196 EPITHELIAL–MESENCHYMAL TRANSITION IN EQUINE AMNIOTIC PROGENITOR CELLS INDUCES CHANGES OF THE CELL GLYCAN PROFILE

Abstract

Epithelial to mesenchymal transition (EMT) is the process by which epithelial cells dramatically alter their shape and motile behaviour as they differentiate into mesenchymal cells. The EMT and the reverse process, termed mesenchymal–epithelial transition, play central roles in embryogenesis. Gastrulation and neural crest formation are processes governed by EMT in amniotes. It is noteworthy that in placental mammals, the epithelial layer of amnion originates from the trophectoderm and it is continuous with the epiblast. On this basis, it is reasonable to speculate that some amniotic epithelial cells may escape the specification that accompanies gastrulation, and may retain some of the characteristics of epiblastic cells, such as pluripotency, behaving as stem cells that are able to preserve intrinsically the ability to transdifferentiate. Because it seems that malignant cells use the same mechanisms during the formation of tumours in vivo, the amniotic epithelial cells (AEC) could represent a good model to study in vitro this phenomenon that we observed to occur spontaneously in our culture conditions. The aim of this study was to characterise the glycoprotein pattern expressed in fresh or cryopreserved equine AEC, mesenchymal (AMC), and transdifferentiated cells by means of lectin histochemistry. AEC and AMC were cultured until passage (P) 3, while transdifferentiated cells at P1(EMT1) and P2 (EMT2). All cell lines were frozen for 1 month at –196°C in liquid nitrogen. The glycoanalysis was performed with a panel of twelve lectins to detect the glycans terminating with sialic acids (MAL II, SNA, PNA after sialidase digestion (K-s), K-s-DBA), galactose (PNA, RCA₁₂₀, GSA I-B₄,), N-acetylgalactosamine (DBA, HPA, SBA), N-acetylglucosamine (GSA II), fucose (UEA I, LTA), or with internal mannose (Con A). After freezing: 1) AEC exhibited decrease of binding sites for DBA, SBA, HPA, GSA II, and disappearance of GSA I-B₄ and UEA I binders; 2) AMC displayed increase of SBA reactivity, decrease of K-s-PNA, HPA, GSA II staining, and absence of GSA I-B₄ affinity; 3) EMT1 cells showed the appearance of K-s-DBA staining, the increase of K-s-PNA, RCA₁₂₀, SBA, GSA I-B₄, and UEA I reactivity, the decrease of MAL II, SNA, HPA, GSA II binders, and the disappearance of DBA and LTA binding sites; 4) EMT2 cells revealed the increase of K-s-PNA, GSA I-B₄, UEA I affinity, the decrease of MAL II, SNA, RCA₁₂₀, HPA, GSA II binders, and the lack of DBA, SBA, and LTA reactivity. In conclusion, this study demonstrates that the EMT induces changes in cell surface glycan profile of equine amniotic progenitor cells, and for the first time revealed that freezing modifies the lectin binding pattern of these cells. The observed glycan pattern modification may represent one aspect of the spontaneous complex process of EMT.