Pre-vascularized Scaffolds From Spinach Leaves Can Grow Human Tissue

Plants may be able to help create pre-vascularized scaffolds for tissue engineering technologies, according to a multidisciplinary team of scientists from Worcester Polytechnic Institute (WPI), the University of Wisconsin-Madison, and Arkansas State University-Jonesboro. The team felt that experts from different fields would look at the problem from different angles for the emergence of novel solutions. The team included experts from the field of biomedical engineering, biotechnology, human stem cell and plant biology..

Reason for Research

The research team felt that currently available vascular grafts and scaffolds have been unable to provide an entirely satisfactory solution of forming a vascular network, to provide nourishment to the implant. They hope to address the existing gaps in the field by turning to plants in their new research.

"Plants and animals exploit fundamentally different approaches to transporting fluids, chemicals and macromolecules, yet there are surprising similarities in their vascular network structures," the authors wrote. "The development of decellularized plants for scaffolding opens up the potential for a new branch of science that investigates the mimicry between plant and animal."

Details of the Research

• The scientists employed spinach leaves that were stripped of plant cells leaving behind the transport network.
• They were able to flow fluids and microbeads similar in size to the human blood cells successfully.
• They were also able to seed the spinach venous network with cells that line human blood vessels (endothelial cells)
• Finally, the scientists were able to cultivate beating human heart cells on these spinach leaves.

These proofs of concept studies may pave the way for using multiple spinach leaves to generate multiple layers of healthy heart cells, that could in turn, be used in heart attack patients.

How the Spinach Leaves Were Stripped of Their Cells

The paper's first author is Joshua Gerslak, a graduate student who was instrumental in designing and conducting the experiments, and in fact developed an effective method of decellularizing the spinach leaves, by perfusing the venous network on the leaf with a detergent solution.

"I had done decellularization work on human hearts before and when I looked at the spinach leaf its stem reminded me of an aorta. So I thought, let's perfuse right through the stem," Gershlak said. "We weren't sure it would work, but it turned out to be pretty easy and replicable. It's working in many other plants."

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Once the plant cells are washed away, what remains is a framework composed of cellulose that is bio-compatible and not harmful to humans.

Other Leaves that Have Been Used to Form Vascular Scaffolds

In addition to spinach leaves, the research team was able to successfully decellularize parsley, Artemesia annua (sweet wormwood), and peanut hairy roots. The authors believe that the unique physical properties of each plant itself could be exploited for use in various tissue engineering techniques.

• For instance, spinach leaf might be apt in a highly vascularized tissue like the heart.
• Jewelweed, with its hollow cylindrical stem, could be more suited to arterial grafts
• The vascular columns of wood with its innate strength and geometrical structure might be useful in bone grafts.

"By exploiting the benign chemistry of plant tissue scaffolds, we could address the many limitations and high costs of synthetic, complex composite materials. Plants can be easily grown using good agricultural practices and under controlled environments. By combining environmentally friendly plant tissue with perfusion-based decellularization, we have shown that there can be a sustainable solution for pre-vascularized tissue engineering scaffolds."

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Current Scenario in Vascular Tissue Engineering

As mentioned earlier, tissue engineering offers a solution to replace damaged tissues by implantation of natural, synthetic, or semisynthetic tissue and organ substitutes, that are fully functional initially by itself, or grow into the required functionality within a limited time span.

• Development of autogenous vascular substitutes have been a major advance in the field of reconstructive arterial surgery, but these tissue sources are insufficient or not available. These methods are also time consuming and expensive.
• Currently, synthetic polymers such as polytetrafluoroethylene (ePTFE), polyethylene terephthalate (Dacron^®) and polyurethane are extensively employed to generate synthetic vascular grafts. However, these are associated with the risk of thrombus formation and compliance mismatch, and in addition are non-biodegradable, though degradable scaffolds are also available, but are expensive.

Future Research Plans

• Optimization of the decellularization process
• To assess how human tissues grow in response to various vascular scaffolds
• To generate a secondary vascular network to permit outflow of blood or fluids from human tissue.

In conclusion, if plant scaffolds prove successful, we could have a potentially simple, cheap, compatible and sustainable solution to the existing gaps in vascular tissue engineering.

References:

1. Joshua R. Gershlak, Sarah Hernandez, Gianluca Fontana, Luke R. Perreault, Katrina J. Hansen, Sara A. Larson, Bernard Y.K. Binder, David M. Dolivo, Tianhong Yang, Tanja Dominko, Marsha W. Rolle, Pamela J. Weathers, Fabricio Medina-Bolivar, Carole L. Cramer, William L. Murphy, Glenn R. Gaudette. Crossing kingdoms: Using decellularized plants as perfusable tissue engineering scaffolds. Biomaterials, 2017; 125: 13 DOI: 10.1016/j.biomaterials.(2017).02.011
2. Biomaterials for vascular tissue engineering - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2822541/)

Source-Medindia