Lif-jak1-stat3 signaling delays contact inhibition of human corneal endothelial cells

Abstract

Human corneal endothelial cells (HCECs) responsible for corneal transparency have limited proliferative capacity in vivo because of “contact-inhibition.” This feature has hampered the ability to engineer HCECs for transplantation.Previously we have reported an in vitro model of HCECs in which contact inhibition was re-established at Day 21, eventhough cell junction and cell matrix interaction were not perturbed during isolation. Herein, we observe that such HCECmonolayers continue to expand and retain a normal phenotype for 2 more weeks if cultured in a leukemia inhibitoryfactor (LIF)-containing serum-free medium. Such expansion is accompanied initially by upregulation of Cyclin E2colocalized with nuclear translocation of phosphorylated retinoblastoma tumor suppressor (p-Rb) at Day 21 followed bya delay in contact inhibition through activation of LIF-Janus kinase1 (JAK1)-signal transducer and activator oftranscription 3 (STAT3) signaling at Day 35. The LIF-JAK1-STAT3 signaling is coupled with upregulation of E2F2colocalized with nuclear p-Rb and with concomitant downregulation of p16INK4a, of which upregulation is linked tosenescence. Hence, activation of LIF-JAK1-STAT3 signaling to delay contact inhibition can be used as another strategyto facilitate engineering of HCEC grafts to solve the unmet global shortage of corneal grafts.