Summarized from the article: A Semi-Three-Dimensional Bioprinted Neurocardiac System for Tissue Engineering of a Cardiac Autonomic Nervous System Model by Hernandez et al.

By Adam Pederson

The cardiac autonomic nervous system (CANS) controls how blood flows through the circulatory system by regulating a number of factors, such as heart rate and heart contractions. Two diseases affected by dysregulation of the CANS – ischemic heart disease and chronic coronary syndrome – are some of the most common causes of heart failure, in which the levels of oxygen in the blood are lowered and the tissues that make up the heart become weak and its ability to contract effectively is decreased. Two common approaches that are used to combat this disease are the use of antianginal drugs, along with various surgical interventions. The goal of this study was thus to generate a model of the CANS by bioprinting a 3D structure made up of a combination of both cardiac (heart) and neuronal (nerve) cell types. Because the relationship between neurons and cardiac cells in relation to ischemic heart disease is not fully understood, generating a model like this would help improve our understanding of the disease, as well as aid in developing new ways to treat it using regenerative medicine-based strategies. 

In this study, a semi-three-dimensional (3D) bioprinting strategy was used. Because of the physical properties of cardiac and neuronal bioinks, a purely 3D bioprinting approach would require two different types of bioprinters to be used. Since neuronal bioinks are more suitable with microfluidic bioprinters and cardiac bioinks are better suited for the use of extrusion-based printers, printing the cardiac cells with a bioprinter and simply pipetting the neuronal bioink over the cardiac cells is a more streamlined approach. Using a cardiac bioink composed of gelatin-alginate and AC16 cardiomyocytes (heart muscle cells), a 3D accordion-like arrowhead pattern was used to print the cardiac cells. This pattern was inspired by the honeycomb-like lattice framework of human heart tissue to best mimic the native heart structure. After extrusion printing the heart cells, the neuronal bioink, provided and prepared by Axolotl Biosciences, composed of alginate-genipin-fibrin and retinoic acid-differentiated SH-SY5Y neuronal cells, was dispensed over the printed cardiac scaffold. The semi-3D structure was then stabilized and strengthened by adding both neuronal and cardiac crosslinkers. These crosslinkers help to solidify the 3D construct, because on their own, the two bioinks do not have much structural integrity.

Semi-3D-printed neurocardiac structure

The success of the crosslinking was evaluated via multiple methods, including a visual observation of colour change and Fourier transform infrared (FTIR) spectroscopy, which both confirmed successful crosslinking when compared to the non-crosslinked structures. Fluorescence images obtained of the 3D tissue structures also confirmed that the cardiac and neuronal cells were successfully linked together and remained viable through experimentation. The results of this study also showed that in comparison with 2D constructs, the semi-3D bioprinting strategy showed enhanced linking between the two cell types due to the spatial positioning of having the cardiac cells on the bottom and the neurons on top. This strategy shows great potential in combining cardiac and neuronal cells into a single engineered structure to help advance our understanding of neuronal dysregulation, how it contributes to various heart diseases, and how we might be able to treat them in the future.

For more information: https://doi.org/10.3390/bioengineering10070834