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Biomedical subjects

Steven E Wilson

Publications and source records attributed to Steven E Wilson.

15 recordsLinked to original sources
PubMed2003

Corneal cells: chatty in development, homeostasis, wound healing, and disease.

PURPOSE: To provide an overview of cell-cell interactions in the cornea that have a critical role in corneal development, homeostasis, wound healing, and disease. DESIGN: Review. METHODS: Review of the literature. RESULTS; Cell-cell interactions make critical contributions to development, homeostasis, and wound healing in the cornea. Many of these interactions are mediated by cytokines, growth factors, and chemokines. The best characterized are stromal-epithelial interactions between epithelial cells and stromal cells such as keratocytes, keratoblasts, and myofibroblasts. However, interactions also occur between corneal nerves and epithelial cells and between corneal cells (epithelial cells and stromal cells) and corneal immune cells. Although investigations are limited, it is likely that there are interactions between corneal endothelial cells and keratocytes in the posterior stroma. CONCLUSIONS: Cellular communications in the cornea are critical during development, homeostasis, and wound healing. Disorders of cellular communication likely contribute to many corneal diseases.

Animals↗
PubMed2003

Apoptosis, necrosis, proliferation, and myofibroblast generation in the stroma following LASIK and PRK.

The aim of this study was to semi-quantitatively analyze stromal cell apoptosis, stromal cell proliferation, and myofibroblast generation over time points from 4hr to 3 months in rabbit eyes having photorefractive keratectomy (PRK) or laser in situ keratomeliusis (LASIK). Stromal cell necrosis and inflammatory cell infiltration were also studied. PRK for low myopia (-4.5diopters [D]), PRK for high myopia (-9.0D), and LASIK for high myopia (-9.0D) were performed in rabbit eyes, and corneas were obtained for examination at 4, 24, and 72hr, 1 and 4 weeks, and 3 months after surgery. A total of 144 rabbits were included in the study. Stromal cell apoptosis, proliferation, and myofibroblast generation were evaluated semi-quantitatively by TUNEL assay, immunocytochemical analysis of Ki67, and immunocytochemical analysis of alpha-smooth muscle actin, respectively. Stromal cell necrosis and characteristics of other cell types in the stroma were evaluated by electron microscopy. Keratocyte apoptosis and the subsequent proliferation and generation of myofibroblasts were qualitatively and quantitatively different in PRK for high myopia compared to either PRK for low myopia or LASIK for high myopia. Stromal cell necrosis becomes a significant form of cell death by 24hr after injury and may involve corneal fibroblasts, myofibroblasts, and inflammatory cells. Large numbers of polymorphonuclear cells and monocytes invade the cornea by 24hr after surgery and persist for over 1 week. The qualitative and quantitative differences in the cellular wound healing response after PRK for high and low myopia and LASIK for high myopia are likely determinants of the clinical differences in refractive outcome and some of the complications, such as regression and haze, seen after these procedures.

Animals↗
PubMed2003

Gene transfer into rabbit keratocytes using AAV and lipid-mediated plasmid DNA vectors with a lamellar flap for stromal access.

