Effects produced by different types of laser in cornea of Guinea pigs: Identification of a laser capable of producing superficial lesions without leaving scars.

PURPOSE: Climatic droplets keratopathy (CDK) is closely associated with superficial corneal erosions and lack of protective mechanisms against the harmful effects of ultraviolet radiation (UVR) during a prolonged period of time. One of the difficulties in studying the pathogenic mechanisms involved in this human disease is the lack of an experimental animal model. In this paper, a study is conducted on the effects of 4 types of lasers at various powers and time conditions on the normal guinea pig corneas in order to select only one laser condition that reversibly injures the epithelium and superficial stroma, without leaving scarring. METHODS: Damage was induced in the cornea of Guinea pigs using different powers and exposure times of 4 types of laser: argon, CO2, diode and Nd-Yag, and any injuries were evaluated by biomicroscopy (BM) and optical microscopy. Corneas from other normal animals were exposed to argon laser (350 mW, 0.3s, 50 µm of diameter), and the induced alterations were studied at different times using BM, optical coherence tomography (OCT) and transmission electron microscopy (TEM). RESULTS: Only argon laser at 350 mW, 0.3s, 50 µm of diameter produced epithelium and superficial stroma lesions. Some leukomas were observed by BM, and they disappeared by day 15. Corneal thickness measured by OCT decreased in the eyes treated with argon laser during the first week. Using TEM, different ultra structural alterations in corneal epithelium and stroma were observed during the early days, which disappeared by day 15. CONCLUSIONS: It was possible to develop reproducible corneal epithelium and anterior stroma injuries using Argon laser at 350 mW, 0.3s, 50 µm of diameter. In vivo and in vitro studies showed that injured corneas with these laser conditions did not leave irreversible microscopic or ultra structural alterations. This protocol of corneal erosion combined with exposure to UVR and partial deficiency of ascorbate in the diets of the animals for an extended period of time has been used in order to try to develop an experimental model of CDK.

On the Cornea of Healthy Merino Sheep: A Detailed Ex Vivo Confocal, Histological and Ultrastructural Study.

Our study performed qualitative and quantitative studies on the corneal ultrastructure of healthy female Merino sheep of ages 4 months and 6 years old from the Argentinean Pampa. The corneas were evaluated using ex vivo laser-scanning confocal microscopy, light microscopy and transmission electron microscopy. Those studies allowed us to obtain detailed images of the corneal layers as well as quantitative data of the cellular and sub-basal nerve densities in the cornea from sheep of different ages. The density of the corneal cells was significantly different in the anterior versus the posterior epithelium and stroma. Moreover, the density of the epithelial, stromal cells and endothelial cells, as well as the sub-basal nerve density were significantly lower in adult than in young animals. Our work provided a wide-ranging description of the corneal ultrastructure of healthy female Merino sheep, which adds to the current knowledge about the ophthalmological aspects of this species and undoubtedly benefits veterinarians.

Participación de componentes inmunológicos en la etiopatogenia de la queratopatía climática esferoidea / Involvement of immune components in the etiopathogenia of climatic droplet keratopathy

