제대혈-분만시 탯줄에서 채취하는 혈액[Cord blood]

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제대혈에는 골수와 마찬가지로 혈액을 새롭게 만들어내는 조혈모세포뿐 아니라 연골·뼈·근육·신경 등을 만드는 줄기세포가 들어 있어 의학적으로 중요하게 활용된다. 특히 조혈모세포의 이식은 1988년 프랑스에서 판코니 빈혈을 앓고 있는 5세의 남자아이에게 시행하여 처음으로 성공하였는데, 골수 이식에 비해 6가지 항원 중 4가지만 맞아도 실시할 수 있으며 부작용이 적고 완치율도 높다.

현재 제대혈이나 조혈모세포 이식을 통해서 치료가 가능한 질병은 백혈병을 비롯한 각종 암, 재생불량성 빈혈이나 겸상적혈구 빈혈과 같은 난치성 혈액질환, 고셰병, 선천성 면역결핍증과 같은 선천성 질병 등이다. 또한 당뇨와 심근경색증, 치매와 뇌졸중 같은 신경계 질환 등의 치료법이 연구되고 있다. 이러한 제대혈의 장점 때문에 필요할 때에 녹여서 사용하기 위해 제대혈을 채취하여 냉동보관하는 제대혈 은행이 운영되고 있다.

Cord blood

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Umbilical cord blood is blood from a newborn baby, collected from its placenta and umbilical cord after the cord has been clamped. Blood collected this way at birth is utilized as a source of stem cells for transplantation, being rich in hematopoietic stem cells.

Cord blood is stored by both public and private cord blood banks. Public cord blood banks store cord blood for the benefit of the general public, and most U.S. banks coordinate matching cord blood to patients through the National Marrow Donor Program (NMDP). Private cord blood banks are for-profit organizations which store cord blood for the exclusive use of the donor or donor's relatives.

Public cord blood banking is strongly supported by the medical community. However, private cord blood banking is generally not recommended unless there is a family history of specific genetic diseases. Private banking is unlawful in France and Italy, and opposed by the European Group on Ethics in Science and New Technologies.

Cord blood harvesting is a controversial practice in the medical and parenting community. The American Academy of Pediatrics 2007 Policy Statement on Cord Blood Banking[1] states that:

"Physicians should be aware of the unsubstantiated claims of private cord blood banks made to future parents that promise to insure infants or family members against serious illnesses in the future by use of the stem cells contained in cord blood;"

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 Properties

Stem cells from the blood of newborns are more proliferate and have a higher chance of matching family members than stem cells from bone marrow. Parents and siblings match 50% of the genetic markers of the donor's stem cell. However, since many different genetic markers are required for a match, the probability of a potential implant in a parent or sibling is considerably lower.

 Collection, storage and costs

Main article: Cord blood bank

Additional stem cells may be collected from the placenta via Placenta Cord Banking. After the health care provider draws the cord blood from the umbilical cord, the placenta is couriered to the stem cell laboratory where it is processed for additional stem cells. By banking stem cells derived from the placenta as well as umbilical cord blood, families may save more CD34+ stem cells for use in transplants. Having as many of these stem cells as possible is medically important: published research shows that the size of the stem cell transplant (especially the number of CD34+ cells) is consistently a significant factor in achieving a successful treatment and patient survival.

There are two methods of cord blood collection from the umbilical vein: before the placenta is delivered (in utero), and after (ex utero)

With the ex utero collection method, the cord blood is collected after the placenta is delivered and the umbilical cord is clamped off from the newborn. The placenta is placed in a sterile supporting structure with the umbilical cord hanging through the support. The blood is collected by gravity drainage yielding 40-150 mL of cord blood.

A similar collection method is performed in utero, except that the cord blood is collected after the baby has been delivered but before the delivery of the placenta.

After collection, the cord blood units must be immediately shipped to a cord blood bank facility. At public cord blood banks, this blood is then analyzed for infectious agents and the tissue type is determined. Cord blood is processed and depleted of red blood cells before being stored in liquid nitrogen for later use.

