On-Slide Heat Sterilization Enables Mass Spectrometry Imaging of Tissue Infected with High-Threat Pathogens Outside of Biocontainment: A Study Directed at Mycobacterium tuberculosis

The clinical-stage drug BTZ-043 accumulates in murine tuberculosis lesions and efficiently acts against Mycobacterium tuberculosis

The development of granulomas with central necrosis harboring Mycobacterium tuberculosis (Mtb) is the hallmark of human tuberculosis (TB). New anti-TB therapies need to effectively penetrate the cellular and necrotic compartments of these lesions and reach sufficient concentrations to eliminate Mtb. BTZ-043 is a novel antibiotic showing good bactericidal activity in humans in a phase IIa trial. Here, we report on lesional BTZ-043 concentrations severalfold above the minimal-inhibitory-concentration and the substantial local efficacy of BTZ-043 in interleukin-13-overexpressing mice, which mimic human TB pathology of granuloma necrosis. High-resolution MALDI imaging further reveals that BTZ-043 diffuses and accumulates in the cellular compartment, and fully penetrates the necrotic center. This is the first study that visualizes an efficient penetration and accumulation of a clinical-stage TB drug in human-like centrally necrotizing granulomas and that also determines its lesional activity. Our results most likely predict a substantial bactericidal effect of BTZ-043 at these hard-to-reach sites in TB patients.

Frontiers in Mass Spectrometry-Based Spatial Metabolomics: Current Applications and Challenges in the Context of Biomedical Research

Metabolites are critical products and mediators of cellular and tissue function, and key signals in cell-to-cell, organ-to-organ and cross-organism communication. Many of these interactions are spatially segregated. Thus, spatial metabolomics can provide valuable insight into healthy tissue function and disease pathogenesis. Here, we review major mass spectrometry-based spatial metabolomics techniques and the biological insights they have enabled, with a focus on brain and microbiota function and on cancer, neurological diseases and infectious diseases. These techniques also present significant translational utility, for example in cancer diagnosis, and for drug development. However, spatial mass spectrometry techniques still encounter significant challenges, including artifactual features, metabolite annotation, open data, and ethical considerations. Addressing these issues represent the future challenges in this field.

A consensus conference to define the utility of advanced infectious disease diagnostics in solid organ transplant recipients

The last decade has seen an explosion of advanced assays for the diagnosis of infectious diseases, yet evidence-based recommendations to inform their optimal use in the care of transplant recipients are lacking. A consensus conference sponsored by the American Society of Transplantation (AST) was convened on December 7, 2021, to define the utility of novel infectious disease diagnostics in organ transplant recipients. The conference represented a collaborative effort by experts in transplant infectious diseases, diagnostic stewardship, and clinical microbiology from centers across North America to evaluate current uses, unmet needs, and future directions for assays in 5 categories including (1) multiplex molecular assays, (2) rapid antimicrobial resistance detection methods, (3) pathogen-specific T-cell reactivity assays, (4) next-generation sequencing assays, and (5) mass spectrometry-based assays. Participants reviewed and appraised available literature, determined assay advantages and limitations, developed best practice guidance largely based on expert opinion for clinical use, and identified areas of future investigation in the setting of transplantation. In addition, attendees emphasized the need for well-designed studies to generate high-quality evidence needed to guide care, identified regulatory and financial barriers, and discussed the role of regulatory agencies in facilitating research and implementation of these assays. Findings and consensus statements are presented.

Mass spectrometry imaging: new eyes on natural products for drug research and development

Natural products (NPs) and their structural analogs represent a major source of novel drug development for disease prevention and treatment. The development of new drugs from NPs includes two crucial aspects. One is the discovery of NPs from medicinal plants/microorganisms, and the other is the evaluation of the NPs in vivo at various physiological and pathological states. The heterogeneous spatial distribution of NPs in medicinal plants/microorganisms or in vivo can provide valuable information for drug development. However, few molecular imaging technologies can detect thousands of compounds simultaneously on a label-free basis. Over the last two decades, mass spectrometry imaging (MSI) methods have progressively improved and diversified, thereby allowing for the development of various applications of NPs in plants/microorganisms and in vivo NP research. Because MSI allows for the spatial mapping of the production and distribution of numerous molecules in situ without labeling, it provides a visualization tool for NP research. Therefore, we have focused this mini-review on summarizing the applications of MSI technology in discovering NPs from medicinal plants and evaluating NPs in preclinical studies from the perspective of new drug research and development (R&D). Additionally, we briefly reviewed the factors that should be carefully considered to obtain the desired MSI results. Finally, the future development of MSI in new drug R&D is proposed.

Single cell metabolism: current and future trends

Single cell metabolomics is an emerging and rapidly developing field that complements developments in single cell analysis by genomics and proteomics. Major goals include mapping and quantifying the metabolome in sufficient detail to provide useful information about cellular function in highly heterogeneous systems such as tissue, ultimately with spatial resolution at the individual cell level. The chemical diversity and dynamic range of metabolites poses particular challenges for detection, identification and quantification. In this review we discuss both significant technical issues of measurement and interpretation, and progress toward addressing them, with recent examples from diverse biological systems. We provide a framework for further directions aimed at improving workflow and robustness so that such analyses may become commonly applied, especially in combination with metabolic imaging and single cell transcriptomics and proteomics.

Spatial quantitation of antibiotics in bone tissue compartments by laser-capture microdissection coupled with UHPLC-tandem mass spectrometry

Bones are the site of multiple diseases requiring chemotherapy, including cancer, arthritis, osteoporosis and infections. Yet limited methodologies are available to investigate the spatial distribution and quantitation of small molecule drugs in bone compartments, due to the difficulty of sectioning undecalcified bones and the interference of decalcification methods with spatially resolved drug quantitation. To measure drug concentrations in distinct anatomical bone regions, we have developed a workflow that enables spatial quantitation of thin undecalcified bone sections by laser-capture microdissection coupled to HPLC/tandem mass spectrometry, and spatial mapping on adjacent sections by mass spectrometry imaging. The adhesive film and staining methods were optimized to facilitate histology staining on the same sections used for mass spectrometry image acquisition, revealing drug accumulation in the underlying bone tissue architecture, for the first time. Absolute spatial concentrations of rifampicin, bedaquiline, doxycycline, vancomycin and several of their active metabolites are shown for both small rodent bones and larger rabbit bones that more closely resemble human bone density. Overlaid MALDI mass spectrometry images of drugs and histology staining enabled the generation of semi-quantitative data from regions of interest within anatomical bone compartments. These data correlated with absolute drug concentrations determined by HPLC-MS/MS in laser-capture microdissection samples. Collectively, these techniques enable semi- and fully quantitative drug distribution investigations within bone tissue compartments for the first time. Our workflow can be translated to image and quantify not only drugs but also biomarkers of disease to investigate drug penetration as well as mechanisms underlying bone disorders.