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Spanish to English: Stem Cells General field: Medical
Source text - Spanish Las células madre adultas más estudiadas, hasta ahora, son las que se derivan de la médula ósea; allí se han identificado por lo menos tres grupos: células madre estromales, células madre hematopoyéticas y un grupo que algunos autores identifican como side population y del cual se conoce muy poco. Las células madre estromales se han identificado por marcadores de superficie que han permitido aislarlas como SH2, SH3, CD29, CD44, CD71 y CD90. Las células madre estromales no expresan antígenos de superficie típicos de las células madre hematopoyéticas como el CD34 y CD45; además, pruebas recientes han demostrado in vitro que las células madre estromales son capaces de diferenciarse a tejidos mesodérmicos funcionales y constituyen un modelo muy útil en aplicaciones clínicas para ciertas enfermedades tanto en terapia regenerativa como en terapia génica (Jiang et al., 2002).
Otro ejemplo de las células madre adultas identificadas en médula ósea son las células madre hematopoyéticas, responsables de la renovación constante de las células sanguí- neas, es decir, de la producción de billones de nuevas células cada día (Weissman IL. 2000). Las células madre hematopoyéticas aparecen en el embrión entre la tercera y cuarta semana de gestación, estas células migran desde el saco vitelino hasta el hígado y el bazo y por último llegan a la médula ósea a través de la circulación fetal durante el segundo y tercer trimestre de gestación.
Estas células han sido aisladas de sangre periférica y de médula ósea; tienen la capacidad de autorrenovarse y diferenciarse en dos grupos de progenitores hematopoyéticos: progenitor mieloide y progenitor linfoide, los cuales a su vez se diferencian hacia linajes de células sanguíneas especializadas (Gasparoni et al., 2000; Fliedner et al., 1998).
El proceso de movilización de las células madre hematopoyéticas está caracterizado por la migración y la tendencia selectiva de estas células para retornar a la médula ósea. La capacidad de autorrenovación, proliferación y diferenciación de las célu- las madre hematopoyéticas está regulada por un complejo mecanismo en el cual se encuentran involucrados el microambiente medular, citocinas estimuladoras e inhibidoras, así como también las
interacciones célula-célula y célula-matriz extracelular.
Estas interacciones están mediadas por moléculas de adhesión celular las cuales se expresan en las células madre hematopoyéticas, células endoteliales y células del estroma medular (Timeus et al., 1998). Durante el desarrollo embrionario, las células madre hematopoyéticas que van a dar lugar a las células sanguíneas, migran desde el hígado fetal hacia la médula ósea a través de los vasos sanguíneos; una vez allí re-invaden este tejido con altos niveles de células maduras e inmaduras, las cuales son liberadas nuevamente a la circulación, mientras que un pequeña cantidad de células madre indiferenciadas se mantiene dentro de la médula ósea produciendo de forma continua células maduras e inmaduras del linaje mieloide y linfoide (Lapidot y Petit, 2002).
Las células madre hematopoyéticas son la base biológica de los transplantes de médula ósea para pacientes que padecen de patologías como leucemias y aplasias medulares; sin embargo, la obtención de donantes compatibles con el receptor y los costos que implican estos procedimientos han creado la necesidad de buscar fuentes alternas para la obtención de éste tipo de células. Una alternativa interesente para la obtención de células madre hematopoyéticas constituye la sangre de cordón umbilical (SCU); las principales ventajas del uso de SCU como una fuente alternativa de células madre hematopoyé- ticas son: fácil obtención de la muestra, viable aprobación de donantes voluntarios, ausencia de riesgo para los donantes, menor riesgo de enfermedad aguda del injerto contra el huésped y bajos costos. Estas ventajas se reconocieron inicialmente en trasplantes de SCU realizados con donan- tes emparentados; posteriormente, se establecieron bancos de SCU, los cuales estandarizaron el método de recolección de la muestra, su almacenamiento, procesa- miento y criopreservación para realizar tras-plantes de células madre hematopoyéticas de SCU en donantes no emparentados y así apoyar el tratamiento de enfermedades hematológicas malignas y no malignas (Barker et al., 2002).
Las células madre constituyen entonces una interesante alternativa de investigación, principalmente por el potencial terapéutico que es descifrado cada vez más por los investigadores. Sin embargo, cuando se discute sobre temas como la clonación y ahora sobre células madre, es importante considerar las implicaciones éticas que con- lleva su manipulación y no desconocer que en el campo de la biología de las células madre queda aún mucho por hacer.
