Mass spectrometry imaging of lipids in a gut epithelial cell model

Scope: The Caco2/HT29-MTX co-culture system is widely used as a cell model of the intestinal epithelium. Although the gut epithelium plays an important role in the uptake of free fatty acids and the resynthesis of triglycerides, the lipid distribution profile of the two-dimensional co-culture system is not well understood. Desorption electrospray ionisation (DESI) mass spectrometry (MS) imaging has been widely used to study the main classes of lipid molecules on different tissues. This has been used to map the lipid distribution in the Caco2-HT29-MTX co-culture system. Methods and results: Caco2 and HT29-MTX cells were seeded on coverslips either individually or as co-cultures at different ratios. Cells were cultured for 21 days before MS imaging using a DESI source in both positive and negative ionisation modes, with the identity of the selected lipid confirmed using tandem MS. Although many lipids were common to both cell lines, there were distinctive patterns in the lipidomes. Thus, the lipidome of Caco2 cells was more heterogeneous and richer in cholesterol esters and certain triglycerides while HT29-MTX cells have a distinctive lipidome including phosphatidylethanolamines and odd chain phosphatidylcholines and C17 fatty acids. Conclusion: DESI-MS imaging has shown that Caco2 and HT29-MTX cells have distinctive lipidomes that are still evident when the cells are co-cultured. It has the potential to both allow further validation of these widely used cell models and provide insights into how dietary components may modify lipid metabolism in the future.