Welcome to the California Institute for Regenerative Medicine

Right Column

Creating New Types of Stem Cells

Generating new stem cell lines is a major focus of many CIRM funded researchers. Learn why these new lines are considered so important for the field to move forward.

What is stem cell line?

A stem cell line is a group of identical pluripotent stem cells that can be grown and multiplied in a lab dish. A line originates with either a single iPS cell or from the cells of a five day old blastocyst, and all resulting cells in the line are replicates of the original cells. Researchers working with these lines can grow up large volumes of cells and freeze some in liquid nitrogen for future use or to share with colleagues.

Researchers are still learning the best way to grow and maintain pluripotent stem cells. The cells need nutrients and a number of biological factors in the lab dish in order to grow well. Figuring out the best combination of factors to maintain a stem cell line is the focus of several CIRM grants. 

Related Information

VIDEO: Dr. Peter Donovan talks about maintaining stem cell lines in the lab

Aren't there already stem cell lines approved by President Bush?

On August 9, 2001 President Bush announced that only human embryonic stem cell lines created before that date could be used for federally funded research. Although he initially announced that there were more than 70 lines available, it turns out there are only 22 lines, of which only a handful have proven valuable in research. Some of the lines have developed genetic defects that make them difficult to work with. All of the cell lines approved for federal funding were generated from left over in vitro fertilization (IVF) embryos that were destined to be destroyed.

Why do we need more human embryonic stem cell lines?

Of the human embryonic stem cell lines available for federal funding many don’t grow well in the lab. Others have genetic anomalies that make them a poor choice for most research, and all were initially grown on lab dishes that contained so-called feeder cells from other animals. These human embryonic stem cell lines might have picked up virus or other animal components from those animal cells and are difficult to safely transplant into people. What’s more, recently some investigators have learned that five of the lines were created without proper consent from the IVF embryo donors.

One reason why these early lines have so many problems is that they were the first human embryonic stem cell lines to be generated. Researchers were in the early phases of learning the best ways of isolating and maintaining those cells. As the work progresses researchers are learning more and more about better ways of creating and growing the new cells lines.

Another problem with the human embryonic stem cell lines available for federal funding is that they represent the genetics of the mostly white people who underwent IVF then donated the embryos. This means that any discoveries that come out of research with those cell lines may only apply to that population. For example, if experiments with those cells reveal drugs to treat Alzheimer’s disease, that drug may be less effective in non-Caucasians. In additions, the cells may cause a more severe immune reaction if transplanted into genetically diverse people as a cell based therapy.

New human embryonic cell lines would represent the breadth of human diversity and could be grown in a way that makes them more useful for future transplantation. What’s more, many research groups are developing new embryonic stem cell lines that contain disease genes. These are expected to be a powerful tool for understanding how devastating diseases develop and for discovering drugs to help treat these diseases.

For example, a researcher working with a cell line that has the cystic fibrosis mutation could grow those cells into lung cells and learn more about why the lung tissue can’t work effectively. They could then test drugs that allow those lung cells to work more effectively.

Related Information

VIDEO: Dr. Martin Pera talks about the need to create new embryonic stem cell lines

What are the different ways of creating pluripotent stem cell lines?

Researchers are taking many different approaches to creating new pluripotent cell lines. CIRM considers this to be such an important endeavor that it has funded $23 million in grants dedicated to the creation of new cell lines and to techniques that make the process more efficient.

In vitro

All human embryonic stem cell lines in use today were created from embryos generated by vitro fertilization (IVF) and donated for research purposes after the couple had completed their family. After fertilization, the cells divide for about five days to form a ball of cells called a blastocyst. At this point the blastocyst would still be in the fallopian tube and a woman would likely not know that she is pregnant. For IVF, this is the stage when a doctor would transfer the blastocyst into a woman’s uterus.

The blastocyst is essentially a hollow ball of cells containing an inner clump that is known as the inner cell mass. This clump is what give rise to embryonic stem cells if grown in a dish. To generate an embryonic stem cell line, a researcher removes the outer layer of the five day old blastocyst then puts it on a lab dish containing factors that allow cells of the inner cell mass to grow and thrive. These cells form the basis of a new embryonic stem cell line.

Related Information

VIDEO: Dr. Amander Clark talks about creating embryonic stem cell lines

Nuclear Transfer

Nuclear transfer is a technique to create embryonic stem cells that are genetically identical to a person’s own cells. This technique is also known as therapeutic cloning because it essentially clones a person’s cell to be used in a therapy.

The process of nuclear transfer involves removing the genetic material from an egg, then injecting the genetic material from an adult person’s cell into the egg. Researchers then stimulate the egg to begin maturing. About five days later the egg develops into a hollow ball of about 150 cells called a blastocyst. This is the same type of blastocyst that would be used to create cell lines from donated IVF embryos. Researchers remove the inner cell mass from the blastocyst and grow those cells in a lab dish to create a new embryonic stem cell line.

Researchers have used nuclear transfer to create stem cell lines from a wide range of animals including non-human primates. So far nobody has successfully used nuclear transfer to create a human embryonic stem cell line. In 2004 researchers in South Korea announced success with the technique, but that work was later found to be fraudulent.

Embryonic stem cells created through nuclear transfer would have the advantage of being genetically identical to a person’s own cells. If that person received a transplant of these cells to replace cells damaged by spinal cord injury or destroyed in diabetes, the cells would probably not be rejected by the immune system.

Related Information

VIDEO: Dr. Robert Blelloch talks about creating embryonic stem cell lines through SCNT

Stanford Publication: Illustration of SCNT

iPS

The first human induced pluripotent stem (iPS) cells were created by inserting four genes into the DNA of human skin cells. Those introduced genes caused the cells to revert back to a form that is similar to the very early embryonic state, rendering them pluripotent.

These cells are an exciting and valuable research tool, however, iPS cells currently face some hurdles before they can be used in clinical trials of a cell based therapy. The initial versions of the technique used a virus to shuttle the genes into the skin cell, which can integrate into the cell’s DNA and possibly cause hazardous mutations. What’s more, some of the genes used to create the iPS cells have some cancer-causing potential.

Many CIRM-funded researchers are trying to identify safer ways of creating iPS cells, which would allow researchers to create patient-specific stem cells that can be transplanted as a treatment for disease. These researchers are looking into using methods that don’t require the genes to incorporate into the cell’s DNA or finding a combination of chemicals or proteins to replace those genes as alternative ways of creating iPS cells.

Related Information

VIDEO: Dr. Jerome Zack talks about creating iPS cells

UCLA Publication: Profile of Kathrin Plath