Regenerative Medicine and Stem Cells 101

Regenerative medicine and stem cell therapy is a relatively new area of medicine. The purpose of this article series is to help you understand related terminology, and explain where human stem cells originate and how they develop.

SpineUniverse: What is regenerative medicine? Is it a new medical specialty?
Dr. Kamhi: Regenerative medicine is a new medical specialty that focuses on helping the body heal itself by its own cells. The interest in regenerative medicine and cellular research, which has been ongoing during the past 25 years, continues to advance.

SpineUniverse: Is there a medical board that oversees physician education and credentialing in regenerative medicine?
Dr. Kamhi: The American Academy of Regenerative Medicine and American Board of Regenerative Medicine are respected credentialing organizations. Member physicians who meet strict qualifications can receive education and training in regenerative medicine and practices. It is through the American Board of Regenerative Medicine that physicians, who pass rigorous written and oral examinations, can become board certified.

SpineUniverse: What is a stem cell?
Dr. Kamhi: A stem cell is an organism with the ability to develop into any type of human body cell. At first, a stem cell is undifferentiated—meaning, it hasn’t yet become specialized to perform a specific function.

Stem cells divide, and after dividing many times, it becomes specialized—meaning the stem cell may become a bone cell, muscle cell, cartilage cell, or other specialized cell type. When a cell becomes specialized it is called differentiated because the cell performs complex functions specific to its cell type (eg, bone cell, muscle cell).

SpineUniverse: Are there different types of stem cells?
Dr. Kamhi: Embryonic (from an embryo) and adult stem cells are more readily known. More recently, induced pluripotent stem cells have been added to the classification of stem cell types.

SpineUniverse: What is an embryonic stem cell?
Dr. Kamhi: An embryonic stem cell is derived from an inner cell mass of a 5-day-old human embryo, when the embryo is still in the ovarian tubes, prior to implantation into the uterus. The cell is called a blastocyst.

human embryonic developmentHuman embryonic development.

The human embryo is microscopic in size. It consists of a fluid-filled ball of inner cells (embryoblast) and outer cells (trophoblast). The inner cells are destined to become the developing embryo and the outer cells the placenta. Embryonic stem cells are also called totipotent cells, meaning these cells have the potential to develop into any type of body cell.

blastocyst with trophoblast and embryoblast cells labeledBlastocyst with trophoblast and embryoblast cells illustrated.

Embryonic stem cells are not therapeutically utilized because of ethical limitations and the risk of rejection by the patient’s immune system. However, these stem cells remain research tools in the laboratory.

SpineUniverse: What is the significance of a blastocyst?
Dr. Kamhi: The blastocyst is an organizer—blastocysts organize cells (tissues) into subtypes. When a blastocyst divides to form the germ layers, it’s organizing the development of the embryo. Germ cell layers are an integral part of embryonic development.

Reproducing cells in a blastocyst form three germ cell layers of the embryo:

  1. Ectoderm gives rise to the outer layer of the fetus’ skin.
  2. Mesoderm gives rise to bone, cartilage, muscles, connective tissue.
  3. Endoderm gives rise to the gastrointestinal, respiratory tracts.

ectoderm cells become skin, brain, pigment cellsEctoderm cells become skin, brain, and pigment cells. Used by Permission. CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1290887

mesoderm gives rise to cardiac, skeletal, and blood cellsMesoderm gives rise to cardiac, skeletal, and blood cells.

endoderm gives rise to lung, thyroid, pancreas cellsEndoderm gives rise to lung, thyroid, pancreas cells.

After the ectoderm, mesoderm and endoderm develop into their specific cell types, the germ cells lose their ability to become another type of cell. In other words, a bone cell will always be a bone cell, and cannot develop into a muscle cell, or other types of cells.

Not all germ cells mature or fully specialize—instead, they continue to replicate and are stored in the human body until needed. For example, if a bone in the body is broken (eg, arm), the mesoderm or mesenchymal stem cells are called into action to make bone cells that mend and eventually heal the fracture.

stem cells can become different types of body cellsStem cells have the ability to become different types of body cells.

Off-label Statement: The US Food and Drug Administration (FDA) has not approved stem cell-based products, except for blood forming stem cells used to treat certain types of cancers.1 When certain products (eg, platelet-rich plasma) are used by a medical professional, it’s use is termed “off-label”.2

 

Updated on: 05/23/18
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Adult Stem Cells and Induced Pluripotent Stem Cells
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Adult Stem Cells and Induced Pluripotent Stem Cells

The question what are adult stem cells and pluripotent stem cells is answered along with information about where these cells come from.
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