Cultured HCECs have been suggested to be useful for in vivo transplantation in corneal endothelial diseases
9 ; thus, it is important in regenerative medicine to develop suitable HCEC culture media.
10 The culture medium regulates cell phenotypes, including survival, differentiation, transdifferentiation, migration, and proliferation.
10 In this study, we investigated the differences in cellular phenotype in response to culture in different types of media. We found that the shapes of HCECs differed depending on the medium used. Media A and D caused the HCECs to become elongated and fibroblast-like compared with the other media types used. Conversely, HCECs cultured in media E and N reverted to a polygonal shape, similar to cells in vivo. Cell shape is related to various cell functions, such as the communication with other cells, regulation of cell movement,
17 and collagen I expression.
21 Polygonal cells can fit together and cover surfaces with an apparent tendency to minimize surface-free energy.
22 It has been reported that more elongated cells express higher levels of collagen type I than less stretched cells, even when the cell coverage area is the same.
21 Nevertheless, COL8A2 expression was not affected by the different media, or different cell shapes observed, as COL8A2 was expressed in all four media types. It has been reported that COL8A2 is abundant in Descemet's membrane, which is a basement membrane for HCECs in vivo; COL8A2 has been described as a marker of HCECs.
23 However, Na
+-K
+ ATPase expression was higher in medium D compared with the other media types. Sodium-potassium adenosine triphosphatase is the largest protein complex in the family of P-type cation pumps, and its minimum functional unit is a heterodimer of α- and β-subunits.
24 It is expressed in the basolateral membrane of corneal endothelial cells, and is primarily responsible for the pump functions of the corneal endothelium.
25 Sodium-potassium adenosine triphosphatase is activated by phosphorylation of alpha(1)-subunit and translocation of the α1-subunit and translocation of the α1 and β1 subunits to the basolateral membrane via the extracellular-signal-regulated kinase 1/2 pathway.
26 Sodium-potassium adenosine triphosphatase and COL8A2 have been described as differentiation markers of HCECs.
23 Medium D induced Na
+-K
+ ATPase expression, whereas COL8A2 expression did not differ between the media types. These results suggest that there may be different pathways that increase Na
+-K
+ ATPase and COL8A2 expression. It has been reported that the α1 isoform of the Na+/K+ ATPase is upregulated in dedifferentiated progenitor cells.
27 Further study is necessary to investigate the mechanism of increased Na
+-K
+ ATPase and COL8A2 expression.