[Pathomorphological observation of the hypertrophic scar induced by injury to conical structure in female red Duroc pig].
To further explore the relationship between hypertrophic scar and injury to conical structure of skin and the pathogenesis of hypertrophic scar, and to reproduce an optimal animal model of hypertrophic scar.


METHODS
The back of two FRDP pigs were shaved, and a piece of normal skin was harvested for the observation of conical structure of skin. Skin wounds with depth of 0.38 mm, 0.76 mm, 1.14 mm and 1.52 mm, respectively, were created by gas-driven dermatome. Eight wounds measuring 7.0 cm x 7.0 cm were created on each pig. The wounds were divided into 4 groups according to the wound depth with 4 wounds in each group, i.e. 0.38 mm group, 0.76 mm group, 1.14 mm group and 1.52 mm group. The 0.38 mm and 0.76 mm groups were designated as superficial wound groups and 1.14 mm and 1.52 mm groups as deep wound groups. The wounds were allowed to heal without treatment. Tissue samples from the wound were harvested on 0, 10, 30, 60, 90 and 150 post injury day (PID) , and they were sectioned for HE staining and staining for elastic fibers (VVG). The wound healing and the scar formation were observed with naked eye. The skin conical structures in normal and injured skin were also observed. The morphology of hypertrophic scar was observed, and the thickness of the scar tissue was determined and scored.


RESULTS
The wounds in superficial wound groups healed within 3 weeks with flat surface without scar formation. The wounds in deep wound groups healed later than 4 weeks with thick, hairless, hard in texture, with depigmentation or pigmentation, finally forming contracture. The skin conical structure could be found on the back of FRDP with HE and VVG staining, and it was similar to that of human in terms of the structure. In superficial wound groups, the upper part of the skin conical structure was injured, but fat fornix and glands were intact. In deep wound groups, the lower part of the skin cone, together with the fat fornix and gland were all injured. On the 150th post injury day, the histological picture of the tissue in superficial wound groups was similar to that of normal skin. But the skin conical structure could not be found in deep wound groups, and the wounds were filled by a large accumulation of disarrayed and irregularly arranged collagen fibers. With passage of time, the scar became thicker and thicker, and the scar hypertrophy reached the zenith in 150th PID.


CONCLUSIONS
The injury of skin conical structure can lead to the formation of hypertrophic scar. FRDP can be used to reproduce and ideal model of hypertrophic scar.
Liang
Zhi
Z
Department of Burns and Plastic Surgery, The Sixth People's Hospital, Shenzhen 518052, PR China.
Xie
Cheng-yu
CY
Lin
Hai-bo
HB
Guo
Zheng-dong
ZD
Yang
Wei-guo
WG