Injection of mesenchymal stromal cells into a mechanically stimulated in vitro model of cardiac fibrosis has paracrine effects on resident fibroblasts.
OBJECTIVE
Myocardial infarction results in the formation of scar tissue populated by myofibroblasts, a phenotype characterized by increased contractility and matrix deposition. Mesenchymal stromal cells (MSC) delivered to the myocardium can attenuate scar growth and restore cardiac function, though the mechanism is unclear.


METHODS
This study describes a simple yet robust three-dimensional (3D) in vitro co-culture model to examine the paracrine effects of implanted MSC on resident myofibroblasts in a controlled biochemical and mechanical environment. The fibrosis model consisted of fibroblasts embedded in a 3D collagen gel cultured under defined oxygen tensions and exposed to either cyclic strain or interstitial fluid flow. MSC were injected into this model, and the effect on fibroblast phenotype was evaluated 48 h after cell injection.


RESULTS
Analysis of gene and protein expression of the fibroblasts indicated that injection of MSC attenuated the myofibroblast transition in response to reduced oxygen and mechanical stress. Assessment of vascular endothelial growth factor and insulin-like growth factor-1 levels demonstrated that their release by fibroblasts was markedly upregulated in hypoxic conditions but attenuated by strain or fluid flow. In fibroblast-MSC co-cultures, vascular endothelial growth factor levels were increased by hypoxia but not affected by mechanical stimuli, whereas insulin-like growth factor-1 levels were generally low and not affected by experimental conditions.


CONCLUSIONS
This study demonstrates how a 3D in vitro model of the cardiac scar can be used to examine paracrine effects of MSC on the phenotype of resident fibroblasts and therefore illuminates the role of injected progenitor cells on the progression of cardiac fibrosis.
Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
Peter A
PA
Galie
Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA. Electronic address: jpsteg@umich.edu.
Jan P
JP
Stegemann
D000818:Animals; D002454:Cell Differentiation; D015687:Cell Hypoxia / Q000235:genetics; D002921:Cicatrix / Q000473:pathology; D018920:Coculture Techniques; D005355:Fibrosis; D006801:Humans; D066298:In Vitro Techniques; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism; D009203:Myocardial Infarction / Q000378:metabolism* / Q000473:pathology; D058628:Myofibroblasts / Q000473:pathology; D010100:Oxygen / Q000378:metabolism; D019899:Paracrine Communication / Q000235:genetics; D051381:Rats; D013002:Somatomedins / Q000378:metabolism; D013314:Stress, Mechanical; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D013002:Somatomedins; D042461:Vascular Endothelial Growth Factor A; D010100:Oxygen
cardiac fibrosis; cell therapy; co-culture; hypoxia; mesenchymal stromal cells