Researchers have created new nerve cells in the brains and spinal cords of mice without the need for stem cell transplants to replenish lost cells.
The research indicates that someday it may be possible to regenerate neurons from the body's own cells to repair traumatic brain injury or spinal cord damage or to treat conditions such as Alzheimer's disease.
However, the researchers stressed that it is too soon to know whether the neurons created in these initial studies resulted in any functional improvements.
Scientists at University of Texas' Southwestern's Department of Molecular Biology turned astrocytes - the most common non-neuronal brain cells - into neurons that formed networks in mice.
They then successfully turned scar-forming astrocytes in the spinal cords of adult mice into neurons.
"Our earlier work was the first to clearly show in vivo (in a living animal) that mature astrocytes can be reprogrammed to become functional neurons without the need of cell transplantation," said Dr Chun-Li Zhang, assistant professor of molecular biology at UT Southwestern and senior author of the study.
"The current study did something similar in the spine, turning scar-forming astrocytes into progenitor cells called neuroblasts that regenerated into neurons," Zhang said.
"Astrocytes are abundant and widely distributed both in the brain and in the spinal cord. In response to injury, these cells proliferate and contribute to scar formation. Once a scar has formed, it seals the injured area and creates a mechanical and biochemical barrier to neural regeneration," Zhang said.
The scientists introduced a biological substance that regulates the expression of genes, called a transcription factor, into areas of the brain or spinal cord where that factor is not highly expressed in adult mice.
Of 12 transcription factors tested, only SOX2 switched fully differentiated, adult astrocytes to an earlier neuronal precursor, or neuroblast, stage of development, Zhang said.
The researchers then gave the mice a drug called valproic acid (VPA) that encouraged the survival of the neuroblasts and their maturation (differentiation) into neurons.
Neuron creation occurred in the spinal cords of adult and aged (over one-year old) mice of both sexes, although the response was much weaker in the aged mice.
Neuroblasts took four weeks to form and eight weeks to mature into neurons, slower than neurogenesis reported in lab dish experiments, so researchers plan to conduct experiments to determine if the slower pace helps the newly generated neurons properly integrate into their environment.
The findings are published in journal Nature Communications.
