Tissue engineering of nearly transparent corneal stroma

We determined whether a polyglycolic acid (PGA) scaffold bearing an adherent corneal stromal cell insert could be integrated into the ultrastructure of rabbit corneal stroma without compromising tissue transparency. Stromal cells were isolated from 10 newborn rabbits and expanded by tissue culture. After reaching confluence, the cells were harvested and mixed with nonwoven PGA fibers to form cell-scaffold constructs. After 1 week of culturing, they were implanted into the corneal stroma of female rabbit recipients. Green fluorescent protein (GFP) expression in transplanted corneal stromal cells was monitored at the protein level to determine cellular origin in the reconstructed stroma. Eight weeks after implantation, transmission electron microscopy and histological evaluation were performed on stromal tissue. Insertion of PGA scaffold alone served as a sham control. After stromal implantation, implants gradually became transparent over an 8-week period. During this time stromal histology was gradually restored, as collagen fibril organization approached that of their normal counterpart. GFP-labeled corneal stromal cells were preponderant in the regions bearing inserted scaffolds, suggesting that they were derived from the implants rather than from neighboring corneal stromal cells. No reconstructed stroma developed in regions where naked PGA was implanted instead. We conclude that intrastromal implantation of PGA fiber scaffold implants bearing corneal stromal cells is a useful procedure for corneal stromal tissue reconstruction because, over an 8-week period, the implants become progressively more transparent. Marked losses of translucence during this period combined with restoration of ultrastructure indicate that the implants provide the functions needed for deturgescing initially swollen stroma.