Mobilization of Auto-Stem Cells in the Thalassemia Major and Relationship with Iron Overload

Objectives: The hematopoietic stem cells transplantation (HSCT) is the only curable treatment in current for thalassemia major (TM).The quantity of auto stem cell of TM patients are very important for rescue the patients in case of failure of HSCT, and auto stem cells of TM will be used as target cells for gene therapy (GT) in the near future. Iron overload (IOL) can damage the hematopoiesis of TM. How to collect the auto stem cells in TM patients? How about the affects of iron overload in the mobilization and collection of auto stem cell? The aim of this study was to analyze quantity of auto stem cells in the TM and the affects of iron overload (IOL).

Methods: We retrospectively analyzed a total of 134 patients and 25 normal donors undergoing PBSCs collection between January 2012 and December 2019. Patients with serum ferritin levels over 1,000 ng/mL and with a history of red blood cell transfusions prior to stem cell collection were defined as a group having transfusion-associated iron overload (IOL). In total one hundred and thirty-four patients and twenty-five donors were subcutaneous administrated G-CSF (Granulocyte Colony Stimulating Factor) 10 mg/kg/d Injection for 5 days, PBSCs was collected using a large volume leukapheresis (LVL) procedure. The data of WBC, MNC and CD34+ in product were analyzed by SPSS 20 software.

Results: In 134 patients, median age is 8.60 range: (1-17),and 25 Normal donors, median age is 7.5 range: (1-18). The results demonstrated that cells either in patients with thalassemia or normal donors were effectively mobilized by G-CSF (10 mg / kg/d),as these children showed a marked increase in white blood cells and MNC cells in peripheral blood, reaching a peak in 4 to 5 days after the injection of G- CSF alone. Comparison of the MNC [(6.7±3.5) ×10⁸/kg vs (7.2±4.77) ×10⁸/kg] and CD34+cells [(10.29±4.5)×10⁶/kg vs (10.9±6.8)×10⁶/kg] in collected product in TM patients and normal donors groups revealed no significant difference. There was no significant difference between different Ferritin level (Mild, Intermediate and Severe) on WBC, MNC, and CD34+ in each group at the time point studied. But there was significant difference on MNC number (Normal liver iron (7.73±2.69)×10⁸/kg, Mild liver iron overload (7.66±4.64)×10⁸/kg, Intermediate (6.18± 2.84) ×10⁸/kg compared to Severe liver iron (4.45±3.34)×10⁸/kg, P=0.039. Significant difference was also can be seen in number of MNC of product in patients with intermediate cardiac iron overload compared to normal cardiac iron overload and mild cardiac iron overload (2.76±0.97) ×10⁶/kg vs(6.86±3.39) ×10⁶/kg and (6.88±3.72)×10⁶/kg, P=0.030. There was a statistically significant difference positive correlation between median age (P=0.011) and MNC/Kg (P=0.030).

Conclusion:The quantity of mobilization of PBSC in TM patients had no significant difference compare to normal donor. The MNC in product was statistically decreased in intermediate cardiac iron overload and severe liver iron overload (IOL) subgroup. It indicated that iron overload (IOL) in organs may negatively relate to proliferation and mobilization of stem cells in TM. Further quality study of PBSC such as stem cell culture and ability of proliferation should be more evaluated. The sufficient quantity and high quality auto stem cell from TM patient can be more used in the future.