This method could help overcome the shortage of donated corneal tissue.
Spheroids of corneal tissue about 5 mm in diameter have been grown in a bioreactor from an in vitro culture of primary rabbit corneal cells to illustrate the production of optic cells from aggregates and tissue. In comparison with corneal tissues previously grown in vitro by other techniques, this tissue approximates intact corneal tissue more closely in both size and structure. This novel three-dimensional tissue can be used to model cell structures and functions in normal and abnormal corneas. Efforts continue to refine the present in vitro method into one for producing human corneal tissue to overcome the chronic shortage of donors for corneal transplants: The method would be used to prepare corneal tissues, either from in vitro cultures of a patient's own cells or from a well-defined culture from another human donor known to be healthy.
As explained in several articles in prior issues of NASA Tech Briefs, generally cylindrical horizontal rotating bioreactors have been developed to provide nutrient-solution environments conducive to the growth of delicate animal cells, with gentle, low-shear flow conditions that keep the cells in suspension without damaging them. The horizontal rotating bioreactor used in this method, denoted by the acronym "HARV," was described in "High-Aspect-Ratio Rotating Cell-Culture Vessel" (MSC-21662), NASA Tech Briefs, Vol. 16, No. 5 (May, 1992), page 150.
To start a culture, the nutrient medium in the bioreactor is inoculated with a mixture of primary corneal cells, including endothelial cells, epithelial cells, and keratinocytes. Because these cells depend on attachment, microcarrier beads are also introduced to provide support. In the initial experiments, insoluble beads were used; alternatively, one could use microcarriers that dissolve as the tissue grows, leaving only the tissue. Another alternative would be to introduce other cells so that the cells of all types present could use each other for support.
In the culture, the cells grow, multiply, migrate into clusters, and produce an intracellular matrix via the functional interrelationship of cell-to-cell contact. The cells differentiate and grow along boundaries characteristic of normal functional tissue. The tissue thus formed has a layered structure similar to that of an intact cornea.
This work was done by Glen F. Spaulding, Thomas J. Goodwin, and Laurie Aten of Johnson Space Center; Tacey Prewett and Wendy S. Fitzgerald of Krug Life Sciences; and Kim O'Connor, Delmar Caldwell, and Karen M. Francis of Tulane University. Tulane and NASA have joint undivided property interests in this technology.
This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, Johnson Space Center, (281) 483-0837. Refer to MSC-22368.