Grahame Kidd, PhD, is Scientific Director for 3D EM at Renovo Neural Inc. For several years, Renovo Neural has provided “large volume 3DEM” (serial block face imaging) services and assays, and recently began working with the FEI Teneo VolumeScope, the latest generation of SBFI tools. We met with Grahame and asked him about the advantages of this technology.
Grahame, thanks for taking the time to speak with us today. First of all, what tissues do you work the most with and what questions do you answer with 3D EM SBFI ?
Renovo Neural, as the name suggests, focuses on neurology. Our main pre-clinical drug testing arm utilizes brain tissue to investigate the effects of potential MS drugs in a myelination/demyelination model. As well as myelin, we use SBFI to look at axonal health in neuroprotection assays, which includes parameters such as mitochondrial structure, distribution, and cytoskeletal integrity. Synapse number and morphology, including PSD sizes and glial cell proximity are also informative, particularly for our academic customers, who also undertake comparative nano-connectomics studies using the retina. In addition, we have imaged parasites, flies, worms, and many tissues from mice and other mammals. The inventiveness of our academic clients keeps us on our toes, and at the cutting edge – no pun intended.
New readouts are possible using SBFI data. 3D views of brain blocks showing intact myelin (black) surrounding and insulating numerous axons (“normal”). Little myelin is present after demyelination treatment (“demyelinated”), but recover with short-term and extended remyelination. For the first time, 3DEM allows myelin lengths to be measured over hundreds of micrometers (e, 300 um, boxes indicate nodes of Ranvier). Myelin lengths turn out to be a better indicator of remyelination than traditional g-ratios, a simpler metric based on cross sectional diameters.
What is the driver behind using 3D SEM for this kind of analysis?
Most of the structures and effects we investigate are so small that we have to rely on electron microscopy to see them. In addition, many critical structures – like mitochondria - have complex, highly elongated structures, and are assymetrically distributed within cells that also have highly polarized 3Dshapes. There are a lot of useful indicators of cell health in organelle structure and localization.. Traditional 3D-EM (i.e. serial section TEM) is too time-consuming to even think of multiple datasets, conditions, dose/response curves or time points. Therefore, many informative metrics of cell function have not been traditionally accessible. The advent of automated 3D SEM gives us very easy access to large amounts of comparative ultrastructural data. This allows us to make the step from a single descriptive 3D-EM dataset to statistically significant analysis. We now have the possibility to gain real insight in the effect and mechanisms (i.e. mutations) on an ultrastructural level. This is a fundamental difference in the way electron microscopy has been used in the past; we can use it’s resolving power to see disease modalities and drug effects in a truly quantitative way. For example we are now have several ways to quantify remyelination using 3DEM datasets, in contrast to a short time ago, when only one way was possible.
What will the future bring for you and your work?
We are currently revising and expanding our prototcols and assays to take advantage of the new VolumeScope platform, and are also looking to speed up the throughput of existing assays. In particular, we are interested in identifying changes in very early stages of disease or recovery that may be useful as endpoints. In the longer term, we are expanding the range of tissues in which such changes are useful in preclinical and toxicological studies. We would like to change the way drug discovery is done for appropriate diseases.
Renovo Neural Inc. is a specialized preclinical research organization offering preclinical model systems and automated large volume electron microscopy applications to provide high-quality standard and customizable solutions for basic science, preclinical and clinical research.