Visualization of renal rotenone accumulation after oral administration and in situ detection of kidney injury biomarkers via MALDI mass spectrometry imaging

Mini Review: Highlight of Recent Advances and Applications of MALDI Mass Spectrometry Imaging in 2024

Matrix-assisted laser desorption/ionisation mass spectrometry imaging (MALDI-MSI) is an emerging imaging tool that allows visualisation of hundreds of analytes unbiasedly in a single experiment. This paper highlights the adaptations of MALDI-MSI in different context in 2024, such as clinical diagnostic, pharmacology, forensics applications, plant metabolism and biology. Challenges and advancements were also discussed regarding sample preparation, instrumentations, data analysis, and integration of machine learning in the trend of single cell resolution and multi-omics. There are still rooms for improvements in sensitivity, spatial resolution, acquisition algorithm and data integration across multi-omics data to enable MALDI-MSI at subcellular level.

Mass Spectrometry Imaging Distinguishes Biliary Toxicants on the Basis of Cellular Distribution

Mass spectrometry imaging (MSI) was used to investigate and provide insights into observed biliary pathology found in dogs and rats after administration of two different compounds. Both compounds were associated with peribiliary inflammatory infiltrates and proliferation of the bile duct epithelium. However, MSI revealed very different spatial distribution profiles for the two compounds: Compound A showed significant accumulation within the bile duct epithelium with a much higher concentration than in the parenchymal hepatocytes, while Compound T exhibited only a slight increase in the bile duct epithelium compared to parenchymal hepatocytes. These findings implicate cholangiocyte uptake and accumulation as a key step in the mechanism of biliary toxicity. In both cases, compounds are shown at the site of toxicity in support of a direct mechanism of toxicity on the biliary epithelium. MSI is a powerful tool for localizing small molecules within tissue sections and improvements in sensitivity have enabled localization down to the cellular level in some cases. MSI was also able to identify biomarker candidates of toxicity by differential analysis of ion profiles comparing treated and control cholangiocytes from tissue sections.

Spatial Metabolomics in Acute Kidney Injury

Acute kidney injury (AKI) is a common condition linked to increased morbidity, mortality, and substantial health care costs both in the United States and globally. Early diagnosis, prompt intervention, and effective therapeutic management of AKI are vital for improving patient outcomes. Recent advancements in renal imaging and omics technologies have provided new perspectives and deeper insights into kidney injury while also presenting challenges in developing a comprehensive cellular and molecular atlas of the condition. This review focuses on the application of mass spectrometry imaging-based spatial metabolomics in studying ischemia- and toxin-induced AKI in animal models and human patients. Spatial metabolomics offers a deeper understanding of the pathophysiological connections between various processes, such as dysregulated lipid metabolism and the shift from the tricarboxylic acid cycle to glycolytic flux, which contribute to functional impairment and structural damage in AKI. Continued research in renal multimodal imaging and omics is essential to further our understanding of kidney injury from diagnostic, mechanistic, and therapeutic perspectives.