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Volkova YL, Pickel C, Jucht AE, Wenger RH, Scholz CC. The Asparagine Hydroxylase FIH: A Unique Oxygen Sensor. Antioxid Redox Signal 2022; 37:913-935. [PMID: 35166119 DOI: 10.1089/ars.2022.0003] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Significance: Limited oxygen availability (hypoxia) commonly occurs in a range of physiological and pathophysiological conditions, including embryonic development, physical exercise, inflammation, and ischemia. It is thus vital for cells and tissues to monitor their local oxygen availability to be able to adjust in case the oxygen supply is decreased. The cellular oxygen sensor factor inhibiting hypoxia-inducible factor (FIH) is the only known asparagine hydroxylase with hypoxia sensitivity. FIH uniquely combines oxygen and peroxide sensitivity, serving as an oxygen and oxidant sensor. Recent Advances: FIH was first discovered in the hypoxia-inducible factor (HIF) pathway as a modulator of HIF transactivation activity. Several other FIH substrates have now been identified outside the HIF pathway. Moreover, FIH enzymatic activity is highly promiscuous and not limited to asparagine hydroxylation. This includes the FIH-mediated catalysis of an oxygen-dependent stable (likely covalent) bond formation between FIH and selected substrate proteins (called oxomers [oxygen-dependent stable protein oligomers]). Critical Issues: The (patho-)physiological function of FIH is only beginning to be understood and appears to be complex. Selective pharmacologic inhibition of FIH over other oxygen sensors is possible, opening new avenues for therapeutic targeting of hypoxia-associated diseases, increasing the interest in its (patho-)physiological relevance. Future Directions: The contribution of FIH enzymatic activity to disease development and progression should be analyzed in more detail, including the assessment of underlying molecular mechanisms and relevant FIH substrate proteins. Also, the molecular mechanism(s) involved in the physiological functions of FIH remain(s) to be determined. Furthermore, the therapeutic potential of recently developed FIH-selective pharmacologic inhibitors will need detailed assessment. Antioxid. Redox Signal. 37, 913-935.
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Affiliation(s)
- Yulia L Volkova
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Christina Pickel
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | | | - Roland H Wenger
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Carsten C Scholz
- Institute of Physiology, University of Zurich, Zurich, Switzerland
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Ruiz M, González S, Bonnet C, Deng SX. Extracellular miR-6723-5p could serve as a biomarker of limbal epithelial stem/progenitor cell population. Biomark Res 2022; 10:36. [PMID: 35642012 PMCID: PMC9153202 DOI: 10.1186/s40364-022-00384-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 05/16/2022] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Dysfunction or loss of limbal stem cells can result in limbal stem cell deficiency (LSCD), a disease that cause corneal opacity, pain, and loss of vision. Cultivated limbal epithelial transplantation (CLET) can be used to restore stem cell niche homeostasis and replenish the progenitor pool. Transplantation has been reported with high success rate, but there is an unmet need of prognostic markers that correlate with clinical outcomes. To date, the progenitor content in the graft is the only parameter that has been retrospectively linked to success. METHODS In this study, we investigate extracellular micro RNAs (miRNAs) associated with stem/progenitor cells in cultivated limbal epithelial cells (cLECs). Using micro RNA sequencing and linear regression modelling, we identify a miRNA signature in cultures containing high proportion of stem/progenitor cells. We then develop a robust RNA extraction workflow from culture media to confirm a positive miRNA correlation with stem/progenitor cell proportion. RESULTS miR-6723-5p is associated with cultures containing high proportion of stem/progenitor cells, and is detected in the basal layer of corneal epithelium. CONCLUSIONS These results indicate that miR-6723-5p could potentially serve as a stem/progenitor cell marker in cLECs.
