Stem cells are characterized by the ability to replicate themselves limitlessly. After being created, these identical copies can remain undifferentiated for a long period of time. When receiving specific signals from internal and external environments, they transform themselves to a particular type of cell in the body with specialized functions and features. Therefore, they act as an essential system for tissue repair and growth (National Institutes of Health, 2009). Based on their origins, stem cells can be divided into three categories: human embryonic stem cells (hESCs), adult stem cells (ASCs) and induced pluripotent stem cells (iPSCs).
According to National Institutes of Health, hESCs are stem cells taken from human embryos, which are fertilized under an artificial laboratory environment rather than in the productive system of a woman. These embryos are not initially made for scientific research, but they are redundant ones from in vitro fertilization (2009). After five days since fertilized, the zygote develops into a blastocyst, which is a hollow ball with an inner cell mass. And it is in this stage that the hESCs are extracted and then grown in the …show more content…
While hESCs are pluripotent, which means that they have ability to turn into a wide range of specialized types of cells, ASCs have limits in their differentiation capacity. They are able to transform into some major types of cells only. In terms of origins, ASCs are assumed to locate in a separated area within each tissue, where they remain inactive for long periods of time. Only when they receive signals do they become specialized to repair damaged cells. After removed from the body, ASCs still need to be expanded in population in laboratories. Generally, ASCs exist in lower quantities and it is more challenging to grow a high number of ASCs than that of hESCs. (National Institutes of Health,
According to National Institutes of Health, hESCs are stem cells taken from human embryos, which are fertilized under an artificial laboratory environment rather than in the productive system of a woman. These embryos are not initially made for scientific research, but they are redundant ones from in vitro fertilization (2009). After five days since fertilized, the zygote develops into a blastocyst, which is a hollow ball with an inner cell mass. And it is in this stage that the hESCs are extracted and then grown in the …show more content…
While hESCs are pluripotent, which means that they have ability to turn into a wide range of specialized types of cells, ASCs have limits in their differentiation capacity. They are able to transform into some major types of cells only. In terms of origins, ASCs are assumed to locate in a separated area within each tissue, where they remain inactive for long periods of time. Only when they receive signals do they become specialized to repair damaged cells. After removed from the body, ASCs still need to be expanded in population in laboratories. Generally, ASCs exist in lower quantities and it is more challenging to grow a high number of ASCs than that of hESCs. (National Institutes of Health,