Abstract 1387: Malignant Tumor Formation after Transplantation of Bone Marrow Stromal Cells in a Mouse Model of Acute Myocardial Infarction and Diabetic Neuro-Vascularopathy
Background: Cell therapy using bone marrow (BM)-derived stem cells holds a great potential to repair cardiovascular diseases. Since marrow stromal or mesenchymal stem cells (MSCs) are multipotent and can be easily expanded in culture, it has been widely investigated for this purpose. Accordingly, we investigated whether MSCs can effectively repair a mouse model of acute myocardial infarction (MI) and diabetic neuro-vasculopathy.
Methods and Results: Preparation and expansion of the murine MSCs was done based on published methods. We cultured BM mononuclear cells from 8 week-old C57Bl mice in DMEM with 10% FBS. Adherent cells were cultured in plastic dishes. Primary culture (P0) were passaged to disperse the colony-forming cells and serially seeded into new culture dishes. After 4 passages, 99% of these cells expressed mesenchymal stem cell markers such as CD44 and CD29, and were negative for c-kit, CD45, and CD34 via FACS analysis. We used MSCs at passages 4 to 10 for the following animal experiments. We used two animal models (C57Bl mice): MI and streptozotocin-induced diabetic neuro-vasculopathy(three months after DM). We injected 1x105 mouse MSCs into the peri-infarct area immediately after creation of MI. We injected 1x106 MSCs directly into the hindlimb muscle of the mice with diabetic neuro-vasculopathy. Between 4 and 7 weeks after cell transplantation, we observed growing tumors in the heart in 3 of 10 (30%) MI mice, and in proximal hindlimb in 16/35 (46%) diabetic mice. Histologic examination revealed that the tumors have hypercelluarity, pleomorphic nucleoli, cytologic atypia, necrosis, and positive staining for α-smooth muscle actin compatible with leiomyosarcoma. Karyotyping of MSCs showed multiple chromosomal abnormalities including fusion, fragmentation, and ring formation.
Conclusions: We demonstrated that MSCs underwent chromosomal abnormalities at early passages of cultures and transplantation of these cells induced malignant tumors in ischemic hearts and diabetic limbs. Careful monitoring of karyotyping needs to be warranted for using culture expanded MSCs for cell therapy.