Histopathological and immunohistochemical studies of lenticules after epikeratoplasty for keratoconus

Aims: To examine histopathological and immunohistochemical changes in lenticules and host of corneal buttons from patients who previously underwent epikeratoplasty for keratoconus. Methods: 12 penetrating keratoplasty specimens from patients with keratoconus who had previously undergone epikeratoplasty, eight keratoconus, and seven normal corneas were examined, Immunostaining for Sp1, α1-proteinase inhibitor (α1-PI), and α2-macroglobulin (α2M) were performed. Results: In nine of the 12 lenticules, the keratoconus-like disruptions were found in Bowman's layer. Peripheral and posterior keratocyte repopulation of the lenticules was observed in all cases. Keratocyte repopulation in the anterior and mid-stromal regions of the lenticules appeared related to the time since epikeratoplasty. Sp1 nuclear staining of the basal and wing epithelial cells was more intense in lenticules and keratoconus corneas than in normal corneas. Lenticular, host, and keratoconus keratocytes showed positive Sp1 staining, whereas staining was absent in normal corneas. Compared to normal corneas, α1-PI and α2M immunostaining was lower in the lenticules, host, and keratoconus specimens. Conclusions: The epithelial cells and keratocytes repopulated in the lenticules retain keratoconus-like biochemical abnormalities such as upregulation of Sp1 and downregulation of α1-PI and α2M. The authors speculate that both keratocytes and the corneal epithelium may participate in the development of keratoconus.