Stem cells have two similar attributes: self-renewal and differentiation. The former means an ability to make copies of themselves. The latter implies an ability to develop into more specialized cells. Despite these two essential abilities, some dissimilarities also exist among them.

Embryonic Stem Cells

These stem cells form in the blastocyst, a hollow ball of cells that emerges between 72 to 120 hours after fertilizing an egg by a sperm. The blastocyst is what later becomes the embryo. Cell differentiation begins with the implanting of the embryo in the uterus. This type of stem cell differentiates into more cell types than the adult type. Embryonic stem cells are pluripotent. This means they can differentiate into every cell type in the human body apart from the placenta and umbilical cord cells.  (Research purposes only)

Embryonic stem cells originate from the blastocyst, a hollow sphere of cells that develops 3 to 5 days after fertilization. Upon implantation in the uterus, cell differentiation starts to occur. Embryonic stem cells are known for their pluripotency, as they are able to differentiate into a wide range of cell types found in the human body, except for cells of the umbilical cord and placenta. Compared to adult stem cells, they possess greater differentiation potential. (Research purposes only)

Adult Stem Cells

Adult stem cells are also known as tissue-specific or somatic stem cells. They start forming as soon as the embryo emerges and can be found in adult tissues like bone marrow. They are not as abundant as embryonic cells. Scientists previously believed that tissue-specific cells could not differentiate into other cells. But this notion no longer holds, according to recent research. For instance, bone marrow cells can differentiate into brain cells, etc.

Adult stem cells, also called somatic or tissue-specific stem cells, begin to develop as soon as the embryo forms and can be located in adult tissues such as bone marrow. Although not as prevalent as embryonic cells, they have the ability to differentiate into other cell types, contrary to previous beliefs. Recent research has demonstrated that tissue-specific cells can differentiate into diverse cell types, such as brain cells, from bone marrow cells, for example.

Induced Pluripotent Stem Cells

These are adult cells that are genetically programmed to exhibit the characteristics of embryonic stem cells. They help scientists in the invention and testing of new therapies and medications, among other uses. Notable advancements in this field include reprogramming regular connective tissue cells into functional heart cells in animals. Injecting these new heart cells into animals with failing hearts led to improvements in heart function and survival time.

Perinatal Stem Cells

Perinatal stem cells were discovered in amniotic fluid and umbilical cord blood. Amniotic fluid is found in the sac that surrounds and protects a growing fetus in the womb. One of their characteristics is the ability to develop into specialized cells. This area requires more scientific scrutiny for further comprehension of the potential of amniotic fluid stem cells.

Mesenchymal Stem Cell (MSC)

Mesenchymal stromal cells are rare, non-hematopoietic progenitor cells of mesodermal and neuroectodermal derivation. At birth, these cells can be found in certain tissue niches, usually in a perivascular distribution.

MSCs can be used to develop new body tissues such as cartilage, bone, and fat cells. There is a possibility of using them to tackle a broad range of health challenges in the future.

Classification of Stem Cells by Differentiation Potential

• Totipotent stem cells
• Pluripotent stem cells
• Multipotent stem cells
• Oligopotent stem cells