BIOTECHNOLOGY - Inshyna N.M. - 2009

CHAPTER 3. CELL ENGINEERING

Embryonic Stem Cells

Billions of Cells in The Human Body originate from a single Cell—the zygote, formed by the fusion of male and female Gametes. This single cell contains not only the blueprint for the Organism but also the developmental program governing its sequential growth (Fig. 3.2).

Embryonic stem cells (ESCs) serve a singular primary function: the transmission of genetic material to subsequent generations.

Geneticists utilize ESCs to investigate Organogenesis. Their use represents the only experimental approach available for studying human organogenesis anomalies. Furthermore, ESCs serve as source material for generating human somatic cells.

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Fig. 3.2. Scheme of organism development

The primary source of material for generating laboratory somatic cells consists of ESC clones isolated from human embryos at the blastocyst stage. A blastocyst comprises an outer cell layer and an internal fluid-filled cavity containing stem cells. Stem cells are derived from the inner cell mass by disrupting the blastocyst. A blastocyst contains approximately 150 cells, of which only 30 are stem cells. During embryonic development, stem cells disappear after the 7th day of gestation.

A secondary source of ESCs is Germ Cells. ESCs are obtained from in vitro fertilized oocytes (Artificial Insemination). ESCs are easily cultivated due to their capacity for unlimited division. Certain human ESCs can divide 300–400 times, while mouse ESCs can be maintained in culture for several decades.

Identifying substances that direct ESC differentiation is a critical area of research. American scientists conducted an experiment in which they propagated a human ESC culture in a nutrient medium containing two Proteins that direct Cell Differentiation. Due to the presence of these growth factors, more than 80% of the stem cells transformed into cardiomyocytes (specialized Heart Muscle cells). Previously, the yield of cardiomyocytes did not exceed 1%. The resulting cardiomyocytes were transplanted into the hearts of rats that had undergone experimentally induced myocardial infarction four days prior. Prior to transplantation, these cells were treated with compounds that facilitate the integration of new tissue and protect it against premature degradation. This resulted in a 100% graft survival rate and improved myocardial function in the treated animals. When only cardiomyocytes without protective additives were transplanted into post-infarction rats, the engraftment rate did not exceed 18%. Researchers plan to use cardiomyocytes to replace myocardial areas necrotic following an infarction.

Studies have been conducted on generating Insulin-secreting Langerhans islet cells from ESCs. When transplanted into the Pancreas of immunodeficient mice, these cells protected the animals from sharp spikes in Blood glucose levels. Scientists have high hopes for technology enabling The production of pancreatic cells from ESCs, which yield 250 generations per year in culture (a new generation every 1.5 days). These studies open new Perspectives in the Treatment of Diabetes Mellitus.

Research involving mice has confirmed that the administration of ESCs mitigates symptoms of conditions such as diabetes mellitus, Parkinson's disease, cardiovascular disorders, and Spinal Cord injuries. However, evidence suggests that ESCs may also serve as a source of certain types of Cancer in vivo.