or fuse together to form replacement myofibers. In parallel, a proportion of satellite cells self-renew, to maintain the stem cell pool. To date, Pax7 is the marker of choice for identifying quiescent satellite cells. Co-immunostaining of skeletal muscle with Pax7 and laminin allows both identification of satellite cells, and the myofiber that they are associated with. Furthermore, satellite cells can be followed through the early stages of the myogenic program by co-immunostaining with myogenic regulatory factors such as MyoD. To test genetically modified mice for satellite cell expression, co-immunostaining can be performed for Pax7 and reporter genes such as eGFP. Here, we describe a method for identification of satellite cells in skeletal muscle sections, including muscle isolation, cryosectioning and co-immunostaining for Pax7 and laminin.

Effect of Native Gastric Mucus on in vivo Hybridization Therapies Directed at Helicobacter pylori

Helicobacter pylori infects more than 50% of the worldwide population. It is mostly found deep in the gastric mucus lining of the stomach, being a major cause of peptic ulcers and gastric adenocarcinoma. To face the increasing resistance of H. pylori to antibiotics, antimicrobial nucleic acid mimics are a promising alternative. In particular, locked nucleic acids (LNA)/2'-OMethyl RNA (2'OMe) have shown to specifically target H. pylori, as evidenced by in situ hybridization. The success of in vivo hybridization depends on the ability of these nucleic acids to penetrate the major physical barriers-the highly viscoelastic gastric mucus and the bacterial cell envelope. We found that LNA/2'OMe is capable of diffusing rapidly through native, undiluted, gastric mucus isolated from porcine stomachs, without degradation. Moreover, although LNA/2'OMe hybridization was still successful without permeabilization and fixation of the bacteria, which is normally part of in vitro studies, the ability of LNA/2'OMe to efficiently hybridize with H. pylori was hampered by the presence of mucus. Future research should focus on developing nanocarriers that shield LNA/2'OMe from components in the gastric mucus, while remaining capable of diffusing through the mucus and delivering these nucleic acid mimics directly into the bacteria.

Accuracy of Molecular Data Generated with FFPE Biospecimens: Lessons from the Literature

Formalin-fixed and paraffin-embedded (FFPE) tissue biospecimens are a valuable resource for molecular cancer research. Although much can be gained from their use, it remains unclear whether the genomic and expression profiles obtained from FFPE biospecimens accurately reflect the physiologic condition of the patient from which they were procured, or if such profiles are confounded by biologic effects from formalin fixation and processing. To assess the physiologic accuracy of genomic and expression data generated with FFPE specimens, we surveyed the literature for articles investigating genomic and expression endpoints in case-matched FFPE and fresh or frozen human biospecimens using the National Cancer Institute's Biospecimen Research Database (http://biospecimens.cancer.gov/brd). Results of the survey revealed that the level of concordance between differentially preserved biospecimens varied among analytical parameters and platforms but also among reports, genes/transcripts of interest, and tumor status. The identified analytical techniques and parameters that resulted in strong correlations between FFPE and frozen biospecimens may provide guidance when optimizing molecular protocols for FFPE use; however, discrepancies reported for similar assays also illustrate the importance of validating protocols optimized for use with FFPE specimens with a case-matched fresh or frozen cohort for each platform, gene or transcript, and FFPE processing regime. On the basis of evidence published to date, validation of analytical parameters with a properly handled frozen cohort is necessary to ensure a high degree of concordance and confidence in the results obtained with FFPE biospecimens.

The innovative safe fixative for histology, histopathology, and immunohistochemistry techniques: "pilot study using shellac alcoholic solution fixative"

