UCLA

The goal of biomedical research is first to understand the mechanism of the diseases, then develop a therapy to mitigate such disease. In the process, animal models and in vitro culture systems comprising primary human cells would be utilized as a study platform. An in vitro system representing small intestine is of great interest. However, attempts to develop an in vitro system which accurately reflect the phenotype and function of the human small intestinal epithelium has so far proven unsatisfactory. Hence the accuracy of the experimental results conducted on such systems might be hampered. The goal of this research is to develop an in vitro intestinal epithelium model which accurately recapitulate the human epithelium in vivo.

A natural progression of the epithelial monolayer development was observed in vitro. The morphology of the monolayer went from organized toward disorganized as the cells underwent apoptosis. The innate variabilities among different enterocyte lines which manifested especially in monolayer development were also observed.

Air-Liquid Interface (ALI) culturing condition had proven to have positive effects on monolayer development in vitro. The integrity of the monolayer was able to be maintained up to 14 days due to decreased cellular apoptosis. The enterocytes under ALI condition exhibited increased polarity and adopted columnar morphology which closely resemble the human enterocytes in vivo. The permeability of the ALI cultured monolayer was more physiologically relevant. The ALI condition further demonstrated an effect in enhancing the existing differentiation signal resulted in increased cellular differentiation.

Through co-culture epithelial monolayer with intestinal subepithelial myofibroblast, the cellular apoptosis was further decreased, yielded a well-maintained epithelial monolayer. The additional differentiation signal for goblet cell differentiation was also provided by myofibroblast and was able to be enhanced through ALI culturing condition. It is also confirmed that myofibroblast exerts its effect on intestinal monolayer development via Bone morphogenetic protein (BMP) signaling pathway.

The overall goal of this research was to develop a more physiologically relevant human intestinal epithelium model in vitro. Through combination of ALI culturing condition and co-culture with intestinal subepithelial myofibroblast, a monolayer consisted of polarized, columnar enterocytes with appropriate cellular differentiation was developed.