Sapna Tibrewal

Ocular Surface Extracellular DNA and Nuclease Activity Imbalance: A New Paradigm for Inflammation in Dry Eye Disease

PURPOSE We determined whether nucleases are deficient in the tear fluid of dry eye disease (DED) patients, and whether this causes extracellular DNA (eDNA) and neutrophil extracellular trap (NET) accumulation in the precorneal tear film, thus causing ocular surface inflammation. METHODS Exfoliated cells adhered to Schirmer test strips were collected on glass slides, and immunofluorescence confocal microscopy was used to evaluate neutrophils, eDNA, NETs, and their molecular components. Similar experiments were performed with mucoid films collected from the inferior conjunctival fornix or bulbar conjunctiva. We used quantitative PCR to evaluate eDNA signaling pathways and inflammatory cytokine expression. We also determined the amount of ocular surface eDNA and evaluated tear fluid nuclease activity. RESULTS eDNA, NETs, and neutrophils were present on the ocular surface in DED patients and abundant in mucoid films. NETs consisted of eDNA, histones, cathelicidin, and neutrophil elastase. Tear fluid nuclease activity was decreased significantly in DED patients, whereas the amount of eDNA on the ocular surface was increased significantly. Expression of genes downstream of eDNA signaling, such as TLR9, MyD88, and type I interferon, as well as the inflammatory cytokines interleukin-6 and tumor necrosis factor-α, was significantly increased in DED patients. CONCLUSIONS Extracellular DNA production and clearance mechanisms are dysregulated in DED. Nuclease deficiency in tear fluid allows eDNA and NETs to accumulate in precorneal tear film, and results in ocular surface inflammation. These findings point to novel therapeutic interventions in severe DED based on clearance of eDNA, NETs, and other molecular components from the ocular surface.

Hyperosmolar Stress Induces Neutrophil Extracellular Trap Formation: Implications for Dry Eye Disease

PURPOSE To determine if hyperosmolar stress can stimulate human neutrophils to form neutrophil extracellular traps (NETs) and to investigate potential strategies to reduce formation of NETs (NETosis) in a hyperosmolar environment. METHODS Neutrophils were isolated from peripheral venous blood of healthy subjects and incubated in iso-osmolar (280 mOsM) or hyperosmolar (420 mOsM) media for 4 hours. Neutrophil extracellular traps were quantified using a PicoGreen dye assay to measure extracellular DNA. Two known inhibitors of NETosis, staurosporine and anti-β2 integrin blocking antibody, and two proresolution formyl peptide receptor 2 (FPR2) agonists, annexin/lipocortin-1 mimetic peptide and 15-epi-lipoxin A4, were evaluated as possible strategies to reduce hyperosmolarity-induced NETosis. RESULTS The amount of NETs induced by hyperosmolar medium (420 mOsM) increased linearly over time to 3.2 ± 0.3 times that induced by iso-osmolar medium at 4 hours (P < 0.05). NETosis increased exponentially with increasing osmolarity and was independent of the stimulus used to increase osmolarity. Upon neutrophil exposure to hyperosmolar stress, restoration of iso-osmolar conditions decreased NET formation by 52.7% ± 5% (P < 0.05) but did not completely abrogate it. Among the strategies tested to reduce NETosis in a hyperosmolar environment, annexin-1 peptide was the most efficacious. CONCLUSIONS Hyperosmolarity induces formation of NETs by neutrophils. This NETosis mechanism may explain the presence of excessive NETs on the ocular surface of patients with dry eye disease. Because they reduce hyperosmolarity-induced NETosis, FPR2 agonists may have therapeutic potential in these patients.

CD11b+GR1+ Myeloid Cells Secrete NGF and Promote Trigeminal Ganglion Neurite Growth: Implications for Corneal Nerve Regeneration

