Scaffolds for 3-D Cell Structure
Almost 20 years ago, researchers developed porous polymeric scaffolds that enabled scientists to grow tissue in thick layers. Since then, a number of functional tissue equivalents have been grown in the laboratory, including skin, cartilage, tendon, bone, and blood vessels.
Engineered scaffolds are created from anything from loofa sponges to complexes of polymers, such as polyglycolic acid, polylactic acid, or many other mixtures.
"The choice of which type of scaffold to use has an impact on how cells will look and function," says Richard Fry, managing director, Cellon (www.cellon.lu), "as it is clear that form and function are closely linked in biological systems. Cells grown in normal tissue culture flasks look different than cells that grow in vivo.
"If you cultivate cells on two different scaffolds, they may look different. Cells produced on less rigid supports, such as hydrogel scaffolds, are less spatially constricted, particularly when grown in a rotary cell culture system. This allows them to look and potentially function in a similar way to the parental tissue."
Scaffold properties that researchers consider include mechanical strength, degradation time, degradation byproducts, porosity, and fiber orientation.
"There are many types of scaffolds. Some are standard and some need custom mixing, says Fry. "They can come in sheets or tubes. Nonaligned scaffolds are manufactured from spun fibers using a nonwoven textile process. You can further modify the basic scaffold material to enhance cell attachment and growth or modify the physical properties and resorption rate."
Another type of scaffold is an aligned scaffold. These also are fabricated from spun fibers but are available in a variety of custom 3-D shapes and tubular structures. The main advantage of aligned scaffolds is that structures, such as tubing, are then seamless.
In recent years, some attention has focused on multipotential cells that give rise to various specific cell types. BioTissue Technologies (www.biotissue-tec.com) is developing multipotential cells, such as mesenchymal progenitors and periosteal cells. These cells are an attractive tissue engineering approach because they possess the ability to undergo extensive replication and develop into mesenchymal tissue, such as bone and cartilage.
According to the company, challenges in this arena include developing necessary procedures for cell isolation, expansion, and preservation. It is also important to establish methods for phenotypic and functional characterization, as well as characterize how the cells differentiate in vitro.