Embryonic Stem Cell Contamination Responsible for STAP Research Snafu

STAP or stimulus-triggered acquisition of pluripotency cells were allegedly derived from mature, adult cells by simply subjecting those cells to environmental stresses. These environmental stresses, such as low pH treatments and so on, were thought to cause cells to express genes that pushed them into an embryonic stem cell-like state. Researchers from the RIKEN institute reported these reports in the prestigious international journal Nature, and these advances were hailed as a stupendous advancement in stem cell biology.

However, as soon as stem cell scientists tried to repeat the results from these papers and failed, trouble started. Major laboratories had no success in recapitulating the results in the RIKEN institute papers, and, on-line post-publication reviews noticed some nagging problems in the published papers. RIKEN institute launched an investigation into the matter, and concluded that the lead researcher in these papers was guilty of scientific misconduct.

Now, new work as suggested that the whole thing was the result of contamination of the RIKEN group cells with embryonic stem cells. How that contamination occurred, however, remains unknown.

The RIKEN institute investigation was instigated by the institute and was carried out by a committee composed of seven outsiders. The committee analyzed DNA samples and laboratory records from two research teams who had participated in the STAP cell research. Those Nature papers have been retracted, but were once thought to provide a shortcut to producing pluripotent stem cells. The latest investigation suggests that the STAP findings resulted from contamination by embryonic stem cells. The investigation found signs of three separate embryonic stem cell lines, and they noted that it is difficult to imagine how contamination by three distinct lines could be accidental, but that they could also not be certain that it was intentional.

“We cannot, therefore, conclude that there was research misconduct in this instance,” the committee wrote. It did, however, find evidence that lead investigator Haruko Obokata, the lead author of the STAP papers, who formerly worked at the RIKEN Center for Developmental Biology in Kobe, Japan, had fabricated data for two figures in the original STAP publications.

Children’s Hospital Los Angeles Researchers Grow Functional Tissue-Engineered Intestine from Human Cells

Children’s Hospital Los Angeles is the home of a remarkable new study that has succeeded in growing tissue-engineered small intestine from human cells. This tissue engineered intestine recapitulates several key functional characteristics of human intestine such as the ability to absorb sugars. It also has structural features of human small intestine, such as a mucosal lining, support structures tiny and ultra-structural components like cellular connections.

This work was published in the American Journal of Physiology; GI and Liver and brings surgeons one step closer to using tissue engineered intestines in human patients.

Tissue-engineered small intestines are grown from stem cells isolated from the intestine. These laboratory-grown tissues offer a promising treatment for clinical conditions such as short-bowel syndrome (SBS), which is a major cause of intestinal failure, particularly in premature babies and newborns with congenital intestinal anomalies. Tissue engineered small intestines may also, perhaps in the future, offer a therapeutic alternative to intestinal transplantations, which is fraught with the problems of donor shortage and the need for lifelong immunosuppression.

Senior author Dr. Tracy Grikscheit, who is a principal investigator at the Saban Research Institute, which is housed at the Children’s Hospital of Los Angeles (CHLA), and the Developmental Biology and Regenerative Medicine program at the Children’s Hospital of Los Angeles. Dr. Grikscheit is also a pediatric surgeon at CHLA and assistant professor of surgery at the Keck School of Medicine of the University of Southern California.

Grikscheit main interest, as a clinician, is to find strategies to treat the most vulnerable young patients. For example, babies who are born prematurely can sometimes develop a devastating disease called necrotizing enterocolitis (NEC), in which life-threatening intestinal damage demands that large portions of the small intestine be surgically removed. Without a long enough intestine, NEC babies are dependent on intravenous feeding. This intravenous feeding is costly and may cause liver damage. NEC and other contributors to intestinal failure occur in 24.5 out of 100,000 live births, and the incidence of SBS is increasing and nearly a third of patients die within five years.

CHLA scientists had previously shown that tissue-engineered small intestine could be generated from human small intestine donor tissue implanted into immunocompromised mice. These initial studies were published in July 2011 in the biomedical journal Tissue Engineering, Part A, and while it was a hopeful study, only basic components of the intestine were identified in the implanted intestine. To be clinically relevant, it is necessary to make tissue engineered intestines that form a healthy barrier that can still absorb nutrition and regulate the exchange of electrolytes.

