Browsing by Subject "cornea"
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Item A Method for Real-Time Assessment of Mitochondrial Respiration Using Murine Corneal Biopsy(Association for Research in Vision and Ophthalmology, 2023-08-29) Liang, Wentao; Huang, Li; Yuan, Tian; Cheng, Rui; Takahashi, Yusuke; Moiseyev, Gennadiy P.; Karamichos, Dimitrios; Ma, Jian-XingPURPOSE: To develop and optimize a method to monitor real-time mitochondrial function by measuring the oxygen consumption rate (OCR) in murine corneal biopsy punches with a Seahorse extracellular flux analyzer. METHODS: Murine corneal biopsies were obtained using a biopsy punch immediately after euthanasia. The corneal metabolic profile was assessed using a Seahorse XFe96 pro analyzer, and mitochondrial respiration was analyzed with specific settings. RESULTS: Real-time adenosine triphosphate rate assay showed that mitochondrial oxidative phosphorylation is a major source of adenosine triphosphate production in ex vivo live murine corneal biopsies. Euthanasia methods (carbon dioxide asphyxiation vs. overdosing on anesthetic drugs) did not affect corneal OCR values. Mouse corneal biopsy punches in 1.5-mm diameter generated higher and more reproducible OCR values than those in 1.0-mm diameter. The biopsy punches from the central and off-central cornea did not show significant differences in OCR values. There was no difference in OCR reading by the tissue orientations (the epithelium side up vs. the endothelium side up). No significant differences were found in corneal OCR levels between sexes, strains (C57BL/6J vs. BALB/cJ), or ages (4, 8, and 32 weeks). Using this method, we showed that the wound healing process in the mouse cornea affected mitochondrial activity. CONCLUSIONS: The present study validated a new strategy to measure real-time mitochondrial function in fresh mouse corneal tissues. This procedure should be helpful for studies of the ex vivo live corneal metabolism in response to genetic manipulations, disease conditions, or pharmacological treatments in mouse models.Item Arginine Supplementation Promotes Extracellular Matrix and Metabolic Changes in Keratoconus(MDPI, 2021-08-13) McKay, Tina B.; Priyadarsini, Shrestha; Rowsey, Tyler; Karamichos, DimitriosKeratoconus (KC) is a common corneal ectatic disease that affects 1:500-1:2000 people worldwide and is associated with a progressive thinning of the corneal stroma that may lead to severe astigmatism and visual deficits. Riboflavin-mediated collagen crosslinking currently remains the only approved treatment to halt progressive corneal thinning associated with KC by improving the biomechanical properties of the stroma. Treatments designed to increase collagen deposition by resident corneal stromal keratocytes remain elusive. In this study, we evaluated the effects of arginine supplementation on steady-state levels of arginine and arginine-related metabolites (e.g., ornithine, proline, hydroxyproline, spermidine, and putrescine) and collagen protein expression by primary human corneal fibroblasts isolated from KC and non-KC (healthy) corneas and cultured in an established 3D in vitro model. We identified lower cytoplasmic arginine and spermidine levels in KC-derived constructs compared to healthy controls, which corresponded with overall higher gene expression of arginase. Arginine supplementation led to a robust increase in cytoplasmic arginine, ornithine, and spermidine levels in controls only and a significant increase in collagen type I secretion in KC-derived constructs. Further studies evaluating safety and efficacy of arginine supplementation are required to elucidate the potential therapeutic applications of modulating collagen deposition in the context of KC.Item Novel Correlation between TGF-beta1/-beta3 and Hormone Receptors in the Human Corneal Stroma(MDPI, 2023-09-09) Choi, Alexander J.; Hefley, Brenna S.; Nicholas, Sarah E.; Cunningham, Rebecca L.; Karamichos, DimitriosThis study investigated the interplay between transforming growth factor beta (TGF-beta1/T1 and TGF-beta3/T3), and sex hormone receptors using our 3D in vitro cornea stroma model. Primary human corneal fibroblasts (HCFs) from healthy donors were plated in transwells at 10(6) cells/well and cultured for four weeks. HCFs were supplemented with stable vitamin C (VitC) and stimulated with T1 or T3. 