Pluripotent Stem Cells Derived From Mouse and Human White Mature Fat Cells


Several studies have shown that adult white fat cells can differentiate into other cell types by first dedifferentiating into a less committed cell type and then differentiating into heart, bone, cartilage, fat or other cell types. These dedifferentiated fat cells, which are also called DFAT cells, do not have any of the characteristics of the stem cell population normally found in fat (fat-based mesenchymal stromal cells).

No one has studied DFAT cells in much detail. One study of rat DFAT cells showed that a very low percentage of cultured rat DFAT cells (0.4% – 1.2%) expressed embryonic stem cell-specific genes after 2 weeks. Beyond that, there is little known about DFAT cells. Could they be a potential source of pluripotent cells?

A new study by Medet Jumabay and colleagues at the David Geffen School of Medicine at UCLA have isolated DFAT cells from adult white fat of mice and humans and characterized them. The results are fascinating and potentially useful for regenerative medicine.

This paper utilizes a new way to isolate fat cells that guarantees their initial purity and a culture system that encourages isolated of DFAT cells. After the fat cells were isolated from liposuction the fat cells showed the characteristics of pluripotent stem cells for five to seven days in culture. In culture, DFAT cells spontaneously clumped into clusters that expressed several stem cell-specific genes. Once these stem cell-specific genes faded, genes associated with specific cell types, such as liver or nerves, or muscle, were expressed. Interestingly, when DFAT cells were implanted into mice with non-functional immune systems, they did not form tumors.

Thus, fat-derived DFAT cells represent a highly plastic stem cell population for pluripotent cell research that is very responsive to changes in culture conditions and may benefit the development of cell-based therapies.

A Protein from Fat-Based Stem Cells Prevents Light-Induced Damage to the Retina


Japanese researchers from Gifu Pharmaceutical University and Gifu University have reported that a type of protein found in stem cells taken from adipose (fat) tissue can reverse and prevent age-related, light-induced retinal damage in mice. These results may lead to treatments for patients faced with permanent vision loss.

According to the work done by these two research teams led by Drs. Hideaki Hara and Kazuhiro Tsuruma, a single injection of fat-derived stem cells (ASCs) reduced the retinal damage induced by light exposure in mice. This study also discovered that when fat-derived stem cells were grown in culture with retinal cells, the stem cells prevented the retinal cells from suffering damage after exposure to hydrogen peroxide and visible light both in the culture and in the retinas of live mice.

Additionally, Hara and Tsuruma and their colleagues discovered a protein in fat-derived stem cells called “progranulin.” This protein, progranulin, seems to play a central role in protecting other cells from suffering light-induced eye damage.

In the retina, which lies at the back of the eye, excessive light exposure causes degeneration of the photoreceptor cells that respond to light. Several studies have suggested that a long-term history of exposure to light might be an important factor in the onset of age-related macular degeneration. Photoreceptor loss is the primary cause of blindness in particular eye-specific degenerative diseases such as age-related macular degeneration and retinitis pigmentosa.

“However, there are few effective therapeutic strategies for these diseases,” Hideaki Hara, Ph.D., R.Ph., and Kazuhiro Tsuruma, Ph.D., R.Ph.

“Recent studies have demonstrated that bone marrow-derived stem cells protect against central nervous system degeneration with limited results. Just like the bone marrow stem cells, ASCs also self-renew and have the ability to change, or differentiate, as they grow. But since they come from fat, they can be obtained more easily under local anesthesia and in large quantities.”

The fat tissue used in the study was taken from mice and processed in the laboratory to isolate the fat-based stem cells. Afterwards, those cells were tested with cultured mouse retinal cells, and they show a robust protective effect. These successes suggested to the team to test their theory on a live group of mice that had retinal damage after exposure to intense levels of light.

Five days after receiving injections of the fat-based stem cells, the animals were tested for photoreceptor degeneration and retinal dysfunction. The results showed the degeneration had been significantly inhibited.

“Progranulin was identified as a major secreted protein of ASCs, which showed protective effects against retinal damage in culture and in animal tests using mice,” Drs. Hara and Tsuruma said. “As such, it may be a potential target for the treatment of degenerative diseases of the retina such as age-related macular degeneration and retinitis pigmentosa. The ASCs reduced photoreceptor degeneration without engraftment, which is concordant with the results of previous studies using bone marrow stem cells.”

