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Stem Cell Basics: Types and How They Work

Here's a walkthrough of what stem cells actually are, and why they matter so much in medicine.

  1. What is a stem cell?

    A stem cell is an undifferentiated cell that hasn't yet developed a specific function, meaning it still has the potential to develop into many different types of cells.

  2. Embryonic stem cells

    Embryonic stem cells are obtained from the inner cell mass of a blastocyst, an early stage of embryonic development, and they have the pluripotency to develop into nearly every type of cell that makes up the body.

  3. Adult stem cells

    Adult stem cells exist in already-developed tissue, such as bone marrow or umbilical cord blood, and unlike embryonic stem cells, they're multipotent stem cells that can only develop into a limited range of cell types.

  4. Induced pluripotent stem (iPS) cells

    An induced pluripotent stem cell is an already-differentiated adult cell that has been reprogrammed back to a state similar to an embryonic stem cell by introducing specific genes (Yamanaka factors) β€” a technique developed by Shinya Yamanaka in 2006, for which he received the Nobel Prize in Physiology or Medicine in 2012.

  5. Differentiation

    Differentiation is the process by which a stem cell, as the expression of specific genes is regulated, becomes a cell with a distinct shape and function β€” such as a muscle cell or a nerve cell.

  6. Medical applications

    Stem cells are being used across a range of fields, including regenerative medicine research aimed at repairing damaged tissue or organs, and research that tests new drugs' effectiveness and toxicity at the cellular level before further testing.

  7. Ethical debates

    Because obtaining embryonic stem cells requires destroying an embryo, they're the subject of bioethical controversy β€” which is part of why iPS cell technology, which can achieve similar effects without using an embryo, has drawn so much attention as an alternative.

How one cell grows into many different kinds of cells

A single fertilized egg divides repeatedly and develops into countless different types of cells with distinct functions β€” muscle, nerve, skin, and more. This kind of undifferentiated cell, capable of differentiating into such a wide variety of cell types, is called a stem cell, and it has drawn enormous attention in the field of regenerative medicine.

The virus used to help create stem cells, too

When Shinya Yamanaka first created induced pluripotent stem (iPS) cells, he used a retroviral vector to deliver the necessary genes into the cells. If you're curious how a virus differs from a bacterium, that's what virus vs. bacteria basics covers.

Frequently Asked Questions

What's the difference between embryonic stem cells and iPS cells?

Embryonic stem cells can only be obtained by destroying an embryo, while iPS cells are made by introducing specific genes into an already-differentiated adult cell to artificially revert it β€” so they can achieve similar pluripotency without using an embryo at all.

Why do people use cord blood banks?

Cord blood, obtained from the umbilical cord and placenta, is rich in adult stem cells such as hematopoietic (blood-forming) stem cells, so it's often frozen and stored for potential future use in treating blood disorders such as leukemia.