This new study, however, showed that mouse tissue engineered small intestines are quite similar to the tissue-engineered small intestines made from human intestinal stem cells. Both contain important building blocks such as the stem and progenitor cells that continue to regenerate the intestine throughout the lie of the organism. These cells are found within the engineered tissue in specific locations and are close to other specialized cells that are known to be necessary for the intestine to function as a fully functioning organ.

“We have shown that we can grow tissue-engineered small intestine that is more complex than other stem cell or progenitor cell models that are currently used to study intestinal regeneration and disease, and proven it to be fully functional as it develops from human cells,” said Grikscheit. “Demonstrating the functional capacity of this tissue-engineered intestine is a necessary milestone on our path toward one day helping patients with intestinal failure.”

Grafted Stem Cells Display Robust Growth in Spinal Cord Injury Model

University of San Diego neuroscientists have used an animal model of spinal cord injury to test the ability of engrafted stem cells to regenerate damaged nerves. Mark Tuszynski and his team built on earlier work with implanted neural stem cells and embryonic stem cell-derived neural stem cells in rodents that had suffered spinal cord injuries.

In this study, Tuszynski and others used induced pluripotent stem cells that were made from a 86-year-old male. This shows that skin cells, even from human patients who are rather elderly, have the ability to be reprogrammed into embryonic stem cell-like cells. These cells were differentiated into neural stem cells and then implanted into the spinal cords of spinal cord-injured rodents.

The injured spinal cord is a very hostile place for implanted cells. Inflammation in the spinal cord summons white blood cells to devour cell debris. White blood cells are rather messy eaters and they release enzymes and toxic molecules that can kill off nearby cells. Also, regenerating cells run into a barrier made by support cells called glial cells that inhibit regenerating neurons from regenerating. Thus, the injured spinal cord is quite the toxic waste dump.

To get over this, Tuszynski and his coworkers treated their induced pluripotent stem cell-derived neural stem cells with growth factors. In fact, when the cells were implanted into the animal spinal cords, they were embedded in a matrix that contained growth factors. After three months, Tuszynski and his colleagues observed extensive axonal growth projecting from grafted neurons that reached long distances in both directions along the spinal cord from the brain to the tail end of the spinal cord. These sprouted axons appeared to make connections with the existing rat neurons. Importantly, these axons extended from the site of the injury, which is astounding given that the injured area of the spinal cord has characteristics that are inimical to neuronal and axon growth.

Even though Tuszynski and others showed that neural stem cells made from embryonic stem cells can populate the damaged spinal cord, using induced pluripotent stem cell-derived neural stem cells has an inherent advantage since these cells are less likely to be rejected by the patient’s immune system. Furthermore, the induced pluripotent stem cell-derived neural stem cells showed dramatic growth in the damaged spinal cord, but the implanted animals did not regain the use of their forelimbs. The implanted human cells were fairly young when the implanted animals were tested. Therefore, they might need to mature before they could restore function to the implanted animals.

“There are several important considerations that future studies will address,” Tuszynski said. “These include whether the extensive number of human axons make correct or incorrect connections; whether the new connections contain the appropriate chemical neurotransmitters to form functional connections; whether connections once formed are permanent or transient; and exactly how long it takes human cells to become mature. These considerations will determine how viable a candidate these cells might before use in humans.”

Tuszynski and his group hope to identify the most promising neural stem cell type for repairing spinal cord injuries. Tuszynski emphasized their commitment to a careful, methodical approach:

“Ultimately, we can only translate our animal studies into reliable human treatments by testing different neural stem cell types, carefully analyzing the results, and improving the procedure. We are encouraged, but we continue to work hard to rationally to identify the optimal cell type and procedural methods that can be safely and effectively used for human clinical trials.”

Mesenchymal Stem Cell Transplantation Improves Atherosclerotic Lesions

Several animal studies have shown that transplantation of mesenchymal stem cells from several different sources is beneficial in myocardial infarction and hind limb ischemic. However, can these cells improved atherosclerosis, otherwise known as hardening of the arteries?

Shih-Chieh Hung and colleagues from National Yang-Ming University in Taipei, Taiwan tested this very hypothesis.

Hung and others used to lines of experimentation to address this question. First, they used cultured endothelial cells that had been treated with oxidized low-density lipoprotein particles. Secondly, they fed mice mutant for ApoE-deficient a high-fat diet.  ApoE-deficient humans and mice develop atherosclerotic plaques rather quickly.