3D construct proteins were analyzed for the androgen receptor (AR), progesterone receptor (PR), estrogen receptor alpha (ERalpha) and beta (ERbeta), luteinizing hormone receptor (LHR), follicle-stimulating hormone receptor (FSHR), gonadotropin-releasing hormone receptor (GnRHR), KiSS1-derived peptide receptor (KiSS1R/GPR54), and follicle-stimulating hormone subunit beta (FSH-B). In female constructs, T1 significantly upregulated AR, PR, ERalpha, FSHR, GnRHR, and KiSS1R. In male constructs, T1 significantly downregulated FSHR and FSH-B and significantly upregulated ERalpha, ERbeta, and GnRHR. T3 caused significant upregulation in expressions PR, ERalpha, ERbeta, LHR, FSHR, and GNRHR in female constructs, and significant downregulation of AR, ERalpha, and FSHR in male constructs. Semi-quantitative Western blot findings present the interplay between sex hormone receptors and TGF-beta isoforms in the corneal stroma, which is influenced by sex as a biological variable (SABV). Additional studies are warranted to fully delineate their interactions and signaling mechanisms.Item Peroxisome proliferator-activated receptor-alpha (PPARalpha) regulates wound healing and mitochondrial metabolism in the cornea(National Academy of Science, 2023-03-22) Liang, Wentao; Huang, Li; Whelchel, Amy E.; Yuan, Tian; Ma, Xiang; Cheng, Rui; Takahashi, Yusuke; Karamichos, Dimitrios; Ma, Jian-XingDiabetes can result in impaired corneal wound healing. Mitochondrial dysfunction plays an important role in diabetic complications. However, the regulation of mitochondria function in the diabetic cornea and its impacts on wound healing remain elusive. The present study aimed to explore the molecular basis for the disturbed mitochondrial metabolism and subsequent wound healing impairment in the diabetic cornea. Seahorse analysis showed that mitochondrial oxidative phosphorylation is a major source of ATP production in human corneal epithelial cells. Live corneal biopsy punches from type 1 and type 2 diabetic mouse models showed impaired mitochondrial functions, correlating with impaired corneal wound healing, compared to nondiabetic controls. To approach the molecular basis for the impaired mitochondrial function, we found that Peroxisome Proliferator-Activated Receptor-alpha (PPARalpha) expression was downregulated in diabetic human corneas. Even without diabetes, global PPARalpha knockout mice and corneal epithelium-specific PPARalpha conditional knockout mice showed disturbed mitochondrial function and delayed wound healing in the cornea, similar to that in diabetic corneas. In contrast, fenofibrate, a PPARalpha agonist, ameliorated mitochondrial dysfunction and enhanced wound healing in the corneas of diabetic mice. Similarly, corneal epithelium-specific PPARalpha transgenic overexpression improved mitochondrial function and enhanced wound healing in the cornea. Furthermore, PPARalpha agonist ameliorated the mitochondrial dysfunction in primary human corneal epithelial cells exposed to diabetic stressors, which was impeded by siRNA knockdown of PPARalpha, suggesting a PPARalpha-dependent mechanism. These findings suggest that downregulation of PPARalpha plays an important role in the impaired mitochondrial function in the corneal epithelium and delayed corneal wound healing in diabetes.Item Prospective Observational Study Evaluating Systemic Hormones and Corneal Crosslinking Effects in Keratoconus(Elsevier B.V., 2023-10-23) Van, Lyly; Bennett, Sashia; Nicholas, Sarah E.; Hjortdal, Jesper; McKay, Tina B.; Karamichos, DimitriosPURPOSE: To evaluate associations between hormone levels and corneal parameters in patients with keratoconus (KC), before and after photooxidative corneal collagen crosslinking (CXL). DESIGN: Prospective, observational cohort study. PARTICIPANTS: Twenty-eight patients with KC who were scheduled for CXL at Aarhus University Hospital in Denmark. METHODS: Androgen (dehydroepiandrosterone sulfate [DHEA-S]) and estrogen (estrone and estriol) plasma levels were measured and clinical assessments were performed before CXL and 2 to 3 months post-CXL, comparing the CXL eye with the control eye from the same participant. MAIN OUTCOME MEASURES: Associations between hormone levels and maximum corneal curvature (K(max)) and minimum central corneal thickness (CCt(min)) before and after CXL. RESULTS: Corneal collagen crosslinking was associated with a 2% reduction in K(max) values in the CXL eye, post-CXL, from baseline (median, 56.8 diopters [D]; 95% confidence interval [CI], 50.4-60.3) to the second visit (55.7 D; 95% CI, 50.4-58.8; P < 0.001). Systemic DHEA-S levels were 5 to 6 orders of magnitude higher than estriol or estrone concentrations in plasma. Importantly, estriol levels, rather than DHEA-S or estrone levels, were more closely correlated with K(max) before CXL (Spearman's r = 0.55, P = 0.01). Post-CXL K(max) and CCt(min) were not associated with DHEA-S, estrone, or estriol plasma levels at the same timepoint. CONCLUSIONS: This study provides supporting evidence based on a KC clinical population that systemic estrogen levels may influence corneal parameters (curvature and thickness) pre-CXL. Further studies evaluating the interplay between the therapeutic benefits of CXL