Master thesis presentation Julia Johansson, MPBIO

Abstract: Preclinical testing is a crucial part of the pharmaceutical development process to evaluate toxicology and safety of a drug candidate, which often involves cell cultures and in vivo animal models. However, these are unsatisfactory representations of the human body, and thus do not always translate into successful clinical results. Furthermore, as the liver plays an essential role in several vital functions related to drug detoxification and is often subjected to adverse drug reactions, there is a pressing need for models with better predictability and physiological relevance. One approach relies on microfluidics and has brought forward the organ-on-a-chip technology, which generates models that can bridge the gap between in vitro cell cultures and animal models, as they allow the culturing of multiple cell types on the microscale under in vivo-like conditions. However, before such models can be implemented in pharmaceutical and biomedical research, their functional relevance and reliability need to be proven. This thesis describes the work to validate a liver-on-chip model through microfluidic experiments utilizing two liver cell lines. The key points of the validation included studying the cellular functionality, viability, and reproducibility of the model across multiple experiments. Cellular functionality was evaluated through protein measurement with Enzyme Linked Immunosorbent Assays (ELISA), and cellular viability was assessed through on-chip live/dead staining and fluorescence imaging. The results showed that the cells proliferate over time and produce albumin throughout the experiments. There was also a considerably high amount of cell death, indicating the cells could possibly be subjected to oxygen or nutrient deficiency when growing too dense. These results suggest the model to be more suitable for nonproliferating cells and paves the way for future establishment of realistic 3D cultures of primary or human derived stem cells on the chip.
Beyond the application in drug testing, liver-on-a-chip models are useful in the study of liver-typical diseases. Therefore, the chip was also utilized in some initial experiments to mimic the disease non-alcoholic fatty liver disease (NAFLD) on-chip. This was attempted by supplying the cells with free fatty acids (oleic and palmitic acid) for 48 hours. Live/dead staining was performed to study the effect of the treatment and lipid staining to assess whether the cells accumulated the fatty acids in the cytosol. Results showed a high cell death and unreliable results of lipid uptake. It was discussed whether the cell death was a result of the fatty acid treatment or due to the previously mentioned deficiency. These findings provided valuable insights and indicated the potential for future experiments to establish a disease-model on-chip using this liver model.

Supervisor: Caroline Adiels

Examiner: Julie Gold

Opponent: Selma Antonsson