Progress in monitoring molecular, cellular and metabolic dynamics using mass spectrometry imaging.

Mass spectrometry imaging (MSI) enables the visualization of hundreds to thousands of analytes in biological tissues. MSI is also capable of mapping time-dependent processes that, combined with these static metabolite profiles, provides a clearer picture of the molecular underpinnings of tissue function. This perspective is organized into sections demonstrating how MSI-based methods can provide unique functional data on systems ranging from single step enzyme-catalyzed transformations to complex metabolic network activities and cellular dynamics. This multisystem capability can be exploited to provide detailed descriptions of the molecular mechanisms contributing to tissue function. An aspect missing in many studies are corresponding maps of tissue microenvironments including oxygenation and pH which influence functional activities. Some progress has been made to map hypoxic and acidic tissue using MSI methods, but further development is needed. This includes pairing in vivo MSI functional studies to in vitro models. Additionally, integrating the capabilities of other imaging methods, such as magnetic resonance and vibrational spectroscopy, that are proven to detect tissue microenvironments, with dynamic MSI methods offer a route to match environment with functional activities. The combination of static molecular profiles, metabolic and cellular dynamics, and environmental mapping will provide the most detailed understanding of tissue function.