Development of gene transfer methods that can precisely deliver therapeutic genes to the localized or targeted tissue(s) would be highly beneficial in developing new gene therapy approaches and may also extend animal models for studying in vivo gene function and regulation at molecular levels in the selected tissues. We investigated lipid- and AAV-mediated gene transfer in rabbit cornea using a lamellar flap-technique. The goals of this study were to (1) analyze methods for in situ gene transfer into keratocytes, (2) identify efficient and suitable vectors for gene transfer into keratocytes, and (3) characterize times of first detectable expression, localization and duration of transgene expression in keratocytes with different vectors. A lamellar flap was produced in the rabbit cornea with a microkeratome. Recombinant adeno-associated viral vector (rAAV) expressing either beta-galactosidase (rAAV-beta-gal) or chloramphenicol acetyltransferase (rAAV-CAT) reporter genes, or plasmid-cationic lipid complexes expressing CAT (pMP6-CAT) or beta-galactosidase (pTR-beta-gal) were applied beneath the lamellar flap for two minutes. The flap was repositioned and eyelids sutured overnight. Corneas were removed at 4hr, 12hr, 36hr, 3 days, 7 days, or 10 days after application and either fixed in 2% formaldehyde, cryosectioned and stained for beta-galactosidase activity or homogenized and measured for CAT levels by ELISA. Corneas infected with rAAV-beta-gal vector showed positive beta-gal staining in the center and periphery of the flap interface in whole corneas and corneal beds at 3, 7, and 10 days, but not at earlier time points. Corneas treated with pTR-beta-gal plasmid vector showed positive beta-gal expression at the interface at 4, 12 and 36hr, but not at 3 or 7 days. The posterior surface of the lamellar interface where the vector was applied showed more expression than the overlying anterior surface with both plasmid and viral vectors. The level of gene expression was less with plasmid vector than viral vector monitored using beta-gal staining. CAT-ELISA confirmed expression of the CAT reporter gene with either the plasmid or rAAV vector. These results demonstrate that foreign genes can be introduced into keratocytes with plasmid or viral vectors using a lamellar flap to gain access to the stroma. The expression profile of the reporter genes depended on the vector. Transfection of keratocytes with plasmid vectors produced rapid expression of the reporter genes, but for a short duration. Reporter gene expression following transduction by rAAV vector was delayed several days, but was at higher levels and for a longer duration. This is the first report to demonstrate selective gene transfer into keratocytes and would be highly useful in studying function and regulation of genes in vivo and may eventually furnish a tool for the treatment of corneal dystrophies.

Adenoviridae↗
PubMed2003

Effect of ectopic epithelial tissue within the stroma on keratocyte apoptosis, mitosis, and myofibroblast transformation.

The purpose of this study was to examine the effects of the epithelium on processes involved in stromal wound healing. Lamellar epithelial-stromal flaps were produced in rabbit corneas with a microkeratome. Peripheral corneal epithelial tissue, central corneal epithelial tissue, or no epithelial tissue (control) was introduced beneath the flap. Corneas were removed at time points from 4 hr to 1 month after surgery. Tissue sections were analyzed with immunocytochemistry for Keratin 3 (K3) to detect epithelial antigen, terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labelling (TUNEL) assay to detect apoptosis, immunocytochemistry for Ki67 to detect cell proliferation, and immunocytochemistry for alpha-smooth muscle actin (SMA) to detect myofibroblasts. K3 was detected at the level of the interface from 4 hr to 1 month after surgery in corneas in which epithelial tissue was introduced, but not control corneas, with the exception of one that developed epithelial in growth. Keratocyte apoptosis was significantly higher at 4 hr after flap formation in both groups in which corneal epithelial tissue was introduced beneath the flap compared with controls. Keratocyte proliferation was significantly greater at 72 hr in corneas in which epithelial tissue was introduced beneath the flap compared to the controls. Corneas in which epithelial tissue was introduced into the interface, but not control corneas, had stromal cells expressing alpha-SMA in the stroma anterior and posterior to the interface at 1 week and 1 month after surgery. This was also noted in the control cornea in which there was epithelial ingrowth. Signals derived from the corneal epithelium promote keratocyte apoptosis. Keratocyte proliferation is higher in corneas that have lamellar surgery when epithelial tissue is introduced into the interface. Epithelium-derived signals also participate in the generation and/or maintenance of myofibroblasts in the corneal stroma.

Actins↗
PubMed2003

Development of genetically engineered tet HPV16-E6/E7 transduced human corneal epithelial clones having tight regulation of proliferation and normal differentiation.

Lack of an optimal in vitro model of human corneal epithelial (HCE) cells is a major limitation in studying normal functions and gene regulations in HCE. Moreover, availability of a multi-layered HCE culture can reduce the usage of animals in the toxicity testing of consumer products. We have developed tetracycline-responsive human papilloma virus (HPV) 16-E6/E7 transduced HCE clones showing tight regulation of proliferation and normal differentiation. Expression of HPV16-E6/E7 mRNA and HPV16-E7 and keratin K3 proteins was examined by RNase protection assay and western blotting, respectively, in presence and absence (+/-) of Dox in identified clones. Localization of cornea-specific keratin k3 in +/- of Dox was evaluated by immunocytochemistry. The response of growth factors such as hepatocyte growth factor (HGF) and epidermal growth factor to the cellular proliferation in +/- of Dox in the newly identified clones was measured by cell counting. Cellular morphology, formation of multi-layered cultures at air-liquid interface and ultrastructural features were evaluated by light and transmission electron microscopy. The physical barrier established by the newly developed clones was determined by the transepithelial permeability to sodium fluorescein and transepithelial electrical resistance assays in the airlifted-stratified cultures.

