BACKGROUND:  Prolonged periods of marrow hypoplasia have been a problem in cord blood transplantation. DMSO is thought to produce osmotic shock to the progenitors when the thawed cells are infused into the patients. To solve this problem, a 2× dilution method originally developed in the New York Blood Center showed earlier myeloid engraftment,1 although follow-up clinical studies have not performed.

STUDY DESIGN AND METHODS:  To clarify the influence of the removal of DMSO by this method on the speed of engraftment in unrelated cord blood transplantation, 46 adult patients with cord blood units processed by the Tokyo Cord Blood Bank from September 1998 to March 31, 2002 were studied. Twenty-four patients received 2.6 ± 0.71 × 107 nucleated cells per kg without washing (nonwashed group), while 22 patients were received 2.7 ± 0.52 × 107 nucleated cells per kg after 2× dilution washing (washed group).

RESULTS:  The cumulative incidence of engraftment was not significantly different between the two groups. Median neutrophil recovery (≥5 × 109/L) in the nonwashed and washed groups was 26 and 25 days, respectively, and the median platelet recovery (≥20 × 109/L) in patients with myeloid engraftment was 44 and 40 days, respectively (NS). On the other hand, the doses of CFCs and CD34+ cells showed the influence on myeloid and platelet recovery.

CONCLUSION:  A 2× dilution after thawing cord blood did not result in the improvement of myeloid engraftment speed.