[Angiogenesis in hypertrophic scar of rabbit ears and effect of extracellular protein with metalloprotease and thrombospondin 1 domains on hypertrophic scar].

Objective: To investigate the angiogenesis in hypertropic scar tissue of rabbit ears at different periods and to explore a new method to prevent hyperplastic scar.

Methods: Nineteen Japanese white rabbits (weigthing 2.0-2.5 kg) were made animal models of hypertropic scar of ear. At 10th, 30th, 60th and 90 days, after epithelization, the microvessel and microcirculation in hyperplastic scar of 8 rabbits were studied by microcirculation microscope and laser Doppler flowmetry. The other 11 rabbits' right or left ears were randomly chosen into experimental group and control group. At 10 days after epithelization, 40 microL of adenovirus extracellular protein with metalloprotease and thrombospondin 1 domains (Ad-METH1) was injected into tissue of scar along the perimeter of the scar in experimental group. The same volume of empty adenovirus was injected in control group. After 30 days of injection, the gross appearance of 10 rabbits' ears scar was recorded, the number of microvessel in scar was counted and HE stainning of scar tissue was performed in experimental and control groups. One additional rabbit was used to evaluate the mRNA and protein expression of METH1 by RT-PCR and Western blot after 3 days of injection.

Results: The average number of microvessel at 10, 30, 60 and 90 days after epithelization was 42.37 +/- 3.89, 49.46 +/- 4.13, 33.12 +/- 4.34 and 13.24 +/- 2.31, respectively; the average value of microcirculatory perfusion at 10, 30, 60 and 90 days after epithetlization was (37.75 +/- 2.11), (59.87 +/- 6.46), (44.53 +/- 6.14) and (29.21 +/- 1.84) PU; the density of microvessels and perfusion of microcirculation in scar tissues during proliferative stage (from 10 to 60 days after epithelization) were markedly higher than that during mature period (90 days after epithelization, P < 0.05). At 10 to 30 days after epithelization, the histoligical features of scar showed early stage of proliferation and proliferative stage appearance; at 60 days after epithelization, it is still in proliferative stage, while some of scars were in mature phase; at 90 days after epithelization, the histoligical features of scar were mature period appearance. At 3 days after Ad-METH1 injection, METH1 gene was successfully expressed at both mRNA and protein levels in experimental group, but not in control group. At 30 days after injection, the gross appearance observation showed that scars in experimental group were flat and soft with the color close to normal, but scars in control group were obvious and hard. The number of microvessel of scar tissue was 12.38 +/- 2.56 in experimental group and 48.12 +/- 6.46 in control group, showing statistically significant difference between two groups (P < 0.01). In experimental group, HE staining shows that the density of microvessel and the number of fibroblasts were greatly decreased and collagen fibers arranged regularly. In control group, plenty of fibroblasts and abundant microvessels were observed. Thick and tight collagen fibers were seen in the outer layer of dermis with a irregular arrangement.

Conclusion: The anti-angiogenesis by Ad-METH1 may have a promising application in the prevention of human hyperthropic scar.