Epithelial-Mesenchymal Transition and Senescence in the Retinal Pigment Epithelium of NFE2L2/PGC-1α Double Knock-Out Mice

Abstract

Age-related macular degeneration (AMD) is the most prevalent form of irreversible blindness worldwide in the elderly population. In our previous studies, we found that deficiencies in the nuclear factor, erythroid 2 like 2 (NFE2L2) and peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α) genes caused AMD-like pathological phenotypes in mice. In the present work, we show hijacked epithelial-mesenchymal transition (EMT) due to the common loss of PGC-1α and NFE2L2 (double knock-out, dKO) genes in aged animals. The implanted area was assessed by histology, immunohistochemistry and transmission electron microscopy. Confocal microscopy revealed altered regions in the filamentous actin ring. This contrasted with hexagonal RPE morphology in wild-type mice. The ultrastructural RPE features here illustrated loss of apical microvilli, alteration of cell-cell contact, loss of basal in-folding with deposits on Bruch’s membrane, and excessive lipofuscin deposition in dKO samples. We also found the expression of epithelial-mesenchymal transition transcription factors, such as Snail, Slug, collagen 1, vimentin and OB-cadherin, to be significantly different in dKO RPEs. An increased immunoreactivity of senescence markers p16, DEC1 and HMGB1 was also noted. These findings suggest that EMT and senescence pathways may intersect in the retinas of dKO mice. Both processes can be activated by damage to the RPE, which may be caused by increased oxidative stress resulting from the absence of NFE2L2 and PGC-1α genes, important for antioxidant defense. This dKO model may provide useful tools for studying AMD pathogenesis and evaluating novel therapies for this disease.

Potential of Telomerase in Age-Related Macular Degeneration—Involvement of Senescence, DNA Damage Response and Autophagy and a Key Role of PGC-1α

“…Autophagy can directly regulate EMT by selective degradation of EMT molecular triggers [128]. We partly confirmed Saint-Geniez's conclusions, showing that cells obtained from PGC-1α/NFE2L2 dKO aged mice underwent EMT [129]. In that study, we also observed an increased immunoreactivity of senescence markers p16, DEC1 (deleted in esophageal cancer 1), and HMGB1 (high mobility group box protein 1).…”

Epithelial–mesenchymal transition‐related serum markers ET‐1, IL‐8 and TGF‐β2 are elevated in a Finnish wet age‐related macular degeneration cohort

“…The possibility of EMT occurring in the RPE during the advanced stages of AMD is well established, and it has also been observed in AMD-simulating cell and animal models (Ishikawa et al 2016;Chen et al 2020;Shu et al 2020;Zhou et al 2020;Wang et al 2021). In a recent article of ours, we showed an AMDresembling mouse model exhibiting typical EMT-style morphological changes in the RPE, as well as alterations in the cellular levels of EMTrelated transcription factors and cellular-level markers such as Snail, vimentin and OB-cadherin (Blasiak et al 2021). Studies specifically focusing on EMT-related markers in the systemic circulation of AMD patients have not been published previously.…”

Immune Cells in Subretinal Wound Healing and Fibrosis

“…Multiple pathways (e.g., TGF-β, Wnt, miRNA, oxidative stress/Nrf2, etc.) are known to play a role in EMT by RPE and this topic has been reviewed extensively recently by others (Yang et al, 2015;Shu et al, 2020;Zhou et al, 2020;Blasiak et al, 2021). However, the molecular cues that guide RPE cells transdifferentiating into macrophage-or fibroblast-like phenotypes remain to be fully elucidated.…”