and systemic hormone distributions are needed to determine if perturbation of the local corneal microenvironment influences endocrine function. FINANCIAL DISCLOSURES: The authors have no proprietary or commercial interest in any materials discussed in this article.Item Quercetin and Related Analogs as Therapeutics to Promote Tissue Repair(MDPI, 2023-10-28) McKay, Tina B.; Emmitte, Kyle A.; German, Carrie; Karamichos, DimitriosQuercetin is a polyphenol of the flavonoid class of secondary metabolites that is widely distributed in the plant kingdom. Quercetin has been found to exhibit potent bioactivity in the areas of wound healing, neuroprotection, and anti-aging research. Naturally found in highly glycosylated forms, aglycone quercetin has low solubility in aqueous environments, which has heavily limited its clinical applications. To improve the stability and bioavailability of quercetin, efforts have been made to chemically modify quercetin and related flavonoids so as to improve aqueous solubility while retaining bioactivity. In this review, we provide an updated overview of the biological properties of quercetin and proposed mechanisms of actions in the context of wound healing and aging. We also provide a description of recent developments in synthetic approaches to improve the solubility and stability of quercetin and related analogs for therapeutic applications. Further research in these areas is expected to enable translational applications to improve ocular wound healing and tissue repair.Item Sex Hormones, Growth Hormone, and the Cornea(MDPI, 2022-01-11) McKay, Tina B.; Priyadarsini, Shrestha; Karamichos, DimitriosThe growth and maintenance of nearly every tissue in the body is influenced by systemic hormones during embryonic development through puberty and into adulthood. Of the ~130 different hormones expressed in the human body, steroid hormones and peptide hormones are highly abundant in circulation and are known to regulate anabolic processes and wound healing in a tissue-dependent manner. Of interest, differential levels of sex hormones have been associated with ocular pathologies, including dry eye disease and keratoconus. In this review, we discuss key studies that have revealed a role for androgens and estrogens in the cornea with focus on ocular surface homeostasis, wound healing, and stromal thickness. We also review studies of human growth hormone and insulin growth factor-1 in influencing ocular growth and epithelial regeneration. While it is unclear if endogenous hormones contribute to differential corneal wound healing in common animal models, the abundance of evidence suggests that systemic hormone levels, as a function of age, should be considered as an experimental variable in studies of corneal health and disease.Item The Role of Estriol and Estrone in Keratoconic Stromal Sex Hormone Receptors(MDPI, 2022-01-14) Escandon, Paulina; Nicholas, Sarah E.; Cunningham, Rebecca L.; Murphy, David A.; Riaz, Kamran M.; Karamichos, DimitriosKeratoconus (KC) is a progressive corneal thinning disease that manifests in puberty and worsens during pregnancy. KC onset and progression are attributed to diverse factors that include: environmental, genetics, and hormonal imbalances; however, the pathobiology remains elusive. This study aims to determine the role of corneal stroma sex hormone receptors in KC and their interplay with estrone (E1) and estriol (E3) using our established 3D in vitro model. Healthy cornea stromal cells (HCFs) and KC cornea stromal cells (HKCs), both male and female, were stimulated with various concentrations of E1 and E3. Significant changes were observed between cell types, as well as between males and females in the sex hormone receptors tested; androgen receptor (AR), progesterone receptor (PR), estrogen receptor alpha (ERalpha), and estrogen receptor beta (ERbeta) using Western blot analysis. E1 and E3 stimulations in HCF females showed AR, PR, and ERbeta were significantly upregulated compared to HCF males. In contrast, ERalpha and ERbeta had significantly higher expression in HKC's females than HKC's males. Our data suggest that the human cornea is a sex-dependent, hormone-responsive tissue that is significantly influenced by E1 and E3. Therefore, it is plausible that E1, E3, and sex hormone receptors are involved in the KC pathobiology, warranting further investigation.Item The Underlying Relationship between Keratoconus and Down Syndrome(MDPI, 2022-09-24) Akoto, Theresa; Li, Jiemin J.; Estes, Amy J.; Karamichos, Dimitrios; Liu, YutaoKeratoconus (KC) is one of the most significant corneal disorders worldwide, characterized by the progressive thinning and cone-shaped protrusion of the cornea, which can lead to severe visual impairment. The prevalence of KC varies greatly by ethnic groups