Name: Cell-Free DNA Extraction and Analysis from Eye Humor
Uploaded: 2024-01-12T12:55:00
Description: Watch this Scientific Journal Video about Cell-Free DNA Extraction and Analysis from Eye Humor at JoVE.com

cell-free dna extraction and analysis from eye humor

Diagnóstico del linfoma vitreorretiniano mediante ADN libre de células

Vitreoretinal lymphoma (VRL) is an aggressive lymphoma associated with primary central nervous system diffuse large B-cell lymphoma1,2,3. VRL is typically fatal due to its involvement in the central nervous system1,2. Although rare1,4, VRL often presents with symptoms similar to posterior uveitis and other vitreoretinal diseases4,5. Consequently, patients exhibiting uveitis symptoms require a diagnosis to either confirm or rule out VRL.
Recently, consensus criteria for diagnosing VRL were published, which involve a combination of clinical examination and laboratory findings6. Specimens commonly used to diagnose VRL include vitreous humor and, more recently, aqueous humor7. Vitreous humor is obtained through a surgical procedure called pars plana vitrectomy, which allows access to the posterior segment of the eye8.
In the presented protocol, both aqueous humor and vitreous humor specimens were collected for cellular and cfDNA extraction. After anesthetizing the patients and placing trocars approximately 4 mm from the corneal limbus, an aqueous humor sample of approximately 100-200 &#181;L was obtained using a 1 mL tuberculin syringe at the corneal limbus. For pseudophakic patients, undiluted vitreous was obtained by introducing sterile air into the infusion, enabling the collection of a larger amount of undiluted vitreous (up to 3.5 mL). In phakic patients, approximately 500 to 1000 &#181;L of undiluted vitreous was removed before turning on an infusion of balanced salt solution. In some cases, secondarily diluted vitreous (500 to 2,000 &#181;L) was collected by switching the infusion to fluid and placing the vitrector within the vitreous skirt to obtain this sample. The most dilute vitreous fraction was collected by preserving the cassette bag (Supplemental Figure 1) at the end of the surgery. Once this bag reached the pathology department, dilute vitreous was obtained from draining fluid out of this bag into conical tubes for subsequent DNA extraction.
Cytopathology of vitreous fluid is often considered the gold standard9. However, several studies have demonstrated limited sensitivity due to processing and minimal cellularity10,11,12. Flow cytometry can aid in identifying clonal B-cells but can also be limited by low cellularity and the fragility of large lymphoma cells13,14,15. Both cytopathology and flow cytometry requires intact whole cells. Many of these cells are destroyed during collection, storage, and processing. When molecular testing is performed using DNA extracted from intact cells (cellular DNA), it suffers from this same limitation. In addition, dividing the limited vitreous specimen for all of these tests reduces the amount of material available for each test.
Cell-free DNA (cfDNA) represents another source of DNA that does not require intact cells. cfDNA from vitreous specimens has been used for the detection of VRL16,17 as well as uveal melanoma18. In this protocol, cellular and cell-free DNA are extracted from vitreous and aqueous fluid to detect VRL.

Autor destacado: Avance en el diagnóstico de VRL mediante la extracción de ADN libre de células del humor vítreo 

Extracción de ADN libre de células de muestras de humor vítreo y acuoso para el diagnóstico y seguimiento del linfoma vitreorretiniano

With this research, we are attempting to use molecular testing of vitreous humor collected from the eye by vitrectomy to diagnose vitreoretinal lymphoma or VRL, which is an aggressive disease whose symptoms overlap those of common inflammatory ocular conditions. Cytopathology flow cytometry and molecular testing are current methods used to diagnose VRL. Published sensitivities of non molecular methods are 44 to 90%for cytopathology and 50 to 60%for flow cytometry, cytopathology, flow cytometry and molecular testing with cellular DNA requires intact neoplastic cells.That poses a problem in vitreous humor specimens because the volume and cellularity of these specimens is low and cells can be degraded by apoptosis as well as specimen collection, processing and storage. We found that cell-free DNA extracted from vitreous fluid specimens provides another source of DNA from molecular testing that does not require intact cells, and that also shows evidence of VRL and can be used to diagnose this lymphoma. Cell-free DNA extraction offers molecular testing without intact neoplastic cells.This allows maximizing the utility of vitreous specimens as intact cells can be reserved for cytopathology and flow cytometry while utilizing the remaining supernatant fluid that would otherwise be discarded for molecular testing.

Watch this Scientific Journal Video about Cell-Free DNA Extraction and Analysis from Eye Humor at JoVE.com

Cell-Free DNA Extraction and Analysis from Eye Humor  

Extracción y análisis de ADN libre de células a partir del humor ocular

Para empezar, añade 70 microlitros de tampón acondicionador por cada mililitro de la infracción supernada libre de células del humor ocular. Agite las perlas de limpieza para mezclarlas bien. A continuación, agregue las perlas a la muestra, luego haga un vórtice de la muestra y las mezclas de perlas.Centrifugar esta mezcla a 3000 G durante 15 minutos a temperatura ambiente. Sin desalojar el gránulo, extraiga el supernadado, luego agregue un volumen igual de tampón de digestión de gránulos de orina al gránulo. Pipetee la solución hacia arriba y hacia abajo para volver a suspender el gránulo.Ahora agregue proteinasa K a la mezcla de gránulos resuspendidos. Incubar la mezcla a 55 grados centígrados durante 30 minutos, luego agregar un volumen igual de tampón de lisis genómica a la mezcla de digestión. Agite bien la solución para mezclarla bien.Ahora, coloque la columna de centrifugación disponible comercialmente en un nuevo tubo de recolección. Agregue 200 microlitros de tampón de preparación de ADN de orina a la columna de centrifugación. Centrifugar a 16.000 G durante un minuto a temperatura ambiente y desechar el flujo.Ahora pipetee 700 microlitros de tampón de lavado de ADN de orina en la columna y centrifugue como se demuestra. Después de descartar el flujo, transfiera la columna de centrifugación a un tubo de microcentrífuga sin DNasa y RNasa. Por último, agregue el volumen apropiado de tampón de elución de ADN directamente a la matriz de la columna y déjelo reposar durante tres a cinco minutos a temperatura ambiente, luego centrifugue nuevamente para obtener ADN libre de células.Los rendimientos de ADN de los componentes celulares y libres de células de los fluidos oculares fueron similares. Se realizó un análisis por PCR de los componentes celulares y libres de células de una mutación asociada al linfoma vitreorretiniano. Una mayor tasa de mutación estuvo presente en el componente libre de células, como lo demuestra un umbral de ciclo más bajo.

Research

JoVE Journal

Cancer Research

Cell-Free DNA Extraction and Analysis from Eye Humor

Cell-Free DNA Extraction of Vitreous and Aqueous Humor Specimens for Diagnosis and Monitoring of Vitreoretinal Lymphoma

Vitreoretinal lymphoma (VRL) represents an aggressive lymphoma, often categorized as primary central nervous system diffuse large B-cell lymphoma. To ...

Investigación

Investigación sobre el cáncer

Separation of Cellular and Cell-Free Fractions of the Vitreous and Aqueous Humor for DNA Extraction

Separación de fracciones celulares y libres de células del humor vítreo y acuoso para la extracción de ADN

Extraction and Analysis of DNA from the Cellular Component of the Eye Humor

Extracción y Análisis de ADN del Componente Celular del Humor Ocular