MSACL 2016 EU Plenary Abstract

Molecular Tissue-Typing in Clinical Translational Research: Towards Precision Medicine

Ron Heeren
Maastricht University

Bio: Prof. Dr. Ron M.A. Heeren obtained a PhD degree in technical physics in 1992 at the University of Amsterdam on plasma-surface interactions. He was the research group leader at FOM-AMOLF for macromolecular ion physics and biomolecular imaging mass spectrometry. In 2001 he was appointed professor at the chemistry faculty of Utrecht University lecturing on the physical aspects of biomolecular mass spectrometry. In the period 1995-2015 he has been developing new approaches towards high spatial resolution and high throughput molecular imaging mass spectrometry using Secondary Ion Mass Spectrometry and Matrix Assisted Laser Desorption and Ionization. In 2014 he was appointed as distinguished professor and Limburg Chair at the University of Maastricht and director of M4I, , the Maastricht MultiModal Molecular Imaging institute and heads the division of imaging MS

Authorship: Ron M.A. Heeren
The Maastricht MultiModal Molecular Imaging institute, Maastricht University.

Short Abstract A multimodal approach for molecular imaging for clinical studies is trending the field of imaging mass spectrometry. More and more researchers realize that a single technology provides only a subset of the molecular information needed to obtain an in depth understanding of a clinical problem. Multimodal approaches enable the study of clinical samples at a variety of molecular and spatial scales. The molecular complexity on the genome, proteome and metabolome level all needs to be taken into account. The distribution of several hundreds of molecules on the surface of complex (biological) surfaces can be determined directly in complementary imaging MS experiment with different desorption and ionization strategies.

Long Abstract

Introduction and methods

A multimodal approach for molecular imaging for clinical studies is trending the field of imaging mass spectrometry. More and more researchers realize that a single technology provides only a subset of the molecular information needed to obtain an in depth understanding of a clinical problem. Multimodal approaches enable the study of clinical samples at a variety of molecular and spatial scales. The molecular complexity on the genome, proteome and metabolome level all needs to be taken into account. The distribution of several hundreds of molecules on the surface of complex (biological) surfaces can be determined directly in complementary imaging MS experiment with different desorption and ionization strategies. State-of-the-art molecular imaging mass spectrometry has evolved to bridge the gap between different disciplines such as MRI, PET, fluorescence imaging and histology. The combination with tools from structural biology makes it possible to perform imaging experiments at length scales from cells to patients. High throughput, high resolution MALDI techniques offer three dimensional molecular data on the tissue level. Ambient desorption and ionization techniques complement MALDI in their capabilities to reveal different molecular signatures that can be employed for direct tissue typing in molecular pathology. .

Results

This approach can be applied to meet a critical need for biomarkers capable of predicting ischemic tissue damage prior to organ transplants. Histological analysis of pre-transplant biopsies struggle to discriminate between organs with immediate, delayed or primary non graft functions. One of the major contributors to tissue damage leading to unsuccessful transplantations is acute ischemic damage occurring between the donors death and transplantation. This enables molecular pathway analysis as well as the analysis of the role and evolution of the different molecular signals during e.g. tumor development. Ultimately the tissue profiles can be employed towards precision medicine. In this work we applied high-speed MALDI imaging in a double blind study of renal biopsies to distinguish the lipidomics and proteomic profiles of kidneys having experienced severe or mild ischemic injury in 16 porcine kidneys. In addition we present the extension of this work to ~30 human pre-transplant biopsies with a variety of transplant outcomes.

We have additionally employed rapid MALDI-MSI instrumentation has been employed for the analysis of large numbers of tissues, 10 tumor xenografts (obtained from breast, lung and colon cancers) which were analysed in a single analysis with a 50 µm step size with DHB as the matrix. The resulting dataset contained >160,000 pixels and was acquired in ~90 minutes using 200 laser shots per raster position. Unsupervised tissue segmentation performed using SCiLS lab software(SCiLS Gmbh, Bremen, Germany) revealed distinct molecular profiles within the different tissue/tumor regions. In addition, high speed MALDI-MSI for the analysis of drugs of abuse in single human hairs will be presented. For example a single 4.8 cm long, longitudinally sections human hair could be imaged with 20µm pixel size in a matter of minutes.

Data demonstrating that such acquisition speeds enable the use of alternative matrices that previously could not be used in axial-ToF instruments for long imaging experiments due to their rapid evaporation in the high vacuum ion source. In particular we have used dithranol and 2,6-Dihydroxyacetophenone (DHA) for the imaging of lipids in both positive and negative mode sequentially from the same tissue section. Both matrices were found to yield excellent spectra in both polarities for a variety of lipids where dual polarity imaging provides highly complementary data for different lipid classes. Even for highly volatile DHA an entire sagittal mouse brain section could be imaged in both polarities in ~ 30 min before matrix evaporation significantly affected the acquisition.

Conclusion

We have demonstrated how new MS based chemical microscopes that target biomedical tissue analysis in various diseases as well as other chemically complex surfaces. In concert they elucidate the way in which local environments can influence molecular signaling pathways on various scales. The integration of this pathway information in a surgical setting is imminent, but innovations that push the boundaries of the technology and its application are still needed.

Financial Disclosure

IP Royalty: no

Planning to mention or discuss specific products or technology of the company(ies) listed above:

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