Abstract P034: Bone Marrow--Derived Cells Are Not an Essential Component in Cardiosphere Formation
Background:Cardiospheres (CS) are composed of heterogeneous population of cells but it is unknown whether bone marrow derived cells are an essential cell component in CS formation.
Methods:Chimera mice were generated by transplantation of bone morrow cells from GFP transgenic mice to irradiated C57BL mice. Mice were randomized into 3 groups 5 months after transplantation: 1) myocardial infarction; 2) sham operated; 3) un-operated (n=5/group). Hearts were harvested 2-weeks post-surgery. Cardiac explants were cultured and putative cardiosphere forming cells (CFCs) (small cells migrating out from the explants) were collected 14 days later and reseeded on new culture dishes for CS formation. The number of CS from each heart was counted at 3 days. CS cell composition was analyzed by FACS. To further analyze the role of bone marrow derived CD45+ cells in forming CS, CD45+ cells was isolated from CFCs by CD45 antibody coated immunomagnetic beads. The number of CS formed from 1×105 putative CFCs, CFCs without CD45+ cells and CD45+ cells from CFCs (n=6-9/cell type) respectively were also counted at 3 days in culture.
Results:Compared to sham (122± 23/heart) and un-operated hearts (18± 5/heart), infarcted hearts formed more CS (357± 64/heart, P<0.01). In all groups, irrespective of any surgery, 18.4± 4.5% of cells in CS co-expressed GFP and CD45, indicating they originated in bone marrow. Low percentage of bone marrow stem/progenitor cells (3.9% Sca-1+GFP+CD45+ and 1% c-Kit+GFP+CD45+ cells) were detected in CS, but a high percentage of cells within CS were cardiac stem/progenitor cells (26.3± 9.4% cells were Sca-1+GFP-CD45-, 0.10± 0.04% c-Kit+GFP-CD45-). Depleting CD45+ cells from putative CFCs actually increased the formation of CS (67±10 CS/1×105 cells) compared to un-depleted CFCs (51± 6 CS/1×105 cells, P<0.0001). Purified CD45+ cells from CFCs did not form CS in culture.
Conclusion:Myocardial infarction increases the formation of CS in culture. Bone marrow derived CD45+ cells make up a small percentage of CS, but are not necessary for CS formation.
- © 2011 by American Heart Association, Inc.