Induced Pluripotent Stem Cells Used to Make New Bone In Monkeys


Cynthia Dunbar, MD and her colleagues at the National Heart, Lung, and Blood Institute, which is a division of the National Institutes of Health (NIH) in Bethesda, Maryland have shown for the first time that it is possible to make new bone from induced pluripotent stem cells that are derived from a patient’s own skin cells.

This study, which was done in monkeys, shows that there is some risk that induced pluripotent stem cells (iPSCs) can form tumors, but that the risk of tumor formation is less than what was shown in immuno-compromised mice.

iPSCs are made from adult cells by means of a process called “reprogramming.” To reprogram adult cells, genetic engineering techniques are used to introduce specific genes into adult cells. These introduced genes drive the adult cells to de-differentiate into a less mature state, until they eventually become pluripotent, much like embryonic stem cells.

Originally, discovered by Nobel-prize winner Shinya Yamanaka, reprogramming was initially done with genetically engineered viruses that insert genes into the genome of cells. Even though these viruses do a passable job of reprogramming cells, they also introduce insertion mutations. Yamanaka and others originally used four transcription factors (Oct4, Sox2, Klf4, c-Myc) to reprogram adult cells. Several of these genes are overexpressed in a variety of tumors, and therefore, the use of these genes does create a risk of forming cells that overgrown and become tumorous. Secondly, The reprogramming process does put cells under the types of stresses that increase the mutation rate, and these mutations can also increase the risk of forming tumor cells. However, it is clear that not all reprogramming protocols cause the same rate of mutations, and that the mutation rate of iPSCs was originally overestimated. What is required is a good way to screen iPSC lines for mutations and for safety, especially since not all iPSC lines are equal when it comes to their safety.

The advantage of using iPSCs over embryonic stem cells is that the immune system of the patient should not reject tissues and cells made from iPSCs. This would eliminate the need for immune suppression drugs, which can be rather toxic.

Cynthis Dunbar from the National Heart, Lung, and Blood Institute said of her experiments, “We have been able to design an animal model for testing of pluripotent stem cell therapies using the rhesus macaque, a small monkey that is readily available and has been validated as being closely related physiologically to humans.

Dr. Dunbar continued: “We have used this model to demonstrate that tumor formation of a type called a ‘teratoma’ from undifferentiated autologous iPSCs does occur; however, tumor formation is very slow and requires large numbers of iPSCs given under very hospitable conditions. We have also shown that new bone can be produced from autologous iPSCs as a model for their possible clinical application.”

Dunbar and her team used a excisable polycistronic lentiviral vector called STEMCCA (Sommer et al., 2010) that expressed four genes: human OCT4, SOX2, MYC, and KLF4 to make iPSCs from skin cells. After they had derived culturable iPSCs from rhesus monkeys (made under feeder-free conditions), Dunbar and her group seeded them on ceramic scaffolds that are used by reconstructive surgeons to fill in or rebuild bone. Interestingly, these cells regrew bone in the monkeys.

The differentiated iPSCs formed no teratomas, but monkeys that had received implantations of undifferentiated iPSCs formed teratomas in a dose-specific manner.

Dunbar and her colleagues note that this approach might be beneficial for people with large congenital bone defects or other types of traumatic injuries. Having said that, it is doubtful that bone replacement therapies will be the first human iPSC-based treatment, since bone defects are not life-threatening, even though they can seriously compromise the quality of a patient’s life.

“A large animal preclinical model for the development of pluripotent or other high-risk/high-reward generative cell therapies is absolutely issues of tissue integration of homing, risk of tumor formation, and immunogenicity,” said Dunbar. “The testing of human-derived cells in vitro or in profoundly immunodeficient mice simply cannot model these crucial preclinical safety and efficiency issues.”

This NIH team is now collaborating with other labs to differentiate macaque iPSCs into liver, heart, and white blood cells for to test them for eventual pre-clinical trials in hepatitis C, heart failure, and chronic granulomatous disease, respectively.

Arsenic turns stem cells into cancer-causing cells


National Institutes of Health (NIH) scientists have made an interesting discovery with regard to arsenic and its effects on stem cells. Arsenic can turn normal stem cells into cancerous cells that grow uncontrollably and cause tumors. Arsenic is a common pollutant of drinking water in some parts of the world, and has previously been shown to be a cancer-causing chemical (carcinogen). Interestingly, cancer is probably a stem cell-based disease. Therefore, arsenic seems to convert the healers of our bodies from profitable entities to the makers of tumors.