The concerns over health and workplace hazards of formalin fixative, joined to its cross-linking of molecular groups that results in suboptimal immunohistochemistry, led us to search for an innovative safe fixative. Shellac is a natural material which is used as a preservative in foods and pharmaceutical industries. This study was undertaken to evaluate the fixation adequacy and staining quality of histopathological specimens fixed in the "shellac alcoholic solution" (SAS), and also to determine the validity of immunohistochemical staining of SAS-fixed material in comparison to those fixed in formalin. Fresh samples from 26 cases from various human tissues were collected at the frozen section room of King Abdulaziz University Hospital, and fixed in SAS fixative or in neutral buffered formaldehyde (NBF) for 12, 18, 24, and 48 h, and processed for paraffin sectioning. Deparaffinized sections were stained with hematoxylin and eosin (H&E) and immunostained for different antigens. The tissues fixed in SAS for >18 h showed best staining quality of H&E comparable to NBF-fixed tissues. Comparison of the immunohistochemical staining of different tissues yielded nearly equivalent readings with good positive nuclear staining quality in both fixatives. These findings support the fixation and preservation adequacy of SAS. Furthermore, it was concluded that the good staining quality obtained with SAS-fixed tissues, which was more or less comparable with the quality obtained with the formalin fixed tissues, supports the validity of this new solution as a good innovative fixative.

Tissue fixation and the effect of molecular fixatives on downstream staining procedures

It is impossible to underplay the importance of fixation in histopathology. Whether the scientist is interested in the extraction of information on lipids, proteins, RNA or DNA, fixation is critical to this extraction. This review aims to give a brief overview of the current “state of play” in fixation and focus on the effect fixation, and particularly the effect of the newer brand of “molecular fixatives” have on morphology, histochemistry, immunohistochemistry and RNA/DNA analysis. A methodology incorporating the creation of a fixation tissue microarray for the study of the effect of fixation on histochemistry is detailed.

Peptide-fluorescent bacteria complex as luminescent reagents for cancer diagnosis

Currently in clinic, people use hematoxylin and eosin stain (H&E stain) and immunohistochemistry methods to identify the generation and genre of cancers for human pathological samples. Since these methods are inaccurate and time consuming, developing a rapid and accurate method to detect cancer is urgently demanded. In our study, binding peptides for lung cancer cell line A549 were identified using bacteria surface display method. With those binding peptides for A549 cells on the surface, the fluorescent bacteria (Escherichia coli with stably expressed green fluorescent protein) were served as specific detecting reagents for the diagnosis of cancers. The binding activity of peptide-fluorescent bacteria complex was confirmed by detached cancer cells, attached cancer cells and mice tumor xenograft samples. A unique fixation method was developed for peptide-bacteria complex in order to make this complex more feasible for the clinic use. This peptide-fluorescent bacteria complex has great potential to become a new diagnostic tool for clinical application.

Optimal antigen retrieval for ethanol-fixed cytologic smears

BACKGROUND

Antigen retrieval, a crucial technique for immunostaining, is often carried out on formalin-fixed, paraffin-embedded (FFPE) tissue sections. The role of antigen retrieval in immunostaining of ethanol-fixed smears remains unclear. The authors evaluated the effects of 2 common antigen retrieval procedures, heat-induced antigen retrieval and protease-induced antigen retrieval, for immunostaining using a broad panel of antibodies.

METHODS

Papanicolaou-stained ethanol-fixed smears from 36 surgical specimens were immunostained with 43 antibodies. Three widely used heat-induced antigen retrieval solutions, namely, citrate buffer (pH 6.0 and pH 7.0) and ethylenediaminetetraacetic acid solution (pH 8.0) for heat-induced antigen retrieval, and pronase were used. The staining results were compared between the ethanol-fixed smears and the corresponding FFPE tissue sections.

RESULTS

Heat-induced antigen retrieval was essential for all the 9 antibodies examined against nuclear antigens, and for 7 of 26 antibodies against cytoplasmic and cell membrane antigens. Superior results were obtained using lower-pH heat-induced antigen retrieval solutions for ethanol-fixed smears than was the case for FFPE tissue sections; use of citrate buffer (pH 6.0) was optimal for most antibodies. For 17 antibodies against cytoplasmic/cell membrane antigens, satisfactory results were obtained even without antigen retrieval on the ethanol-fixed smears, whereas antigen retrieval was necessary for detection on the FFPE tissue sections. Protease-induced antigen retrieval frequently exerted deleterious effects on ethanol-fixed smears. Despite antigen retrieval, detection of 2 lymphocytic markers failed on ethanol-fixed smears. This limitation was overcome by heat-induced antigen retrieval on formalin vapor-fixed smears.