Translation - English Up to now the most well studied stem cells are those which are derived from bone marrow.
Here at least three types of stem cells have been identified: stromal stem cells, hematopoietic stem cells and another type which some authors have identified as side population cells and of which very little is known. The stromal stem cells have been identified by surface markers which make it possible to isolate them as SH2, SH3, CD29, CD44, CD71 and CD90. Stromal stem cells do not express antigens with a different surface to those produced by hematopoietic stem cells such as CD34 and CD35. Furthermore recent studies in vitro have shown that stromal stem cells are capable of differentiating themselves from functional mesodermic tissue. This constitutes a very useful model for clinical applications for certain illnesses as well as in regenerative therapy such as gene therapy (Jiang et al 2002)
Another example of adult stem cells found in bone marrow are the hematopoietic stem cells which are responsible for the constant renovation of blood cells, in other words, the production of billions of new cells each day (Weissman IL 2000). Hematopoietic stem cells appear in the embryo between the third and fourth week of gestation. These cells migrate from the yolk sac to the liver and the spleen until they finally reach the bone marrow through fetal circulation during the third trimester of gestation.
In experiments these cells have been separated from peripheral blood and bone marrow. They have the ability to restore themselves and differentiate themselves into two different hematopoietic progenitor cells, the myeloid progenitor and the lymphoid progenitor.
The mobilization process of these hematopoietic stem cells is characterized by migration and the selective tendency of these cells to return to the bone marrow. Their capacity for self-renewal, proliferation and differentiation from hematopoietic stem cells is regulated by a complex mechanism in which the marrow microenvironment, stimulating cytokines as well as cell-cell and cell-extracellular matrix interactions are involved.
These interactions are mediated by cell adhesion molecules which are expressed in the
hematopoietic stem cells, endothelial cells and cells from the marrow stroma (Timeus et all 1998). During embryonic development the hematopoietic stem cells which give rise to blood cells migrate from the fetal liver to the blood marrow through blood vessels: Once they have arrived they invade the tissue with high levels of mature and immature cells, which are released into the circulation, while a small amount of undifferentiated stem cells remains within the bone marrow and continually produces mature and immature cells of myeloid and lymphoid lineage.
Hematopoietic stem cells are the biological basis for the transport of bone marrow to patients who suffer from pathological conditions such as leukaemia or marrow aplasia. However the difficulty in obtaining donors compatible with the receptor and the costs involved with these procedures have made it necessary to investigate alternative sources of obtaining this type of cell. An interesting alternative for obtaining hematopoietic stem cells involves blood from the umbilical cord. The main advantages of using cord blood as an alternative source of hematopoietic stem cells are as follows: samples are easily obtained, it is viable to get permission from voluntary donors, there is no risk to the donor, there is a low risk of acute illness in the recipient from the graft and it is a low cost procedure.
These advantages were initially recognised in cord blood transplants carried out with donors who were related to each other. Subsequently cord blood banks were established in which the method of sample collection, its storage, it’s processing and its cryopreservation were standardized. This made it possible to carry out transplants of cord blood hematopoietic stem cells from donors who are not related to the patient and in this way support the treatment of malignant and nonmalignant hematopoietic illnesses.
Stem cells are therefore an interesting alternative for investigation, principally because of their therapeutic potential which is constantly being better understood by scientists. Nevertheless, when discussing topics related to cloning and now stem cells it is important to consider the ethical implications that accompany their manipulation and the fact that there is still a lot we do not know about this field of biology.
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Translation education
Master's degree - Queen's University Belfast
Experience
Years of experience: 13. Registered at ProZ.com: Mar 2011.
I am a Swedish & Spanish into English translator based in Belfast, UK, with ten years of professional experience and a Master's Degree in Translation Studies. I specialise in the translation of marketing and promotional materials for the tourism and leisure industry. I have worked for a number of high profile clients in this area, including Expedia, Hotels.com, Sail Training International, and Carlson Wagonlit Travel. I also have ample experience with a range of additional text types, including journalistic, legal and financial documents.
I am the winner of the 11th Proz competition for my translation of an excerpt from 'El superhombre y otras novedades' by Juan Valera. (http://www.proz.com/translation-contests/pair/1828)
My rates are 0.10€ per source word for translation and 0.05€ per source word for proof reading.
Please don't hesitate to get in touch if you would like any more information about my skills and abilities, or if you would like to request a reference or short sample translation.
Michael Purvis 
