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Therapies with human embryonic stem cells Several diseases such as Parkinson and Juvenile Diabetes Mellitus are resulting from the death of dysfunction of one or some cell types. So, the replacement of these cells for tissues produced from human embryonic stem cells could provide a long lasting therapy. The capacity for human embryonic stem cells to differentiate into several cell types in vitro allows that these cells may become an almost unlimited source for the production of tissues that could be used for transplant and for several diseases. However, therapies with embryonic stem cells have not been performed yet. These cells must be cultivated and differentiated in vitro for long periods before being transplanted, since once injected in its undifferentiated form they can multiply and differentiate in an uncontrolled way, giving rise to tumors instead of the desired therapeutic tissue.

Research on human embryonic stem cell in Brazil In Brazil, it has been recently approved the law for the researches with human embryonic stem cells, but many ethical issues regarding the topic are discussed. As these cells until now are obtained from the inner mass cell of the blastocyst, i.e. from an embryo, it is necessary the destruction of these embryos to obtain these cells. Some conflicts between religion and science are inevitable. Most of the researches are performed with lines of human embryonic stem cells, i.e. these cells had already been obtained and expanded in vitro for trading. In Brazil there are only two centers of authorized researches to establish embryonic stem cells lines that can be used by other centers, which becomes a controlled and regulated proceeding.

This material was produced as part of the subject of a post-graduate program at the Medical School of Ribeirão Preto (FMRP)

Authors:

Maristela Delgado Orellana, Costa and Rodrigo Guarischi.

House of Science - 2011

Everton

Translation and Revision: Alessandra and Fernanda Almeida Udinal Layout: Gisele Oliveira Subject of the post-graduate program: Cell Therapy and Cytogenomics: Progress and Perspectives – Prof. Dr. Dimas Tadeu Covas, Dr. Aparecida Maria Fontes and Dr. Fábio Morato Oliveira. Reference ZAGO, MA; COVAS, DT. Células-tronco: a nova fronteira da medicina. São Paulo: Atheneu, 2006. Publishing:

Fundação Hemocentro de Ribeirão Preto Rua Tenente Catão Roxo, 2501 Campus Universitário - Monte Alegre Ribeirão Preto - SP (16) 2101-9308 http://hemocentro.fmrp.usp.br/casadaciencia e-mail: casadaciencia@hemocentro.fmrp.usp.br

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Did you know that some researchers have differentiated human embryonic stem cell into blood cells? At the Regional Blood Center of RibeirĂŁo Preto researches on human embryonic stem cells are performed. Following specific methodologies, these cells can be differentiated into red blood cells, granulocytes, megakaryocytes, natural killer cells and lymphocytes. The cell produced by some research groups are very similar to blood cells found in the adult organism, but they still present features very similar to embryonic and fetal phases. These discoveries constitute models for the study of the genetic mechanisms involved in the production of blood cells and in the origin of blood disorders. It is necessary to consider that the conditions used in the in vitro production of these cells are not identical to the in vivo organism. Thus, the issue is whether these cells perform the same work of the cells found naturally in the human organism. Currently, many studies have been conducted to answer this issue. The production of blood cells for clinical use depends on the solution of some problems such as: risk of tumor when injected in vivo, chromosomal instability of these cells during their cultivation, presence of contamination derived from products of animal origin used in the institute, cultivation and differentiation of embryonic stem cells, large scale production and low cost, and incompatibility between the cells generated and those from the donor.

What are stem cells and what are the types? Stem cells are cell without specific function, with high potential of multiplying, which differentiate and specialize giving origin to mature and functional cells of the adult tissue.

The stem cells are divided into: embryonic and somatic. Embryonic: as the name says, cells found in the embryonic period. They are pluripotent, since they are able to multiply unlimited and differentiate into all the cells that compose the adult individual, but are unable to form the placenta and the fetal annex. Somatic: are found in the tissues of an adult individual and are able to differentiate into only some types of specific cells.

How do they raise and where are human embryonic stem cells found? Do you remember embryonic development? After the fertilization of the egg by the sperm, there is the formation of a cell with 46 chromosomes, named zygote, the beginning of the embryonic development. The mitotic division of the zygote into two daughter cells called blastomeres begins a few days after fertilization (see the scheme beside – figure 1). At the initial stages of this process, the multiple cell divisions of the blastomeres take to a stage known as morula, which consists of a massive Figure 1: Scheme of embryonic stem cells origin structure of cells. Following, there is the formation of blastocysts or blastula that has the inner cell mass and an external cell mass. The cells of the inner part form the fetus and some extra-embryonic tissues such as amnion and allantois. Besides, they have an unlimited potential of proliferation and can differentiate into all the cell types that compose that adult organism, they are, pluripotent stem cells or embryonic. The cells that constitute the external layer of the blastocyst will give rise to tissues related to the placenta. In 1998, for the first time, James Thomson and colleagues took cells from the inner cell mass of human blastocysts and cultivated them in vitro, giving rise to the first line of embryonic stem cells. Figure 2: Colonies of embryonic stem cells cultivated in vitro


Folhetins-Human Embryonic Stem Cells