Prospective Observational Study Evaluating Systemic Hormones and Corneal Crosslinking Effects in Keratoconus.

Purpose: 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 (Kmax) and minimum central corneal thickness (CCtmin) before and after CXL. Results: Corneal collagen crosslinking was associated with a 2% reduction in Kmax 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 Kmax before CXL (Spearman's r = 0.55, P = 0.01). Post-CXL Kmax and CCtmin 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.

Cell sheet-based approach to study the diabetic corneal stroma.

Prolonged hyperglycemia during diabetes mellitus (DM) is associated with severe complications that may affect both the anterior and posterior ocular segments, leading to impaired vision or blindness. The cornea is a vital part of the eye that has a dual role as a protective transparent barrier and as a major refractive structure and is likewise negatively affected by hyperglycemia in DM. Understanding the cellular and molecular mechanisms underlying the phenotypic changes associated with DM is critical to developing targeted therapies to promote tissue integrity. In this proof-of-concept study, we applied a cell sheet-based approach to generate stacked constructs of physiological corneal thickness using primary human corneal fibroblasts isolated from cadaveric control (healthy), Type 1 DM and Type 2 DM corneal tissues. Self-assembled corneal stromal sheets were generated after 2 weeks in culture, isolated, and subsequently assembled to create stacked constructs, which were evaluated using transmission electron microscopy. Analysis of gene expression patterns revealed significant downregulation of fibrotic markers, α-smooth muscle actin, and collagen type 3, with stacking in Type 2 DM constructs when compared to controls. IGF1 expression was significantly upregulated in Type 2 DM constructs compared to controls with a significant reduction induced by stacking. This study describes the development of a thicker, self-assembled corneal stromal construct as a platform to evaluate phenotypic differences associated with DM-derived corneal fibroblasts and enable the development of targeted therapeutics to promote corneal integrity.

Exploring the Pathophysiology of Delirium: An Overview of Biomarker Studies, Animal Models, and Tissue-Engineered Models.

Delirium is an acute brain disorder associated with disorganized thinking, difficulty focusing, and confusion that commonly follows major surgery, severe infection, and illness. Older patients are at high risk for developing delirium during hospitalization, which may contribute to increased morbidity, longer hospitalization, and increased risk of institutionalization following discharge. The pathophysiology underlying delirium remains poorly studied. This review delves into the findings from biomarker studies and animal models, and highlights the potential for tissue-engineered models of the brain in studying this condition. The aim is to bring together the existing knowledge in the field and provide insight into the future direction of delirium research.

Quercetin and Related Analogs as Therapeutics to Promote Tissue Repair.

Quercetin 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.

Role of Oxidative Stress in Ocular Diseases: A Balancing Act.

Redox homeostasis is a delicate balancing act of maintaining appropriate levels of antioxidant defense mechanisms and reactive oxidizing oxygen and nitrogen species. Any disruption of this balance leads to oxidative stress, which is a key pathogenic factor in several ocular diseases. In this review, we present the current evidence for oxidative stress and mitochondrial dysfunction in conditions affecting both the anterior segment (e.g., dry eye disease, keratoconus, cataract) and posterior segment (age-related macular degeneration, proliferative vitreoretinopathy, diabetic retinopathy, glaucoma) of the human eye. We posit that further development of therapeutic interventions to promote pro-regenerative responses and maintenance of the redox balance may delay or prevent the progression of these major ocular pathologies. Continued efforts in this field will not only yield a better understanding of the molecular mechanisms underlying the pathogenesis of ocular diseases but also enable the identification of novel druggable redox targets and antioxidant therapies.

Nighttime dexmedetomidine for delirium prevention in non-mechanically ventilated patients after cardiac surgery (MINDDS): A single-centre, parallel-arm, randomised, placebo-controlled superiority trial.