PURPOSE We characterized fluorescent bone marrow cells (YFP(+) BMCs) in the thy1-YFP mouse and determine if they promote trigeminal ganglion (TG) cell neurite growth. METHODS Excimer laser annular keratectomy was performed in thy1-YFP mice, and corneas were imaged. BMCs were harvested from femur and tibia, and the expression of surface markers on YFP(+) BMCs was analyzed by flow cytometry. The immunosuppressive action of BMCs (YFP(+) and YFP(-)) was evaluated in an allogenic mixed lymphocyte reaction (MLR). Neurotrophic action of BMCs (YFP(+) and YFP(-)) was determined in compartmental and transwell cultures of dissociated TG cells. RESULTS Following annular keratectomy, YFP(+) BMCs infiltrated the cornea. YFP(+) BMCs shared surface markers (CD11b+Gr1+Ly6C+Ly6G-F4/80(low)) with monocytic myeloid-derived suppressor cells (MDSCs), had similar morphology, and suppressed T-cell proliferation in allogenic MLR in a dose-dependent manner. YFP(+) BMCs, but not YFP(-) BMCs, significantly increased growth of TG neurites in vitro. When cultured in a transwell with TG neurites, YFP(+) BMCs expressed neurotrophins and secreted nerve growth factor (NGF) in conditioned medium. YFP(+) BMCs that infiltrated the cornea maintained their phenotype and actions (neuronal and immune). CONCLUSIONS YFP(+) BMCs in thy1-YFP mice have immunophenotypic features of MDSCs. They secrete NGF and promote neuroregeneration. Their immunosuppressive and neurotrophic actions are preserved after corneal infiltration. These findings increase our understanding of the beneficial roles played by leukocyte trafficking in the cornea and may lead to therapeutic strategies that use NGF-secreting myeloid cells to repair diseased or injured neurons.

Depressive Symptoms in Patients With Dry Eye Disease: A Case-Control Study Using the Beck Depression Inventory.

Purpose: To measure depressive symptoms in patients with dry eye disease (DED) and controls using the Beck Depression Inventory (BDI) and to determine the association between depressive and DED symptoms. Methods: Fifty-three patients with DED and 41 controls were recruited to the study. DED symptoms were assessed using the Symptom Burden Tool and Ocular Surface Disease Index tool. Depressive symptoms were assessed using the BDI. Regression diagnostics were performed to detect outliers. Linear statistical models and polynomial regression were used to determine the relationship between depressive symptoms and DED symptoms. An independent t test was performed to determine differences in BDI scores between cases and controls. Scatter plots were generated and linear regression was used to estimate the association between scores. Logistic regression was used for the DED dichotomous outcome and depression status as exposure. Results: Regression models revealed that the association is linear more than quadratic or cubic. After adjusting for age, sex, race, and psychiatric medication, the regression coefficient between DED symptoms and depressive symptoms among DED cases was 1.22 (95% confidence interval, 0.27–2.18). DED symptom scores and depression scores were statistically significantly different between DED cases and controls. Adjusted logistic regression revealed an odds ratio of 2.79 (95% confidence interval, 0.96–8.12). Conclusions: This study provides further evidence regarding the association between DED and depression and their symptoms. Prospective studies are needed to understand the mechanisms underlying the association between symptoms of depression and symptoms of DED.

Single Nucleotide Polymorphisms in the BDNF, VDR, and DNASE 1 Genes in Dry Eye Disease Patients: A Case-Control Study

PURPOSE To identify single nucleotide polymorphisms (SNPs) in the brain-derived neurotrophic factor (BDNF), vitamin D receptor (VDR), and DNASE1 genes that may be associated with dry eye disease (DED), and determine whether this association varies by the presence of depression. METHODS A case-control study was performed with 64 DED cases and 51 controls. We collected 2 mL of saliva following a routine eye exam. Genotyping was performed using both custom and predesigned TaqMan SNP genotyping assays for 12 hypothesized SNPs. Genotype and allele frequencies of cases and controls were evaluated. Odds ratios were calculated for allele frequencies. Stratified analysis was performed to determine if the association between SNPs and DED varied by depression status. RESULTS A total of 18% of cases had the minor allele A of Val66Met (rs6265) SNP in the BDNF gene compared with 9% of the controls (P = 0.05). Odds ratio was 2.22. Two SNPs (Fokl-rs2228570 and Apal-rs7975232) in the VDR genes also varied between DED cases and controls. Cases were 1.72 and 1.66 times more likely to have the minor allele A in rs2228570 and rs7975232, respectively, than controls (P = 0.06 for both). While not statistically significant, among patients with depression, DED cases were 3.93 times more likely to have the minor allele A of the Val66Met SNP compared to controls. CONCLUSIONS This pilot study showed that Val66Met in the BDNF gene and two SNPs, Fokl and Apal, in the VDR gene may potentially be associated with DED. Additionally, the association between DED and Val66Met may vary by depression status.

