Stem Cells from Amniotic Fluid: An Untapped Resource

Many of us have seen reports in the news about stem cells and their wondrous potential for treating a wide variety of ailments. We’ve likely also read about the controversies surrounding obtaining these stem cells- either the ethics behind embryonic stem cells or the difficulties in obtaining, matching, and using bone marrow stem cells.

Dr. Margaret Dziadosz, Dr. Basch, and Dr. Young from New York University have spent years studying a different source for stem cells: amniotic fluid. They published a review in the March 2016 issue of the American Journal of Obstetrics and Gynecology about the current state of affairs for amniotic fluid stem cells (here).

Before diving into the specifics of amniotic fluid stem cells, let’s briefly review stem cells in general. Stem cells are generalized cells that haven’t yet become a certain cell type yet, called “undifferentiated.” Stem cells can replicate without further specializing into a certain cell type, called “self-replication without differentiation.” When a stem cell does change into a specific cell type (like a bone cell or a nerve cell), the process is called “differentiation.”

The promise of stem cell therapy is that the cells can be used to treat injuries or abnormalities in tissue. For instance, bone marrow transplants take advantage of stem cells that will replicate and form (differentiate into) normal blood cells in place of abnormal ones.

There are several known sources for stem cells, but many of them have issues. Sources include: embryonic, bone marrow, umbilical cord blood and cells, placenta, amniotic membranes, amniotic fluid, peripheral blood, and mature cells that scientists manipulate to return to the stem cell state. The most commonly used are embryonic stem cells and bone marrow stem cells. However, embryonic stem cells can form into tumors, and bone marrow stem cells have limited ability to continue to replicate. (See chart for more information on stem cell sources.)

Amniotic fluid has several characteristics that make it a favorable source for stem cells. First, it is relatively easy to obtain and is routinely extracted during pregnancy through amniocentesis. The risk of miscarriage with amniocentesis is 0.1% in the mid trimester. Stem cells from amniotic fluid grow well in the petri dish, and scientists have even had luck freezing them. Scientists have coaxed stem cells from amniotic fluid to differentiate into a wide variety of cell types: fat, bone, cartilage, muscle, and nerve. After replicating the cells lines, they did not form tumors or become cancerous.  In fact, the cells have a remarkable ability to proliferate. One study replicated a single stem cell line 250 times! One 5 milliliter sample of amniotic fluid could result in up to 1.2 million viable stem cells.

Stem cells from amniotic fluid are a motley crew, comprising a wide variety of types of cells with different potentials. However, researchers believe that it might not be necessary to separate out a certain single type from the masses. The authors of the review were successful in creating bone, cartilage, and nerve cells without isolating a certain type of stem cell.

Thus far, quite a few studies have been conducted on stem cells from amniotic fluid using animals. Scientists were able to heal wounds on mice, show promise for treating spina bifida before birth for lambs, and engineer tissue to treat congenital defects for rabbits. There is currently one human study run by NuCell in Birmingham, AL, studying stem cells from amniotic fluid to treat knee pain from osteo-arthritis.

This is only the beginning for stem cell research, and it will be exciting to watch the progress of this promising source for stem cell therapy.