Cryopreservation
Because HSCs have a short shelf life when refrigerated, cryopreservation may be necessary to prolong the storage and viability of these cells. The most commonly used cryopreservative is dimethyl sulfoxide (DMSO). This chemical will be incorporated into the cells and prevents ice crystals from forming when the cells are frozen. Some facilities use a combination of DMSO and hydroxyethyl starch (HES) which provides more viable cells than DMSO alone. After freezing, the cells can be stored in liquid nitrogen at -196° C.
Infusion of HSCs
Frozen HSCs are thawed in a 37° C water bath and then rapidly infused into the patient. Prior to the infusion, the patient may be given an antihistamine to prevent an allergic reaction to the DMSO. Other common side effects during infusion are fever, chills, shortness of breath, nausea, and vomiting. Some facilities remove the DMSO by washing the cells before infusion to lessen these side effects.
Engraftment
Successful engraftment occurs when the absolute neutrophil count is greater than 0.5 x 109/L. The presence of chimerism in an allogeneic transplant is another indicator of engraftment. The rate of engraftment is dependent on the number of CD34 positive cells in the transplant, control of GVHD, and use of growth factors. Graft failure is usually the result of inadequate numbers of CD34 cells, toxic reactions to chemotherapeutic drugs, or infection with cytomegalovirus (CMV) or other opportunistic infections.
Successful platelet engraftment occurs when the platelet count exceeds 20,000/uL without transfusion.
