Researchers have developed a new gene-editing method to produce more mature and functional liver cells from pluripotent stem cells, overcoming a significant obstacle that has long hindered progress in disease modeling and drug development. By deactivating a specific gene, scientists were able to prevent lab-grown liver cells from developing undesirable intestinal characteristics, resulting in a purer and more effective cell culture.
This breakthrough provides a much-needed tool for studying a range of liver diseases, including hepatitis, fatty liver disease, and cancer. The improved, stem cell-derived hepatocytes offer a more reliable platform for testing drug toxicity and efficacy, which could reduce the reliance on animal testing. The work, led by scientists at the Leibniz Research Center for Working Environment and Human Factors in Dortmund, Germany, addresses the fundamental challenge of coaxing stem cells to fully transform into a single, specific cell type, opening new avenues for both research and future cell-based therapies.
The Challenge of Cellular Identity
The ability to generate liver cells, or hepatocytes, from pluripotent stem cells holds enormous potential for medical research. However, the process has been persistently difficult. Existing methods often produced immature cells or a mix of cell types. Scientists frequently observed that stem cell-derived hepatocytes also expressed traits of intestinal cells, creating a “hybrid phenotype” that does not accurately reflect the function of a mature liver.
This issue stems from the cells’ shared developmental origins. According to Antonia Titzk, a doctoral student on the research team, hepatocytes and intestinal epithelial cells develop from the same embryonic tissue. During natural development, different gene regulatory networks guide these primitive cells to mature into their distinct final forms. In the artificial environment of a lab, this process can go awry, leading to cells that are caught between two identities and are therefore limited in their usefulness for precise research applications.
Pinpointing a Genetic Culprit
The research group, headed by Dr. Patrick Nell, made a significant advance by identifying the specific genetic mechanism responsible for the unwanted intestinal traits. Their work focused on gene regulatory networks, which are complex systems of molecules that control the expression of genes within a cell, determining its identity and function. Through careful investigation, they discovered that a network controlled by a gene called CDX2 was the key driver of the intestinal characteristics in their stem cell-derived liver cultures.
The CDX2 gene is known to be crucial for the development of the intestines. The team hypothesized that its persistent activity during the differentiation process was confusing the cells, preventing them from fully committing to becoming hepatocytes. By identifying the CDX2 network as the primary cause of the hybrid cell problem, the researchers were able to devise a highly targeted strategy to solve it.
A Precise Gene-Editing Solution
To eliminate the influence of the CDX2 gene, Dr. Nell’s team turned to the powerful CRISPR-Cas9 gene-editing technique. Often described as “gene scissors,” CRISPR allows scientists to make precise changes to the DNA of a cell. The researchers applied this tool to target and disable the CDX2 gene in the stem cells as they were being differentiated into liver cells.
This innovative approach acted as a genetic switch, effectively turning off the instructions that were pushing the cells toward an intestinal fate. By deactivating CDX2, the team could ensure that only the gene regulatory networks responsible for liver development remained active. This prevented the mixed messaging that had previously plagued lab-grown hepatocytes, allowing for the creation of a more uniform and specialized cell population.
Results: Purer and More Functional Cells
The outcome of the experiment was a clear success. The modified cells developed a distinct liver phenotype without the intestinal qualities that had been the target of the research. These new hepatocytes were not only purer but also functionally superior. The team observed significant improvements in key liver functions that are critical for accurately modeling human physiology.
Among the noted enhancements were the correct formation of bile ducts and more efficient bile acid transport. These are complex, specialized functions that indicate a higher level of cellular maturity and organization. The ability to create cells that better replicate the structure and function of an actual liver is a major step forward for creating high-fidelity models for use in the lab.
Advancing Liver Research and Medicine
The implications of this study, published in the journal Stem Cell Research and Therapy, are far-reaching. By providing a method to generate more reliable and functional liver cells, the research offers immediate benefits for disease modeling and drug discovery. Scientists can now create more accurate “disease-in-a-dish” models to investigate conditions like cirrhosis and inherited metabolic disorders. Furthermore, pharmaceutical companies can use these improved cells to test the potential toxicity of new drug candidates more effectively.
Dr. Nell emphasized that understanding the influence of these gene networks is fundamental to advancing stem cell technology. This work paves the way for developing robust alternatives to animal testing, a long-standing goal in biomedical research. In the long term, these refined techniques could also contribute to the development of cell therapies, where healthy lab-grown liver cells could one day be used to treat patients with liver failure.
