ABCs of Organ Engineering

Inside the Wake Forest Institute for Regenerative Medicine, more than 300 scientists in the fields of biomedical and chemical engineering, cell and molecular biology, biochemistry, pharmacology, physiology, materials science, nanotechnology, genomics, proteomics, surgery and medicine work side by side to translate the science of regenerative medicine into clinical therapies.

It All Starts with Cells

Engineering an organ or tissue begins with having the right kinds of cells. In some cases, cells are isolated from a small tissue sample the size of a postage stamp. They are then mixed with growth factors and multiplied in the lab. The cells multiply in quantity so rapidly that, in about 6 weeks, a layer one cell thick could theoretically cover a football field.

For cell types that cannot be adequately grown outside the body (like heart, nerve, liver and pancreas cells, for example), stem cells may be an option because of their ability to become multiple cell types. Scientists in our lab identified a new source of stem cells -- amniotic fluid and placental tissue. These cells are readily obtainable and, unlike embryonic stem cells, do not form tumors. We are currently using the cells to explore potential treatments for diabetes and for liver and heart disease.

These images show muscle precursor cells in culture. When differentiated, the cells become muscle fibers (the “streaks” in the photo on the right).

 

Making a Scaffold

After cell expansion, the next step in engineering a tissue or organ is to create a mold, or scaffold, in the shape of the tissue. Electrospinning is one technique used to make scaffolds for blood vessels, as well as muscles and tendons. The technique involves dissolving a biomaterial into a solvent, loading it into a syringe, and then applying a high voltage to the solution as it is slowly ejected from the syringe.

Watch a video example of electrospinning below:

At some distance away, there is a collection mandrel that is grounded so that when the charged solution leaves the syringe, it is attracted to the mandrel. You can actually see in this video the fibers shooting from the syringe to the mandrel and forming a tubular structure. 

Bioprinting

Using 3D Printing Technology to Print Organs and Tissue

Can replacement organs one day come from a printer? That's the ultimate goal of the institute's bioprinting program. Institute scientists were the first to create a laboratory-grown organ implanted into a human, but they quickly realized the need to scale up the manufacturing process.

Living tissues are composed of many cell types that are arranged in a very specific order. When engineering replacement tissues and organs in the lab, maintaining this order is essential to ensuring that the replacement tissues have the same function that original body parts have.

Because of the precision of printing, researchers at the Wake Forest Institute for Regenerative Medicine have been investigating the possibility printing tissues and organs. In their first efforts, they used an actual inkjet desktop printer that was modified to print cells into a 3D shape. Cells were placed in the wells of the ink cartridge and the printer was programmed to print them in a certain order. The printer is now part of the permanent collection of the  National Museum of Health and Medicine.

In 2016, the institute announced  success printing living tissue structures using a specialized 3D printer that its researchers designed over a decade. The scientists printed ear, bone and muscle structures that, when implanted in animals, matured into functional tissue and developed a system of blood vessels. These early results indicate that the printed structures have the right size, strength and function for use in humans. The series of experiments proved the feasibility of printing living tissue structures to replace injured or diseased tissue in patients.

Skin Printing

In the not too distant future, a bioprinter filled with a patient's own cells can be wheeled right to the bedside to treat large wounds or burns by printing skin, layer by layer, to begin the healing process. WFIRM scientists have created such a mobile skin bioprinting system -- the first of its kind -- that allows bi-layered skin to be printed directly into a wound. The mobility of the system and the ability to provide on-site management of extensive wounds by scanning and measuring them in order to deposit the cells directly where they are needed to create skin is what makes it so unique.

Affecting millions of Americans, chronic, large or non-healing wounds such as diabetic pressure ulcers are especially costly because they often require multiple treatments. It is also estimated that burn injuries account for 10-30 percent of combat casualties in conventional warfare for military personnel. The researchers demonstrated proof-of-concept of the system by printing skin directly onto pre-clinical models. The next step is to conduct a clinical trial in humans.

Quality Assurance

Using High-Powered Microscopes to Ensure the Effectiveness of Engineered Cells

High-powered microscopes are critical to the field of tissue engineering and regenerative medicine.  Light microscopes, which use light to detect small objects, allow scientists to assess the size, shape and activity of engineered cells to ensure that they will function properly in the body. Light microscopy is also commonly used to visualize whole engineered tissues and organs.

Conofocal laser scanning microscopy is used to obtain high-resolution images of thick samples, including tissue. Using a process known as optical sectioning, the technology enables images to be acquired point-by-point and then reconstructed with a computer, which provides three-dimensional images.

Scanning electron microscopy uses electrons to create images of the tiny details on the surface of materials. The scanning electron microscope at the Wake Forest Institute for Regenerative Medicine is specially designed to investigate biological specimens such as scaffolds and engineered tissue. Because scanning electron microscopy provides images that greatly exceed the magnification of conventional microscopes, this technology allows us to view scaffolds intricately to determine if cells are adhering properly.

Testing Functionality

Organ Baths Test the Functionality of Engineered Tissue

Tissues and organs that are developed in the laboratory have to do more than simply look like the tissue and organs they will replace; they have to function like them as well. We utilize an organ bath, an experimental set-up, to test laboratory-engineered tissue. With organ bath experiments, we can study how our generated tissues respond to chemical agents and electrical impulses to ascertain whether their responses are normal.

In our organ baths, tissue is suspended in a temperature-controlled chamber. The tissue's contractile function is recorded on a computer. Through a comparison of the tissue's contraction and relaxation responses to that of normal tissue, we're able to assess the functionality of engineered tissue.