High-content screening (HCS) may seem like an esoteric term to many in the general public. For researchers across the globe, like Vance Lemmon, Ph.D., the Walter G. Ross Distinguished Chair in Developmental Neuroscience, Professor, Department of Neurological Surgery and The Miami Project to Cure Paralysis, it is an important tool that is helping to turbo charge the discovery process. Some labs are studying one gene at a time, and they do it effectively in various environments, but by using HCS, The Miami Project scientists have taken it not to the next level, but lightyears beyond.
Through the high-content screening process in the labs of The Miami Project, literally thousands of compounds or drugs can be tested to see how they may play a role in the promotion of axon growth. Axons are the threadlike part of a nerve cell along which electrical impulses are conducted from the cell body to other cells. HCS uses an automated microscope that takes pictures of cells in the multi-well dishes, instead of taking pictures of histological slides. Each dish may have 24, 96, or 384 wells into which cells are placed. The microscope automatically focuses and takes pictures in each one of those wells and each well can contain different treatments. This allows researchers to learn about how neurons control axon growth. The hope is that the things that look positive in the study in dishes will then allow scientists to translate those to pre-clinical studies.
“Our group, co-lead by Professors John Bixby and Hassan Al-Ali, published a paper last year, (Scaffold Ranking and Positional Scanning Identify Novel Neurite Outgrowth Promoters with Nanomolar Potency) where we tested over 440 million different chemicals on primary neurons. That’s mind boggling. I think we’ve tested more “things” on primary neurons than the rest of the world combined. And that’s given us lots of insight into the kinds of gene families that are really powerful at turning axon growth on and off,” said Dr. Lemmon.
It is impossible to efficiently screen hundreds of different treatments in-vivo in the mammalian system the way scientists can test thousands and thousands of different treatments in a week in a dish using high-content screening. It is much more economical, in time and resources, to find new things for testing in-vivo having this in-vitro step that HCS provides. By testing neurons in dishes, scientists can pick “hits” that they think are really effective and then test them in-vivo.
A “hit” is jargon for a treatment, such as a chemical or a gene or an FDA approved drug, that has a big effect in the high-content screening assay. Most of the treatments tested do nothing in the in-vitro assays. However, when one is identified that has a very large effect, that would be called a “hit”, and then scientists take that and test it further to see if it really causes the effect in animals that they are trying to mirror using their in-vitro assays.
What is important for these kinds of in-vitro experiments is whether they reproduce something that’s going on in-vivo. Over the years, our researchers have been able to show that a potential treatment, whether genes or chemical, that make neurites grow longer in the dish have typically shown success in making axons grow in-vivo. Some things work better than others, but Dr. Lemmon and his team have seen that treatments that work well in the dish, have positive effects in-vivo. That is exciting news in terms of discovering potential promising new paths to treatments.
When high-content screening started at The Miami Project in 2003, it was very unusual for academic labs to use the technology. Over the years, this technology has become much more common, with many other medical schools now having one or two of these instruments. Still, they are not widely used in neuroscience because the infrastructure and expertise needed to make it work properly takes quite a while to acquire. This is another factor that helps The Miami Project, at the University of Miami Miller School of Medicine, stand out as one of the leaders in spinal cord and brain injury research.