Calcium↗
PubMed2002

Lymphedema-distichiasis syndrome and FOXC2 gene mutation.

PURPOSE: To describe the clinical characteristics of a family with autosomal dominant lymphedema-distichiasis syndrome and to report the results of analysis of the FOXC2 gene DESIGN: Observational and experimental study. METHODS: The setting was a clinical practice. The study population was 17 members of a family with lymphedema-distichiasis. Observation procedures were complete ophthalmologic examinations and collection of blood samples. DNA was extracted. Mutation analysis of the coding region of the FOXC2 gene was performed using direct sequencing of polymerase chain reaction (PCR) product and a restriction enzyme assay. The main outcome measure was inheritance of mutation in FOXC2 gene. RESULTS: Nine patients had distichiasis or lymphedema or both and eight did not. Sequencing of the coding region of the only translated exon of the FOXC2 gene revealed a C to A transversion at position 939 resulting in a Tyr313Stop codon with premature termination of translation and a truncated protein product. The mutation was present in all nine affected individuals and in an asymptomatic 9-year-old boy. CONCLUSIONS: Distichiasis-lymphedema syndrome results from mutations in FOXC2, a member of the forkhead/winged family of transcription factors. There is intrafamilial variation in the clinical expression of the mutation.

Base Sequence↗
PubMed2002

Early pellucid marginal corneal degeneration: case reports of two refractive surgery candidates.

PURPOSE: To report two refractive surgery candidates who demonstrated early corneal topographic findings of pellucid marginal degeneration. METHODS: Case reports. RESULTS: Two candidate patients for corneal laser surgery were examined. The patients had normal examinations, including normal slit lamp biomicroscopy results and corrected visual acuity that was 20/20 or better in each eye. The corneal topography in one eye of patient I and both eyes of patient 2 was characterized by the presence of irregular astigmatism and inferior corneal steepening with a pattern consistent with pellucid marginal degeneration. Marked asymmetry between the eyes was noted. The inferior cornea was thinner than the central cornea in both eyes of each patient. CONCLUSION: Patients with early corneal ectasia often present as refractive surgery candidates with normal corrected visual acuity and normal pachymetry of the central cornea. Corneal topography and regional pachymetry measurements can be used to identify these patients. Patients with pellucid marginal degeneration are not good candidates for refractive surgery because of the potential for poor outcomes and the possibility that iatrogenic thinning of the cornea could lead to progression of the disease.

Aged↗
PubMed2002

Sporadic diffuse lamellar keratitis (DLK) after LASIK.

PURPOSE: To examine the incidence of sporadic diffuse lamellar keratitis (DLK) in a large series of LASIK eyes and to suggest the hypothesis that the etiology of sporadic DLK differs from that of epidemic DLK. METHODS: The incidence and severity of DLK was noted in 1352 consecutive eyes that had primary LASIK for myopia or hyperopia and 217 consecutive eyes that had LASIK enhancement. RESULTS: Twelve of the eyes having primary LASIK had stage 1 DLK and 5 had stage 2 DLK (.9% total). No eyes had stage 3 or stage 4 DLK. Three of the 217 eyes (1.4%) that had LASIK enhancement had stage 1 DLK. The difference in the rate of DLK for primary LASIK compared with LASIK enhancement was not statistically significant (p = 0.69). All eyes responded to intensive corticosteroid therapy, with the addition of flap lifting and irrigation for the eyes with stage 2 DLK. Two of the eyes (one primary LASIK and one LASIK-enhancement) had implanted epithelial nests associated with the DLK. None of the cases of DLK occurred in eyes of patients who had surgery on the same operating day in this series. Two other eyes that had epithelial abrasions more than 3 months after LASIK or LASIK enhancement developed stage 1 DLK. CONCLUSIONS: Many cases of sporadic DLK, including cases associated with epithelial trauma after LASIK, are likely attributable to endogenous factors that trigger inflammation. One trigger is the release of epithelium-derived cytokines such as interleukin-1 that stimulate keratocytes to produce chemokines that are chemotactic to inflammatory cells. Cells likely accumulate at the interface because it is potential space, representing a path of least resistance for cell movement. Some sporadic cases may also be related to exogenous factors such as Betadine. Epidemic DLK is likely associated with exogenous factors that stimulate inflammation, such as endotoxin contaminating sterilizer reservoirs or detergents on instruments.

