Ribonuclease 5 facilitates corneal endothelial wound healing via activation of PI3-kinase/Akt pathway

Abstract

To maintain corneal transparency, corneal endothelial cells (CECs) exert a pump function against aqueous inflow. However, human CECs are arrested in the G1-phase and non-proliferative in vivo. Thus, treatment of corneal endothelial decompensation is limited to corneal transplantation, and grafts are vulnerable to immune rejection. Here, we show that ribonuclease (RNase) 5 is more highly expressed in normal human CECs compared to decompensated tissues. Furthermore, RNase 5 up-regulated survival of CECs and accelerated corneal endothelial wound healing in an in vitro wound of human CECs and an in vivo cryo-damaged rabbit model. RNase 5 treatment rapidly induced accumulation of cytoplasmic RNase 5 into the nucleus, and activated PI3-kinase/Akt pathway in human CECs. Moreover, inhibition of nuclear translocation of RNase 5 using neomycin reversed RNase 5-induced Akt activation. As a potential strategy for proliferation enhancement, RNase 5 increased the population of 5-bromo-2′-deoxyuridine (BrdU)-incorporated proliferating CECs with concomitant PI3-kinase/Akt activation, especially in CECs deprived of contact-inhibition. Specifically, RNase 5 suppressed p27 and up-regulated cyclin D1, D3, and E by activating PI3-kinase/Akt in CECs to initiate cell cycle progression. Together, our data indicate that RNase 5 facilitates corneal endothelial wound healing, and identify RNase 5 as a novel target for therapeutic exploitation.

A fine-tuned β-catenin regulation during proliferation of corneal endothelial cells revealed using proteomics analysis

“…Based on the described role of β-catenin in dividing rCEnC and on the effect of growth factors in eliciting in vitro CEnC proliferation 19 , we sought to understand whether specific growth factors would act via β-catenin activation. β-catenin was shown to be involved in orchestrating the downstream activity of FGF in various cell types 54,80 , and, as previously introduced, bFGF stimulates CEnC proliferation through PI3K/Akt activation 4,[19][20][21] , while TGF-β 19,22 inhibits cell proliferation elicited by bFGF 54 . Here we investigated how the pro-and antiproliferative activities of these two specific growth factors might crosstalk through β-catenin signalling.…”

“…Among them, basic fibroblast growth factor (bFGF) 14 – 16 , insulin-like growth factor (IGF) 16 and hepatocyte growth factor (HGF) 16 , all present in the aqueous humor, stimulate CEnC proliferation, while transforming growth factor beta (TGF-β), which is also found in the aqueous humor, induces CEnC mitotic block 17 , 18 . Intracellular pathways, activated by these growth factors, are shown not to act in parallel but rather to build a network of cross-regulation: bFGF promotes cellular proliferation in CEnC through PI3K/Akt 4 , 19 – 21 , while its activity is counteracted by the presence of TGF-β 19 , 22 . Nevertheless, in CEnC, the complexity of pathway regulation is not limited to the cross-talk between them but also implies the alternative functions, which the same pathway can overtake in different cellular conditions.…”

Angiogenin and Copper Crossing in Wound Healing

“…The corneal endothelial cells (CECs) form the innermost monolayer of the cornea and need to be physiologically protected against injuries [ 62 ]. A scratch wound assay carried out on CECs shows that ANG promotes cell migration and wound closure by the activation of the phosphatidylinositol 3-kinase (PI3-k) signaling pathway [ 63 ]. In the same study, the healing effect is also observed in an in vivo test.…”

Endothelial Heterogeneity in Development and Wound Healing

“…EVPs have been identified to reside in vasculature and can give rise to mature endothelial cells, forming a vascular network independent of angiogenesis in ischemic situations of skin would healing [ 7 , 81 ]. Increased angiogenesis and neovascularisation has also been observed in skin wound healing using human EPC as a therapy, selectively blocking αVβ3 integrins, endothelial extracellular vesicles, antioxidant administration such as bee venom and also the activation of the PI3-kinase/Akt pathway [ 82 , 83 , 84 , 85 , 86 , 87 , 88 ]. As a further demonstration of endothelial cell plasticity, mouse studies of myocardial infarction have shown that endothelial cells can engage in localised clonal expansion in response to injury, allowing for a rapid expansion of the existing vessel architecture [ 89 ].…”