Replacing Cells - Biotechnology and Your Health: Pharmaceutical Applications - page 110

both before and after the introduction of biotechnology techniques
that let scientists design protein at will. Scientists focused first on
hemoglobin purified from human blood, and then on forms of
hemoglobin engineered in the laboratory. Their goal was to come
up with a protein that could be dehydrated for storage at room tem-
perature and dissolved in a salt solution to provide the life-saving
capacity to transport oxygen similar to that of intact red blood cells.
Researchers have even packaged the hemoglobin in a fat and protein
sack to mimic the structure of a red blood cell. Despite all the
elegant and laborious efforts, no red cell substitute has yet proven
safe and effective. Now researchers are analyzing how hemoglobin
is tethered inside red cells so that it is efficient at picking up and
delivering the oxygen and carbon dioxide as needed.
STEM CELLS
Blood cells are not the only type of cell therapy on the horizon.
Scientists are now working on another type of cell therapy, called
stem cell therapy, which would take immature cells and coax them
into becoming specialized cells in the laboratory to repair damaged
or poorly functioning organs. Stem cells are potentially the raw
material that could make medical repairs that are currently impos-
sible with drugs. To use these cells, scientists must understand how
stem cells have the ability to divide repeatedly without specializing,
yet under the right conditions, turn into all kinds of cells: liver cells,
heart muscle cells, bone-producing cells, and so forth.
The human body's entire system of a billion or more cells devel-
ops from a single cell—the egg fertilized by the sperm. As this
cell divides to form all the different tissues and structures of the
growing fetus, the daughter cells become specialized in the kinds of
proteins they produce. Think of the entire set of genes as inherited
instructions to form more than 100,000 proteins when and where
they are needed. Going from the single-cell embryo to the enor-
mous collection of specialized cells that make up our body is an