Keratin 13 immunostaining in corneal impression cytology for the diagnosis of limbal stem cell deficiency

The aim of this study was to develop a validated, reliable, and minimally invasive technique for diagnosing limbal stem cell deficiency (LSCD) by immunocytochemical detection of conjunctival and corneal keratins on epithelial cells collected by impression cytology (IC). After validation of labeling techniques on a cohort of 10 healthy control patients, keratins K12, K13, and K19 were labeled on corneal IC of 10 eyes suspected of LSCD. Positive scores for the conjunctival markers K13/K19, coupled with the rarity of the corneal marker K12, were diagnostic proof of LSCD. IC is a reliable and noninvasive technique for collecting epithelial cells. The labeling validation phase has permitted K3 labeling to be eliminated due to lack of corneal specificity. Among patients with LSCD, nine samples were diagnosed with LSCD (K13+/K19+), which was severe (K12-) in eight cases and mild (K12+) in one case. One sample could not be analyzed due to lack of cells. K13 has shown to be a new marker of conjunctival differentiation. The immunocytochemical search for the K13/K19 couple by corneal IC provides a simple and reliable method for diagnosing LSCD, whereas the level of K12 could provide a score of disease severity. On the other hand, the authors question the corneal specificity of K3 as conventionally established.