More the Merrier
There are three distinct sources for stem cells for transplantation.
- From peripheral blood of adult donors
- Directly from the bone marrow of adult donors (ouch!)
- Last but not least, from umbilical cord blood – something considered a biological waste product until recently, to be thrown away after the birth of babies.
Back in the ‘old’ days, most of the transplants were done using stem cells harvested directly from the bone marrow of willing donors. I am willing to bet most of these donors were sibling matches. Not too many people would be willing to have transplant surgeons messing around in their bone marrow to harvest stem cells directly, for the benefit of total strangers.
Peripheral blood stem cells are easier and less painful to harvest. The donor may have to get GM-CSF (trade name “Leukine”) injections to get enough of his / her stem cells flushed out from the bone marrow and into general blood circulation. Then a needle is inserted into one arm, blood drawn through it and fed into a machine that separates out the desired stem cells. The remaining blood is fed back into the donor through another needle in his other arm. Younger donors are preferred, since they have more stem cells to spare and less likely to have problems with harvesting sufficient quantity of them for transplant.
Below are two diagrams from a recent article by Dr. Juliet Barker. Lovely lady, I spent a couple of hours on the phone with her when she was still at the U. of Minnesota working on their pivotal double cord transplant protocol. She is now at MSKK, heading their cord blood transplant program.
As you can see, the total number of stem cell transplants done in the USA are increasing at a rapid clip. Stem cells obtained directly from the bone marrow of donors are falling out of favor, as you would expect. Cord blood transplants are becoming a larger percentage of the mix. Back in 2002 when I first started keeping track of cord blood transplant technology, they did fewer than 80 such transplants per year in the USA. In 2006 that number has blossomed to ~ 450. I am sure the numbers are even larger by 2008.
Here is a detailed and important review article by Dr. Barker that discusses the pros and cons of the various sources of stem cells. If this technology is in your future, this article is a good place to start your education.