The Proview™ Express Probes Story
I’m excited to be writing for the blog again, this time to share my experiences at Inscopix working toward our goal of providing scientists with full solutions for their circuit neuroscience research. Given the multidisciplinary scientific expertise needed to successfully conduct studies at the level of circuits in behaving animals, we recognize how critical this is. When I joined Inscopix just over 5 years ago, I was immediately drafted into efforts by the company’s Science team to speed up the time it takes our customers to obtain their first quality in vivo images. One particular area I’ve focused on has been the optimization step (e.g. serial dilution studies) typically required for AAV-mediated expression of appropriate levels of calcium indicator (e.g. GCaMP) in specific brain regions and cell types of interest. For successful in vivo imaging, it is critical that there is enough GCaMP in neurons to produce high signal-to-noise (SNR) calcium dynamics and detectable calcium ‘events’, but not too much GCaMP which can paradoxically lead to reduced SNR (due to reduced dynamic range) and eventually an alteration to natural dynamics and cytotoxicity. Unfortunately, viruses obtained from commercial suppliers or academic viral cores can vary widely in their infectivity, and the often-reported physical titer of the virus does not allow for accurate prediction regarding in vivo GCaMP expression levels. The solution we developed allows customers to completely skip the optimization step and instead rely on ‘Ready-to-Image’ GCaMP viruses which Inscopix provides. These are concentration-optimized and ready to inject and image for specific brain region applications, including mouse and rat neocortex and CA1 hippocampus and mouse dorsal striatum. It’s an entirely new way of receiving viruses for circuit neuroscience studies, with a comprehensive and quantitative report from in vivo functional validation studies, saving weeks to months for scientists to initiate their studies.
Developing ‘Ready-to-Image’ GCaMP viruses was my first taste of the type of innovative product development and science I have grown accustomed to here at Inscopix. More recently, we decided to take on an even greater challenge - to streamline the entire surgical workflow for preparing animals for miniscope imaging, which until recently typically required 3 separate surgeries: virus injection, lens implantation and miniscope baseplate installation. Separate virus injection and lens implantation steps created the need for careful procedures to co-align GCaMP expression and the lens to the same region of interest in the brain. It always struck me as a missed opportunity to not take advantage of the lens itself for virus delivery, and so I set out with one of our Research Associates, David Cheng, to see what was possible. We entered into this work aware of the many challenges and low likelihood of success, but when we observed early signs of GCaMP expression several days following our first virus-coated lens implantations, our initial cynicism turned into dubious intrigue. About a week later when we conducted an nVista™ imaging session in that mouse, we were floored by the large number of cells and strong signal quality that we observed. In fact, a completely unexpected but important advantage of this approach was the negligible GCaMP expression beyond the immediate vicinity of the lens, resulting in very low background fluorescence levels. Of course, the immediate next question from management was whether we could transform this ‘skunkworks’ project into a legitimate product for our community; and that’s where the hard work started.
In case you didn’t know, Inscopix products are rigorously tested by our Engineers on the bench and by our Scientists in the lab to confirm performance for the scientific use cases and applications they were designed to address. This was no different for the virus-coated lenses which we would ultimately release as a new product line called Express Probes - combining ‘Ready-to-Image’ GCaMP virus, lens and microscope baseplate into a single device for a one-step (rather than 3 surgical steps) implant with guaranteed alignment between GCaMP-expressing cells and imaging field of view in the brain. It took about a year of intensive bench and in vivo testing at Inscopix as well as Beta testing in customer labs to develop an Express Probe product that we could consistently manufacture, store and ship, and that is capable of producing reliable in vivo performance within and across labs. It was actually a lot of fun for me to be part of this entire process from beginning to end, from initial discovery to released product.
The Express Probes have the potential to truly revolutionize so many important aspects of how miniscope imaging is conducted, both at academic labs and in pharma/biotech companies. Not only does this significantly streamline the surgical workflow and increase overall yields for successful imaging, both of which are important for larger scale studies often conducted in the preclinical setting, but it is also an important step forward toward standardizing experimental conditions for the field, which has important implications for the prospects of replication of scientific findings between academic and preclinical labs. It has been enormously gratifying being a part of the Inscopix team, innovating with my fellow scientists, and creating exciting new products and solutions that will continue to break down barriers for circuit neuroscience research and lead down the road to a better understanding and improved therapeutics for neurological and neuropsychiatric disease.