This protocol describes a net mold-based method to create three-dimensional scaffold-free cardiac tissues with satisfactory structural integrity and synchronous beating behavior.
This protocol describes a novel and easy net mold-based method to create three-dimensional (3-D) cardiac tissues without additional scaffold material. Human-induced pluripotent stem-cell-derived cardiomyocytes (iPSC-CMs), human cardiac fibroblasts (HCFs), and human umbilical vein endothelial cells (HUVECs) are isolated and used to generate a cell suspension with 70% iPSC-CMs, 15% HCFs, and 15% HUVECs. They are co-cultured in an ultra-low attachment “hanging drop” system, which contains micropores for condensing hundreds of spheroids at one time. The cells aggregate and spontaneously form beating spheroids after 3 days of co-culture. The spheroids are harvested, seeded into a novel mold cavity, and cultured on a shaker in the incubator. The spheroids become a mature functional tissue approximately 7 days after seeding. The resultant multilayered tissues consist of fused spheroids with satisfactory structural integrity and synchronous beating behavior. This new method has promising potential as a reproducible and cost-effective method to create engineered tissues for the treatment of heart failure in the future.
The goal of current cardiac tissue engineering is to develop a therapy to replace or repair the structure and function of injured myocardial tissue1. Methods to create 3-D cardiac tissue models exhibiting the important contractile and electrophysiological properties of native cardiac tissue have been rapidly expanding2,3. A variety of strategies have been explored and used in studies4,5. These methods range from the use of specific synthetic and natural bioactive hydrogels, such as gelatin, collagen, fibrin, and peptides6, to bio-ink deposition technologies2 and bioprinting technologies7.
It has been shown that scaffold-free methods can produce comparable tissues as biomaterial-based methods, without the drawbacks of incorporating foreign scaffolding material8. Oren Caspi et al. demonstrated that the incorporation of various types of cells enables the generation of highly vascularized human engineered cardiac tissue9. Chin et al. developed a 3-D printing method for cardiac patch creation from spheroids. Resulting patches are composed of cardiomyocytes, fibroblasts, and endothelial cells in a 70:15:15 ratio10. Spheroids have been shown to be effective “building blocks” of scaffold-free cardiac tissue creation, as they are resistant against hypoxia and possess sufficient mechanical integrity for implantation11,12. Previous studies have demonstrated several fabrication methods for spheroid creation, including the use of the hanging drop method, spinner flasks13, microfluidic systems14, and non-adherent culture surfaces uncoated or coated with agarose micro-molds15. In this protocol, we use the hanging drop device, which contains micropores for condensing hundreds of spheroids at one time.
This study presents a novel and efficient scaffold-free method for cardiac tissue creation, which includes manually seeding the spheroids into a square mold cavity and incubating the tissue on a shaker for maturation. Under usual static culture conditions, oxygen diffusion is limited to the outer aspects of the tissue construct, resulting in central necrosis. However, with the net mold, all the spheroids seeded into the mold are immersed in media with a constant fluidic motion, allowing for the increased diffusion of nutrients and oxygen. Additionally, this mold-based method allows for the simultaneous creation of different-sized tissue patches with minimal manual effort and the resultant tissue can be easily removed from the mold. This novel method allows for the efficient and reproducible creation of scaffold-free, multilayered cardiac patches.
The significance of this method lies in its reproducibility and the effectiveness of the resultant multilayered cardiac tissue. In the field of cardiac tissue engineering, one of the current goals is to identify a method to construct beating, multilayered, and functional 3-D cardiac patches. We report an efficient and reproducible method of creating multilayered cardiac tissues by direct manual seeding of spheroids composed of cardiomyocytes, endothelial cells, and fibroblasts into a novel net mold. The net mold used in …
The authors have nothing to disclose.
The authors acknowledge the following funding source: the Magic That Matters Fund for Cardiovascular Research.
Human Cardiac fibroblasts (HCF) | Sciencell | 6310 | |
FM-2 Consists of Basal Medium | Sciencell | 2331 | HCF culture medium |
Human umbilical vein endothelial cells (HUVEC) | Lonza | CC-2935 | |
EGM+Bullet Kit | Lonza | CC5035 | HUVEC culture medium |
E8 media | Invitrogen | A1517001 | HiPSC culture medium |
Geltrex | Invitrogen | A1413202 | |
TrypLE Express Enzyme (1X) | Thermo Fisher | 12604013 | Trypsin and Cell dissociation reagent |
RPMI media | Invitrogen | 11875093 | RPMI media with B-27 supplement is hiPSC-CM culture medium |
B-27 supplement (50x) | Thermo Fisher | 17504044 | RPMI media with B-27 supplement is hiPSC-CM culture medium |
Trypan Blue Solution, 0.4% | Thermo Fisher | 15250061 | |
Novel net mold | TissueByNet Co.,Ltd | NM25-1 | |
Hanging drop plate | Kuraray Co.,Ltd | MPc350 | |
6 well plates | Sigma-Aldrich | CLS-3516 |