cardiac

3D Bioprinting Replacement Heart Valves

allevi advanced biomatrix collagen aortic pulmonary heart valve bioprint 3d bioprinted

Throwing it back today to show you this heart valve that was 3d bioprinted using the Allevi 2 with collagen from Advanced BioMatrix.

Your heart has four valves (one for each chamber) that are made up of thin flaps of tissue called cusps. These flaps open and close to allow blood to move through the heart while beating.  The cusps attach to an outer ring of tougher tissue called the annulus. The annulus helps the valve maintain proper shape under the normal strains and stresses of a heartbeat. 

 
heart-valve-labelled-diagram
 

It is essential that your valves open and close tightly to ensure proper blood flow through the heart and onto the rest of your body. A diseased or damaged valve can give you an irregular heartbeat and eventually lead to heart failure. More than 5 million Americans are diagnosed with heart valve disease every year.

 
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Many people can live with valve disease and do not require surgery. However, in some cases, the valve needs to be fixed or replaced. Current methods for replacing a damaged valve included plastic parts or animal tissues.

Allevi users are working towards a future where your #doctor is able to 3d bioprint a custom replacement valve from your own heart cells to reduce the rate of failure and rejection. 3D bioprinting is an amazing design tool that allows you to print custom geometries and tune the rheological properties to provide your cells with the support structure they need to do their job. Just another amazing way our users are changing the future of medicine. #buildwithlife #healwithlife

Allevi Author - Valentine's Day Edition: GWU Bioprints Heart Tissue

cardiac muscle myocytes fibroblasts george washington university allevi 3d bioprinters and bionk

George Washington University joins the #AlleviAuthor club with their new paper titled, “Use of GelMA for 3D printing of cardiac myocytes and fibroblasts” and published in Journal of 3D Printing in Medicine.

First let’s review some basics about your heart! Heart tissue is composed of two main cell types; cardiac fibroblasts (CFB) & cardiomyocytes (CMC).

 
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Cardiomyocytes are the contracting cells which allow the heart to pump. Each cardiomyocyte needs to contract in coordination with its neighboring cells to efficiently pump blood from the heart, and if this coordination breaks down then the heart may not pump at all.

Fibroblast cells give support to the muscle tissue. They are unable to provide forceful contractions like cardiomyocytes, but instead are largely responsible for creating and maintaining the extracellular matrix which forms the mortar in which cardiomyocyte bricks are embedded. Fibroblasts also play a crucial role in responding to injury by creating collagen while gently contracting to pull the edges of the injured area together.

In previous academic studies, tests of pure populations of cardiomyoctes have failed to stay viable making it difficult to study the heart in a lab setting. In their recent paper, the team at George Washington University set out to determine how 3D bioprinting affects these two types of cells and if there is a way to create viable 3D tissue in the lab by bioprinting both CMCs and CFBs in tandem.

The team studied the effects of temperature, pressure, bioink composition, and UV exposure to determine the best conditions for 3D bioprinting heart muscle.

Through LIVE/DEAD assays, bioluminescence imaging and morphological assessment, they determined that cell survival within a 3D bioprinted CMC-laden GelMA construct was MORE sensitive to extruder pressure and bioink composition than the fibroblast-laden constructs. Also they determined that BOTH cell types were adversely impacted by the UV curing step. And finally they determined that using a mixture of cardiomyocytess and cardiac fibroblasts increased viability of the tissue- showing that CMCs <3 CFBs.

Cheers to the team at GWU! Their research creates an important foundation for future studies of 3D bioprinted heart tissue.

Read their paper here.

Allevi Author: Lattices vs Sheets for Cardiac Tissue Bioprinting

There are so many variables that go into creating viable 3d bioprinted tissues; bioink selection, print geometry, cure times, rigidity, flexibility, degradation time and cell viability to name a few. Not to mention, each of these parameters needs to be analyzed and perfected for every cell line in the body. As a community, we are still figuring out the perfect protocol for each organ system.

