Human ß-defensin 2 is up-regulated during re-epithelialization of the cornea

Purpose - Human ß-defensins 1 and 2 (hBD-1, -2) are antimicrobial peptides found in several epithelia including corneal epithelium. Breach of the epithelium leaves the cornea vulnerable to infection so we sought to determine if there is an increase in defensin expression after injury. Methods - The epithelium from human cadaver corneas was collected by scraping (original samples). The corneas were then placed into organ culture to permit regeneration of the epithelium. Samples of re-grown epithelium were collected when healing was partially and 100% complete as determined by fluorescein staining. Total RNA was extracted from original and re-grown samples and used in RT-PCR reactions using primers specific for hBD-1 and hBD-2 and the constitutively expressed gene glyceraldehyde-3-phosphate dehydrogenase. Immunoblotting was performed to detect defensin peptide in original and re-grown samples. Results - hBD-1 mRNA was detected in all original epithelial tissue samples (n = 10) examined suggesting that it is constitutively expressed. hBD-2 mRNA was detectable in only two of the ten samples. Of six corneas placed in to organ culture, hBD-1 mRNA expression was unchanged in the re-grown epithelial samples compared to the original epithelium samples, however the expression of hBD-2 mRNA was markedly increased. hBD-1 and hBD-2 peptides showed the same pattern of expression as their respective transcripts. Conclusions - These data show that hBD-2 mRNA and peptide is up-regulated in the corneal epithelium during re-epithelialization which is in keeping with the role of this defensin as an antimicrobial peptide.