Cryopreservation and long-term culture of transformed murine corneal endothelial cells

Purpose To characterize the morphology and gene expression of transformed murine corneal endothelial cells. Methods Primary immortomouse corneal endothelial cells were continuously cultured before and after cryopreservation. Morphologic assessment, real time-reverse transcriptase polymerase chain reaction ((RT)-PCR) and immunofluorescence studies were performed using newly cultured cells, cells that had been continuously in culture for 1 year, and cryopreserved cells, to assess for structural and functional integrity. The expression of corneal endothelial markers zonula occludens-1 (ZO1), NaK-ATPase and collagen VIII (α2) (COL8A2), and myofibroblast markers Desmin, alpha smooth muscle actin (αSMA), and Vimentin was assessed and compared by both RT-PCR and immunofluorescence. Results Cells in culture formed a monolayer, and exhibited a polygonal shape after reaching confluence. Cells retained this morphology during the full observation time of 12 months and when reused after cryopreservation. Immunofluorescence experiments exhibited positive staining for NaK-ATPase and COL8A2 with low variability between the three groups. In RT-PCR experiments, ZO1, COL8A2 and Desmin were increased in fresh and thawed cells, αSMA was decreased, and NaK-ATPase and Vimentin remained unchanged, compared to 12-month-old cells. Comparing fresh and thawed cells, COL8A2 was increased in thawed cells, while Desmin was increased in fresh cells. Conclusions Using the immortomouse strain, murine corneal endothelial cells can be propagated over a long time period and be used after cryopreservation. Cells retain the expression of NaK-ATPase, but show some decline in ZO1 and COL8A2 over time and after cryopreservation. The expression of myofibroblast markers suggests an endothelial-to-mesenchymal transformation process in culture.