Michael Waalkes, who heads a research team at the National Toxicology Program Laboratory, National Institute of Environmental Health Sciences (which is part of the NIH), has shown previously that treatment of normal cells with arsenic causes them to become cancerous. However, the present study shows that when these converted cancer cells are placed in proximity to normal stem cells, but not in contact with them, the normal stem cells quickly acquire the characteristics of cancer stem cells. Thus malignant cells can send molecular signals that transfer the message to grow uncontrollably to other cells. In fact, the placement of a semi-permeable membrane, between the cancer cells and the normal stem cells does not prevent the transformation from occurring. This demonstrates that small molecules that are made by the arsenic-transformed cell can are small enough to pass through the membrane and signal to the normal stem cells to turn them into cancer stem cells.

“This paper shows a different and unique way that cancers can expand by recruiting nearby normal stem cells and creating an overabundance of cancer stem cells,” said Waalkes. “The recruitment of normal stem cells into cancer stem cells could have broad implications for the carcinogenic process in general, including tumor growth and metastases.”

Waalkes’ lab started working with stem cells about five years ago. The researchers used a prostate stem cell line, not embryonic stem cells. “Using stem cells to answer questions about disease is an important new growing area of research. Stem cells help to explain a lot about carcinogenesis, and it is highly likely that stem cells are contributing factors to other chronic diseases,” Waalkes said.

Stem cells are unique in the body. They stay around for a long time and are capable of dividing and renewing themselves. “Most cancers take 30 or 40 years to develop,” said Linda Birnbaum, Ph.D., director of NIEHS and NTP. “It makes sense that stem cells may play a role in the developmental basis of adult disease. We know that exposures to toxicants during development and growth can lead to diseases later in life.”

Next, Waalkes’ group will look to see if this finding is unique to arsenic or if other organic and inorganic carcinogens also show these effects on normal stem cells.

This paper reveals an extremely important aspect of arsenic carcinogenesis. Additionally it may explain why arsenic often causes multiple tumors of many types that form on the skin or inside the body. The paper is online in Environmental Health Perspectives.

California Stem Cell Report Includes No Critics


Wesley Smith at his blog notes that the California Stem Cell Report, which will include public testimony to the Institute of Medicine (IOM), an arm of the National Institutes of Health (NIH), will include scientists who were awarded lucrative grants by the California Institute for Regenerative Medicine (CIRM), but no critics of the program.  His source is a very critical Los Angeles Times article.

The critics of CIRM are not pro-life advocates who oppose embryonic stem cell research on principle.  Instead critics include the Little Hoover Commission, which issued this blistering report of CIRM, and the Oakland-based Center for Genetics and Society.  These organizations were afraid that there were too many conflicts of interest on the grant-awarding panel.  In the words of the Little Hoover Commission:

CIRM’s 29-member oversight committee includes representatives from institutions that have benefitted from grants the committee approved. This structure, along with overly long terms and the inability to nominate its own leaders or hold them accountable, fuels concerns that the committee never can be entirely free of conflict of interest or self-dealing, notwithstanding a court ruling that established the legality of such a structure. Legal is not necessarily optimal, however, and litigation over this issue delayed CIRM from beginning its work. As long as the board remains in its present form, its structure will draw scrutiny, diverting CIRM resources.

No representatives from either of these critical institutions are on the witness list.  Why aren’t members of the public allowed to address the IOM?  According to the LA Times,  the proprietor of the California Stem Cell Report, David Jensen, says he asked the IOM why no objective witnesses were on the hearing list, and an IOM public relations person directed him to a survey form members of the public could fill out (though the link for the form on the IOM’s website was dead when I checked it).  Apparently, members of the public will also be permitted to address the IOM panel at Tuesday’s hearing. They’ll each get up to five minutes.

CIRM is selling the people of California a bill of goods.  In 2014, CIRM will be back to the people of California with their hand out for more money.  If the process is so objective, then what do they have to hide?  3 billion dollars later and little to show for it except for lots of dead human embryos.  People will be more than a little miffed; and they should be.