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In this work, we aimed to establish subgroups of clinical severity in a global cohort of β-thalassemia through unsupervised random forest (RF) clustering. We used a large global dataset of 7910 β-thalassemia patients and evaluated 19 indicators of phenotype severity (IPhS) to determine their contribution and relatedness in grouping β-thalassemia patients into clusters using RF analysis. RF clustering suggested that three clusters with minimal overlapping exist (classification error rate: 4.3%), and six important IPhS were identified: the current age of the patient, the mean serum ferritin level, the age at diagnosis, the age at first transfusion, the age at first iron chelation, and the number of complications. Cluster 3 represented patients with early initiation of transfusion and iron chelation, considerable iron overload, and early mortality from heart failure. Patients in Cluster 2 had lower serum ferritin levels, although they had a higher number of complications manifesting overtime. Patients in Cluster 1 represented a subgroup with delayed or absent transfusion and iron chelation, but with a high morbidity rate. Hepatic disease and cancer were dominant causes of death in patients in Cluster 1 and 2. Our findings established that patients with β-thalassemia can be clustered into three groups based on six parameters of phenotype severity.

Successful gene therapy for β-thalassemia requires optimal numbers of autologous gene-transduced hematopoietic stem and progenitor cells (HSPCs) with high repopulating capacity. Previous studies suggested superior mobilization in these patients by the combination of granulocyte–colony stimulating factor (G-CSF) plus plerixafor over single agents. We mobilized four adult patients using G-CSF+plerixafor to assess the intra-individual variation of the circulating CD34+ cells number and subtypes preand post-plerixafor administration. The procedure was well-tolerated and the target cell dose of ≥8×106 CD34+ cells/kg was achieved in three of them with one apheresis procedure. The addition of plerixafor unanimously increased the number of circulating CD34+ cells, and the frequency of the most primitive CD34+ subtypes: CD34+/38- and CD34+/133+/38- as well as the in vitro clonogenic potency. Microarray analyses of CD34+ cells purified from the leukapheresis of one patient mobilized twice, with G-CSF and with G-CSF+plerixafor, highlighted in G-CSF+plerixafor-mobilized CD34+ cells, higher levels of expression genes involved in HSPC motility, homing, and cell cycles. In conclusion, G-CSF+plerixafor in β-thalassemia patients mobilizes optimal numbers of HSPCs with characteristics that suggest high capacity of engraftment after transplantation. β地中海贫血的成功基因治疗需要最佳数量具有较高再生能力的自体基因转导的造血干细胞和祖细胞（HSPC）。之前的研究表明，与单药相比，通过组合粒细胞集落刺激因子（G-CSF）加普乐沙福在这些患者中有出色的动员作用。我们使用G-CSF+普乐沙福对四例成年患者进行了动员，以评估服用普乐沙福之前和之后的循环CD34+细胞数量和亚型的个体内差异。这种方式的耐受性好，其中的三例患者仅通过一次分离技术即获得≥8×106 CD34+细胞/kg的细胞采集目标。加用普乐沙福毫无例外地增加了循环CD34+细胞的数量和最原始CD34+亚型（CD34+/38-和CD34+/133+/38+）的频率以及体外克隆效力。一例血细胞分离术中纯化的CD34+细胞微阵列分析（患者使用G-CSF和G-CSF+普乐沙福动员两次）强调，在G-CSF+普乐沙福动员的CD34+细胞中，有更高水平的表达基因牵涉到HSPC运动性、归巢和细胞周期。总之，G-CSF+普乐沙福在β地中海贫血病患者中可以动员最优数量的HSPC，具有移植后的移植成活率高的特征。