Alternatively, the researchers propose, one can rely on thenatural ability of stem cells to self-organize and provide cardiac progenitorstogether with a supportive matrix to achieve
in-vitro or
in-situtissue engineering. Several biomaterials are currently used for cardiac tissueengineering, such as fibrin, hyaluronic acid, collagen or polyethylene
glycol. In the current study, the scientists used a fibrinmatrix that is a natural polymer, fully biocompatible and biodegradable andcapable of supporting cell growth, migration and differentiation.
Cardiac-committed mouse ESCs were committed toward thecardiac fate using a protein growth factor called BMP2, then embedded into thefibrin hydrogel. The cells were loadedwith superparamagnetic iron oxide nanoparticles so they could be tracked usingmagnetic resonance imaging, which also enabled the researchers to moreaccurately assess regional and global heart function.
The patches were then engrafted onto the hearts oflaboratory rats that had induced heart attacks. Six weeks later, the hearts ofthe animals receiving the mouse ESC-seeded patches showed significantimprovement over those receiving patches loaded with iron oxide nanoparticlesalone. The patches had degraded, the cells had colonized the infarcted tissueand new blood vessels were forming in the vicinity of the transplanted patch.Improvements reached beyond the part of the heart where the patch had beenapplied to manifest globally.
"We demonstrated that bone morphogenetic protein 2(BMP2)-primed cardiac-committed ESCs seeded into these fibrin patchesefficiently engraft and reduce remodeling and deterioration of cardiac functionsfollowing myocardial infarction," they concluded.
"Altogether, our data provide evidence that stem-cell basedcardiopatches represent a promising therapeutic strategy to achieve efficientcell implantation and improved global and regional cardiac function aftermyocardial infarction," says Dr. Marisa Jaconi of the Geneva UniversityDepartment of Pathology and Immunology and one of the study's authors.
Jaconi notes that "this was sort of a preliminary test tosee if we could improve engraftment—whether we could use cardiac embryonic stemcells without a purification procedure to see if engrafting the cells this wayand applying this type of gel could obtain an effect immediately after creatinga myocardial infarction. This was, in essence, a preliminary work exercise ofstyle, if you will. Now we have to think about how to secure these cells oncethey are committed in bigger animal models, like sheep."
The work was supported in part by the
Leenaards Foundationand the
Swiss National