In most cell therapies, the transplanted cells do not survive for long, or in large numbers. They produce beneficial effects, such as reduced inflammation or enhanced regeneration, via signaling that changes the behavior of native cell populations.
Considerable effort is going into finding ways to make cells used in therapy survive for a longer period of time following transplantation. The approach taken here is to engineer a fraction of the transplanted cells to produce a growth factor that improves the survival of the others. The results are demonstrated in an animal model, showing a greater regeneration of heart muscle.
Source: Fight Aging!