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.