In the cultured endothelial cells, oxidized LDL turned off the production of nitric oxide (NO). NO is a signaling molecule produced by several cell types, but in particular, endothelial cells use NO to dilate blood vessels. NO also is a good signal of endothelial health. Therefore, when oxidized LDL causes cultured endothelial to decrease NO production, it is affecting endothelial cell health. However, when cultured endothelial cells that had been treated with oxidized LDL were cocultured with mesenchymal stem cells, NO production and the enzymes that synthesize NO increased precipitously. Thus in a cultured system, MSCs have the ability to prevent the deleterious of oxidized LDL.

In ApoE-deficient mice fed a high fat diet, the arteries of the mice showed extensive plaque formation. However, if these animals were implanted with bone-marrow-derived mesenchymal stem cells, plaque formation was greatly decreased. Further work showed that a protein secreted by mesenchymal stem cells called macrophage inflammatory protein-2 (MIP-2) was responsible for these ameliorative effects. If MIP-2 was applied without mesenchymal stem cells, plaque formation was limited, and if antibodies that neutralize MIP-2 were co-administered with mesenchymal stem cells, the cells failed to reduced plaque formation.

Thus, this interesting study shows that transplantation of mesenchymal stem cells can limit plaque formation in atherosclerotic animals and they do this through secretion of MIP-2. Secondly, mesenchymal stem cells can improve the health of endothelial cells, which are the cells that form the inner layer of blood vessels, which are so adversely affected by atherosclerosis. By utilizing the encore of proteins secreted by mesenchymal stem cells, scientists should be able to develop a cocktail of proteins that can ameliorate atherosclerosis in human patients.

Safety and Feasibility of Epicardial Delivery of Umbilical Cord Blood-Derived Mononuclear Cells in a Porcine Model System

Most of the studies that have examined the effects of stem cell transplantation into the heart after a heart attack have only examined the effects of these cells for 4-6 weeks. There are very few long-term studies on the effects of implanted cells.

Fortunately, Timothy Nelson at the Mayo Clinic has published a long-term study of the effects of transplantation of umbilical cord mononuclear cells into the hearts of pigs. In this study, Nelson and his coworkers aimed to evaluate the feasibility and long-term safety of autologous umbilical cord blood mononuclear cells (UCB-MNCs) that were transplanted into the right ventricle (RV) of juvenile porcine hearts. The results are very encouraging.

In this study, piglets were born by means of Caesarean section in order to enable the collection of umbilical cord blood. 12 animals were assigned to either the placebo or test group, which half of them in one group and the other half in the other. 3 × 106 cells per kilogram were injected into the hearts of the test group and 10% DMSO were injected into the hearts of the placebo animals. These animals were monitored for 3 months after implantations, and the performance of their hearts was assessed in addition to biochemical markers, followed by terminal necropsy. None of the animals died as a result of these treatments.

The worse side effect of the surgeries was that two animals from the placebo group developed local skin infection after surgery that successfully responded to antibiotic treatment. Electrocardiograms (EKGs) of the treated animals showed no abnormalities in either group throughout the 3-month study. Two animals in the cell-therapy group had some issue right after surgery, but this is almost certainly a response to the anesthesia. Overall, this study demonstrated that autologous umbilical cord blood mononuclear cells can be safely collected and surgically delivered in a pediatric setting. The safety profile of these cells shows that they can be used to safely treat juvenile hearts. These studies should accelerate cell-based therapies to clinical trials for chronic heart disease.

Lung Stem Cells Heal Lungs and Point to Possible New Treatments

Frank McKeon, Ph.D., and Wa Xian, Ph.D. from Jackson Laboratory and their colleagues have identified the a certain lung stem cell, and the role it plays in regenerating lungs.

This work, which appeared in the Nov. 12 issue of the journal Nature, provides some much-needed clarification of the nuts and bolts of lung regeneration and provides a way forward for possible therapeutic strategies that harness these lung stem cells.

“The idea that the lung can regenerate has been slow to take hold in the biomedical research community,” McKeon says, “in part because of the steady decline that is seen in patients with severe lung diseases like chronic obstructive pulmonary disease (known as COPD) and pulmonary fibrosis.”

McKeon noted that there is ample evidence of a robust system for lung regeneration. “Some survivors of acute respiratory distress syndrome, or ARDS, for example, are able to recover near-normal lung function following significant destruction of lung tissue.”

This is a capacity that humans share with mice. Mice infected with the H1N1 influenza virus show progressive inflammation in the lung followed by the death and loss of important lung cell types. However, over the course of several weeks, the lungs of these mice recover and show no signs of previous lung injury.

