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Embryonic stem cells are derived from the inner cell mass of 3 to 5 day old mammalian embryos. Human ES cells are sourced from spare embryos remaining after in vitro fertilization procedures. These cells are then grown in culture medium where they can divide indefinitely, creating ES cell lines for research and therapeutic applications.

ES cells are pluripotent, meaning they can transform into any cell type in the body. By providing specific growth factors or manipulating culture conditions, researchers can direct ES cells to differentiate into terminally differentiated cells such as muscle cells, neurons, pancreatic beta cells, blood, heart, bone, or liver cells.

Regenerative medicine uses ES cells to create living, functional tissues replacing dead, diseased, or malfunctioning ones. Because ES cells differentiate into any cell type, they offer therapeutic potential. Clinical studies have begun testing their safety and effectiveness, with promising initial results including paralyzed patients regaining movement after receiving ES-derived nervous system cells.

ES cell therapy carries several risks. Embryonic cells may trigger immune rejection in recipient patients because they are foreign to the patient's body. Additionally, ES cells carry the risk of tumor formation when implanted. The use of human ES cells is also controversial because it involves using human embryos, raising ethical concerns among scientists, religious leaders, and policy-makers.

Scientists control ES cell differentiation by manipulating culture conditions, such as changing the culture dish surface or adding specific growth factors to the culture medium. Genetic modification of the cells also enables directed differentiation. These methods allow researchers to generate desired cell types, including blood, nerve, heart, bone, liver, and pancreatic cells.

Beyond tissue repair, ES cells are used to study early events in human development and provide specific cell types for drug testing and scientific research. Their ability to differentiate into various cell types makes them valuable for screening drugs, diagnosing genetic disorders, and understanding developmental processes in humans.

Embryonic stem cells are derived directly from 3 to 5 day old embryos, while induced pluripotent stem cells are created by reprogramming adult somatic cells. Both are pluripotent and can differentiate into any cell type. However, induced pluripotent stem cells avoid the ethical concerns associated with using human embryos, making them an alternative approach in stem cell research and eps and ips cells in disease research.