Four sugar-coated faces made by stem cells as they differentiate into brain cells during development have been identified by researchers.

These unique expressions of sugar on the cell surface may one day enable stem cell therapy to repair brain injury or disease by helping stem cells navigate the adult brain, says Robert K. Yu, director of the Institute of Neuroscience and the Institute for Molecular Medicine and Genetics at the Medical College of Georgia.

“ These glycoconjugate markers are like specific addresses that characterize the cell at that particular moment. We call them stage-specific embryonic antigens,” says Yu, molecules that assist in the unbelievably rapid assemblage of 100 billion to 200 billion cells into a brain in nine months.

The four compounds – two glycolipids, GD3 and O-acetylated GD3, and two glycoproteins, Stage-specific Embryonic Antigen-1 and Human Natural Killer Cell Antigen 1 – were known, but their role in helping cells migrate where and when needed was unknown.

During brain formation cells are constantly changing their sugar face and their function to meet the immediate biological needs. They travel a sort of neuron interstate laid out by the first stem cells formed in development before rapid cell migration and transformation begins. “ These ‘interstates’ are called Bergmann glia or glial fibers. They serve as guidance for the neuronal cells to migrate,” Yu says.

Conditions such as trauma, spinal cord injury and stroke can destroy these travel networks as well as brain cells.

Labs such as Yu’s are doing stem cell transplants to re-establish roadways and get undifferentiated stem cells to repopulate such ravaged areas.

Two of the biggest problems facing stem cell transplantation are functional recovery – getting the cells to do the right job once they arrive at a target organ – and controlling their proliferation so they don’t start forming tumors, says Yu.

MCG biochemist Erhard Bieberich is exploring the potential of the lipid ceramide, which helps eliminate potentially harmful cells during brain development, to halt unwanted proliferation of transplanted stem cells.

Source: Medical College of Georgia, 2005


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