Hematopoietic Reconstitution of Human Umbilical Cord Mesenchymal Stem Cells after Leukemia Chemotherapy: Effectiveness and Safety

Objective: As the incidence of tumors increases, more patients need chemotherapy. Patients receiving chemotherapy also inevitably suffer side effects from treatment. Damage to the immune and hematopoietic system causes the failure of therapies. Mesenchymal stem cells have excellent capabilities in immune regulation and hematopoietic support. This study preliminarily explored the safety and effectiveness and of human umbilical cord mesenchymal stem cells (UCMSC) in myelosuppressive patient-derived tumor xenograft (PDX) models of acute myeloid leukemia (AML).

Methods: B-NDG mice were used to establish the PDX models. The mice were randomly divided into three groups: AML group, AML+Ara-C group and AML+Ara-C+MSC group. Mice in the AML+Ara-C group and AML+Ara-C+MSC group were injected intraperitoneally with cytarabine (Ara-C) 60mg/kg on day1-day3 to induce myelosuppression. Mice in the AML+Ara-C+MSC group were injected 3×10 ⁶ UCMSC through the tail vein on day4. We observed the changes in peripheral blood, bone marrow signaling pathways, and AML progression in mice.

Results: The experiment found that UCMSC rescued the body weight and peripheral blood. We also found that UCMSC could increase the number of bone marrow CD117 ⁺ hematopoietic stem/progenitor cells and CD41 ⁺ megakaryocytes through flow cytometry. We verified at protein level that the hematopoiesis-related signaling pathway JAK2/STAT3 was up-regulated in AML+Ara-C+MSC group compared with AML+Ara-C group through flow cytometry and immunohistochemistry. At the same time, the infusion of UCMSC after Ara-C had no influence on disease progression. On day15, the proportion of human CD45 ⁺ cells in the bone marrow of between AML+Ara-C+MSC group and AML+Ara-C group was similar, and there was no statistical difference (21.96±3.10 vs. 23.04±1.51; P=0.6792).

Conclusion: Infusion of exogenous UCMSC after chemotherapy in PDX models could promote the recovery of hematopoiesis without affecting the efficacy of Ara-C. A reasonable UCMSC infusion scheme is potential to be used in the treatment of AML patients and it requires a lot of preclinical exploration in the future.