My Medical Reviews

New UC Irvine research is among the first to demonstrate that neural stem cells may help to restore memory after brain damage.

In the study, mice with brain injuries experienced enhanced memory -- similar to the level found in healthy mice -- up to three months after receiving a stem cell treatment. Scientists believe the stem cells secreted proteins called neurotrophins that protected vulnerable cells from death and rescued memory. This creates hope that a drug to boost production of these proteins could be developed to restore the ability to remember in patients with neuronal loss.

"Our research provides clear evidence that stem cells can reverse memory loss," said Frank LaFerla, professor of neurobiology and behavior at UCI. "This gives us hope that stem cells someday could help restore brain function in humans suffering from a wide range of diseases and injuries that impair memory formation."

The results of the study appear Oct. 31 in the Journal of Neuroscience.

LaFerla, Mathew Blurton-Jones and Tritia Yamasaki performed their experiments using a new type of genetically engineered mouse that develops brain lesions in areas designated by the scientists. For this study, they destroyed cells in the hippocampus, an area of the brain vital to memory formation and where neurons often die.

To test memory, the researchers gave place and object recognition tests to healthy mice and mice with brain injuries. Memories of place depend upon the hippocampus, and memories of objects depend more upon the cortex. In the place test, healthy mice remembered their surroundings about 70 percent of the time, but mice with brain injuries remembered it just 40 percent of the time. In the object test, healthy mice remembered objects about 80 percent of the time, while injured mice remembered as poorly as about 65 percent of the time.

The scientists then set out to learn whether neural stem cells from a mouse could improve memory in mice with brain injuries. To test this, they injected each mouse with about 200,000 neural stem cells that were engineered to appear green under ultraviolet light. The color allows the scientists to track the stem cells inside the mouse brain after transplantation.

Three months after implanting the stem cells, the mice were tested on place recognition. The researchers found that mice with brain injuries that also received stem cells remembered their surroundings about 70 percent of the time -- the same level as healthy mice. In contrast, control mice that didn't receive stem cells still had memory impairments.

Next, the scientists took a closer look at how the green-colored stem cells behaved in the mouse brain. They found that only about 4 percent of them turned into neurons, indicating the stem cells were not improving memory simply by replacing the dead brain cells. In the healthy mice, the stem cells migrated throughout the brain, but in the mice with neuronal loss, the cells congregated in the hippocampus, the area of the injury. Interestingly, mice that had been treated with stem cells had more neurons four months after the transplantation than mice that had not been treated.

"We know that very few of the cells are becoming neurons, so we think that the stem cells are instead enhancing the local brain microenvironment," Blurton-Jones said. "We have evidence suggesting that the stem cells provide support to vulnerable and injured neurons, keeping them alive and functional by making beneficial proteins called neurotrophins."

If supplemental neurotrophins are in fact at the root of memory enhancement, scientists could try to create a drug that enhances the release or production of these proteins. Scientists then could spend less time coaxing stem cells to turn into other types of cells, at least as it relates to memory research.

"Much of the focus in stem cell research has been how to turn them into different types of cells such as neurons, but maybe that is not always necessary," Yamasaki said. "In this case, we did not have to make neurons to improve memory."

Stem cells from a patient's fat may be used to create new nerves that can repair severed peripheral nerves (nerves outside the spinal cord), say scientists from Manchester University, England. The researchers say this route for creating new nerves could be part of medical practice by the year 2011.

The scientists said their aim is to put the new nerve tissue inside a biodegradable plastic tube, insert in at the broken ends of the severed nerve, and rejoin them in a human. This procedure could help a considerable number of people. They say they have had promising results with rats.

Current medicine offers very limited procedures to help restore peripheral nerves. Nerves from elsewhere can sometimes be used- however, the risk of additional damage is significant, and even when there are results they hardly ever restore perfect function, say the authors.

The team managed to extract stem cells from the fat tissue of rats, and tweaked them to become neurons in the lab. Their aim now is to do the same, but with stem cells that come from human fat. They plan to create a replacement nerve, place it in a biodegradable sheath, and attach it to the severed part of the nerve. The result would be that the severed nerve would be joined again.

If successful, this technique could be used in any part of the body.

"The differentiated stem cells have great potential for future clinical use, initially for treatment of patients with traumatic injuries of nerves in the arms and legs," said team leader. As a study to find out how effective the biodegradable tube is is now being carried out, he believes we could be about four years away from an effective treatment for severed peripheral nerves.

Severed nerves can be caused by an accident, as well as surgery - a surgeon in his/her attempt to remove a large tumor may have to cut and damage nerves in order to do so.

Your body's own stem cells could trigger alterations in cancer cells which facilitate their spreading around the body. Scientists have found that human breast cancer in mice have a higher chance of spreading if they are blended with bone marrow stem cells. Fortunately, say the scientists, it is perhaps feasible to reverse the process, undermining the deadliness of the cancer.

When metastasis occurs it is much harder to treat the cancer. Metastasis is when the cancer invades other parts of the body and forms new tumors. In this study, the scientists intended to find out whether it was possible to stop this from happening - they wanted to find a means of isolating the cancer to one part of the body; stopping it from metastasizing (spreading, invading other parts).

The researchers have found an association with a specific type of stem cell, which encourages the breast cancer cells to spread to other parts of the body. They are found in the bone marrow, and are called Mesenchymal stem cells. These stem cells generally turn into cartilage, bone fat and muscle.

Previous studies had indicated that these stem cells generally migrated in huge numbers to where tumors were situated, meaning they were probably involved in the spread of the cancer. The researchers mixed these stem cells with human breast cancer cells in mice and found they spread to the lungs at seven times their normal rate.

The scientists believe the stem cells alter the cancer cells so that they metastasize. However, they add that as soon as they had spread, those cancer cells returned to their original genetic make-up. The bad news here is that as they revert back to their original genetic make up they are hard to identify, the good news, say the researchers, is that it is most likely they can find a way of blocking the whole process.