“This study, suggesting that the protein progranulin may play a pivotal role in protecting against retinal light-induced damage, points to the potential for new therapeutic approaches to degenerative diseases of the retina,” said, Anthony Atala, MD, editor of STEM CELLS Translational Medicine and director of the Wake Forest Institute for Regenerative Medicine, where this work was published.

An Efficient Method for Converting Fat Cells to Liver Cells


I have a friend whose wife has systemic lupus erythematosis, and her liver has taken a beating as a result of this disease. She has never had a drop of alcohol for decades and yet she has a liver that looks like the liver of a 70-year-old alcoholic. The scarring of the liver as result of repeated damage and healing has seriously compromised her liver function. She is now a candidate for a liver transplant. Wouldn’t it be nice to simply give her liver cells to heal her liver?

This dream came a little closer to becoming reality in October of this year when scientists at Stanford University developed a fast and efficient way to convert fat cells isolated from routine liposuction into liver cells. Even though these experiments used mice, the stem cells were isolated from human liposuction procedures.

This experiment did not use embryonic stem cells or induced pluripotent stem cells to generate liver cells. Instead it used adult stem cells from fat.

Fat-based stem cells

The liver builds complex molecules, filters and breaks down waste products and toxic substances that might otherwise accumulate to dangerous concentrations.

The liver, unlike other organs, has a capacity to regenerate itself to a significant extent, but the liver’s regenerative abilities cannot overcome the consequences of acute liver poisoning, or chronic damage to the liver, as a result of hepatitis, alcoholism, or drug abuse.

For example, acetaminophen (Tylenol) is a popular pain-reliever, but abusing acetaminophen can badly damage the liver. About 500 people die each year from abuse of acetaminophen, and some 60,000 emergency-room visits and more than 25,000 hospitalizations annually are due to acetaminophen abuse. Other environmental toxins, such as poisonous mushrooms, contribute more cases of liver damage.

Fortunately, the fat-to-liver protocol is readily adaptable to human patients, according to Gary Peltz, professor of anesthesia and senior author of this study. The procedure takes about nine days, which is easily fast enough to treat someone suffering from acute liver poisoning, who might die within a few weeks without a liver transplant.

Some 6,300 liver transplants are performed annually in he United States, and approximately 16,000 patients are on the waiting list for a liver. Every year more than 1,400 people die before a suitable liver can be found for them.

Even though liver transplantations save the lives of patients, the procedure is complicated, not without risks, and even when successful, is fraught with after effects. The largest problem is the immunosuppressant drugs that live patients must take in order to prevent their immune system from rejecting the transplanted liver. Acute rejection is an ongoing risk in any solid organ transplant, and improvements in immunosuppressive therapy have reduced rejection rates and improved graft survival. However, acute rejection still develops in 25% to 50% of liver transplant patients treated with immunosuppressants. Chronic rejection is somewhat less frequent and is declining and occurs in approximately 4% of adult liver transplant patients.

Peltz said, “We believe our method will be transferable to the clinic, and because the new liver tissue is derived from a person’s own cells, we do not expect that immunosuppressants will be needed.”

Peltz also noted that fat-based stem cells do not normally differentiate into liver cells. However, in 2006, a Japanese laboratory developed a technique for converting fat-based stem cells into induced liver cells (called “i-Heps” for short). This method, however, is inefficient, takes 30 days, and relies on chemical stimulation. In short, this technique would not provide enough material to regenerate a liver.

The Stanford University group built upon the Japanese work and improved it. Peltz’s group used a spherical culture and were able to convert fat-bases stem cells into i-Heps in nine days and with 37% efficiency (the Japanese group only saw a 12% rate). Since the publication of their paper, Peltz said that workers in his laboratory have increased the efficiency to 50%.

Dan Xu, a postdoctoral scholar and the lead author of this study, adapted the spherical culture methodology from early embryonic-stem-cell literature. However, instead of growing on flat surfaces in a laboratory dish, the harvested fat cells are cultured in a liquid suspension in which they form spheroids. Peltz noted that the cells were much happier when they were grown in small spheres.

