Optimizing Blended Collagen-Fibrin Hydrogels for Cardiac Tissue Engineering with Human iPSC-derived Cardiomyocytes

Abstract

Natural polymer hydrogels are used ubiquitously as scaffold materials for cardiac tissue engineering as well as for soft tissue engineering more broadly because of FDA approval, minimal immunogenicity, and well-defined physiological clearance pathways. However, the relationships between natural polymer hydrogels and resident cell populations in directing the development of engineered tissues are poorly defined. This interaction is of particular concern for tissues prepared with iPSC-derived cell populations, in which population purity and batch-to-batch variability become additional critical factors to consider. Herein, the design space for a blended fibrin and collagen scaffold is characterized for applications in creating engineered myocardium with human iPSC-derived cardiomyocytes. Stiffness values of the acellular hydrogel formulations approach those of native myocardium in compression, but deviate significantly in tension when compared to rat myocardium in both transverse and longitudinal fiber orientations. A response surface methodology approach to understanding the relationship between collagen concentration, fibrin concentration, seeding density, and cardiac purity found a statistically significant predictive model across three repeated studies that confirms that all of these factors contribute to tissue compaction. In these constructs, increased fibrin concentration and seeding density were each associated with increased compaction, while increased collagen concentration was associated with decreased compaction. Both the lowest (24.4% cTnT+) and highest (60.2% cTnT+) cardiomyocyte purities evaluated were associated with decreased compaction, whereas the greatest compaction was predicted to occur in constructs prepared with a 40–50% cTnT+ population. Constructs prepared with purified cardiomyocytes (≥75.5% cTnT+) compacted and formed syncytia well, although increased fibrin concentration in these groups was associated with decreased compaction, a reversal of the trend observed in unpurified cardiomyocytes. This study demonstrates an analytical approach to understanding cell–scaffold interactions in engineered tissues and provides a foundation for the development of more sophisticated and customized scaffold platforms for human cardiac tissue engineering.

Digital Design and Automated Fabrication of Bespoke Collagen Microfiber Scaffolds

“…5). Young's modulus of the 30°composites in the longitudinal direction (22.28 -2.50) approached that of native myocardium (30.80 -2.71 kPa 39 ), demonstrating that this fabrication method can produce composite materials that approach the passive stiffness of native tissues, before compaction by resident cells, which is anticipated to further increase the mechanical properties. Perhaps more importantly, the ratio of longitudinal to transverse Young's modulus values for the 60°composites was found to be 1.7:1, which closely approximates the range of anisotropic ratios reported in the literature for left ventricular native myocardium (*1.4:1 to *2.0:1).…”

“…3D-F). After 96 h of incubation, the Young's modulus of the noncrosslinked fibers increased to 1.51 -0.11 MPa orders of magnitude greater than both conventional collagen hydrogels used for tissue engineering (0.5-12 kPa 39,43 ) as well as most native soft tissues. [44][45][46][47] In addition, the tensile strain at failure after 96 h of incubation (37.70 -1.85) exceeds the tensile strain regularly experienced by many native soft tissues (including cardiac muscle 48 and tendon 49 ).…”

“…Perhaps more importantly, the ratio of longitudinal to transverse Young's modulus values for the 60°composites was found to be 1.7:1, which closely approximates the range of anisotropic ratios reported in the literature for left ventricular native myocardium (*1.4:1 to *2.0:1). 39,52,53 Beyond the simple scaffold patterns that were evaluated in this study for the purpose of characterizing the capabilities and limitations of this platform, many other sophisticated designs can be created for a range of applications (Supplementary Fig. S9).…”

Engineering Myocardium for Heart Regeneration—Advancements, Considerations, and Future Directions

“…Numerous natural (e.g., collagen, fibrin, and native ECM) and synthetic [e.g., poly(glycerol sebacate), polyurethane, and polyethylene glycol] scaffold materials have been tested for myocardial regeneration. These materials enable fine-tuning of various important tissue properties including degradation kinetics, elastic modulus, porosity, and immune response (21)(22)(23)(24)(25)(26)(27)(28)(29)(30). In addition, several studies have sought to identify or integrate various signaling factors that can modulate cardiac healingespecially cardiomyocyte proliferation-including growth factors (e.g., NRG-1, FGFs, VEGF, IGF-1), ECM components (e.g., Agrin, Fibronectin, Periostin), and modulators of the Wnt and Hippo pathways (31)(32)(33)(34)(35)(36).…”

Naturally Prefabricated Marine Biomaterials: Isolation and Applications of Flat Chitinous 3D Scaffolds from Ianthella labyrinthus (Demospongiae: Verongiida)

“…Beyond the scope of this study, the investigation of further aspects, especially with respect to the structural and functional maturation of iPSC-CMs, as well as the culture in combination with cardiac fibroblasts, are inevitable to clarify the potential of I. labyrinthus scaffolds for cardiac tissue engineering. These aspects will further enable the determination of quantitative data and thus the comparison of chitin scaffolds to other materials described for the cultivation of iPSC-CMs and cardiac tissue engineering, including using decellularized hearts (reviewed by [60]), plant scaffolds [61], and hydrogels [62]. Previous studies further highlight the lack of a vascular network as a major limitation of current tissue engineering approaches, because the oxygen diffusion limit in tissues is approximately 100-200 µm [61], and recent studies have tried to address this issue using porous scaffolds [63].…”