Background: The delirium-sparing effect of nighttime dexmedetomidine has not been studied after surgery. We hypothesised that a nighttime dose of dexmedetomidine would reduce the incidence of postoperative delirium as compared to placebo. Methods: This single-centre, parallel-arm, randomised, placebo-controlled superiority trial evaluated whether a short nighttime dose of intravenous dexmedetomidine (1 µg/kg over 40 min) would reduce the incidence of postoperative delirium in patients 60 years of age or older undergoing elective cardiac surgery with cardiopulmonary bypass. Patients were randomised to receive dexmedetomidine or placebo in a 1:1 ratio. The primary outcome was delirium on postoperative day one. Secondary outcomes included delirium within three days of surgery, 30-, 90-, and 180-day abbreviated Montreal Cognitive Assessment scores, Patient Reported Outcome Measures Information System quality of life scores, and all-cause mortality. The study was registered as NCT02856594 on ClinicalTrials.gov on August 5, 2016, before the enrolment of any participants. Findings: Of 469 patients that underwent randomisation to placebo (n = 235) or dexmedetomidine (n = 234), 75 met a prespecified drop criterion before the study intervention. Thus, 394 participants (188 dexmedetomidine; 206 placebo) were analysed in the modified intention-to-treat cohort (median age 69 [IQR 64, 74] years; 73.1% male [n = 288]; 26·9% female [n = 106]). Postoperative delirium status on day one was missing for 30 (7.6%) patients. Among those in whom it could be assessed, the primary outcome occurred in 5 of 175 patients (2.9%) in the dexmedetomidine group and 16 of 189 patients (8.5%) in the placebo group (OR 0.32, 95% CI: 0.10-0.83; P = 0.029). A non-significant but higher proportion of participants experienced delirium within three days postoperatively in the placebo group (25/177; 14.1%) compared to the dexmedetomidine group (14/160; 8.8%; OR 0.58; 95% CI, 0.28-1.15). No significant differences between groups were observed in secondary outcomes or safety. Interpretation: Our findings suggested that in elderly cardiac surgery patients with a low baseline risk of postoperative delirium and extubated within 12 h of ICU admission, a short nighttime dose of dexmedetomidine decreased the incidence of delirium on postoperative day one. Although non-statistically significant, our findings also suggested a clinical meaningful difference in the three-day incidence of postoperative delirium. Funding: National Institute on Aging (R01AG053582).

Quercetin Decreases Corneal Haze In Vivo and Influences Gene Expression of TGF-Beta Mediators In Vitro.

We have previously reported the flavonoid, quercetin, as a metabolic regulator and inhibitor of myofibroblast differentiation in vitro. Our current study evaluated the effects of topical application of quercetin on corneal scar development using two different animal models followed by RNA analysis in vitro. Wild-type C57BL/6J mice were anesthetized and the corneal epithelium and stroma were manually debrided, followed by quercetin (0.5, 1, 5, or 50 mM) or vehicle application. Corneal scarring was assessed for 3 weeks by slit lamp imaging and clinically scored. In a separate animal study, six New Zealand White rabbits underwent lamellar keratectomy surgery, followed by treatment with 5 mM quercetin or vehicle twice daily for three days. Stromal backscattering was assessed at week 3 by in vivo confocal microscopy. In mice, a single dose of 5 mM quercetin reduced corneal scar formation. In rabbits, stromal backscattering was substantially lower in two out of three animals in the quercetin-treated group. In vitro studies of human corneal fibroblasts showed that quercetin modulated select factors of the transforming growth factor-ß (TGF-ß) signaling pathway. These results provide evidence that quercetin may inhibit corneal scarring. Further studies in a larger cohort are required to validate the efficacy and safety of quercetin for clinical applications.

Sex Hormones, Growth Hormone, and the Cornea.

The 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.

Preliminary Study of Serum Biomarkers Associated With Delirium After Major Cardiac Surgery.

OBJECTIVES: The objective of this study was to identify novel serum biomarkers specific to postoperative delirium after major cardiac surgery to provide insight into the pathologic processes involved in delirium and its sequelae. DESIGN: Nested, case-control study. SETTING: Cardiac surgical intensive care unit in a single-site hospital setting. PARTICIPANTS: The study comprised 24 older adults (aged >60 years) undergoing major cardiac surgery with cardiopulmonary bypass. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The primary outcome was a positive screen for delirium from postoperative days one through three based on criteria included in the long form of the Confusion Assessment Method. A multiplexed proteomic approach was applied using proximity extension assays to identify and quantify proteins found in serum collected on the day of surgery and postoperative day one in delirious and nondelirious patient cohorts. An increase in serum fibroblast growth factor (FGF)-21 levels was identified in the delirious cohort from a presurgery baseline of (mean ± standard deviation) 5.0 ± 1.1 log2 abundance (95% confidence interval [CI], 4.3-5.7) to 6.7 ± 1.6 log2 abundance (95% CI, 5.7-7.7; p = 0.01) postsurgery. A similar increase was identified in FGF-23 from a presurgery baseline of 1.7 ± 1.3 log2 abundance (95% CI, 0.8-2.5) to 3.4 ± 2.2 log2 abundance (95% CI, 2.0-4.8; p = 0.06) postsurgery. An increase in interleukin-6 serum levels also was identified in the delirious cohort from a presurgery baseline of 3.8 ± 1.1 log2 abundance (95% CI, 3.1-4.5) to 8.7 ± 1.9 log2 abundance (95% CI, 7.5-9.9; p < 0.0001) postsurgery. However, the increase in interleukin-6 serum levels of the nondelirious cohort also met the study's threshold for statistical significance (p < 0.0001). Finally, an increase in monocyte chemotactic protein-3 serum levels was identified in the delirious cohort from a presurgery baseline of 4.1 ± 0.9 log2 abundance (95% CI, 3.6-4.7) to 6.1 ± 2.0 log2 abundance (95% CI, 4.8-7; p = 0.009) postsurgery. CONCLUSIONS: FGF-21, FGF-23, interleukin-6, and monocyte chemotactic protein-3 serum levels were increased postoperatively in patients who developed delirium after major cardiac surgery. This study identified two members of the FGF family as potential putative systemic biomarkers for postoperative delirium after cardiac surgery, suggesting a possible role for metabolic recovery in the pathophysiologic mechanisms underlying neurocognitive dysfunction.

