Central nervous system disorders cause most physical disabilities and damaged nerves have a very limited ability to heal. While stem cell research offers the potential for regenerating damaged neurons, true therapeutic treatments are several years off. Also, the process of making adult body cells, such as nerve cells, with embryonic stem cells requires multiple steps and is still poorly understood. Partially developed precursor neural cells isolated from a patient, on the other hand, are already closer to adult nerve cells. These progenitor nerve cells could provide a more practical solution for neural damage therapies in the near future. Unfortunately, the problem is that there are a limited number of these neuronal progenitor cells, and they cannot be isolated from a patient's central nervous system without injuring them.
A research group lead by Osvaldo Delbono and Akiva Mintz at Wake Forest University may have found a way around this problem of limited neuronal progenitor cells. Over a year ago, the researchers found they could isolate neuronal precursor cells from skeletal muscle. Muscle cells expressing a common nerve-cell protein, nestin, could be isolated and easily differentiated into nerve cells in culture.
The same group just recently took this work further and found that these cells, in fact, seem to have almost the same biological characteristics to neural precursor cells. Further, they implanted the cells isolated from both mice and green monkeys, and found they survive in the brain of these animals without forming tumors, which was a concern with early stage progenitor cells. The cells also migrate to the same locations as the endogenous nerve progenitor cells the nerve tissue.
The question now is whether the injected muscle-derived precursor nerve cells can be induced to form mature nerve cells in these animals, which the group is working on. If so, these cells may offer a basis for a therapeutic approach to treat a range of brain and central nervous system injuries.
Another unrelated study by Arturo Alvarez-Buylla's group at UCSF may also provide some insight about the feasibility of using implanted cells to treat brain and nerve injuries. They found that about 15%-20% of precursor nerve cells isolated from mice embryos survived when implanted into mouse brains. The survival rate remained basically unchanged whether as few as 5,000 to as many as a million cells were injected. This surprising result suggests that the brain has a large capacity to integrate added cells which makes it feasible to add large numbers of stem or progenitor cells as part of a potential treatment.