Reassembly of the alpha 6 beta 4 integrin and laminin in rabbit corneal basement membrane after excimer laser surgery: a 12-month follow-up.

Abstract

We investigated the reassembly of hemidesmosomes and epithelial basement membrane (BM) following experimental excimer laser photorefractive keratectomy (PRK) immunohistochemically using monoclonal antibodies against integrin subunits alpha 6 and beta 4 (hemidesmosome components) or laminin (a BM component). The rabbits were killed 3 days, 1, 3, 6, or 12 months after a -5.0 D PRK. For untreated corneas, integrin subunits alpha 6 and beta 4 and laminin showed normal distribution at the basal aspect of the basal epithelial cells, appearing as a distinct fluorescent line. The alpha 6 subunit was also found at the basolateral membranes of the basal epithelial cells. The average healing time for the PRK wound was 6 days, but secondary epithelial defects occurred in 17 of 22 corneas. The subepithelial labeling for all the antibodies investigated showed focal discontinuities at the level of the BM in the wound area up to 12 months after PRK. After 6 months, secondary epithelial defects were very rare. In addition to the patchy subepithelial labeling, lamellar anterior stromal immunoreaction for alpha 6 and beta 4 integrin subunits was also present 1-12 months after PRK. Laminin was also observed in the anterior stroma 1-6 months after PRK. Our results suggest that focal discontinuities of hemidesmosomes or BM observed immunohistochemically in the unexpectedly slow-healing PRK wound areas might correlate with the epithelial healing problems observed in most rabbits.