CFU-GM Assay Can Be Predictive of Umbilical Cord Blood Engraftment.

Cord blood transplantation (CBT) has been considered a treatment modality to hematologic malignancies, marrow failure syndromes and genetic diseases. It has advantages such as immediate availability, lower risk of transmitting infections and higher tolerance to HLA disparities compared to bone marrow. The major drawbacks are slow hematopoietic recovery and a high incidence of graft failure or delayed engraftment, as a result of low stem progenitors (CD34⁺cells) yields. This study aimed at investigating if there was correlation between engraftment and number of total nucleated cells (TNC), number of CD34⁺ cells as well as number of granulocyte/monocyte colony forming units (CFU-GM) and erythroid burst forming units (BFU-E). Eighty four patients (age 0 to 55, M=7) with a variety of diseases (10 AML, 12 ALL, 31 Fanconi Anemia, 1 Hodgkin Lymphoma, 3 JMML, 3 Blackfan Diamond, 6 Wiskott Aldrich, 1 Krabbe Disease, 2 SAA, 4 CML, 3 Osteopetrosis, 3 SCID, 1 Diskeratosis Congenita, 1 Adrenoleukodystrophy, 1 Thalassemia Major, 1 Thrombocytopenia w/chromosome 7 monossomy) who underwent CBT were included in this study; 47.6% (40/84) of these patients had graft failure while 52.4% (44/84) showed successful engraftment. Regarding HLA-A, B and DRB1 matching, 20.2% (17/84) recipient/donor pairs were 6/6, 42.9% (36/84) were 5/6, 35.7% (30/84) were 4/6 and 1.2% (1/84) was 3/4. TNC and CD34⁺ cell counts in addition to hematopoeitic progenitor cells (CFU-GM and BFU-E) testing were performed in cord blood products after thawing and washing procedures. CD34⁺cells were analyzed by two color technique using FACS Calibur (San Jose, CA) and absolute counts were assessed by two-platform ISHAGE method. Colony assays for BFU-E and CFU-GM were performed by plating 3×10⁴ mononuclear cells in methylcellulose medium with human recombinant cytokines (Methocult GF, Stem Cell Technologies); cultures were kept at 37°C in humidified incubator with 5% CO₂ and after 14 days colonies were scored under an inverted microscope. Comparison of pre-thawing TNC [M=1.34×10⁹(0.56–5.00)] and CD34⁺ [M=2.61×10⁵/Kg (0.39–25.48)] cell counts, provided by cord blood banks, with post-thawing TNC [M=1.09×10⁹(0.36–4.20)] and CD34⁺ [M=1.3×10⁵/Kg(0.06–9.8)], performed by Wilcoxon signed rank test, showed a significant decrease in both cases (P<0.001). Descriptive statistics were tabulated separately for the number of TNC, number of CD34⁺ cells, numbers of CFU-GM and BFU-E colonies by whether patient engrafted or had graft failure, and comparison of the median cell counts between these two groups of patients was done by Wilcoxon Mann-Whitney rank sum test. TNC and CD34⁺ cell counts did not show significant difference between patients with graft failure [M=1.08×10⁹(0.36–4.2) and M=1.28×10⁵/Kg(0.09–9.8), respectively] and those who engrafted [M=1.12×10⁹(0.46–2.49) and M=1.41×10⁵/Kg(0.06–6.0), respectively]. Yet, the CFU-GM counts were significantly higher (P=0.005) for patients who engrafted [M=0.079×10⁵(0.0017–0.75)] than for those who did not [M=0.04×10⁵(0.0009–0.50)]. Although BFU-E counts did not differ with statistical significance between engrafted versus graft failure patients (P=0.059), higher counts could be observed in the group of patients who had successful engraftment. These data suggest that results of counts of CFU-GM colonies have a predictive value for engraftment in our center.