Scientists at Harvard University have successfully transplanted neurons into the brains of obesity-prone mice to prevent them from getting fat. The researchers did not have human obesity in mind when conducting the experiment; rather, they used the neuron transplant as an example of a method to restore function to abnormal neural circuits. The results have highlighted the promise in cell therapies. For example, scientists could soon transplant stem cells or fetal cells to treat nervous system diseases.
Throughout the years, research on cell therapies has rarely found success. Experiments using stem cell therapy to treat spinal injuries as well as some trials involving fetal cell therapy for Parkinson’s disease have yielded no positive results. Only until recent years has it been proven that the human brain produces new neurons throughout the lifetime. Some evidence has shown that these new neurons are occasionally integrated into existing neural circuits and actually enhance brain function. This evidence led scientists to postulate that this could be done using transplanted cells as well.
The Harvard University scientists extracted healthy neurons from mouse embryos (the hypothalamus to be exact) and transplanted those neurons into the same region of the brain in obesity prone mice. These mice lack the receptor for leptin, a hormone that regulates metabolism and body weight, and therefore they are prone to being diabetic and obese. The transplanted neurons were labeled with a green fluorescent protein to track them in the neural circuit. The results were quite promising, as the transplanted neurons were able to integrate efficiently into the existing neural circuit and develop into mature neurons that responded to leptin. At the end of the experiment, the treated mice weighed 30% less than mice that had not received a transplant. This suggested that the transplanted neurons actually fixed the damaged neural circuit.
Though the experiment was not directed towards treating human obesity, the success of the experiment gave scientists a light at the end of the tunnel in terms of cell therapies. These results further prove the possibility that key areas of the mammalian brain can be repaired using transplanted neurons to treat nervous system diseases like amyotrophic lateral sclerosis (ALS), Parkinson’s disease, and other nervous system diseases. In response to the question of reconstructing the entire circuitry of the brain itself, one of the scientists responded, “In these cases, can we rebuild circuitry in the mammalian brain? I suspect that we can.”