Association of CFU-Mk with total colony-forming units in thawed cord blood units

Background and Objectives  Cord blood unit (CBU) total colony-forming unit (CFU) count both pre-cryo and post-thaw has been shown to be associated with platelet (PLT) engraftment. Pre-cryo CBUs show good growth of megakaryocytic CFUs (CFU-Mk); however, CFU-Mk have rarely been studied in post-thaw CBUs. Materials and Methods  Nucleated cells (NCs) from post-thaw CB were cultured in a collagen-based assay designed to support growth of CFU-Mk. To ensure accurate counting two independent investigators evaluated four culture chambers per sample for CFU-Mk growth. Post-thaw CFU and other cellular characteristics of the CBUs were enumerated independently and compared to CFU-Mk. Results  The post-thaw CBU total CFU count varied from 0·47 to 4·20 × 106 colonies (median, 0·99 × 106) and total CFU-Mk count from 0·11 to 0·70 × 106 colonies (median, 0·21 × 106). Total CFU-Mk count was closely associated with total CFU count (Spearman’s Rho = 0·86, P = 0·0072), haemoglobinized CFU (Rho = 0·86, P = 0·0072) and CFU-granulocyte/macrophage (CFU-GM; Rho = 0·81; P = 0·0154). Total CFU-Mk count also correlated with the post-thaw total CD34+ cell count (median, 2·55 × 106; range, 1·40–12·5 × 106; Rho = 0·83; P = 0·0154). Conclusion  CFU-Mk growth was associated with total CFU, haemoglobinized CFU, CFU-GM and CD34+ cells in thawed CBUs. This study confirms the preservation of CFU-Mk potential after CB cryopreservation.