In a new paper out this week titled “A Comparative Study of a 3D Bioprinted Gelatin-Based Lattice and Rectangular-Sheet Structures”, our newest Allevi Authors tackled one of these lingering questions, “What is the best print structure for cardiac tissue, lattice or sheet?”

Researchers at University of Texas El Paso and University of Texas at Austin used their Allevi 2 bioprinter and furfuryl gelatin to study and compare 3d bioprinted lattices vs sheets. Through their comparison, they discovered that the lattice structure was more porous with enhanced rheological properties and exhibited a lower degradation rate compared to the rectangular-sheet.

Further, the lattice allowed cells to proliferate to a greater extent compared to the rectangular-sheet. All of these results collectively affirmed that the lattice poses as a superior scaffold design for tissue engineering applications.

Read the full paper here to learn more about the rigorous testing and analysis the team conducted during their study.

Allevi Author - Valentine's Edition: 3D Bioprinting Aortic and Cardiac Scaffolds

Allevi bioprinter bioprint aortic and cardiac scaffolds

On this very special Valentine's Day edition of #AlleviAuthor, we'd like to introduce our newest member of the #alleviauthor club whose work studies bioprinting to repair broken heart...valves. Benjamin Stewart, whose thesis was recently presented to the the faculty of the Daniel Felix Ritchie School of Engineering and Computer Science at the University of Denver, studies cardiac tissue specifically for aortic valve repair. 

Stewart's work focuses on 3D bioprinting hydrogels for tissue engineered ascending aorta scaffolds using the AlleviBeta 3D bioprinter. Biocompatible polymers were tested for extrusion mechanics, mechanical and fluid properties, crosslinking dynamics, and degradation properties. Mechanical stretch properties and dynamic performance were tested extensively.

One of the most important aspects of 3D bioprinting is finding the correct biocompatible materials that mimic the mechanical properties of the tissues in your body. Stewart's extensive materials research lays the groundwork for future bioink development for cardiac clinical applications. With the correct bioink, doctors could one day print replacement parts that mechanically perform just like the healthy cardiac tissue in your body. Read on to learn more.

ABSTRACT: The gold standard in 2016 for thoracic aortic grafts is Dacron®, polyethylene terephthalate, due to the durability over time, the low immune response elicited and the propensity for endothelialization of the graft lumen over time. These synthetic grafts provide reliable materials that show remarkable long term patency. Despite the acceptable performance of Dacron® grafts, it is noted that autographs still outperform other types of vascular grafts when available due to recognition of the host’s cells and adaptive mechanical properties of a living graft. 3D bioprinting patient-specific scaffolds for tissue engineering brings the benefits of non-degrading synthetic grafts and autologous grafts together by constructing a synthetic scaffold that supports cell infiltration, adhesion, and development in order to promote the cells to build the native extracellular matrix in response to biochemical and physical cues.

Using the Allevi 3D bioprinter, scaffold materials we tested non-Newtonian photosensitive hydrogel that formed a crosslinked matrix under 365 nm UV light with appropriate water content and mechanical properties for cell infiltration and adhesion to the bioprinted scaffold. Viscometry data on the PEGDA-HPMC 15%-2% w/v hydrogel (non-Newtonian behavior) informed CFD simulation of the extrusion system in order to exact the pressure-flow rate relationship for every hydrogel and geometry combination. Surface tension data and mechanical properties were obtained from material testing and provide content to further characterize each hydrogel and resulting crosslinked scaffold. The goal of this work was to create a basis to build a database of hydrogels with corresponding print settings and resulting mechanical properties.

Read the full thesis here.

Scientists Create Beating Heart Tissue in a Lab Dish

Check out the amazing work that our collaborators, Dr. Kevin Costa and his lab, are doing at Mount Sinai!

https://www.cbsnews.com/news/scientists-create-beating-heart-tissue-in-a-dish/