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Repressed miR-34a Expression Dictates the Cell Fate to Corneal Endothelium Failure
Junji Hamuro1, Kazuko Asada1, Morio Ueno1
1Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Purpose:
To reveal the mechanism triggering the functional disparity between degenerated and non-degenerated corneal endothelium cells in the water efflux from corneal stroma to the anterior chamber.
Methods:
The varied levels of the microRNA (miR)-34, miR-378, and miR-146 family in human corneal endothelium and cultured cells thereof were investigated using 3D-Gene Human miRNA Oligo Chips. Concomitantly, CD44, p53, c-Myc, matrix metalloprotease (MMP)-2 expression, and Ras homolog gene family member A (Rho A) activity was correlated to the expression intensities of these microRNAs, partly complemented with their altered expression levels with the transfection of the corresponding mimics and inhibitors. The levels of miRs were further associated with intracellular pH (pHi) and mitochondrial energy homeostasis.
Results:
P53-inducible miR-34a/b repressed CD44 expression, and CD44 was repressed with the elevated c-Myc. The repressed miR-34a activated the CD44 downstream factors Rho A and MMP-2. MiR-34a mimics downregulated pHi, inducing the skewing of mitochondrial respiration to oxidative phosphorylation. The oxidative stress (H2O2) induced on human corneal endothelial cells, which repressed miR-34a/b expression, may account for the impaired signaling cascade to mitochondrial metabolic homeostasis necessary for an efficient water efflux from the corneal stroma.
Conclusions:
The upregulated expression of CD44, through repressed miR-34a/b by reactive oxygen species and elevated c-Myc by oxidative stress, may impair mitochondrial metabolic homeostasis, leading to human corneal endothelial failure.
Insights
Oxidative stress impairs corneal endothelium function by repressing miR-34a/b, leading to CD44 upregulation and mitochondrial dysfunction, ultimately causing corneal endothelial failure.
Area of Science:
- Ophthalmology
- Molecular Biology
- Cell Biology
Background:
- Corneal endothelium maintains transparency through active water efflux.
- Functional disparity between degenerated and non-degenerated corneal endothelium impacts water transport.
- MicroRNAs (miRs) play crucial roles in cellular regulation.
Purpose of the Study:
- To elucidate the mechanism behind functional differences in corneal endothelium water efflux.
- To investigate the role of specific microRNAs (miR-34, miR-378, miR-146 families) in corneal endothelium function.
- To correlate microRNA levels with key cellular signaling pathways and mitochondrial function.
Main Methods:
- Quantification of microRNA levels in human corneal endothelium and cultured cells using 3D-Gene Human miRNA Oligo Chips.
- Correlation of microRNA expression with CD44, p53, c-Myc, MMP-2, and Rho A activity.
- Experimental manipulation of microRNA levels using mimics and inhibitors.
- Assessment of intracellular pH (pHi) and mitochondrial energy homeostasis.
Main Results:
- p53-inducible miR-34a/b repressed CD44 expression; elevated c-Myc also repressed CD44.
- Repressed miR-34a activated downstream factors Rho A and MMP-2.
- miR-34a mimics decreased pHi and shifted mitochondrial respiration towards oxidative phosphorylation.
- Oxidative stress (H2O2) repressed miR-34a/b, disrupting mitochondrial homeostasis and impairing water efflux signaling.
Conclusions:
- Upregulated CD44, driven by miR-34a/b repression and elevated c-Myc due to oxidative stress, impairs mitochondrial metabolic homeostasis.
- This impairment leads to human corneal endothelial failure.
- Reactive oxygen species are implicated in the pathogenesis of corneal endothelial dysfunction.
