Season4, Episode 10: What It Feels Like

Mayko is approached by the adoptive parents of the daughter she gave away at birth six years ago. The girl, Hannah, is suffering from aplastic anemia and needs a bone marrow transplant to save her life. When Mayko learns she is not a good donor match, she approaches Hannah's biological father, David, who had no idea that he had a child with Mayko. David isn't a good match either, but at the birth of his first daughter, Lilith, he had saved her umbilical cord blood, which shares some characteristics of bone marrow. Lilith's cord blood cells are successfully used to treat Hannah's aplastic anemia. Meanwhile, Nina experiences increasingly frequent and severe hallucinations and psychotic episodes as a result of the high dopamine levels in her brain.

Image provided courtesy of Shaftesbury Films.

David and Mayko visit their daughter, Hannah, in the hospital.

CAN CORD BLOOD FROM A HALF-SIBLING BE USED TO TREAT APLASTIC ANEMIA?

What is aplastic anemia?

In patients with aplastic anemia, their bone marrow is unable to produce any of the three types of blood cells: red blood cells, which carry oxygen; white blood cells, which fight infection; and, platelets, which aid in clotting. Bone marrow is a spongy tissue inside bones that, in healthy individuals, produces these different blood cells from a type of stem cells called "hematopoietic stem cells." Aplastic anemia is encountered in both adults and children. In some cases, the disease is inherited, but usually it's not; most often, the exact cause for the occurrence of aplastic anemia is unknown.

How is aplastic anemia treated?

The most successful treatment for aplastic anemia is bone marrow transplantation, in which the bone marrow from a healthy donor is transplanted to the anemic patient. However, the bone marrow of the donor has to be similar to that of the patient - in other words, it needs to be a good "match."

In all types of transplantations, there is a risk of rejection, in which the patient's immune system sees the transplanted material as "foreign" and fights it off. In bone marrow transplantation there is an additional risk: graft-versus-host disease, in which the donor material attacks the patient. This happens because the bone marrow contains T-cells, a type of white blood cells that actively attacks foreign material - if the match isn't a good one, the blood cells can see the patient as foreign too!

To prevent rejection and graft-versus-host disease, the donor bone marrow has to very closely resemble the cells in the patient's immune system. The closeness of the match is assessed by looking at Human Leukocyte Antigen (HLA) proteins on the cells in the blood of the potential donor and the patient. HLA proteins are detected by the immune system as either "foreign" or "self." If the donor has almost the same type of HLA proteins as the patient - that is, if they are a close match - there is a good chance that the cells in the patient and the donor material will accept one another as "self" and therefore won't attack each other. Usually, close family members are selected as bone marrow donors, because their HLA proteins will be the best match.

What is cord blood?

During pregnancy, the umbilical cord connects the placenta to the fetus. Because a newborn baby doesn't need the cord anymore after birth, it's usually discarded with the placenta. Recently, however, some people have chosen to save and freeze the blood from the umbilical cord when their child is born.

Why? Because this cord blood contains blood stem cells similar to those found in bone marrow that can be kept in frozen storage for years. The most common use of cord blood is stem cell transplantation into a family member whose own stem cells in their bone marrow are damaged or defective. Usually these kinds of transplants are used to treat a brother or sister to the newborn, but they can also help other family members, including half-siblings.

One of the conditions that can be successfully treated with a cord blood stem cell transplant is aplastic anemia. Because the cells in cord blood are still immature, the HLA type matching doesn't have to be perfect: even with a partial match, graft-versus-host disease or rejection is far less likely to occur than with bone marrow transplantation from an adult.

A number of companies in Canada and around the world have been storing cord blood for families for several years now, for the families' own private use. In addition, Canada is launching a nationwide public cord blood bank, to which parents can anonymously donate cord blood that could be used by others: for example, to potentially save an anemic patient from a similar genetic background. Many other countries already have national cord blood banks.

So?

Yes, it's possible to use a half-sibling's cord blood to treat aplastic anemia, provided the HLA proteins are at least a partial match. But saving cord blood at birth is a quite recent development: The first successful cord blood stem cell transplant took place in 1989. So, in the world of ReGenesis, when Lilith was born, saving cord blood would have still been very unusual.

DID YOU KNOW?

Nina is given the drug aciclovir in this episode to try and get rid of the herpes virus in Bob's brain stem cells, in an attempt to stop these cells from continuing to increase her dopamine levels. Aciclovir is an anti-viral drug, commonly used to fight herpes simplex virus infections, but it has no effect on Nina.

Image provided courtesy of AXS Studio Inc and Shaftesbury Films.

Artist's rendition of the herpes viral DNA integrating into chromosomal DNA.

The team thinks this is due to the fact that the herpes viral DNA had integrated into the chromosomal DNA of the stem cells. Aciclovir works by attacking viral DNA polymerase, the enzyme needed for DNA replication. It has very little effect on mammalian DNA polymerase. If the viral DNA is in the chromosomal DNA of the cell, the cell's DNA polymerase can copy the viral genetic material along with its own, so aciclovir would no longer be able to stop viral DNA replication.

-- Eva Amsen

Want to read and learn more?

The Aplastic Anemia and Myelodysplasia Association of Canada has more information on aplastic anemia:
http://www.aamac.ca

Find out more about HLA-matching and bone marrow donation:
http://www.marrow.org/index.html

Read a statement from Canadian Blood Services on National Public Cord Blood Banking:
http://www.bloodservices.ca/CentreApps/Internet/UW_V502_MainEngine.nsf/page/
national_public_cord_blood_banking_consultation?OpenDocument

Read more about aciclovir:
http://en.wikipedia.org/wiki/Aciclovir