Researchers find possible alternative to stem cells

Pitt researchers may have found an alternative solution to one of the largest and most recent… Pitt researchers may have found an alternative solution to one of the largest and most recent controversies in medical research.

A recent study by Pitt researchers announced the possibility that the amnion – the outer membrane of the amniotic sac found in placental tissue – could have the same potential as embryonic stem cells in treating some diseases.

Stem cells are undifferentiated cells that have the ability to be transformed into other types of cells. Some researchers believe that stem cells have a regenerative power to change certain types of diseases and repair tissue.

But some pro-life groups – which view life as having already begun at the embryonic stage – oppose the use of embryonic stem cells in research.

“If we could develop efficient methods that would allow amnion-derived cells to differentiate into specific cell types, then placentas would no longer be relegated to the trash can,” said Stephen C. Strom, Ph.D., a senior author of the study. “Instead, we’d have a useful source of cells for transplantation and regenerative medicine.”

The placenta is a temporary organ found in pregnant women that partially envelops the fetus. It is delivered from the woman shortly after birth.

Embryonic stem cells are derived from the inner mass cells of an early-stage embryo, called a blastocyst. These cells are able to grow into any of the numerous cell types found in the human body and are able to be obtained from a cloned blastocyst.

One of the benefits of using a cloned blastocyst is that these cells are genetically compatible with the patient, almost completely removing the risk of rejection.

The ethical problem for some is that these blastocysts are harvested from discarded embryos – usually from failed in vitro fertilization processes.

Strom and a group of other researchers, including fellow senior author Dr. Toshio Miki, released a study showing that part of the amniotic sac contains cells with very similar structures and properties as embryonic stem cells.

The researchers refer to these cells as amniotic epithelial cells and believe they may be able to form liver, pancreas, heart and nerve cells if the proper laboratory conditions are developed.

“Provided that research advances to the point that we can demonstrate these cells’ true therapeutic benefit, parents could conceivably choose to bank their child’s amniotic epithelial cells in the event they may someday be needed, as is sometimes done now with umbilical cord blood,” Strom said.

Studies have been completed using cells from full-term pregnancies, but the amnion can be formed as soon as eight days after fertilization.

However, despite the similarities between embryonic stem cells and amniotic epithelial cells, there is one significant difference. The latter can’t grow indefinitely – possibly because of a lack of an enzyme called telomerase that is essential for the beginning stages of cell division.

While this puts a limit on the amount of cells produced, these cells are able to duplicate approximately 20 times without needing another cell type to serve as a feeder layer, as opposed to the perpetually regenerating stem cells that require a bed of cells to replicate, some of which appear in each new generation. The amniotic cells provide their own feeder layer.

“Perhaps it’s to their advantage that the amnion epithelial cells lack telomerase expression, because telomerase is associated with many cancers, and one of the main concerns about stem cell therapies is that transplanted stem cells would replicate in the recipient to form tumors,” Miki said.

Miki and Strom have been researching this possibility since 2001, when they began looking at amnion as a source for these types of cells. That, they say, was their original plan: to find cells that have the same potential for therapy that embryonic stem cells possess.

In order to complete this task, Miki, Strom and the rest of their team of researchers used immune system-deficient mice to see if tumors would occur when these cells were injected directly into tissue. Seven months after the treatment, no tumors had developed.

Strom also said that this is just the first step to see if the amniotic epithelial cells have the potential they believe them to have.

The group does not plan on stopping there. They have plans to study the cells to see if and how they can be used clinically in treatments.