Frequently Asked Questions about Stem Cells and Clinical Trials

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What are stem cells?

We all have stem cells and they are necessary for our survival. For example, skin stem cells renew and repair our skin. Cells in our bone marrow generate the different cell types in our blood. The stem cells in our bodies are ‘adult stem cells’ - unspecialized cells found in a tissue or organ that can yield all the specialized types of cells of that tissue or organ.

The term ‘adult stem cells’ can be misleading because babies and children have them as well. Adult stem cells are also referred to as multipotent stem cells. Multipotent means that they can only generate the cell types in the particular organ in which they are found. However, some studies suggest that under certain conditions, adult stem cells may be able to give rise to cell types of other tissues as well. Another source of multipotent stem cells is umbilical cord blood.

Stem cells that have the potential to generate the cell types in any organ or tissue in the body are called pluripotent stem cells. Embryonic stem cells are pluripotent. Embryonic stem cells come from a blastocyst- a small sphere of cells that results from cell division in a fertilized egg. For research purposes, cells are harvested from the inner cell mass of the blastocyst when it is approximately six days old and consists of around 200 cells. Recently, cells with properties similar to embryonic stem cells, referred to as induced pluripotent stem cells or iPS cells, have been engineered from specialized cells such as skin cells.

What is regenerative medicine?

Regenerative medicine seeks to repair, replace or regenerate organs and tissue that have been damaged by disease, injury or even the natural aging process. Stem cells might be put into the blood or transplanted directly into damaged tissues of patients, or even be recruited from the patient’s own tissues to help restore or establish normal function.

How can stem cells be used to treat disease?

Given their unique abilities to renew themselves, researchers are exploring different avenues for using stem cells to treat disease, including:

  1. Replacing damaged cells and organs. A wide range of diseases (heart disease, Parkinson’s disease, Alzheimer’s disease, diabetes, motor neuron disease, etc.) may be amenable to stem cell therapy if stem cells can be made to go to the appropriate place in the body and become the appropriate cell type. For example, if stem cells could be made to migrate to an injured spinal cord and become nerve cells, it might be possible to treat paralysis.
  2. Developing drug therapies. It is possible to make stem cells that are genetically identical to those of a person with a disease such as amyotrophic lateral sclerosis. The stem cells can be made to generate the cell type that is defective in that disease (e.g. nerve cells). By studying these cells, researchers can gain insight into what goes wrong at the molecular level in the disease. They can also use these cells to test drugs that might block the progression of the disease.
  3. Determining how disease starts. Stem cells are critical for growing and repairing the human body. However, stem cells that have out-of-control proliferation could create precursor cells for cancer. By identifying the mechanisms that enable the ‘cancer stem cell’ to go haywire, researchers might target these specific pathways to treat cancer.

Stem cells offer tremendous potential to advance medicine; however, current applications may be sometimes exaggerated by the media and others who may not fully understand the science or limitations. Treatments based on stem cells are largely new and there is much we still need to learn. Researchers believe it may take many years, possibly decades in some cases, to realize the full potential of stem cells to treat disease.

How much do stem cell treatments cost?

UC San Diego Health doctors, researchers and ethicists advise that it is unethical to charge patients for treatments that have not been validated. Unfortunately, there are people who have taken advantage of stem cell publicity to charge fees for treatments that have not been adequately tested for safety and effectiveness. Alleged treatments are offered for a variety of conditions. The Sanford Stem Cell Clinical Center believes that companies often inaccurately portray treatments as safe and effective for a broad range of injury and disease. Potential side effects are downplayed and testimonials are presented instead of evidence from research articles in reputable scientific journals.

The International Society for Stem Cell Research (ISSCR) has expressed concerns about disreputable clinics.

“Numerous clinics around the world are exploiting patients’ hopes by purporting to offer new and effective stem cell therapies for seriously ill patients, typically for large sums of money and without credible scientific rationale, transparency, oversight, or patient protections. The ISSCR is deeply concerned about the potential physical, psychological, and financial harm to those who pursue unproven stem cell ‘therapies’ and the general lack of scientific transparency and professional accountability of those engaged in these activities.”

See "Nine Things To Know About Stem Cell Treatments" for more information.

Where can I find more information on stem cells?

Clinical Trials

What are clinical trials?

Clinical trials are medical research studies. These studies are carefully conducted to investigate the safety and efficacy of potential new treatments and represent the usual path to approval by the United States Food and Drug Administration (FDA).