and geographic regions and has been observed to be higher in recent years. Although studies reveal a possible link between KC and genetics, hormonal disturbances, environmental factors, and specific comorbidities such as Down Syndrome (DS), the exact cause of KC remains unknown. The incidence of KC ranges from 0% to 71% in DS patients, implying that as the worldwide population of DS patients grows, the number of KC patients may continue to rise significantly. As a result, this review aims to shed more light on the underlying relationship between KC and DS by examining the genetics relating to the cornea, central corneal thickness (CCT), and mechanical forces on the cornea, such as vigorous eye rubbing. Furthermore, this review discusses KC diagnostic and treatment strategies that may help detect KC in DS patients, as well as the available DS mouse models that could be used in modeling KC in DS patients. In summary, this review will provide improved clinical knowledge of KC in DS patients and promote additional KC-related research in these patients to enhance their eyesight and provide suitable treatment targets.Item TOLL-LIKE RECEPTOR-4 INNITIATES AN INFLAMMATORY IMMUNE RESPONE IN ACANTHAMOEBA KERATITIS(2013-04-12) Smith, AshleyPurpose: The purpose of this study is to determine if Toll-like receptors (TLRs) on corneal epithelial cells are responsible for recognition of Acanthamoeba trophozoites. We hypothesize that TLR-4 recognizes the parasite and activates an initiate inflammatory responses. Methods: Human corneal epithelial (HCE), Chinese hamster corneal epithelial (HCORN) cells, or Human embryonic kidney (HEK 293) cells were cultured until confluent. The cells were then stimulated with either 1X 105/mL Acanthamoeba castellanii trophozoites, ultrapure lipopolysaccharides (LPS) at 10µg/mL as a positive control, or left un-stimulated for 24 hours. Once the incubation period was complete, the supernatant was removed and used for ELISA analysis for the production of IL-8 or CXCL2. RNA was collected from each experimental group and RT-PCR was performed using TLR-4 and chemokine primers. A TLR-4 neutralizing antibody was pre-incubated with the corneal cells 1 hr. prior to stimulation, the supernatant was collected for quantification of IL-8 production. Immunocytochemistry was used to visualize the TLR-4 protein on the cell membrane. The pathogenic Acanthamoeba castellanii and non-pathogenic Acanthamoeba neff strains were also compared utilizing this methodology. Results: Up-regulation of TLR-4 mRNA expression was seen in HCE cells and HCORN cells 24 hrs. after treatment. Increased production of cytokine/chemokine mRNA and IL-8 or CXCL2 protein was observed in the cells that were stimulated with Acanthamoeba castellanii trophozoites compared to un-stimulated control cells. This increase, was mitigated when a TLR-4 neutralizing antibody was added to the culture 1 hr. prior to treatment. We found that only the pathogenic Acanthamoeba castellanii strain up-regulates TLR-4 mRNA and chemokine production. Conclusions: These findings suggest that TLR-4 is responsible for the signaling cascade involved in the inflammatory response to Acanthamoeba infection. This cascade begins with the recognition of Acanthamoeba and leads to the production of cytokines and chemokines which attract neutrophils to the site of infection to combat the parasite.Item Unravelling the Impact of Cyclic Mechanical Stretch in Keratoconus-A Transcriptomic Profiling Study(MDPI, 2023-04-28) Akoto, Theresa; Cai, Jingwen; Nicholas, Sarah; McCord, Hayden; Estes, Amy J.; Xu, Hongyan; Karamichos, Dimitrios; Liu, YutaoBiomechanical and molecular stresses may contribute to the pathogenesis of keratoconus (KC). We aimed to profile the transcriptomic changes in healthy primary human corneal (HCF) and KC-derived cells (HKC) combined with TGFbeta1 treatment and cyclic mechanical stretch (CMS), mimicking the pathophysiological condition in KC. HCFs (n = 4) and HKCs (n = 4) were cultured in flexible-bottom collagen-coated 6-well plates treated with 0, 5, and 10 ng/mL of TGFbeta1 with or without 15% CMS (1 cycle/s, 24 h) using a computer-controlled Flexcell FX-6000T Tension system. We used stranded total RNA-Seq to profile expression changes in 48 HCF/HKC samples (100 bp PE, 70-90 million reads per sample), followed by bioinformatics analysis using an established pipeline with Partek Flow software. A multi-factor ANOVA model, including KC, TGFbeta1 treatment, and CMS, was used to identify differentially expressed genes (DEGs, |fold change| >/= 1.5, FDR /= 10 in >/=1 sample) in HKCs (n = 24) vs. HCFs (n = 24) and those responsive to TGFbeta1 and/or CMS. PANTHER classification system and the DAVID bioinformatics resources were used to identify significantly enriched pathways (FDR