Mar.19, 2014

When a human heart gets damaged, such as during a major heart attack, there's no easy fix. But Harvard scientists may have just found a way to repair the vital organ. They have created a layer of heart cells that closely mimics natural heart muscle that beats.

Researchers presented Tuesday their latest results at the 247th National Meeting & Exposition of the American Chemical Society (ACS), the world's largest scientific society. The research was conducted by Ali Khademhosseini and Nasim Annabi from the Harvard Medical School, along with a team from the University of Sydney in Australia led by Anthony Weiss.

Right now, the best treatment option for patients with major heart damage is an organ transplant. But there are far more patients on waitlists for a transplant than there are donated hearts. Even if a patient receives a new heart, complications can arise.

"Repairing damaged hearts could help millions of people around the world live longer, healthier lives," said Nasim Annabi.

The ideal solution would be to somehow repair the tissue, which can get damaged over time when arteries are clogged and starve a part of the heart of oxygen. Scientists have been searching for years for the best fix.

In their previous research, the team had worked with natural proteins that form gelatin-like materials called hydrogels to mimics the mechanical and biological properties of the native heart. But there was one way in which the materials didn't resemble human tissue. Like gelatin, early versions of the hydrogels would fall apart, whereas human hearts are elastic.

The elasticity of the heart tissue plays a key role for the proper function of heart muscles such as contractile activity during beating. So, the researchers developed a new family of gels using a stretchy human protein aptly called tropoelastin. They exposed the tropoelastin to ultraviolet light, which morphed it into a much more resilient and strong substance.

The images on the left show how the MeTro gel is fabricated and patterned by exposing the gel to ultraviolet light for less than one minute. Top right: Heart cell elongation and alignment on the surface of micropatterned MeTro hydrogels. Bottom right: The patterned MeTro hydrogels were stained to show the alignment of heart cells on the 8th day of culture. The green and red colors indicate critical proteins in heart cells, and the blue shows the nuclei of the heart cells.

But "building tissue is not just about developing the right materials. Making the right hydrogels is only the first step. They serve as the tissue scaffold,' Khademhosseini added.

To make sure the cells form the right structure, Khademhosseini's lab uses 3D printing and microengineering techniques to create patterns in the gels. These patterns coax the cells to grow the way the researchers want them to. The result was small patches of heart muscle cells neatly lined up that beat in synchrony within the grooves formed on these elastic substrates. These micropatterned elastic hydrogels can one day be used as cardiac patches.

Khademhosseini's group is now moving into tests with large animals. They are also using these elastic natural hydrogels for the regeneration of other tissues such as blood vessels, skeletal muscle, heart valves and vascularized skin.


Posted in 3D Printing Applications

 

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