While no tissues can be said to be simple, some are simpler than others. In the past decade, tissue engineers have made considerable progress towards the manufacture of these simpler tissues, from the starting point of cells and scaffold materials. Bioprinting, a form of rapid prototyping, has proven to be an important class of approach. The research noted here is a representative example of progress towards the production of corneas to replace those that are damaged by accident or age, and thus eliminate the need for donor tissue.
When a person has a severely damaged cornea, a corneal transplant is required. For this reason, many scientists have put their efforts in developing an artificial cornea. The existing artificial cornea uses recombinant collagen or is made of chemical substances such as synthetic polymer. Therefore, it does not incorporate well with the eye or is not transparent after the cornea implant. Now, researchers have 3D printed an artificial cornea using the bioink which is made of decellularized corneal stroma and stem cells. Because this cornea is made of corneal tissue-derived bioink, it is biocompatible, and 3D cell printing technology recapitulates the corneal microenvironment, therefore, its transparency is similar to the human cornea.
The human cornea is organized in a lattice pattern of collagen fibrils. The lattice pattern in the cornea is directly associated with the transparency of cornea, and many researches have tried to replicate the human cornea. However, there was a limitation in applying to corneal transplantation due to the use of cytotoxic substances in the body, their insufficient corneal features including low transparency, and so on. To solve this problem, the research team used shear stress generated in the 3D printing to manufacture the corneal lattice pattern and demonstrated that the cornea by using a corneal stroma-derived decellularized extracellular matrix bioink was biocompatible.
In the 3D printing process, when ink in the printer comes out through a nozzle and passes through the nozzle, frictional force produces shear stress. The research team successfully produced transparent artificial cornea with the lattice pattern of human cornea by regulating the shear stress to control the pattern of collagen fibrils. The research team also observed that the collagen fibrils remodeled along with the printing path create a lattice pattern similar to the structure of native human cornea after 4 weeks in vivo.