The inhibitory effect of minocycline on hypertrophic scarring

Matrix metalloproteinases are enzymes that serve to degrade the extracellular matrix, giving them a central role in the inflammatory and wound-healing processes; they have been implicated in the pathophysiology of hypertrophic scarring. The purpose of this study was to examine the effect of minocycline, a matrix metalloproteinase inhibitor, on hypertrophic scarring.

Standardized wounds were created on the ears of eight New Zealand White rabbits. Half of the rabbits received daily injections of minocycline, whereas the other half received daily injections of saline (control). After 4 weeks, the resulting ear scars were harvested. Histologic slides were prepared from the thickest cross-sections of the scars, and from these slides the cross-sectional area of each scar was measured. A hypertrophic index was calculated by comparing the area of the scar to the baseline value of unwounded skin. Statistical analysis was performed using the SAS/STAT NESTED Procedure for hierarchical data.

Among the rabbits treated with minocycline, the mean hypertrophic index was 1.08 +/- 0.01, compared with 1.54 +/- 0.03 in the control group (p = 0.03), representing an 85 percent reduction in hypertrophic area.

Systemically administered minocycline significantly reduces the severity of hypertrophic scarring in a rabbit model. Although not directly examined in this study, matrix metalloproteinase inhibition is hypothesized to be responsible for this effect.