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​Stem cells can be donated in two different ways

Blood stem cells can be collected in two different ways: from the blood or from the bone marrow. The collection method is selected chiefly on the basis of the patient’s condition. In some cases, the donor's wishes can also be taken into consideration. In most cases, stem cells are collected from the blood stream.

1) Donating blood stem cells from the circulation

Stem cells can be transferred from the bone marrow to the blood stream using a leukocyte growth factor, The growth factor is a substance that normally occurs in the body in small doses. Before stem cells are collected from the blood stream, the donor is given a growth factor injection for four to five consecutive days at the Meilahti Hospital. The donor will need to attend the Meilahti Hospital in Helsinki on a daily basis for the duration of the growth factor treatment, to receive a daily injection.

Following the growth factor injections, the stem cell volume increases in the bone marrow and stem cells transfer to the blood stream, where they can be collected. Stem cells are collected using cannulas inserted on the inside of the elbow. Collection takes 5–6 hours at a time and is performed over one or two consecutive days. Stem cells are collected from the inside of the elbow without anaesthesia and the procedure requires no overnight stay at the hospital. The donor will be on sick leave for the duration of the growth factor treatment and collection of stem cells, as well as for a couple of days after the procedure.

Around 75% of donations are collected from the blood stream.

Recovery and risks
The growth factor treatment may cause bone pain when the cell volume of the bone marrow increases. If necessary, these pains can be treated with standard pain killers. This pain which will disappear soon after the collection. Possible side effects may also include flu-like symptoms and headache.

Since other cells in the blood are returned to the donor's blood stream during the procedure, collection of stem cells from blood does not notably lower the haemoglobin of the donor. Leukocyte growth factor has been used to treat patients for some years, and is not known to cause long-term adverse effects.

2) Collection of blood stem cells from the bone marrow

Collection of stem cells from the bone marrow is performed under general anaesthesia. Bone marrow is withdrawn from inside the pelvic bones (above both buttocks) with a needle, in small amounts. Approximately 300–1200 ml of bone marrow is collected, with the collection taking a little over an hour.

The donor of blood marrow arrives at the hospital the day before the scheduled donation. The donor will be discharged from the hospital the day after the donation, and will receive sick leave of approximately a week.

Recovery and risks
Bone marrow is self-regenerating tissue. Blood marrow donated will quickly be replaced by new, normally functioning bone marrow.

Only 5% of the cells housed in the donor’s bone marrow are collected from the donation site. This does not even temporarily affect the ability of the bone marrow to produce blood cells. Donation of stem cells from bone-marrow reduces neither the donor’s resistance to infectious diseases nor the effectiveness of any vaccines that may be administered.

Donating bone marrow is equivalent to donating approximately two blood units. This is why the donor's haemoglobin level falls temporarily but will return to normal within a few weeks. If necessary, the donor is given iron tablets to replenish the body’s iron supplies.

The areas from which bone marrow was collected may be tender for approximately a week after the donation. A few needle marks will be visible on the skin, constituting a slight and usually temporary cosmetic problem. Some donors experience tiredness for a few days after donation.