Recent Embryonic Stem Cell Progress
AAAS has compiled a list of peer-reviewed and recommended findings that
demonstrate some achievements in embryonic stem cell research. This is
a sampling of the current data and not reflective of the breadth and scope
of all embryonic stem cell research.
Laboratory Techniques
Central Nervous System
Germ Cell
Endocrine/Pancreas
Liver
Blood Cells
Laboratory Techniques:
The use of embryonic stem cells in the laboratory setting has evolved
considerably in recent years. Embryonic stem cells are relatively difficult
to grow in cell culture (outside of the body). Initially, human embryonic
stem cells had to be grown in the presence of animal growth serum and
mouse feeder cells. A problem is that animal products could harbor viruses
or other problematic agents and render the stem cells useless for human
therapies. Two years ago, a new culture media absent of all animal products
and animal cells was developed and human embryonic cells were successfully
grown (Bio of Repro 70:837-45, 2004). More recently, new human embryonic
stem cells lines were developed that have never been grown in the presence
of animal products (Nature Biotech 24:185-7, 2006) which could allow these
cells to be used in potential therapy. Other cell culture advances include
the use of defined media conditions to maintain human embryonic stem cell
proliferation (and therefore repress differentiation) or direct the cells
toward specific types of differentiation (PNAS 103(18):6907-12, 2005 and
PLOS Medicine 2:0554-60, 2005).
Advancements have also been made in the generation of new cell lines.
Researchers were able to develop embryonic stem cells lines from human
embryos with known genetic diseases (such as myotonic dystrophy, beta-thalassaemia,
and Fanconi anaemia); these cell lines can be used to better understand
the a specific disease (Reproductive BioMedicine Online 10(1):105-110
2005). Another research team was able to develop an embryonic stem cell
line from a single cell biopsy that is routinely taken from human embryos
for diagnostic purposes; this technique may circumvent some of the ethical
issues surrounding the use of human embryos in research (Nature 444(7118):481-5
2006).
The use of somatic cells (all adult cells except for the sex cells) in
combination with embryonic stem cells is a useful yet controversial technology.
One scientific team has developed a technique involving the fusion of
somatic cells with preexisting embryonic stem cell lines. The fusion caused
the somatic cells to undergo genetic reprogramming and resulted in cells
with developmental characteristics similar to human embryonic cells. This
approach could allow for the creation of patient-specific stem cells (Science
309:1369-73, 2005).
Central Nervous System:
Researchers were able to generate neurons from monkey embryonic stem cells
and then transplant them into monkeys with Parkinson's disease. The transplanted
cells were functional and diminished the symptoms of Parkinson's disease
(J Clin Invest 115:102-109, 2005). Other scientists have been able to
produce these same dopaminergic neurons from human embryonic stem cells
in culture (PNAS 101(34): 12543-48, 2004). More recently, scientists demonstrated
that human embryonic stem cells can be injected into developing mouse
brain to form functional neural cells (PNAS 102(51):18644-48). Together,
these finding suggest that embryonic stem cells have the capacity to form
functioning neurons and can be successfully transplanted into brain.
Research on spinal cord regeneration has been extensive; many scientists
have demonstrated that embryonic stem cells can be treated with growth
factors to produce functioning nerve cells in culture (Nat Biotechnol
23(2):215-21, 2005). Paralyzed mice and rats received transplants with
neurons derived from embryonic stem cells; these transplants resulted
in positive therapeutic outcomes including recovery from paralysis (Cell
110:385-397, Ann Neurol 60:32-44, 2006, and Ann Neurol 60:22-34, 2006).
Other researchers have developed oligodendrocytes (the protective cells
surrounding spinal cord nerves) from human embryonic stem cells and recovered
motor function in rats with recent spinal injuries (J Neuroscience 25:4694-4705,
2006).
Germ Cell:
The ability of embryonic stem cells to form germ cells (the primitive
cells in the embryo that mature into sperm or eggs) is important in demonstrating
their totipotentiality (the ability to generate any tissue in the body).
Researchers have reported that mouse embryonic stem cells can be treated
in culture to develop both male and female germ cells and are therefore
totipotent (Science 300:1251-56 2003, Nature 427(6970):148-54 2004 , and
PNAS 100(20):11457-62 2003).
Endocrine/Pancreas:
Research has focused on deriving a use for embryonic stem cells in the
treatment of diabetes (the disease whereby pancreatic cells fail to secrete
insulin). Mouse embryonic stem cells have been successfully differentiated
into pancreas cells that secrete insulin in a culture system (Stem Cells
22:1205-1217, 2004). Later studies have demonstrated that human embryonic
stem cells could be cotransplanted with embryonic mouse pancreas cells
in culture to form insulin producing cells as well (Diabetes 54:2867-74,
2005).
Liver:
Mouse embryonic stem cells have been used to study liver-based genetic
defects such as hemophilia A and B. Researchers differentiated mouse embryonic
stem cells in culture and then injected these cells into the liver of
diseased mice. This treatment reversed a form of hemophilia in mice that
is similar to hemophilia B in humans (PNAS 102: 2958-63, 2005)
Blood Cells:
Most research and subsequent treatment of hematopoietic (blood cell)
disorders involves adult stem cells isolated from bone marrow. For the
past few decades, treatments for blood diseases, such as leukemia, have
utilized bone marrow stem cells. Some research has been dedicated to the
potential use of embryonic stem cells in other blood disorders. Recently,
a team of researchers differentiated human embryonic stem cells into hematopoietic
cells and through a series of treatments in sheep were able to develop
a long term bone marrow transplantation (Blood 107(5): 2180-3, 2006).
Updated July 13, 2007
|
