( . On the other hand in recent years...)Schepens Scientists Identify Key to Integrating Transplanted Nerve,Cells Into Injured Tissue,Health

On the other hand, in recent years, stem cells have been shown to overcome these physical barriers, easily penetrating the scar and integrating into the injured tissue.

For instance, in studies published several years ago, Young and his colleagues demonstrated this special stem-cell talent in damaged mouse retinas. In those studies cells injected into injured retinas quickly integrated into the existing retinal tissue.

Intrigued by this phenomenon, Young and his team believed that if they could identify and harness the key molecules used by stem cells to gain access into the injured retina, they could potentially improve the success of non- stem cell transplants. Based on this idea, the team conducted a series of experiments.

In their initial experiments, the team compared the chemicals that were generated when stem cells were injected into damaged retinas and those produced when they attempted to transplant whole retina tissue into the eyes of mice with degenerated retinas. They found-in the stem cell injected retinas-an increase in the amount of and the level of activity of the molecule MMP-2 in host tissue. They concluded that this molecule dissolved the scar on the outer surface of the retina. There was no increase in MMP-2 when they attempted whole-retina transplants.

The team went on to transplant a layer of stem cells between the degenerating mice retinas and healthy donor tissue (whole retina). They found that MMP-2 induced removal of the scar barrier and allowed healthy donor cells (of the whole retina) to make new connections with the damaged retinas in the mice.

"These are very powerful results," says Young. "We are convinced that the increase of this molecule is a major key to creating a permissive environment for central nervous system regeneration."

The team is now investigating therapeutic approaches that would eliminate the need for stem cells. This would involve the use of just the MMP-2 molecule, w
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