CONCLUSIONS

In ethanol-fixed smears, most of the antibodies can be immunostained successfully without antigen retrieval treatment or mild heat-induced antigen retrieval using citrate buffer (pH 6.0). The optimal antigen retrieval condition for each antibody must be individually determined.

RCL2, a potential formalin substitute for tissue fixation in routine pathological specimens

AIMS

To investigate RCL2 as a fixative for tissue fixation in routine histopathological examination and to assess tissue suitability for ancillary investigations.

METHODS AND RESULTS

  Forty-nine samples from 36 fresh specimens were cut into three equal pieces and fixed in RCL2 diluted in 100% ethanol, RCL2 in 95% ethanol, or neutral buffered formalin as control. Suitability for microtomy, quality of histomorphology, histochemistry, immunohistochemistry, fluorescent and silver in-situ hybridization analysis and extracted genomic DNA were assessed. Microtomy was straightforward in most tissue blocks, but there was difficulty in cutting in approximately a quarter of samples, which required careful handling by an experienced technician. There were no significant differences in tissue morphology between RCL2- and formalin-fixed tissues (P=0.08). Generally, the quality of histochemical staining, immunohistochemistry and in-situ hybridization were comparable to that of formalin-fixed tissues. Inconsistent immunoreactivity was noted, however, with antibodies against pan-cytokeratin and progesterone receptor. Genomic DNA concentration was higher in RCL2-fixed tissues. Using RCL2 diluted in 95% ethanol did not affect fixation quality.

CONCLUSION

RCL2 is a potential formalin substitute suitable as a fixative for use in routine histopathological examination; however, difficulty in microtomy and occasional discrepancies in immunohistochemical reactivity require further optimization of the methodology.

Investigation of nonspecific cross-reacting antigen 2 as a prognostic biomarker in bone marrow plasma from colorectal cancer patients

Carcinoembryonic antigen (CEA) is still the only routinely used biomarker in colorectal cancer (CRC), but its utility is hampered by poor specificity and sensitivity, and the search for novel biomarkers is highly warranted. The nonspecific cross-reacting antigen 2 (NCA-2), a truncated CEA species molecule which is transcribed from the same gene, has been suggested as an alternative biomarker to CEA. In the present work, specific immunofluorometric assays were used for detection of NCA-2 and full-length CEA in bone marrow plasma from 277 CRC patients to assess their value as prognostic biomarkers, and detection was also performed in tumor tissue and a CRC cell line. Elevated plasma CEA was associated with advanced tumor stage at diagnosis and adverse patient outcome, while for NCA-2, although the same trends were observed, no additional prognostic information was gained. While specific detection of NCA-2 was clearly achieved in plasma samples, cross-reactivity with full-length CEA was observed when the antigen was exposed to common fixation chemicals. The results from this study indicate that NCA-2 is probably not a prognostic biomarker in CRC and, furthermore, underline the issue of antibody specificity when investigating CEA species molecules.

Formaldehyde substitute fixatives. Analysis of macroscopy, morphologic analysis, and immunohistochemical analysis

Because formaldehyde is toxic and creates cross-links that may hinder immunohistochemical studies, we tested 3 new cross-linking (F-Solv [Adamas, Rhenen, the Netherlands]) and non-cross-linking (FineFIX [Milestone, Bergamo, Italy] and RCL2 [Alphelys, Plaisir, France]) alcohol-based fixatives for routine staining in comparison with neutral buffered formalin (NBF) as the "gold standard." Fresh tissue samples were divided into 4 equal pieces and fixed in all fixatives for varying times. After paraffin embedding, H&E staining, 7 common histochemical stains, and 9 common immunohistochemical stains were performed. RCL2 fixation resulted in soft and slippery tissue, causing sectioning difficulties. F-Solv and FineFIX led to partial tissue disintegration during fixation. F-Solv performed morphologically similar to NBF but needed considerable protocol adjustments before being applicable in daily histologic and immunohistochemical practice. FineFIX did not necessitate major protocol changes but caused shrinkage artifacts, degranulation, and lysis of RBCs. RCL2 generated morphologically overall good results without major protocol changes but caused pigment deposition, degranulation, and RBC lysis. The alcohol-based fixatives had positive and negative attributes and environmental drawbacks, and none was overall comparable to NBF with regard to macroscopy, morphologic evaluation, and immunohistochemical studies.