Each clinical trial is led by a principal investigator (PI) who is a physician. The principal investigator follows a plan for the trial, called a protocol. The protocol explains what will be done during the trial. It also contains information that helps the doctor decide if this treatment is right for you. The protocol includes information about:

  • The reason(s) for doing the trial
  • Who can join the trial, also called “eligibility requirements”
  • How many people are needed for the trial
  • The types of information that will be collected from study participants
  • Any drugs that will be given, including how they will be given, the dosage and how often
  • What medical tests will be done and how often

Why are clinical trials important?

It is through clinical trials that researchers can determine whether new treatments are safe, effective and work better than current treatments. When people take part in a clinical trial, they add to our knowledge about medical conditions and help improve care.

What should I know if I am thinking about participating?

You should always feel free to ask any questions or bring up any issues concerning the trial at any time. The decision to participate in a clinical trial is always up to you.

Potential Benefits

Well-designed and well-executed clinical trials provide the best approach for participants to:

  • Play an active role in their health care
  • Gain access to new research treatments before they are widely available
  • Receive regular and careful medical attention from a research team that includes doctors and other health professionals
  • Help others by contributing to medical research

Potential Risks

  • Unpleasant, serious, or even life-threatening side effects to experimental treatment
  • More time and attention required than standard treatment, including visits to the study site, additional blood tests, treatments and hospital stays, or complex dosage requirements.

How do I know if I'm eligible to participate in a clinical trial?

Each study has its own guidelines for who can participate, called “eligibility criteria.” To ensure reliable results, researchers must study patients who are alike in key ways, such as having a particular type of spinal cord injury, or stage of cancer, or be a certain gender or age.

These guidelines help protect patients by ensuring that people who could be harmed by study treatments are not enrolled. After the trial is completed, if it is proven to work, eligibility criteria help doctors know which patient groups will benefit from the new treatment.

If I participate in a clinical trial, how will I be protected?

Ethical Guidelines

People who participate in clinical research make it possible to develop knowledge that improves human health. The path to finding out if a new drug is safe or effective is to test it on patient volunteers.

Informed Consent

Informed consent is one of many safeguards in place to ensure patient protection. Informed consent is the process of learning the key facts about a clinical trial before deciding whether to participate. The process of providing information to participants continues throughout the study. To help someone decide whether to participate, members of the research team explain details of the study. The research team provides an informed consent document, which includes such details about the study as its purpose, duration, required procedures, and who to contact for various purposes. The informed consent document also explains risks and potential benefits.

If the participant decides to enroll in the trial, the informed consent document will be signed. Informed consent is not a contract. Volunteers are free to withdraw from the study at any time.

Regulatory Oversight

Clinical trials are approved and monitored by an Institutional Review Board (IRB) in order to ensure that the risks are minimized and are worth any potential benefits. An IRB is an independent committee that consists of physicians, statisticians, and members of the community who ensure that clinical trials are ethical and that the rights of participants are protected. The Food and Drug Administration (FDA) must also approve most clinical trials that involve stem cells in the U.S.

What questions should I ask before participating in a clinical trial?

You should be provided with an informed consent form that can address many of your questions, but you are encouraged to ask any questions or bring up any issues concerning the trial at any time. Make sure you understand the treatment plan and any risks. The decision to participate in a clinical trial is always up to you.

About the Trial
  • Why is this trial being done?
  • Why do researchers believe that the treatment being studied may be better than the one being used now? Why may it not be better?
  • How long will I be in the trial?
  • What kinds of tests and treatments are involved?

Possible Risks and Benefits

  • What are the possible side effects or risks of the new treatment?
  • What are the possible benefits?
  • How will the doctor know if the treatment is working?


  • Will I have to pay for any of the treatments or tests?
  • What costs will my health insurance cover?

Daily Life

  • How could the trial affect my daily life?
  • What other medications or special care might I need?
  • How often will I have to come to the hospital or clinic? Will there be any travel or childcare costs that I need to consider while I am in the trial?

Comparing Choices

  • What are my other treatment choices, including standard treatments?
  • How does the treatment I would receive in this trial compare with the other treatment choices?

How can I find specific clinical trials?

You can search for new clinical trials, and changes in existing trials at the U.S. National Institutes of Health database:

If you see trials that are of interest to you, we recommend that you read about them carefully, and then print the trial descriptions out for discussion with your doctor. Please keep in touch with respected physicians whom you know and trust for all aspects of your health care.