Spontaneous Mesenchymal to Epithelial Like Tissue Transition (MET) in a Long Term Human Skin Culture

In an attempt to isolate multipotent stem cells from foreskin in a long-term culture, we encountered an interesting phenomenon which was the conversion of the fibroblast dominant condition to epithelial-like tissue formation. However, the basic mechanism(s) which may be involved in this conversion is not clear. This study was designed to evaluate the cells protein secretion activity and examine the role of oxidant/antioxidant capacity in this mesenchymal to epithelial cells transition (MET)-like phenomenon. The explanted tissues were obtained by spread out of the small sized foreskin derived tissue onto the cell culture dishes upona 40 –day incubation period in DMEM. After this period, the supernatant was collected and the amounts of glucose, total proteins, antioxidant capacity and protein profiles were determined and compared to the baseline medium. Also, routine hematoxylin and eosin staining was performed. Fibroblasts and uncharacterized fibers emerged from beneath of the specimen during the first week, and gradually overgrew within the first month. Surprisingly, these cells began to disappear around day 30 while epithelial-like cells turned out to be the major cells in cell culture dishes. Ultimately on day 40, the epithelial-like cells appeared. Total protein concentration was 1.44 mg/dl in the old medium versus 0.97 mg/dl in the baseline medium. The concentrations of glucose were 1.6 and 119.2 mg/dl for the old and the baseline medium, respectively. The antioxidant activity of the old medium was 176.29 μM, in comparison with the baseline medium 96.63 μM. There were differences in protein patterns between the two media on SDS-PAGE. The density of some proteins with molecular weight of 8-89 kDa was higher in the old medium corresponding to 40-day culture. The generated data showed that MET can take place in vitro probably through secretion of some small to intermediated sized proteins in a redox favored microenvironment. This can be considered as a good model for in vitro study of MET in metastatic tumors.