Once they had enough cells, Peltz and his co-workers injected them into immune-deficient laboratory mice that accept human grafts. These mice were bioengineered in 2007 as a result of a collaboration between Peltz and Toshihiko Nishimura from the Tokyo-based Central Institute for Experimental Animals. These mice had a viral thymidine kinase gene inserted into their genomes and when treated with the drug gancyclovir, the mice experienced extensive liver damage.

After gancyclovir treatment, Peltz and his coworkers injected 5 million i-Heps into the livers of these mice, using ultrasound-guided injection procedures, which is typically used for biopsies.

Four weeks later, the mice expressed human blood proteins and 10-20 percent of the mouse livers were repopulated with human liver cells. Blood tests also showed that the mouse livers, which were greatly damaged previous to the transplantation, were processing nitrogenous wastes properly. Structurally, the mouse livers contained human cells that made human bile ducts, and expressed mature human liver cells.

Other tests established that the i-Heps made from fat-based stem cells were more liver-like than i-Heps made from induced pluripotent stem cells.

Two months are injection of the i-Heps, there was no evidence of tumor formation.

Peltz said, “To be successful, we must regenerate about half of the damaged liver’s original cell count.” With the spherical culture, Peltz is able to produce close to one billion injectable i-Heps from 1 liter of liposuction aspirate. The cell replication that occurs after injection expands that number further to over 100 billion i-Heps.

If this is possible, then this procedure could potentially replace liver transplants. Stanford University’s Office of Technology Licensing has filed a patent on the use of spherical culture for hepatocyte (liver cell) induction. Peltz’s group is optimizing this culture and injection techniques,talking to the US Food and Drug Administration, and gearing up for safety tests on large animals. Barring setbacks, the new method could be ready for clinical trials within two to three years, according the estimations by Peltz.

Stem Cells From Burnt Tissue May Augment Burn Treatment


Researchers from the Netherlands have discovered that cells from the non-viable tissue that remains after burn injuries, which are normally removed by debridement, to prevent infection, are a potential source of mesenchymal cells that can be used for tissue engineering. In this study, the research team of Magda Ulrich compared cells isolated from burn eschars (dry scabs or sloughs formed on the skin as a result of a burn or by the action of a corrosive or caustic substance) with fat-derived stem cells and dermal fibroblasts, and determined how well they conform to those criteria established for multipotent mesenchymal stromal cells.

According the Dr. Ulrich, who is member of the Association of Dutch Burn Centers in the Netherlands: “In this study we used mouse models to investigate whether eschar-derived cells fulfill all the criteria for multipotent mesenchymal stromal cells as formulated by the International Society for Cellular Therapy (ISCT). The study also assessed the differentiation potential of MSCs isolated from normal skin tissue and adipose tissue and compared them to cells derived from burn eschar.”

Burn treatment advances have increased the percentage of patients who survive severe burn injuries. This growing survival rate has also increased the number of people who are left with burn scars, and these scars cause skin problems, such as contracture (shortening and hardening of muscles, tendons, or other tissues that leads to deformity and rigidity of joints), and the social and psychological aspects of disfigurement.

Tissue engineering attempts to rebuild the skin are some of the most promising approaches to addressing these problems. Unfortunately, two shortcomings with this approach include finding a viable source of stem cells for the therapy and designing the scaffold that produces a suitable microenvironment to guide the stem cells toward those behaviors that engender tissue regeneration.

“The choice of cells for skin tissue engineering is vital to the outcome of the healing process,” Ulrich said. “This study used mouse models and eschar tissues excised between 11 and 26 days after burn injury. The delay allowed time for partial thickness burns to heal, a process that is a regular treatment option in the Netherlands and rest of Europe.”

Since elevated levels of MSCs have been detected in the blood of burn victims, Ulrich and her co-workers suspected that shortly after being burned, the severely damaged tissues attract stem cells from the surrounding tissues,.

“MSCs can only be beneficial to tissue regeneration if they differentiate into types locally required in the wound environment,” Ulrich said. “We concluded that eschar-derived MSCs represent a population of multipotent stem cells. The origin of the cells remains unclear, but their resemblance to adipose-derived stem cells could be cause for speculation that in deep burns the subcutaneous adipose tissue might be an important stem cell source for wound healing.”

Further work is needed to properly identify the origins of the stem cells found in the burn eschar, and how their function is influenced by the wound environment.