Cell cycle CDK1 expression profile of Human Corneal Endothelial Cells (HCECs)

Abstract

Purpose: : To investigate cell cycle CDK1 gene expression profile and proliferation of HCECs in vivo and in vitro.

Methods: : Small strips of human corneal Descemet’s membrane with the attached endothelium was carefully dissected. One part harvested as in vivo non-cultured cells and the other cultured on Descemet's membrane or as monolayers. Cultured and non-cultured HCECs were analyzed by qRT-PCR for CDK1 and selected other related cell cycle genes. All cultures were incubated for 3 weeks at 37º C with 5% CO2 in a humidified atmosphere, and medium was changed every 2-3 days.

Results: : Our study shows that non-cultured HCECs are resting cell, while endothelium cultured on Descemet’s membrane or as monolayers are proliferating cells by Ki-67 gene expression analysis. Non-cultured endothelium does not express CDK1, nor its associated CCNA2 (cyclin A) and CCNB1 (cyclin B)genes. In contrast, when cells were cultured on Descemet’s membrane or as monolayers, expression of these genes was detected. Some related G1/S transition genes, such as CCNE1 (cyclin E), are expressed in non-cultured as well as in cultured HCECs.

Conclusions: : In vitro proliferative potential and in vivo non-proliferative status of HCECs have been demonstrated in many studies and results together strongly suggest that HCECs are arrested in G1-phase of the cell cycle (Joyce, 2011). CDK1 which is activated by A, B and E type cyclins is involved in all phases of cell cycle and is negatively targeted by CDK inhibitors (CKIs) such as p27 and p21 (Bashir, 2005). Our data make obvious that CDK1 and two of its associated cyclin genes, CCNA2 (cyclin A) and CCNB1 (cyclin B) are not expressed at all in in vivo HCECs. We might conclude that the lack of CDK1 expression in absence of mitogenic stimulation plays an essential role in the HCECs cell cycle arrest in vivo and its expression could affect the proliferative status of HCECs.

Keywords: cornea: endothelium • cell survival • proliferation