Because of the presence of such robust lung regeneration in mice, these organisms provide a fine model system to study lung regeneration.

McKeon and his colleagues had previously identified a type of adult lung stem cell known as p63+/Krt5+ in the distal airways. When grown in culture, these p63+/Krt5+ lung stem cells neatly formed alveolar-like structures that were similar to those found within the lung. Alveoli are the tiny, specialized air sacs that form at the ends of the smallest airways, where gas exchange occurs in the lung. Following infection with H1N1, these same stem cells migrated to sites of inflammation in the lung and clustered together to form pod-like structures that resemble alveoli, both visually and molecularly.

McKeon and his colleagues reported that when the lung is damaged by H1N1 infraction, p63+/Krt5+ lung stem cells proliferate and contribute to the development of new alveoli near sites of lung inflammation.

To determine if these cells are required for lung regeneration, McKeon and his coworkers developed a novel system that utilizes genetic tools to selectively remove these cells from the mouse lung. Mice that lack p63+/Krt5+ lung stem cells cannot recover normally from H1N1 infection, and instead exhibit scarring of the lung and impaired oxygen exchange. This demonstrates the key role p63+/Krt5+ lung stem cells play in regenerating lung tissue.

To carry this work one step further, McKeon and his team isolated and subsequently transplanted p63+/Krt5+ lung stem cells into a damaged lung. The transplanted p63+/Krt5+ cells readily contribute to the formation of new alveoli, which nicely illustrates the capacity of these cells to regenerate damaged lung tissue.

In the U.S. about 200,000 people have Acute Respiratory Distress Syndrome, a disease with a death rate of 40 percent, and there are 12 million patients with COPD. “These patients have few therapeutic options today,” Xian says. “We hope that our research could lead to new ways to help them.”

Bone Progenitor Cells Discovered – Might Help Children Who Need Corective Facial Surgery

In children, bone grow thicker and longer and get stronger and denser. When children reach adolescence, they know that the time has come to stop growing longer and stronger. However, even into adulthood, bones still retain the capacity to heal. Why the differences between adolescents and adults? This is a question that has long fed the imaginations of scientists.

Recently, a collaborative team of biomedical researchers from the University of Michigan, Kyoto University and Harvard University has made the answer to this question a little clearer.

Dr. Noriaki Ono, U-M assistant professor of dentistry, and his collaborators discovered that a certain subset of cartilage-making cells – cells known as chondrocytes – proliferate and differentiate into other bone cells that drive bone growth. These discoveries could lead to new treatments for children with facial deformities who normally have to wait until adulthood for corrective surgery. This study appeared in the journal Nature Cell Biology.

A long-held view is that bone-making chondrocytes die once children reach adolescence and their bones stop growing. However, in adults, bone still heal without the benefit of these bone-making chondrocytes. How does this occur? This question has generated a fair amount of disagreement between researchers.

Ono’s group discovered that some of these bone-making chondrocytes don’t die. Instead, they are transformed into other types of bone-growing and bone-healing cells.

“Up until now, the cells that drive this bone growth have not been understood very well. As an orthodontist myself, I have special interest in this aspect, especially for finding a cure for severe bone deformities of the face in children,” he said. “If we can find a way to make bones that continue to grow along with the child, maybe we would be able to put these pieces of growing bones back into children and make their faces look much better than they do.”

According to Ono, one of the challenges in bone and cartilage medicine is that resident stem cells haven’t really been identified. The only widely accepted idea is that certain stem cells like mesenchymal stem cells help bones heal and other help them grow, but the progenitor cells for these cell populations and what goes wrong with them in conditions such as osteoporosis remains mysterious.

Ono and his team used a technique called “fate mapping,” which labels cells genetically and them follows them throughout development. Ono and others came upon a specific precursor cell that gives rise to fetal chondrocytes, and all the other later bone-making cells and . By mesenchymal stromal cells later in life. Most exciting, Ono and his coworkers found a way to identify the cells responsible for growing bone. By identifying these cells, isolating them and even implanting them into the skull or long bones of a child with a bone deformity condition, the cells would make bone that would also grow with the child.

Many factors cause craniofacial deformities. These types of deformities can place pressure on the brain, eyes, or other structures and prevent them from developing normally. For example, children with Goldenhar syndrome have underdeveloped facial tissues that can harm the developing jawbone. Another bone deformity called deformational plagiocephaly causes a child’s head to grow asymmetrically. Maybe the implantation of such cells can provide a way to restart the abnormally growing bones in these children.