Keratocytes Derived from Spheroid Culture of Corneal Stromal Cells Resemble Tissue Resident Keratocytes

Purpose Corneal stromal cells transform to precursor cells in spheroid culture. We determined whether keratocytes derived from spheroid culture of murine corneal stromal cells resemble tissue resident keratocytes. Methods Spheroid culture was performed by seeding dissociated stromal cells onto ultra-low attachment plates containing serum-free mesenchymal stem cell culture medium. Spheroids were characterized with phenotype specific markers and stemness transcription factor genes. Spheroids and adherent cells in culture were induced to differentiate to keratocytes using keratocyte induction medium (KIM) and compared with tissue resident keratocytes. Results Stromal cells formed spheroids in ultra-low attachment plates, but not in polystyrene tissue culture dishes. Keratocan expression and abundance was significantly higher in spheroids as compared to adherent cells whereas alpha-smooth muscle actin (α-SMA) was significantly lower. As compared to adherent culture-derived cells, the expressions of keratocan, aldehyde dehydrogenase (ALDH3A1) and α-SMA in spheroid-derived cells approximated much more closely the levels of these genes in tissue resident keratocytes. Of the stemness genes, Nanog and Oct4 were upregulated in the spheroids. Conclusion Stemness transcription factor genes are upregulated in spheroids. Keratocytes derived from spheroids resemble tissue resident keratocytes, thus increasing manifolds the quantity of these cells for in-vitro experiments.

Dry eye syndrome: Management of post-LASIK dry eye disease

Laser in situ keratomileusis (LASIK) has emerged as the standard surgical procedure for the correction of refractive errors [1]. During LASIK procedure, stromal nerves are transected in the flap area. Post-LASIK, the subbasal nerve plexus density decreases more than 80 % [2]. Although nerve regrowth is observed in the flap area at 6 months post-procedure, preoperative levels are not achieved even 5 years after surgery [2–4]. About 50 % patients experience some degree of dry eye symptoms during the initial postoperative period [5]. Besides symptoms of ocular discomfort, which in the most severe form can be debilitating to the patient, it can also compromise visual acuity if the central cornea develops LASIK-induced neurotrophic epitheliopathy (LINE).

Depressive Symptoms in Dry Eye Disease Patients: A Case-Control Study using the Beck Depression Inventory

Purpose: To measure depressive symptoms in patients with dry eye disease (DED) and controls using the Beck Depression Inventory (BDI) and to determine the association between depressive and DED symptoms. Methods: Fifty-three patients with DED and 41 controls were recruited to the study. DED symptoms were assessed using the Symptom Burden Tool and Ocular Surface Disease Index tool. Depressive symptoms were assessed using the BDI. Regression diagnostics were performed to detect outliers. Linear statistical models and polynomial regression were used to determine the relationship between depressive symptoms and DED symptoms. An independent t test was performed to determine differences in BDI scores between cases and controls. Scatter plots were generated and linear regression was used to estimate the association between scores. Logistic regression was used for the DED dichotomous outcome and depression status as exposure. Results: Regression models revealed that the association is linear more than quadratic or cubic. After adjusting for age, sex, race, and psychiatric medication, the regression coefficient between DED symptoms and depressive symptoms among DED cases was 1.22 (95% confidence interval, 0.27–2.18). DED symptom scores and depression scores were statistically significantly different between DED cases and controls. Adjusted logistic regression revealed an odds ratio of 2.79 (95% confidence interval, 0.96–8.12). Conclusions: This study provides further evidence regarding the association between DED and depression and their symptoms. Prospective studies are needed to understand the mechanisms underlying the association between symptoms of depression and symptoms of DED.

Depressive Symptoms in Patients With Dry Eye Disease

Purpose: To measure depressive symptoms in patients with dry eye disease (DED) and controls using the Beck Depression Inventory (BDI) and to determine the association between depressive and DED symptoms. Methods: Fifty-three patients with DED and 41 controls were recruited to the study. DED symptoms were assessed using the Symptom Burden Tool and Ocular Surface Disease Index tool. Depressive symptoms were assessed using the BDI. Regression diagnostics were performed to detect outliers. Linear statistical models and polynomial regression were used to determine the relationship between depressive symptoms and DED symptoms. An independent t test was performed to determine differences in BDI scores between cases and controls. Scatter plots were generated and linear regression was used to estimate the association between scores. Logistic regression was used for the DED dichotomous outcome and depression status as exposure. Results: Regression models revealed that the association is linear more than quadratic or cubic. After adjusting for age, sex, race, and psychiatric medication, the regression coefficient between DED symptoms and depressive symptoms among DED cases was 1.22 (95% confidence interval, 0.27–2.18). DED symptom scores and depression scores were statistically significantly different between DED cases and controls. Adjusted logistic regression revealed an odds ratio of 2.79 (95% confidence interval, 0.96–8.12). Conclusions: This study provides further evidence regarding the association between DED and depression and their symptoms. Prospective studies are needed to understand the mechanisms underlying the association between symptoms of depression and symptoms of DED.