Beta defensin-3 engineered epidermis shows highly protective effect for bacterial infection

Defensins are small cationic proteins that harbor broad-spectrum microbicidal activity against bacteria, fungi and viruses. This study examines the effects on pathogens of the epidermis engineered to express human beta-defensin 3 (HBD3) to combat bacterial infections. First, we examined the localization of HBD3 in the epidermis and observed HBD3 in the intercellular spaces and lamellar bodies of the upper epidermal layers. This result showed HBD3 expressed and assembled in the outer layers of the epidermis was suspected to counter the invading microorganisms. Next, we established a keratinocyte cell line that stably expressed HBD3 and found that the culture medium showed antibacterial activity. Furthermore, we prepared an epidermal sheet of these cells with the HBD3 gene and grafted this onto a dermal wound on a nude rat. The HBD3 engineered epidermis demonstrated significant antimicrobial activity. Skin ulcers without epidermis are constantly exposed to invading microorganisms. Biopsy samples of re-epithelizing epidermis from patients with skin ulcers were collected, and HBD3 mRNA level measured in the epidermis. The epidermal samples from the ulcer skin expressed 2.5 times higher levels of HBD3 transcript than those in the control skin. These results, taken together, indicate that the therapeutic introduction of the HBD3 gene into somatic cells may provide a new gene therapy strategy for intractable infectious diseases.