Scientists at Harvard University have proposed a new model for studying nutrition, human embryonic stem cells. Human embryonic stem cells are unique in their ability to turn into all the cell types in the body, including the various tissue types in the human gut.
Drs. Doug Melton and Danny Ben-Zvi propose in an essay in Cell that human embryonic stem cell derived tissues populated by gut microbiota may be an ideal system for studying the physiology of digestion and nutrition. The authors state that the mechanisms of human nutrition are largely unknown and that it is difficult to model how nutrition affects human health on a biological front. By developing systems of stem cell derived tissues, it may be possible to model the gut in the petri dish or even on a chip. Significant engineering advances have been made to model biological systems on a chip. These chips are devices with specific cell types in chambers that are connected through microfluidic channels to better model the tissues and organs in the human body and how they interact with one another.
Chips could be developed that are made of up cells of the various organs that make up our gastrointestinal tract. These organoids could then be populated by bacteria that make up the microbiota. Food could be passed through the chip and scientists could watch bacteria break down food that is passing through it and see how the microbiota adapts to changes in diet. Various conditions could be tested such as what bacterial strains are best at digesting complex carbohydrates? The authors state that many combinations of bacterial strains should be tested to find what bacteria conduct these tasks most efficiently. To do this in mice would require thousands of animals and this may be too restrictive to conduct such experiments. This however could be done using chips with stem cell derived tissues that make up our GI tract and connected through microfluidic channels to stem cell derived liver and pancreas cells that are important for nutrition and digestion.
Significant biological and engineering challenges still exist before this is a reality, including the ability for specific strains of bacteria to thrive in such an environment. However, if some challenges can be overcome, the authors propose that the complexity of nutrition and digestion could be better dissected using systems of stem cell derived tissues in the dish. This work would complement existing research using model organisms and epidemiological and other human studies to better address the questions that we ask every day about what food we should eat and the effects this has on the human body.