What model system could be better for predicting the human response than human primary cells? Until recently, human-cell-based model systems held great promise, but weren't ideal for complex disease modeling, for two reasons:
Because of these limitations, most in vitro work with human cells has traditionally been performed in monoculture. Some valuable research can be obtained if the drug being tested targets that one specific cell type (for example, simple steatosis in hepatocytes). But…even the highest quality hepatocyte donor “lot” will contain a substantial percentage of dead cells in each vial, and this typically limits 2D hepatocyte monoculture studies to only ~5 days. As for stellate cells, almost everyone in the field knows that as soon as you culture quiescent/un-activated stellate cells in 2D, they become activated and myofibroblast-like — not an ideal side effect for a negative control. The ultimate downfall to monoculture, however, is that most diseases involve more than a single cell type and require complex cell-cell communications for the disease to progress. In NASH, for example, there are varying theories around initial lipid accumulation in the hepatocytes triggering inflammation in the macrophages, which further activates the stellate cells to become myofibroblast-like and deposit scarring collagen fibers.
“IHC and confocal imaging are certainly appropriate endpoints for visualizing lipid accumulation and fibrosis — and make for pretty publication images. However, they are low throughput, quantitatively limited, and may not truly mimic clinical pathology.”
When InSphero started working on our human liver disease platform, we had a unique advantage in that we had already been perfecting 3D liver co-culture models for almost a decade and we were able to apply our knowledge and expertise to take on the monumental task of developing a 3D in vitro primary human cell model that highlights all major hallmarks of NASH, within 10 days of physiologically relevant NASH stimuli treatment. Our new 3D InSight™ Human Liver NASH model includes all the human cell types required to recapitulate the disease pathophysiology. This includes primary hepatocytes, Kupffer cells, endothelial cells, and stellate cells, all of which self-assemble together in a scaffold-free, media-compatible environment.
This in vitro model has been validated with numerous Phase 1/2 clinical NASH therapeutics, using clinically relevant endpoints for anti-NASH compound screening. The therapeutics tested in this system target numerous pathways within NASH pathogenesis, ranging from de novo lipogenesis, to inflammation and fibrosis. Immunohistochemistry (IHC) and confocal imaging are certainly possible endpoints related to lipid accumulation and fibrosis (and makes for pretty publication images). However, they are low throughput, quantitatively limited, and may not truly mimic clinical pathology (no in vitro model can fully recapitulate the exact liver architecture required for defining clinical F3 and F4 fibrosis). Therefore, our latest model development efforts have focused on clinically relevant and screenable endpoints, such as intracellular tryglyceride levels (TAG), secreted cytokines/chemokines, and secreted procollagens. We work closely with our research partners to identify appropriate endpoints for the pathways their therapeutics target to best reflect the patient response to treatment.
Finally, a complex in vitro human model, which can predict an in vivo human response! I'd love to hear your thoughts on this topic. Leave a comment below or look for me at AASLD 2019 in the scientific sessions and at booth 118.
Watch this video to learn how we applied our scalable Akura™ technology and 10 years of experience in perfecting 3D in vitro human liver models to develop the first automation-compatible 3D in vitro human liver disease platform for NAFLD and NASH. And read about how pharma companies are applying this platform in their drug discovery programs.