Objective      To determine the effect of hypoxia (2% oxygen) on the expression of MMP-9 in main effector cells and epidermal cells and fibroblasts during wound repair.       Methods      Human epidermal HaCaT cells and primarily cultured fibroblasts from fresh foreskin tissues by circumcision were divided into 2 groups

normoxic group (synchronous culture

no treatment)

and hypoxia group (including 2 subgroups with 3 and 6 h under hypoxia). The expressin of MMP-9 in epidermal cells and fibroblasts

extracellular secretion of MMP-9 precursor expressions and changes of MMP-9 at the transcription level were respectively by Western blotting

gelatin zymography and fluorescence quantitative PCR.       Results      MMP-9 had a certain degree of basal expression and extracellular secretion in epidermal cells from normoxic group. Hypoxia significantly promoted the expression levels of MMP-9 protein in the epidermal cells (20% increased in 6 h compared with the normoxic group

P0.01)

and the extracellular secretions of MMP-9 precursor protein in hypoxia group at 6 h and normoxic control group (60.64±3.77 vs 44.03±3.00

P0.01). However

fibroblasts almost never expressed or secreted MMP-9 under normoxic and hypoxic conditions. Fluorescence real-time quantitative PCR indicated hypoxia increased MMP-9 mRNA expression in epidermal cells (hypoxia group at 6 h 5.47±0.51 vs normoxic control group 1.67±0.69

P=0.002).       Conclusion      Hypoxic stimulation significantly induces the expression and secretion of MMP-9 in epidermal cells

rather than dermal fibroblast

which may be related to the promotion of MMP-9 at transcription level in the wound under local hypoxic environment.