Objective To investigate the differential expression of substance P (SP) in normal and hypertrophic scar fibroblasts in vitro and the reason of its high expression in the latter.   Methods The normal and hypertrophic scar fibroblasts were isolated by enzyme digestion and cultured. SP with a final concentration of 10

-7

  mol/L were added into the cell culture media

and those without SP stimulation served as control. Before and 1

3

6

12 and 24 h after SP stimulation

the SP expressions in the media of 4 groups were detected by RT-PCR and its concentrations was mea

sured by ELISA.   Results Without SP treatment

the fibroblasts from normal and hypertrophic scar excreted certain with significant difference between them (P0.01). In presence of SP

the gene and protein expression of SP of normal fibroblasts reached a peak level in 3 to 6 h

and then decreased rapidly to normal level in 24 h. For the fibroblasts from hypertrophic scar

the SP showed similar tendency with normal group after SP treatment

but kept a high level in 24 h. There were significant difference between the normal fibroblasts and the ones from hypertrophic scar after SP treatment (P0.01).   Conclusion SP can induce the secretion of SP in fibroblasts

and SP secreted by normal and hypertrophic scar fibroblasts in vitro was statistically significant.