Advances in corneal preservation

Abstract

The functional status of the endothelium and sustained corneal deturgescence after corneal preservation are of great clinical importance and have been primary goals in the development of corneal storage media. In our investigational studies we have specifically addressed the improvement of the quality of donor tissue after 4 degrees C storage, the extension of corneal preservation time, the enhancement of corneal wound healing, and the reduction of the normal progressive loss of endothelial cells postkeratoplasty. Specifically we have developed in vitro HCE cell and epithelial cell culture models that can accurately reflect the response of human corneal tissue in vivo. These models have been utilized to study the effects of growth factors and medium components in relation to their biocompatibility and efficacy in the development of improved corneal preservation solutions. Our laboratory investigated in vitro conditions that allowed human corneal endothelium to shift from a nonproliferative state, in which they remain viable and metabolically active, to a proliferative, mitotically active state. Isolation techniques developed in our laboratory have enabled the establishment of primary and subsequent subcultures of human corneal endothelium that retain the attributes of native endothelium. These in vitro conditions maintain HCE cells in a proliferative state, actively undergoing mitosis. A quantitative bioassay has been developed to determine the effects of various test medium in the stimulation or inhibition of DNA synthesis. In attempting to learn more about the events that occur during in vitro endothelial cell isolation, cell reattachment, extracellular matrix interaction and migrating during subculture, SEM was done on isolated HCE cells incubated in CSM. These studies suggest that the components of the extracellular matrix modulate the growth response of HCE cells, and play a role in regulating proliferation and migration. These observations are important in view of the fact that anterior chamber environment limits cell regeneration of the endothelium, and supports wound healing via cell migration. In vivo, it is the complex interaction of the HCE cell and the extracellular matrix that signal the cell to respond to cell loss in this manner. As our knowledge of human corneal endothelium has increased so has our anticipation of developing the "optimum" medium. Thus additional components have been added to this basic medium to address specific complications encountered with 4 degrees C corneal preservation. Antioxidants, additional energy sources, and other nutritive substrates have been used to supplement and further define a chondroitin sulfate-based medium. These changes have been a part of our new awareness that, even at 4 degrees C, the cornea is metabolically active.(ABSTRACT TRUNCATED AT 400 WORDS)