Synthetic Antigen Gels as Practical Controls for Standardized and Quantitative Immunohistochemistry

Bioprinted Human Lung Cancer-Mimics for Tissue Diagnostics Applications

Developing a reproducible and secure supply of customizable control tissues that standardizes for the cell type, tissue architecture, and preanalytics of interest for usage in applications including diagnostic, prognostic, and predictive assays, is critical for improving our patient care and welfare. The conventionally adopted control tissues directly obtained from patients are not ideal because they oftentimes have different amounts of normal and neoplastic elements, differing cellularity, differing architecture, and unknown preanalytics, in addition to the limited supply availability and thus associated high costs. In this study, we demonstrated a strategy to stably produce tissue-mimics for diagnostics purposes by taking advantage of the three-dimensional (3D) bioprinting technology. Specifically, we take anaplastic lymphoma kinase-positive (Alk+) lung cancer as an example, where a micropore-forming bioink laden with tumor cells was combined with digital light processing-based bioprinting for developing native-like Alk+ lung cancer tissue-mimics with both structural and functional relevancy. It is anticipated that our proposed methodology will pave new avenues for both fields of tissue diagnostics and 3D bioprinting significantly expanding their capacities, scope, and sustainability.

Quantitative assessment of H&E staining for pathology: development and clinical evaluation of a novel system

BACKGROUND

Staining tissue samples to visualise cellular detail and tissue structure is at the core of pathology diagnosis, but variations in staining can result in significantly different appearances of the tissue sample. While the human visual system is adept at compensating for stain variation, with the growth of digital imaging in pathology, the impact of this variation can be more profound. Despite the ubiquity of haematoxylin and eosin staining in clinical practice worldwide, objective quantification is not yet available. We propose a method for quantitative haematoxylin and eosin stain assessment to facilitate quality assurance of histopathology staining, enabling truly quantitative quality control and improved standardisation.

METHODS

The stain quantification method comprises conventional microscope slides with a stain-responsive biopolymer film affixed to one side, called stain assessment slides. The stain assessment slides were characterised with haematoxylin and eosin, and implemented in one clinical laboratory to quantify variation levels.

RESULTS

Stain assessment slide stain uptake increased linearly with duration of haematoxylin and eosin staining (r = 0.99), and demonstrated linearly comparable staining to samples of human liver tissue (r values 0.98-0.99). Laboratory implementation of this technique quantified intra- and inter-instrument variation of staining instruments at one point in time and across a five-day period.

CONCLUSION

The proposed method has been shown to reliably quantify stain uptake, providing an effective laboratory quality control method for stain variation. This is especially important for whole slide imaging and the future development of artificial intelligence in digital pathology.

Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry Imaging in Biology

Elemental imaging gives insight into the fundamental chemical makeup of living organisms. Every cell on Earth is comprised of a complex and dynamic mixture of the chemical elements that define structure and function. Many disease states feature a disturbance in elemental homeostasis, and understanding how, and most importantly where, has driven the development of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) as the principal elemental imaging technique for biologists. This review provides an outline of ICP-MS technology, laser ablation cell designs, imaging workflows, and methods of quantification. Detailed examples of imaging applications including analyses of cancers, elemental uptake and accumulation, plant bioimaging, nanomaterials in the environment, and exposure science and neuroscience are presented and discussed. Recent incorporation of immunohistochemical workflows for imaging biomolecules, complementary and multimodal imaging techniques, and image processing methods is also reviewed.

Clinical and research applications of multiplexed immunohistochemistry and in situ hybridization

Over the past decade, invention and adoption of novel multiplexing technologies for tissues have made increasing impacts in basic and translational research and, to a lesser degree, clinical medicine. Platforms capable of highly multiplexed immunohistochemistry or in situ RNA measurements promise evaluation of protein or RNA targets at levels of plex and sensitivity logs above traditional methods - all with preservation of spatial context. These methods promise objective biomarker quantification, markedly increased sensitivity, and single-cell resolution. Increasingly, development of novel technologies is enabling multi-omic interrogations with spatial correlation of RNA and protein expression profiles in the same sample. Such sophisticated methods will provide unprecedented insights into tissue biology, biomarker science, and, ultimately, patient health. However, this sophistication comes at significant cost, requiring extensive time, practical knowledge, and resources to implement. This review will describe the technical features, advantages, and limitations of currently available multiplexed immunohistochemistry and spatial transcriptomic platforms. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Development of novel quality control material based on CRISPR/Cas9 editing and xenografts for MLH1 protein deficiency testing

BACKGROUND

Mismatch repair deficiency (dMMR) status induced by MLH1 protein deficiency plays a pivotal role in therapeutic decision-making for cancer patients. Appropriate quality control (QC) materials are necessary for monitoring the accuracy of MLH1 protein deficiency assays used in clinical laboratories.

METHODS

CRISPR/Cas9 technology was used to edit the MLH1 gene of GM12878Cas9 cells to establish MLH1 protein-deficient cell lines. The positive cell lines were screened and validated by Sanger sequencing, Western blot (WB), and next-generation sequencing (NGS) and were then used to prepare formalin-fixed, paraffin-embedded (FFPE) samples through xenografting. These FFPE samples were tested by hematoxylin and eosin (H&E) staining and immunohistochemistry (IHC) for suitability as novel QC materials for MLH1 protein deficiency testing.

RESULTS

We successfully cultured 358 monoclonal cells, with a survival rate of 37.3% (358/960) of the sorted monoclonal cells. Through Sanger sequencing, cell lines with MLH1 gene mutation were identified. Subsequently, two cell lines with MLH1 protein deficiency were identified by WB and named as GM12878Cas9_6 and GM12878Cas9_10. The NGS results further confirmed that the MLH1 gene mutation in these two cell lines would cause the formation of stop codons and terminate the expression of the MLH1 protein. The H&E staining and IHC results also verified the deficiency of the MLH1 protein, and FFPE samples from xenografts proved their similarity and consistency with clinical samples.

CONCLUSIONS

We successfully established MLH1 protein-deficient cell lines. Followed by xenografting, we developed novel FFPE QC materials with homogenous, sustainable, and typical histological structures advantages that are suitable for the standardization of clinical IHC methods.

Validating Immunohistochemistry Assay Specificity in Investigative Studies: Considerations for a Weight of Evidence Approach

Immunohistochemistry (IHC) is a fundamental molecular technique that provides information on protein expression in the context of spatial localization and tissue morphology. IHC is used in all facets of pathology from identifying infectious agents or characterizing tumors in diagnostics, to characterizing cellular and molecular processes in investigative and experimental studies. Confidence in an IHC assay is primarily driven by the degree to which it is validated. There are many approaches to validate an IHC assay's specificity including bioinformatics approaches using published protein sequences, careful design of positive and negative tissue controls, use of cell pellets with known target protein expression, corroboration of IHC findings with western blots and other analytical methods, and replacement of the primary antibody with an appropriate negative control reagent. Each approach has inherent strengths and weaknesses, and the thoughtful use of these approaches provides cumulative evidence, or a weight of evidence, to support the IHC assay's specificity and build confidence in a study's conclusions. Although it is difficult to be 100% confident in the specificity of any IHC assay, it is important to consider how validation approaches provide evidence to support or to question the specificity of labeling, and how that evidence affects the overall interpretation of a study's results. In this review, we discuss different approaches for IHC antibody validation, with an emphasis on the characterization of antibody specificity in investigative studies. While this review is not prescriptive, it is hoped that it will be thought provoking when considering the interpretation of IHC results.