The Potential Of Placental Cells
It took an engineer with intuition to come up with what could be a cutting-edge stem cell solution for limb ischemia, which develops from peripheral artery disease. This chronic disease progressively restricts blood flow in the limbs, requiring amputation in the most severe cases. Surprisingly, cells taken from the placenta could treat this condition.
In 2005, Zami Aberman, a mechanical engineer by training, became head of Israel’s Pluristem Therapeutics, a biotherapeutics company. A year later, he came up with the idea of harvesting placental cells while looking for a stem-cell treatment that did not require a donor-patient match.
When Aberman first presented the idea of using the human placenta as a source for stem cells to colleagues and friends, he recalls, “They said it was rubbish, because it was common knowledge that placenta is dead tissue.” But Aberman wanted evidence.
When I thought of the umbilical cord,” he explains, “my thinking was based on logic that the maternal part of the placenta was the part that should have undergone some kind of immunotolerance, because the mother and the baby live together without rejection.”
Soon Pluristem started harvesting placental cells in its PluriX 3D bioreactor, which tricks stem cells into growing and reproducing as they would in living organs. In 2007, the company bought out this bioreactor, developed by Israel’s Weizmann Institute of Science. In July 2009, the company started trials with its product PLX-PAD, or placental expanded cells for peripheral artery disease. Injecting PLX-PAD into the limb of a patient with ischemia will, hopefully, trigger the development of new blood vessels, just like natural stem cells do in healthy people.
According to a report in November 2009 by Keith Markey, scientific director at New York–based Griffin Securities, patients in the U.S. and other developed countries seeking treatment for limb ischemia could number a half million each year. Consequently, Markey concludes that the potential for PLX-PAD is huge. He expects it to hit the market by 2015 at a cost of $4,500 per patient.
Pluristem’s phase I trials have been very encouraging. In January, it announced that out of a total of nine patients dosed with harvested placental cells, three patients completing their three-month follow-up showed a trend toward reduced limb ischemia. Unlike treatment with bone marrow and other kinds of harvested cells, a patient being treated with PLX-PAD faces no threat of complications associated with donor cells, because placental cells are allogeneic in nature and pre-screened by Pluristem for contamination. Markey says this is a huge advantage.
While Pluristem’s approach bypasses many of the ethical issues that constrain some uses of stem cells, this technology also promises new treatments for a range of diseases.