Extracellular Vesicles in the Cornea: Insights from Other Tissues.

Extracellular vesicles (EVs) are phospholipid bilayer-bound particles secreted by cells that have been found to be important in mediating cell-cell communication, signal transduction, and extracellular matrix remodeling. Their role in both physiological and pathological processes has been established in different tissues throughout the human body. The human cornea functions as a transparent and refractive barrier that protects the intraocular elements from the external environment. Injury, infection, or disease may cause the loss of corneal clarity by altering extracellular matrix organization within the stroma that may lead to detrimental effects on visual acuity. Over the years, numerous studies have identified many of the growth factors (e.g., transforming growth factor-ß1, thrombospondin-1, and platelet-derived growth factor) important in corneal wound healing and scarring. However, the functional role of bound factors encapsulated in EVs in the context of corneal biology is less defined. In this review, we describe the discovery and characterization of EVs in the cornea. We focus on EV-matrix interactions, potential functions during corneal wound healing, and the bioactivity of mesenchymal stem cell-derived EVs. We also discuss the development of EVs as stable, drug-loaded therapeutics for ocular applications.

Arginine Supplementation Promotes Extracellular Matrix and Metabolic Changes in Keratoconus.

Keratoconus (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.

Induction of Irritation and Inflammation in a 3D Innervated Tissue Model of the Human Cornea.

Detection of slight changes in the chemical, thermal, and physical environments of the ocular surface is necessary to protect eyesight. The cornea, as the most densely innervated peripheral tissue in the body, can be damaged as a result of caustic chemical exposure. Such damage can be painful and debilitating, thus underscoring the need to understand mechanisms of ocular irritation. Both ethical and translational limitations regarding the use of animal subjects in part drive the need to develop relevant in vitro cell and tissue models that emulate the physiology of the human cornea. In this study, we utilized our 3D in vitro cornea-like tissue model to study the effects of irritation mediated by transient receptor potential (TRP) channels vanilloid 1 and ankyrin 1 (TRPV1; TRPA1) in response to allyl isothiocyanate (AITC) stimulation. Changes in gene expression were analyzed to characterize wound healing responses of the epithelial, stromal, and neuronal cell populations in the corneal tissue models. Key findings of the study include indications of wound healing, such as stromal myofibroblast differentiation and epithelial barrier re-establishment, amplification of pro-inflammatory cytokines, and downstream ECM protein remodeling due to irritation with the addition of sensory innervation. This study further establishes this in vitro tissue model as a useful tool for studying corneal irritation in vitro in a holistic manner with promise as a novel and sensitive tool for studying chemical exposures and subsequent responses.

Methods for Investigating Corneal Cell Interactions and Extracellular Vesicles In Vitro.

Science and medicine have become increasingly "human-centric" over the years. A growing shift away from the use of animals in basic research has led to the development of sophisticated in vitro models of various tissues utilizing human-derived cells to study physiology and disease. The human cornea has likewise been modeled in vitro using primary cells derived from corneas obtained from cadavers or post-transplantation. By utilizing a cell's intrinsic ability to maintain its tissue phenotype in a pre-designed microenvironment containing the required growth factors, physiological temperature, and humidity, tissue-engineered corneas can be grown and maintained in culture for relatively long periods of time on the scale of weeks to months. Due to its transparency and avascularity, the cornea is an optimal tissue for studies of extracellular matrix and cell-cell interactions, toxicology and permeability of drugs, and underlying mechanisms of scarring and tissue regeneration. This paper describes methods for the cultivation of corneal keratocytes, fibroblasts, epithelial, and endothelial cells for in vitro applications. We also provide detailed, step-by-step protocols for assembling and culturing 3D constructs of the corneal stroma, epithelial- and endothelial-stromal co-cultures and isolation of extracellular vesicles. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Isolating and culturing human corneal keratocytes and fibroblasts Basic Protocol 2: Isolating and culturing human corneal epithelial cells Basic Protocol 3: Isolating and culturing human corneal endothelial cells Basic Protocol 4: 3D corneal stromal construct assembly Basic Protocol 5: 3D corneal epithelial-stromal construct assembly Basic Protocol 6: 3D corneal endothelial-stromal construct assembly Basic Protocol 7: Isolating extracellular vesicles from corneal cell conditioned medium Support Protocol: Cryopreserving human corneal fibroblasts, corneal epithelial cells, and corneal endothelial cells.