Epithelium, Corneal↗
PubMed2002

Analysis of the keratocyte apoptosis, keratocyte proliferation, and myofibroblast transformation responses after photorefractive keratectomy and laser in situ keratomileusis.

PURPOSE: To test the hypothesis that (1) there are quantitative differences in the cellular responses in the corneal stroma after photorefractive keratectomy (PRK) for low myopia compared to high myopia and (2) there are both qualitative and quantitative differences in the cellular responses in the corneal stroma after PRK for high myopia and laser in situ keratomileusis (LASIK) for high myopia. METHODS: PRK for low myopia (-4.5 diopters [D]), PRK for high myopia (-9.0 D), and LASIK for high myopia (-9.0 D) were performed in rabbit eyes, and corneas were obtained for examination at 4, 24, and 72 hours, 1 and 4 weeks, and 3 months after surgery. A total of 144 rabbits were included in the study. Stromal apoptosis, necrosis, mitosis, myofibroblast generation, and inflammatory cell infiltration were evaluated by immunohistochemical methods and electron microscopy. RESULTS: Keratocyte apoptosis/necrosis and the subsequent proliferation and density of myofibroblasts were qualitatively and quantitatively different in PRK for high myopia compared to either PRK for low myopia or LASIK for high myopia. Significant inflammatory cell infiltration was noted in both PRK and LASIK but appeared to be greater in PRK for high myopia. CONCLUSIONS: The qualitative and quantitative differences in the cellular wound healing response after PRK for high and low myopia and LASIK for high myopia are likely determinants of the clinical differences in refractive outcome and some of the complications, such as regression and haze, seen after these procedures.

Actins↗
PubMedDate not supplied

Corneal topographic and pachymetric screening of keratorefractive patients.

PURPOSE: To review the incidence of corneal abnormalities detected in the preoperative examination, using videokeratography and pachymetry that excluded patients from laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK). METHODS: We conducted a chart review of consecutive patients who had a preoperative examination and were excluded from refractive surgery. RESULTS: Eighteen patients from 1,392 refractive candidates (1.3%) were designated as poor candidates for LASIK or PRK based on corneal topography and/or pachymetry. Thirteen patients (0.9%) were identified as having keratoconus suspect, keratoconus, or pellucid marginal degeneration. Five patients (0.4%) were excluded due to thin corneas (<490 microm) despite normal corneal topography. CONCLUSIONS: Corneal topography and pachymetry are indispensable tools in the preoperative screening of refractive surgery candidates.

Adult↗
PubMedDate not supplied

Bilateral marginal sterile infiltrates and diffuse lamellar keratitis after laser in situ keratomileusis.

PURPOSE: To report cases of acute bilateral catarrhal infiltrates in the early postoperative period after laser in situ keratomileusis (LASIK). METHODS: Retrospective review of both eyes of two patients. RESULTS: Two patients developed acute bilateral, marginal, catarrhal infiltrates in the early postoperative period after LASIK. Both patients had moderate to severe chronic meibomian gland dysfunction preoperatively. One patient (both eyes) developed grade 3 diffuse lamellar keratitis (DLK) that required both flaps to be lifted for irrigation and cleaning on postoperative day 5. Fungal and bacterial cultures were negative in both eyes of both patients. The condition resolved with intensive topical corticosteroids and fortified antibiotics. Regression of refractive error and the need for enhancement was encountered in all eyes. There was mild recurrence in one eye of each patient with pretreatment with topical corticosteroids prior to enhancement. CONCLUSIONS: Endogenous factors such as chronic blepharitis and meibomian gland dysfunction may trigger inflammation resulting in sporadic cases of catarrhal infiltrates after LASIK. These patients may have chronic inflammatory milieus that can trigger sporadic cases of catarrhal infiltrates after LASIK, with accompanying diffuse lamellar keratitis.

Anti-Bacterial Agents↗