A tissue engineering approach to progenitor cell delivery results in significant cell engraftment and improved myocardial remodeling

Abstract

Cell replacement therapy has become an attractive solution for myocardial repair. Typical cell delivery techniques, however, suffer from poor cell engraftment and inhomogeneous cell distributions. Therefore, we assessed the hypothesis that an epicardially applied, tissue-engineered cardiac patch containing progenitor cells would result in enhanced exogenous cell engraftment. Human mesenchymal stem cells (hMSCs) were embedded into a rat tail type I collagen matrix to form the cardiac patch. Myocardial infarction was induced by left anterior descending coronary artery ligation in immunocompetent male cesarean-derived fischer rats, and patches with or without cells were secured to hearts with fibrin sealant. After patch formation, hMSCs retained a viability of >90% over 5 days in culture. In addition, >75% of hMSCs maintained a high degree of potency prior to patch implantation. After 4 days in culture, patches were applied to the epicardial surface of the infarct area and resulted in 23% +/- 4% engraftment of hMSCs at 1 week (n = 6). Patch application resulted in a reduction in left ventricle interior diameter at systole, increased anterior wall thickness, and a 30% increase in fractional shortening. Despite this improvement in myocardial remodeling, hMSCs were not detectable at 4 weeks after patch application, implying that improvement did not require long-term cell engraftment. Patches devoid of progenitor cells showed no improvement in remodeling. In conclusion, pluripotent hMSCs can be efficiently delivered to a site of myocardial injury using an epicardial cardiac patch, and such delivery results in improved myocardial remodeling after infarction. Disclosure of potential conflicts of interest is found at the end of this article.

Figure 1

Schematic of infarct generation and epicardial patch placement. Collagen patches seeded with human mesenchymal stem cells are cultured for 4 days before placement. A permanent ligation of the left anterior descending coronary artery is used to induce infarction. Afterward, the patch is placed on the epicardial surface of the infarcted region and held in place with fibrin sealant.

Figure 2

In vitro characterization of the cardiac patch. (A): Human mesenchymal stem cell (hMSC) potency as a function of time measured by monitoring the expression of CD105 and CD73. (B): A patch with representative sections showing hMSC incorporation using hematoxylin and eosin staining. (C): hMSC viability using live/dead staining (magnification, ×20).

Figure 3

Engraftment of human mesenchymal stem cells (hMSCs) in the infarcted rat heart at 1 week. (A): Histological sections stained with Masson's trichrome showing myocardial engraftment of hMSCs beneath and remote from the cardiac patch, outlined by the dotted line, at 1 week (magnification, ×20; scale bars = 100 μm). (B): Engraftment distribution as a function of distance from the cardiac apex. (C): Engraftment distribution beneath and remote from the cardiac patch.

Figure 4

Increased number of α-SMA-positive cells at 4 weeks with patch placement. (A): At 4 weeks, the number of blood vessels was not increased by patch placement. (B): Representative image from patch-treated heart stained for vessels with anti-von Willebrand factor. (C): α-SMA expression was significantly increased with the application of patches compared with controls (n = 4; *, p < .05 vs. controls). Representative fluorescence microscopy using anti-αSMA for control (D) and patch-treated (E) hearts (magnification, ×20). Abbreviation: α-SMA, α-smooth muscle actin.