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Affiliation(s)
- M. Ruiz
- Cornea Division, Stein Eye Institute, University of California, 100 Stein Plaza, Los Angeles, CA 90095 USA
| | - S. González
- Cornea Division, Stein Eye Institute, University of California, 100 Stein Plaza, Los Angeles, CA 90095 USA
| | - C. Bonnet
- Cornea Division, Stein Eye Institute, University of California, 100 Stein Plaza, Los Angeles, CA 90095 USA
- Cornea Department, Paris University, Cochin Hospital, AP-HP, F-75014 Paris, France
| | - S. X. Deng
- Cornea Division, Stein Eye Institute, University of California, 100 Stein Plaza, Los Angeles, CA 90095 USA
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Latta L, Ludwig N, Krammes L, Stachon T, Fries FN, Mukwaya A, Szentmáry N, Seitz B, Wowra B, Kahraman M, Keller A, Meese E, Lagali N, Käsmann-Kellner B. Abnormal neovascular and proliferative conjunctival phenotype in limbal stem cell deficiency is associated with altered microRNA and gene expression modulated by PAX6 mutational status in congenital aniridia. Ocul Surf 2020; 19:115-127. [PMID: 32422284 DOI: 10.1016/j.jtos.2020.04.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 03/09/2020] [Accepted: 04/26/2020] [Indexed: 12/18/2022]
Abstract
PURPOSE To evaluate conjunctival cell microRNA (miRNAs) and mRNA expression in relation to observed phenotype of progressive limbal stem cell deficiency in a cohort of subjects with congenital aniridia with known genetic status. METHODS Using impression cytology, bulbar conjunctival cells were sampled from 20 subjects with congenital aniridia and 20 age and sex-matched healthy control subjects. RNA was extracted and miRNA and mRNA analyses were performed using microarrays. Results were related to severity of keratopathy and genetic cause of aniridia. RESULTS Of 2549 miRNAs, 21 were differentially expressed in aniridia relative to controls (fold change ≤ -1.5 or ≥ +1.5). Among these miR-204-5p, an inhibitor of corneal neovascularization, was downregulated 26.8-fold in severely vascularized corneas. At the mRNA level, 539 transcripts were differentially expressed (fold change ≤ -2 or ≥ +2), among these FOSB and FOS were upregulated 17.5 and 9.7-fold respectively, and JUN by 2.9-fold, all being components of the AP-1 transcription factor complex. Pathway analysis revealed enrichment of PI3K-Akt, MAPK, and Ras signaling pathways in aniridia. For several miRNAs and transcripts regulating retinoic acid metabolism, expression levels correlated with keratopathy severity and genetic status. CONCLUSION Strong dysregulation of key factors at the miRNA and mRNA level suggests that the conjunctiva in aniridia is abnormally maintained in a pro-angiogenic and proliferative state, and these changes are expressed in a PAX6 mutation-dependent manner. Additionally, retinoic acid metabolism is disrupted in severe, but not mild forms of the limbal stem cell deficiency in aniridia.
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Affiliation(s)
- L Latta
- Department of Ophthalmology, Saarland University Medical Center, Homburg, Saar, Germany.
| | - N Ludwig
- Department of Human Genetics, Saarland University, Homburg, Saar, Germany; Center for Human and Molecular Biology, Saarland University, Homburg, Saar, Germany
| | - L Krammes
- Department of Human Genetics, Saarland University, Homburg, Saar, Germany
| | - T Stachon
- Department of Ophthalmology, Saarland University Medical Center, Homburg, Saar, Germany
| | - F N Fries
- Department of Ophthalmology, Saarland University Medical Center, Homburg, Saar, Germany
| | - A Mukwaya
- Department of Biomedical and Clinical Sciences, Faculty of Medicine, Linköping University, Linköping, Sweden
| | - N Szentmáry
- Department of Ophthalmology, Saarland University Medical Center, Homburg, Saar, Germany; Department of Ophthalmology, Semmelweis University, Budapest, Hungary
| | - B Seitz
- Department of Ophthalmology, Saarland University Medical Center, Homburg, Saar, Germany
| | - B Wowra
- Chair and Clinical Department of Ophthalmology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia in Katowice, Poland
| | - M Kahraman
- Chair for Clinical Bioinformatics, Saarland University, Saarbruecken, Germany
| | - A Keller
- Chair for Clinical Bioinformatics, Saarland University, Saarbruecken, Germany
| | - E Meese
- Department of Human Genetics, Saarland University, Homburg, Saar, Germany
| | - N Lagali
- Department of Biomedical and Clinical Sciences, Faculty of Medicine, Linköping University, Linköping, Sweden; Department of Ophthalmology, Sørlandet Hospital Arendal, Arendal, Norway.
