Bone marrow-derived stem cell interactions with adult cardiomyocytes and skeletal myoblasts in vitro.
OBJECTIVE
Secreted growth factors and cell-to-cell contact are both required to elicit cellular functions. We tested the hypothesis that bone-marrow-derived growth factors, together with cell-to-cell contact between bone-marrow-derived stem cells and cardiomyocytes or myoblasts, promote the proliferation of cardiomyocytes and myoblasts.


METHODS
Human cardiomyocytes or skeletal myoblasts were cultured for 4 days in the presence of low and high concentrations of bone-marrow-derived mononuclear cell conditioned medium (MNC-CM) or marrow stromal cell conditioned medium (MSC-CM). The concentrations of vascular endothelial growth factor (VEGF), monocyte chemoattractant protein-1 (MCP-1), hepatocyte growth factor (HGF), and insulin-like growth factor-1 in their respective conditioned media were assayed by enzyme-linked immunosorbent assay. Stem cells were mixed with cardiomyocytes or skeletal myoblasts at a 1:1 ratio and cultured for 7 days to assess the proliferation of these cells. In parallel experiments, equal numbers of various cell types were cultured alone.


RESULTS
The concentrations of VEGF, MCP-1, and HGF increased in MNC-CM and MSC-CM. MNC-CM showed no effect on cardiomyocyte proliferation. A low concentration of MSC-CM increased cardiomyocyte proliferation by 60% (P<.05). Low concentrations of MNC-CM or MSC-CM showed a trend toward an increased proliferation of myoblasts. A high concentration of either conditioned medium showed a toxic effect. In contact coculture, the proliferation of cardiomyocytes and MNC showed no synergistic effect; instead, there was some evidence of inhibition. The proliferation of cardiomyocytes and stromal cells showed an additive effect. Myoblasts in contact coculture with MNC or MSC showed no synergistic effect.


CONCLUSIONS
These in vitro results suggest that paracrine effects may be the mechanism by which stromal cells become beneficial in cardiac therapy. MNC do not induce the proliferation of cardiomyocytes. Stem-cell-secreted growth factors induce the proliferation of myoblasts, which is not influenced by cell-to-cell contact.
Baffour
Richard
R
Division of Cardiology, Washington Hospital Center, Washington, DC 20010, USA.
Pakala
Rajbabu
R
Hellinga
David
D
Joner
Michael
M
Okubagzi
Petros
P
Epstein
Stephen E
SE
Waksman
Ron
R
D000704:Analysis of Variance; D001854:Bone Marrow Cells / Q000378:metabolism*; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D017228:Hepatocyte Growth Factor / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000378:metabolism; D032448:Myoblasts, Skeletal / Q000378:metabolism / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000502:physiology*; D013234:Stem Cells / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D018932:Chemokine CCL2; C032231:IGFBP1 protein, human; D018970:Insulin-Like Growth Factor Binding Protein 1; D042461:Vascular Endothelial Growth Factor A; D017228:Hepatocyte Growth Factor