Researchers in Israel have achieved a significant global milestone in stem cell technology: they have created the first human embryonic stem cell (hESC) lines that are free of animal contamination and whose production complies with Good Manufacturing Practices (GMP). The achievement paves the way for developing clinical treatments that use hESCs to treat degenerative diseases like age-related macular degeneration (AMD), type 1 diabetes, heart failure and Parkinson’s.

The Need for Clinically-Compliant hESCs Numerous studies have shown that hESC transplants offer great potential in the treatment of degenerative diseases because they have the ability to regenerate new cells to replace damaged or diseased tissue. But it is a long journey from showing something works in the research lab to using it safely and ethically in patients, and there are many hurdles. One such hurdle is providing stem cells lines “developed under stringent ethical guidelines, from traceable and tested donors, preferably in an animal-free, GMP-grade culture system,” write the researchers in a comprehensive paper published online on 20 June in the open access journal PLoS ONE. Another, is to ensure the hESCs meet safety criteria, and do not have traces of animal components, such as from mice and cows, as these can introduce the risk of animal pathogens running amok in the patient’s body. Now after 12 years of painstaking work, researchers at the Hadassah University Medical Center in Jerusalem, have announced they have created three new lines of “xeno-free and GMP-grade human embryonic stem cells”. In their paper, lead investigator professor Benjamin Reubinoff, a world-renowned stem-cell pioneer and the new chairman of obstetrics/gynecology at the Ein Kerem medical center, and colleagues, describe the journey they took to produce clinically-compliant hESCs. They conclude that the three hESC lines they produced “may be valuable for regenerative therapy”. And they also suggest that the “ethical, scientific and regulatory methodology” they followed may serve as a model for developing further clinical-grade hESCs.

Producing hESC Cell Lines Most of the cell lines produced worldwide are suitable for basic scientific research but are far from ideal for transplantation in the clinic, Reubinoff told the Jerusalem Post. “Until now, hESCs were produced mostly using feeder cells from mice and albumen from cows. This is not good because it may cause contamination of the human cells with animal-derived viruses,” he explained. “Our cell lines are free of all that,” said Reubinoff. Human embryonic stem cells (hESCs) can differentiate into any type of cell in the body, giving them the potential to serve as a virtually infinite source of regenerative cells for transplantation in patients with severe degenerative diseases, such as age-related macular degeneration (AMD), type 1 diabetes, heart failure and Parkinson’s. Most hESCs are derived originally from human eggs that have been fertilized in an in-vitro fertilization (IVF) clinic, and then donated for research with informed consent of the donors. (The ones that Reubinoff and colleagues used came from from six-day-old embryos donated by couples who had completed IVF treatments). But this method alone does not produce enough hESCs for research: to do this researchers create cell lines. Cell lines are a way of breeding large quantities of identical cells from an initial batch. In the case of hESCs, the researchers place the initial batch taken from the embryo into a culture, a medium that supplies the hESCs with the nutrients they need to multiply. These nutrients come from animal “feeder cells”, usually from mice or cows. This is where the risk of contamination by unwanted pathogens comes in. Instead of animal feeder cells, Reubinoff and colleagues used “GMP-grade feeders from umbilical cord tissue”, and put them in a new type of hESC culture that is completely animal free. “We derived and characterized three hESC lines in adherence to regulations for embryo procurement, and good tissue, manufacturing and laboratory practices,” they write. The researchers also reduced the amount of freezing and thawing that is usually involved in producing cell lines, by continuously expanding the lines from initial outgrowths and then cryopreserving samples as early stocks and banks. Another part of their paper discusses the stringent criteria they imposed for releasing batches of cell lines. These criteria included “DNA-fingerprinting and HLA- typing for identity, characterization of pluripotency-associated marker expression, proliferation, karyotyping and differentiation in-vitro and in-vivo”.