Objetivo. Investigar si componentes de la inmunidad innata están involucrados en la iniciación/perpetuación de las anormalidades estructurales observadas en la capa de Bowman y el estroma superficial de la córnea de pacientes con queratopatía climática esferoidea (QCE). Materiales y métodos. En el estudio participaron 8 pacientes con QCE y 12 individuos sanos del Departamento El Cuy, Provincia de Río Negro, y 10 individuos sanos de la ciudad de Córdoba. Todos ellos, luego de firmar el consentimiento informado, recibieron un examen oftalmológico completo y se recolectaron muestras de lágrima para estudiar las concentraciones de diferentes citocinas, niveles y formas de metaloproteinasas de matriz (MMPs), y el inhibidor natural de MMPs (TIMP-1). Se realizó microscopía confocal in vivo (MCF) en algunos pacientes y controles. Biopsias de córneas provenientes de pacientes que fueron tratados con queratoplastia penetrante también fueron estudiadas mediante inmunohistoquímica (IHQ). Resultados. Los resultados de MCF indicaron claramente una progresión en la cantidad de depósitos a nivel subepitelial, a medida que la enfermedad avanza. El daño progresivo de las fibras nerviosas sub basales y estromales en los estadios 2 y 3 se correlaciona con pérdida de la sensibilidad corneal. Además de estas alteraciones, observamos que el número de células dendríticas (CD) en el limbo corneal aumentó significativamente a medida que la QCE progresa. En lágrimas de pacientes con QCE se detectaron concentraciones significativamente superiores de citocinas proinflamatorias (IL1ß e IL-8) que en individuos controles (p<0,005). No se halló IL-2, IL-17, IL-4, IL-13 ni IL-10 en pacientes y ni controles. Las actividades de gelatinasas (MMP-9 y -2) fueron significativamente mayores en QCE que en los controles (p<0,001), mientras que los niveles de TIMP-1 fueron significativamente menores en los pacientes (p<0,05). La concentración de MMP-8 fue mayor en controles pero los niveles de esta colagenasa-2 fueron 30 veces superiores, tanto en QCE como controles, con respecto a los valores de los individuos de un centro urbano. Mediante IHC observamos reactividad para MMP-9 en la mayoría de las células epiteliales, solamente en córneas con QCE. Conclusión. Demostramos un rol protagónico del eje citocinas proinflamatorias - gela-tinasas en el desarrollo de la QCE. Los altos niveles de IL-1ß e IL-8 en lágrimas de pacientes facilitan la producción de MMP-8 y gelatinasas, y los efectos de las mismas se exacerban, ya que los pacientes tienen bajos niveles de sus inhibidores naturales (TIMP-1). La MMP-9, además de degradar componentes de la matriz extracelular, cataliza la activación postranscripcional de IL-1ß, potenciando el proceso inflamatorio. Estos resultados son los primeros en explicar mecanismos inmunológicos involucrados en la etiopatogénesis de la QCE y aportan nuevas alternativas para el desarrollo de terapias preventivas utilizando inhibidores de IL-1ß y/o gelatinasas(AU)

Objective. To investigate whether components of innate immunity are involved in the initiation / perpetuation of the structural abnormalities observed in Bowman's layer and superficial stroma of the córnea of patients with Climatic droplet keratopathy (CDK). Materials and Methods. The study included 8 CDK patients and 12 healthy individuals from Department El Cuy, Province of Río Negro, and 10 healthy subjects from the city of Córdoba. All of them, after signing informed consent, received a thorough eye exam and tear samples were collected to study the concentrations of different cytokines, and levels and forms of matrix metalloproteinases (MMPs) and their natural inhibitor (TIMP-1). In vivo confocal microscopy (CFM) was performed in some patients and controls. Corneal biopsies from CDK patients treated with penetrating keratoplasty were also studied by immunohistochemistry (IHC). Results. CFM results clearly indicated a progression in the amount of deposits at corneal sub epithelial level as the disease progresses. The progressive damage in the nerve plexus in stages 2 and 3 correlated with a loss of corneal sensitivity. In addition to these alterations, we observed that the number of dendritic cells (DC) in the limbus increased significantly as the disease progresses.In tears of patients with CDK we detected significantly higher concentrations of pro-inflammatory cytokines (IL-1ß and IL-8) than in control subjects (p < 0.005). We found no IL-2, IL-17, IL-4, IL-13 and IL-10 in patients and controls. The activities of gelatinases (MMP-9 and -2) were significantly higher in CDK than in controls (p < 0.001), while TIMP-1 levels were significantly lower in patients (p < 0.05). The concentration of MMP-8 was higher in controls, but levels of this collagenase-2 were 30 times higher, both in CDK and controls, with respect to MMP-8 values of individuals inhabiting an urban area. By IHC we observed reactivity for MMP-9 in most epithelial cells only in CDK corneas. Conclussion. We demonstrated a key role of the axis pro-inflammatory cytokines ­ gelatinases in the development of CDK. High levels of IL-1ß and IL-8 in tears of patients facilitate the production of MMP-8 and gelatinases, and the effects of these molecules are exacerbated because patients have low levels of their natural inhibitors (TIMP-1). Since MMP-9 besides degrading extracellular matrix components, catalyzes the post translational activation of IL-1ß, the inflammatory process is fuelled. These results are the first to explain immunological mechanisms involved in the pathogenesis of the QCE and provide new alternatives for the development of preventive therapies using inhibitors of IL-1ß and / or gelatinases.(AU)