Mitosis increases levels of secretory leukocyte protease inhibitor in keratinocytes.

Chronic wounds are a major health care burden. Multiple factors produced by healing wounds play important roles in efficient and orderly wound healing. Secretory leukocyte protease inhibitor (SLPI) is constitutively expressed in epithelial cells, and its expression is increased by inflammation. SLPI has antimicrobial activities and improves wound healing. We hypothesized that SLPI expression correlates with keratinocyte growth rate and is increased by epidermal growth factor (EGF). Keratinocytes were isolated from neonatal foreskin. Subconfluent and confluent culture conditions were used. SLPI-specific primers were designed for use in quantitative-competitive reverse-transcription polymerase chain reaction assays to detect and quantify SLPI mRNA expression levels. SLPI levels were increased 2-fold in subconfluent cultures and 1.6-fold in confluent cultures to which EGF had been added. Confluent cultures also demonstrated 7-fold (growth factor depleted) and 6-fold (EGF) increase in SLPI RNA copy number, compared to subconfluent cultures. The results indicate that EGF increases SLPI expression.