One-step preservation of phosphoproteins and tissue morphology at room temperature for diagnostic and research specimens

Background

There is an urgent need to measure phosphorylated cell signaling proteins in cancer tissue for the individualization of molecular targeted kinase inhibitor therapy. However, phosphoproteins fluctuate rapidly following tissue procurement. Snap-freezing preserves phosphoproteins, but is unavailable in most clinics and compromises diagnostic morphology. Formalin fixation preserves tissue histomorphology, but penetrates tissue slowly, and is unsuitable for stabilizing phosphoproteins. We originated and evaluated a novel one-step biomarker and histology preservative (BHP) chemistry that stabilizes signaling protein phosphorylation and retains formalin-like tissue histomorphology with equivalent immunohistochemistry in a single paraffin block.

Results

Total protein yield extracted from BHP-fixed, routine paraffin-embedded mouse liver was 100% compared to snap-frozen tissue. The abundance of 14 phosphorylated proteins was found to be stable over extended fixation times in BHP fixed paraffin embedded human colon mucosa. Compared to matched snap-frozen tissue, 8 phosphoproteins were equally preserved in mouse liver, while AMPKβ1 Ser108 was slightly elevated after BHP fixation. More than 25 tissues from mouse, cat and human specimens were evaluated for preservation of histomorphology. Selected tissues were evaluated in a multi-site, independent pathology review. Tissue fixed with BHP showed equivalent preservation of cytoplasmic and membrane cytomorphology, with significantly better nuclear chromatin preservation by BHP compared to formalin. Immunohistochemical staining of 13 non-phosphorylated proteins, including estrogen receptor alpha, progesterone receptor, Ki-67 and Her2, was equal to or stronger in BHP compared to formalin. BHP demonstrated significantly improved immunohistochemical detection of phosphorylated proteins ERK Thr202/Tyr204, GSK3-α/β Ser21/Ser9, p38-MAPK Thr180/Tyr182, eIF4G Ser1108 and Acetyl-CoA Carboxylase Ser79.

Conclusion

In a single paraffin block BHP preserved the phosphorylation state of several signaling proteins at a level comparable to snap-freezing, while maintaining the full diagnostic immunohistochemical and histomorphologic detail of formalin fixation. This new tissue fixative has the potential to greatly facilitate personalized medicine, biobanking, and phospho-proteomic research.

Evaluation of formalin-free tissue fixation for RNA and microRNA studies

FineFix, RCL-2 and HOPE, three formalin-free fixatives, were compared to the common used formalin fixed tissue samples of lung cancer and were evaluated for their effects on quality, quantity and integrity of RNA and microRNA. Two commercially available RNA extraction Kits (RNeasy FFPE by Qiagen and RecoverAll™ Nucleic Acid Isolation by Ambion) were tested and optimized in order to determine an extraction protocol for RNA as well as miRNA independent of the fixative. Two selected miRNAs were quantified via TaqMan MicroRNA assays. The optimized RNA extraction protocol for Qiagen's Kit leads to similar results for RNA quality and integrity for all fixatives. Highest RNA yield was obtained for formalin and the highest average miRNA ratio was found for FineFix. RNA fragments smaller than 500 bases were detected in FineFix, formalin and RCL2 fixed tissues; HOPE was the only fixative showing long fragments in one third of the samples. Our findings demonstrate that formalin-free fixatives are in general not superior for RNA studies. With our optimized RNA extraction protocol, there is no difficulty in extracting great amounts of RNA with high quality. According to the quality obtained, quantitative real-time PCR analysis can be performed without any negative impact. Similar results can be achieved for the tested fixatives and therefore no fixative seems to represent a new "gold-standard" for tissue fixation.