New parents have the option of storing their newborn's cord blood at a private cord blood bank or donating it to a public cord blood bank. The cost of private cord blood banking is approximately $2000 for collection and approximately $125 per year for storage, as of 2007. Donation to a public cord blood bank is not possible everywhere, but availability is increasing. Several local cord blood banks across the United States are now accepting donations from within their own states. The cord blood bank will not charge the donor for the donation; the OB/GYN may still charge a collection fee, although many OB/GYNs choose to donate their time.

After the first sibling-donor cord blood transplant was performed in 1988, the National Institute of Health (NIH) awarded a grant to Dr. Pablo Rubinstein to develop the world's first cord blood program at the New York Blood Center(NYBC),^[1] in order to establish the inventory of non embryonal stem cell units necessary to provide unrelated, matched grafts for patients.

In 2005, University of Toronto researcher Peter Zandstra developed a method to increase the yield of cord blood stem cells to enable their use in treating adults as well as children.^[2]

 Usage

When cryopreserved cord blood is needed, it is thawed, washed of the cryoprotectant, and injected through a vein of the patient. This kind of treatment, where the stem cells are collected from another donor, is called allogeneic treatment. When the cells are collected from the same patient on whom they will be used, it is called autologous treatment and when collected from identical individuals, it is referred to as syngenic. Xenogenetic transfer of cells (between different species) is very underdeveloped and is believed to have little research potential.

Controversy

While there is general support in the medical community for public banking of cord blood, the question of private banking has raised objections from many governments and nonprofit organizations. The controversy centers on varying assessments of the current and future likelihood of successful uses of the stored blood.

Estimates of the odds that a child will need an autologous stem cell implant by age twenty vary widely. Proponents cite odds of around 1:2,700.^[3] The European Union Group on Ethics^[4] has cited a paper^[5] claiming the odds are 1:20,000. The European Union group went on to conclude that "[t]he legitimacy of commercial cord blood banks for autologous use should be questioned as they sell a service, which has presently, no real use regarding therapeutic options. Thus they promise more than they can deliver. The activities of such banks raise serious ethical criticisms."^[4]

In May 2006, The World Marrow Donor Association's Policy Statement for the Utility of Autologous or Family Cord Blood Unit Storage^[6] stated that:

1. The use of autologous cord blood cells for the treatment of childhood leukemia is contra-indicated because pre-leukemic cells are present at birth. Autologous cord blood carries the same genetic defects as the donor and should not be used to treat genetic diseases.
2. There is at present no known protocol where autologous cord blood stem cells are used in therapy.
3. If autologous stem cell therapies should become reality in the future, these protocols will probably rely on easily accessible stem cells.

 Diseases treated with cord blood

Beginning in the late 1980s, following a successful sibling-donor transplant, cord blood stem cells have been used to treat a number of blood and immune-system related genetic diseases, cancers, and disorders. Because of medical issues around using one's own cells, in nearly every instance the treatments are done using cells from another donor, with the vast majority being unrelated donors.

In 1993, Dr. Joanne Kurtzberg, of Duke University Medical Center, performed the first two successful unrelated donor cord blood transplants;^[7] one of which cured acute lymphoblastic leukemia.

The principal diseases and disorders currently treated are listed at the National Donor Marrow Program website.

 Government initiatives to promote usage and research

 United States

In 2005, U.S. Rep. Chris Smith shepherded legislation through Congress to increase usage and research into cord blood stem cells. Smith's “Stem Cell Therapeutic and Research Act of 2005” (P.L. 109-129), authorized $265 million for stem cell therapy, umbilical cord blood and bone marrow treatments.

The bill, which was signed into law by President George W. Bush in December of 2005, authorizes $79 million for the collection of cord blood stem cells with the goal of building the nation’s public umbilical cord blood supply by adding 150,000 new units to the current inventory. The intention of the law is to collect a genetically diverse cross-section of cord blood units in an effort to make matches available to 90 percent of patients in need.

The law also created a national registry to match cord blood for those in need. All the cord blood banks participating in the inventory program will be linked into a search system that would allow transplant physicians to search for cord blood and bone marrow matches through a single access point. In September 2006, the National Marrow Donor Program (NMDP) was selected by the federal government to perform these duties.

“The Stem Cell Therapeutic and Research Act of 2005” is not only aimed at increasing the medical utilization rate for cord blood stem cells, but is also aimed at increasing cord blood stem cell research. All cord blood collected and deemed unsuitable for transplant is required to be donated for research.