Integrin: Basement membrane adhesion by corneal epithelial and endothelial cells.

Integrins mediate adhesion of cells to substrates and maintain tissue integrity by facilitating mechanotransduction between cells, the extracellular matrix, and gene expression in the nucleus. Changes in integrin expression in corneal epithelial cells and corneal endothelial cells impacts their adhesion to the epithelial basement membrane (EpBM) and Descemet's membrane, respectively. Integrins also play roles in assembly of basement membranes by both activating TGFß1 and other growth factors. Over the past two decades, this knowledge has been translated into methods to grow corneal epithelial and endothelial cells in vitro for transplantation in the clinic thereby transforming clinical practice and quality of life for patients. Current knowledge on the expression and function of the integrins that mediate adhesion to the basement membrane expressed by corneal epithelial and endothelial cells in health and disease is summarized. This is the first review to discuss similarities and differences in the integrins expressed by both cell types.

Modeling the cornea in 3-dimensions: Current and future perspectives.

The cornea is an avascular, transparent ocular tissue that serves as a refractive and protective structure for the eye. Over 90% of the cornea is composed of a collagenous-rich extracellular matrix within the stroma with the other 10% composed by the corneal epithelium and endothelium layers and their corresponding supporting collagen layers (e.g., Bowman's and Descemet's membranes) at the anterior and posterior cornea, respectively. Due to its prominent role in corneal structure, tissue engineering approaches to model the human cornea in vitro have focused heavily on the cellular and functional properties of the corneal stroma. In this review, we discuss model development in the context of culture dimensionality (e.g., 2-dimensional versus 3-dimensional) and expand on the optical, biomechanical, and cellular functions promoted by the culture microenvironment. We describe current methods to model the human cornea with focus on organotypic approaches, compressed collagen, bioprinting, and self-assembled stromal models. We also expand on co-culture applications with the inclusion of relevant corneal cell types, such as epithelial, stromal keratocyte or fibroblast, endothelial, and neuronal cells. Further advancements in corneal tissue model development will markedly improve our current understanding of corneal wound healing and regeneration.

Characterization of Tear Immunoglobulins in a Small-Cohort of Keratoconus Patients.

Keratoconus (KC) is classically considered a non-inflammatory condition caused by central corneal thinning that leads to astigmatism and reduced visual acuity. Previous studies have identified increased systemic levels of pro-inflammatory factors, including interleukin-6, tumor necrosis factor-α, and matrix metalloproteinase-9, suggesting that KC may have an inflammatory component in at least a subset of patients. In this study, we evaluated the levels of different immunoglobulins (light and heavy chains) based on Ig α, Ig λ, Ig κ, Ig µ, and Ig heavy chain subunits in non-KC tears (n = 7 control individuals) and KC tears (n = 7 KC patients) using tandem-liquid chromatography mass spectrometry. The most abundant Ig heavy chains detected in both control individuals and KC patients were Ig α-1 and Ig α-2 likely correlating to the higher IgA levels reported in human tears. We identified significant differences in immunoglobulin κ-chain V-II levels in KC patients compared to control individuals with no significant difference in Ig κ/Ig λ ratios or heavy chain levels. Our study supports previous findings suggesting that KC possesses a systemic component that may contribute to the KC pathology. Further studies are required to define causality and establish a role for systemic immune system-dependent factors and pro-inflammatory processes in KC development or progression.

Extracellular Vesicles Secreted by Corneal Epithelial Cells Promote Myofibroblast Differentiation.

The corneal epithelium mediates the initial response to injury of the ocular surface and secretes a number of profibrotic factors that promote corneal scar development within the stroma. Previous studies have shown that corneal epithelial cells also secrete small extracellular vesicles (EVs) in response to corneal wounding. In this paper, we hypothesized that EVs released from corneal epithelial cells in vitro contain protein cargo that promotes myofibroblast differentiation, the key cell responsible for scar development. We focused on the interplay between corneal epithelial-derived EVs and the stroma to determine if the corneal fibroblast phenotype, contraction, proliferation, or migration were promoted following vesicle uptake by corneal fibroblasts. Our results showed an increase in myofibroblast differentiation based on α-smooth muscle actin expression and elevated contractility following EV treatment compared to controls. Furthermore, we characterized the contents of epithelial cell-derived EVs using proteomic analysis and identified the presence of provisional matrix proteins, fibronectin and thrombospondin-1, as the dominant encapsulated protein cargo secreted by corneal epithelial cells in vitro. Proteins associated with the regulation of protein translation were also abundant in EVs. This paper reveals a novel role and function of EVs secreted by the corneal epithelium that may contribute to corneal scarring.