June 1, 2014 (Vol. 34, No. 11)
Alex Philippidis Senior News Editor Genetic Engineering & Biotechnology News
hESCs from Adults, Advances in SCNT Among Developments
Four studies published in recent weeks are giving researchers new hope that key hurdles hobbling stem cell research can finally be overcome—while renewing fears that the reported advances will lead to reproductive cloning.
Researchers published a study April 28 in Nature detailing how they created the first disease-specific diploid-state human embryonic stem cell (hESC) line from one adult donor with type 1 diabetes and a healthy control. Dieter Egli, Ph.D., of the New York Stem Cell Foundation Research Institute and Mark V. Sauer, M.D., of Columbia University Medical Center, added the nuclei of adult skin cells to unfertilized donor oocytes using somatic cell nuclear transfer (SCNT).
The reprogramming process represents a breakthrough since the diploid-state stem cells can be used toward personalized cell therapies against disease. In this case, the researchers’ goal is treating diabetic patients with their own insulin-producing cells through hESC lines of patients with the disease.
“Work performed in parallel by others showed that this advance brings us a significant step closer to the development of cell replacement therapies,” Dr. Egli said on a conference call. There’s no timeframe for development of such therapies.
The Egli-Sauer team overcame the longstanding difficulties of obtaining human oocytes for research and of activating development of those cells to where hESCs could be derived through the addition of histone deacetylase inhibitors and more efficient protocols.
“The histone deacetylase inhibitors really helped that remodeling from a somatic cell to a stem cell. That’s entirely consistent with what has been seen in animal experiments. It’s also very clear in humans. This has made a big difference,” Dr. Egli said, answering a GEN question.
Because of the protocols, he added: “Definitely the number of oocytes required for this has come down, and I expect it to come down further.”
New and Improved
On April 17, researchers led by Dong Ryul Lee, Ph.D., of South Korea’s CHA Stem Cell Institute and Robert Lanza, M.D., CSO of Advanced Cell Technology (ACT), published in Cell Stem Cell details of their SCNT methodology. They derived hESCs using dermal fibroblasts from two adult cell donors, a 75-year-old man and a 35-year-old man.
The team replicated a cloning process first reported last year by a team led by Shoukhrat Mitalipov, Ph.D., of Oregon Health & Science University. However, the Mitalipov team carried out SCNT on infants—not ideal for studying diseases affecting older adults, such as diabetes and Alzheimer’s. Also, while the Mitalipov and Lanza-Lee studies used caffeine to postpone cell division, the former waited 30 minutes to begin the process, versus two hours by the latter.
“One of the main problems before was premature activation. However, caffeine prevents this and allowed us to quadruple the amount of time to reprogram the new DNA before triggering them to divide,” Dr. Lanza told GEN.
“DNA from terminally differentiated adult cells has to undergo massive genetic changes—it has to be brought back in time to an embryonic state. The two-hour incubation period gave the eggs more time to do this.”
The team used 49 eggs from three women, of which two produced hESCs after their DNA was replaced with that from a donor, then stimulated to begin dividing. Dr. Lanza said more research is needed to learn why some eggs were more successful than others.
The Egli-Sauer team offered one possibility. In its study, Dr. Egli said, “Those of a little younger age were slightly more efficient that those of a little more advanced age. But I don’t think this disqualifies eggs of that older age group entirely. They can work.”
The Egli-Sauer and Lanza-Lee studies will likely revive interest in SCNT as an alternative to induced pluripotent stem (iPS) cells generated by direct reprogramming. While SCNT was used in creating Dolly the sheep in 1997, its use in humans has long proven problematic, requiring large quantities of eggs. Deriving them from embryos created through fertility treatments raises moral objections about the resulting destruction of human life—explaining researcher migration in recent years to iPS cells, whose flaws in turn have sparked new interest in SCNT.
Alan Trounson, Ph.D., president of the California Institute for Regenerative Medicine, told GEN researchers will need to study whether SCNT can succeed where iPS hasn’t in easily making some cell types, such as cartilage: “It gives us another option to look at deriving cells that may well be very important. Time will tell how important this is.”
In a paper published March 26 in Nature, Dr. Mitalipov’s group detailed an alternative to human-cell SCNT. It entailed successfully using SCNT on adult mouse body cells to make hESCs using the cytoplasm of two-cell embryos in the later “interphase” stage of the cell cycle, after a fertilized egg first divides into two. The process avoids the need for unfertilized egg cells and does not require embryo destruction—Dr. Mitalipov envisions more plentiful donated or discarded embryos being used—though many who decry embryo destruction also oppose use of discarded embryos.
“Although there’s a shortage of human eggs, it’s important to realize that the future of stem cells technology isn’t making hundreds of millions of patient-specific stem cell lines, but rather, making banks of matching HLA [human leukocyte antigen] lines,” Dr. Lanza told GEN. “In the U.S., just 100 hESC lines would generate a complete HLA haplotype match for over half of the population. And in, say, Korea or Japan, you could probably get a complete haplotype match for most of the population with less than a dozen lines.”
Cloning Fears Resurface
The stem cell advances have reawakened fears they will be used toward human reproductive cloning. In 1998, FDA declared jurisdiction over clinical trials intended to study the practice, citing authority over INDs.
But as Bernard Siegel, J.D., executive director of the Genetics Policy Institute, correctly noted to GEN, the agency didn’t use its notice-and-comment rulemaking or official guidance processes. Instead, FDA’s then-acting commissioner Michael A. Friedman, M.D., simply said so in a radio interview.
“The FDA needs to take the matter seriously and reiterate its authority. The agency should make sure its authority will not be undermined for its ‘casualness’ in establishing its original claims of jurisdiction,” Siegel said. Last year, Siegel and Arnold I. Friede, J.D., whose eponymous law firm specializes in FDA matters, co-authored a Stem Cells and Development article urging FDA to formally establish jurisdiction over cloning, with input from all stakeholders.
The Center for Genetics and Society wants Washington to go further, urging Congress to join some U.S. states and 60 countries in banning reproductive cloning. Marcy Darnovsky, Ph.D., the center’s executive director, cited efforts by several scientists a decade ago to clone humans, and the cost of creating stem cell lines.
“The vision of SCNT-enabled medicine presumes that each patient would have a stem cell line created for him or her—which would be enormously expensive, and thus likely not widely accessible,” Dr. Darnovsky told GEN. “This is an argument about how to think about the promise of regenerative medicine, one consideration for funding agencies and others who are prioritizing the allocation of public moneys.”
Dazzling new cell therapies are more possible than ever based on the recent studies. Researchers must express that publicly to officials and the public—both skeptical audiences—by promoting beneficial cloning toward treatments while joining with others to ban reproductive cloning, which nearly all professionals insist they oppose.