| | - B Käsmann-Kellner
- Department of Ophthalmology, Saarland University Medical Center, Homburg, Saar, Germany
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Lorenzo Y, Haug Berg K, Ringvold A, Petrovski G, Moe MC, Collins A, Nicolaissen B. Levels of oxidative DNA damage are low in ex vivo engineered human limbal epithelial tissue. Acta Ophthalmol 2018; 96:834-840. [PMID: 30239138 PMCID: PMC6667899 DOI: 10.1111/aos.13811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 04/05/2018] [Indexed: 11/21/2022]
Abstract
PURPOSE To examine levels of oxidative DNA base damage and expression of selected genes and proteins related to DNA damage repair in human limbal epithelium engineered ex vivo. METHODS Cells were expanded from limbal tissue on cell culture-treated inserts in medium containing fetal bovine serum, recombinant growth factors, hormones and cholera toxin (COM) and in medium with human serum as the single growth-promoting additive (HS). Cells were analysed after two, three and four weeks in culture for DNA strand breaks and oxidized purine bases (Comet assay using the enzyme formamidopyrimidine DNA glycosylase, Fpg) and for expression of DNA repair enzymes APE1, OGG1 and Polβ by in situ hybridization (ISH) and by immunohistochemistry (IHC). RESULTS Levels of strand breaks were substantial while levels of net Fpg-sensitive sites (8-oxoguanine and ring-opened FaPy bases) were relatively low in cells engineered in COM and in HS. Both types of medium were found to support expression of base excision repair (BER) enzymes APE1, OGG1 and Polβ at the gene level. At the protein level, expression of APE1 and OGG1 was noticeable in both conditions while expression of Polβ was low. CONCLUSION Our findings indicate low levels of oxidative stress and/or efficient DNA purine base damage repair in human limbal epithelium engineered in a medium with human serum as the single growth-promoting additive as well as in traditional medium with xenobiotics.
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Affiliation(s)
- Yolanda Lorenzo
- Center for Eye ResearchDepartment of OphthalmologyOslo University HospitalOsloNorway
| | - Kristiane Haug Berg
- Center for Eye ResearchDepartment of OphthalmologyOslo University HospitalOsloNorway
| | - Amund Ringvold
- Center for Eye ResearchDepartment of OphthalmologyOslo University HospitalOsloNorway
- Faculty of MedicineUniversity of OsloOsloNorway
| | - Goran Petrovski
- Center for Eye ResearchDepartment of OphthalmologyOslo University HospitalOsloNorway
- Faculty of MedicineUniversity of OsloOsloNorway
| | - Morten C. Moe
- Center for Eye ResearchDepartment of OphthalmologyOslo University HospitalOsloNorway
- Faculty of MedicineUniversity of OsloOsloNorway
| | - Andrew Collins
- Department of NutritionInstitute for Basic Medical SciencesUniversity of OsloOsloNorway
| | - Bjørn Nicolaissen
- Center for Eye ResearchDepartment of OphthalmologyOslo University HospitalOsloNorway
- Faculty of MedicineUniversity of OsloOsloNorway
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Emerging Therapeutic Strategies for Limbal Stem Cell Deficiency. J Ophthalmol 2018; 2018:7894647. [PMID: 30050691 PMCID: PMC6040301 DOI: 10.1155/2018/7894647] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Accepted: 04/19/2018] [Indexed: 12/12/2022] Open
Abstract
Identification and characterization of the limbal epithelial stem cells (LESCs) has proven to be a major accomplishment in anterior ocular surface biology. These cells have been shown to be a subpopulation of limbal epithelial basal cells, which serve as the progenitor population of the corneal epithelium. LESCs have been demonstrated to play an important role in maintaining corneal epithelium homeostasis. Many ocular surface diseases, including intrinsic (e.g., Sjogren's syndrome) or extrinsic (e.g., alkali or thermal burns) insults, which impair LESCs, can lead to limbal stem cell deficiency (LSCD). LSCD is characterized by an overgrowth of conjunctival-derived epithelial cells, corneal neovascularization, and chronic inflammation, eventually leading to blindness. Treatment of LSCD has been challenging, especially in bilateral total LSCD. Recently, advances in LESC research have led to novel therapeutic approaches for treating LSCD, such as transplantation of the cultured limbal epithelium. These novel therapeutic approaches have demonstrated efficacy for ocular surface reconstruction and restoration of vision in patients with LSCD. However, they all have their own limitations. Here, we describe the current status of LSCD treatment and discuss the advantages and disadvantages of the available therapeutic modalities.
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