Decellularized extracellular matrix (dECM) derived from myocardium has been widely explored as a nature scaffold for cardiac tissue engineering applications. Cardiac dECM offers many unique advantages such as preservation of organ-specific ECM microstructure and composition, demonstration of tissue-mimetic mechanical properties and retention of biochemical cues in favor of subsequent recellularization. However, current processes of dECM decellularization and recellularization still face many challenges including the need for balance between cell removal and extracellular matrix preservation, efficient recellularization of dECM for obtaining homogenous cell distribution, tailoring material properties of dECM for enhancing bioactivity and prevascularization of thick dECM. This review summarizes the recent progresses of using dECM scaffold for cardiac repair and discusses its major advantages and challenges for producing biomimetic cardiac patch.

We present a novel cell detection device based on a magnetic bead cell assay and microfluidic Coulter counting technology. The device cannot only accurately measure cells size distribution and concentration but also detect specific target cells. The device consists of two identical micro Coulter counters separated by a fluid chamber where an external magnetic field is applied. Antibody-functionalized magnetic beads were bound to specific antigens expressed on the target cells. A high-gradient magnetic field was applied to the chamber closer to the second counter via an external cylindrical magnet. Because of the magnetic interaction between the magnetic beads and the magnetic field, target cells were retarded by the magnetic field; transit time of a target cell (bound with magnetic beads) passing through the second counter was longer than that through the first counter. In comparison, transit times of a nontarget cell remained nearly the same when it passed through both counters. Thus, from the transit time delay we can identify target cells and quantify their concentration in a cell suspension. The transit time and the size of each cell were accurately measured in terms of the width and amplitude of the resistive pulses generated from the two Coulter counters. Experiments demonstrated that for mixed cells with various target cell ratios, the transit time delay increased approximately linearly with the increasing target cell ratio. The limit of detection (LOD) of the assay was estimated to be 5.6% in terms of target cell ratio. Cell viability tests further demonstrated that most cells were viable after the detection. With the simple device configuration and easy sample preparation, this rapid and reliable method is expected to accurately detect target cells and could be applied to facilitate stem cell isolation and characterization.

Prevacularization strategies have been implemented in tissue engineering to generate microvasculature networks within a scaffold prior to implantation. Prevascularizing scaffolds will shorten the time of functional vascular perfusion with host upon implantation. In this study, we explored key variables affecting the interaction between decellularized porcine myocardium slices (dPMSs) and reseeded stem cells toward the fabrication of prevascularized cardiac tissue. Our results demonstrated that dPMS supports attachment of human mesenchymal stem cells (hMSCs) and rat adipose derived stem cells (rASCs) with high viability. We found that cell seeding efficiency and proliferation are dPMS thickness dependent. Compared to lateral cell seeding, bilateral cell seeding strategy significantly enhanced seeding efficiency, infiltration, and growth in 600 μm dPMS. dPMS induced endothelial differentiation and maturation of hMSCs and rASCs after 1 and 5 days culture, respectively. These results indicate the potential of dPMS as a powerful platform to develop prevascularized scaffolds and fabricate functional cardiac patches.

Decellularized porcine myocardium has shown many benefits as a cell delivery scaffold for cardiac therapy. However, using full thickness decellularized myocardium as cardiac patch may lead to poor viability and inhomogeneous distribution of delivered cells, due to perfusion limitations. In this study, we explored the feasibility of decellularized porcine myocardial slice (dPMS) to construct a vascularized cardiac patch for cell delivery. Decellularized porcine myocardium was sliced into thin layers (thickness~300 µm). Adipose-derived Stem cells (ASCs) obtained from rat and pig were seeded on dPMS. The viability, infiltration, and differentiation of seeded ASCs were examined. The mechanical properties of dPMSs of various thickness and native myocardium were tested. We noticed dPMS supported attachment and growth of rat and pig ASCs. Both rat and pig ASCs showed high viability, similar patterns of proliferation and infiltration within dPMS. Rat ASCs showed expression of early-endothelial markers followed by mature-endothelial marker without any additional inducers on dPMS. Using rat myocardial infarction model, we delivered ASCs using dPMS patched to the infarcted myocardium. After 1 week, a higher number of transplanted cells were present in the infarcted area when cells were delivered using dPMS versus direct injection. Compared with MI group, increased vascular formation was also observed.

Acellular cardiac patches made of various biomaterials have shown to improve heart function after myocardial infarction (MI). Extracellular matrix scaffold derived from a decellularized tissue has unique advantages to serve as an acellular cardiac patch due to its biomimetic nature. In this study, we examined the therapeutic outcomes of using a decellularized porcine myocardium slice (dPMS) as an acellular patch in a rat acute MI model. dPMSs with two different thicknesses (300 and 600 μm) were patched to the infarcted area of the rat myocardium, and their effects on cardiac function and host interactions were assessed. We found that the implanted dPMS firmly attached to host myocardium after implantation and prevented thinning of the left ventricular (LV) wall after an MI. A large number of host cells were identified to infiltrate into the implanted dPMS, and a significant number of vessel structures was observed in the dPMS and infarcted area. We detected a significantly higher density of M2 macrophages in the groups treated with dPMSs as compared to the MI group. Contraction of the LV wall and cardiac functional parameters (left ventricular ejection fraction and fractional shortening) was significantly improved in the treatment groups (300 and 600 μm dPMS) 4 weeks after surgery. Our results proved the therapeutic benefits of using dPMS as an acellular cardiac patch for the treatment of acute myocardial infarction.