The Effects Of Continuous Elastic Outside Distraction On The Nipple And Its Supporting Tissues In Minipig

Objective:to observe the effect of continuous elastic outside distraction on female minipig nipples and their supporting tissues, to comprehend the above-mentioned tissues'changes of general morphology, histopathology and expressions of some growth factors during the distraction process;thus,investigate the mechanism of continuous elastic outside distraction correcting inverted nipples, to improve this technique to correct inverted nipples and obtain better results.Methods:Three female 3 months old minipigs, which has 12 nipples, were employed.4 nipples of each minipig were remained without distraction were control group. And the other 8 nipples were continuously distracted with inverted nipple correction instruments which made by ourselves.The minipigs were employed generally anesthetized by intramuscular injection of ketamine (8 mg/kg) and Sumianxinâ…¡injection(1.5ml) for apply inverted nipple correction instruments and excising nipples.One nipple without distraction and two nipples distracted of each minipig were excised at 2,4,8 and 12 weeks after traction, respectively. Before excision, the diameters and heights of nipples were measured with a vernier caliper. Then the excised nipple specimens were employed HE staining for observation the change of their tissue structure and countting the numbers of capillaries.And employed saturated picric acid sirius red staining for observation distribution and content of typeâ… andâ…¢collagen,and employed image analysis software for quantitative analysis. We observed the expressions of vascular endothelial cells growth factor (VEGF), epidermal growth factor (EGF), and CD34 in those tissues, counted percentage of positive cells and microvessel density (MVD) changes with immunohistochemical staining. Results: In general form, the volumes of nipples and areola papillaris all obviously increased after traction.compared with control group, diameters and heights of nipples are significantly different (p<0.01).In addition, there is a trend that following with traction time extension nipple height increase, in which 8w,12w groups compared with 2w and 12w compared with 4w groups all have obviously statistical significance (p<0.01 or p<0.05).Under ordinary light microscope, the traction group epidermis thickened, basal cells, fibroblasts and capillary significantly proliferated. Capillary counts compared with the control group were significantly different (p<0.01),which between 4w and 12w group have statistical significance(p<0.05).Stained with saturated picric acid sirius red,the typeâ… ,â…¢collagen contents of traction group all increased. Compared with control group, the typeâ… collagen contents of 4w,8w,12w group were significantly different (p<0.05 or p<0.01),the typeâ…¢collagen contents of 2w,4w,8w,12w group were significantly different (p<0.01),and the ratio ofâ… /â…¢reduced in the traction beginning, then gradually increased after 4w, to 12w is close to the ratio of control group.In immunohistochemical staining,VEGF,CD34 expressions of all groups were positive.The staining intensity of traction groups is moderate,and control groups were weakly positive.The EGF expression was all negative.The integral optical density of VEGF positive cell and MVD compared with the control group were significantly different (p<0.01),and there have a significant positive correlation in MVD and VEGF.Conclusion:continuous elastic outside distraction can promote female minipig nipple and areola papillaris to change,which is similar with the traction changes of clinical inverted nipple patients.These suggest that the action mechanism of traction for inverted nipples correction is same as the normal nipples. The increased areas of nipples and areola papillaris after traction are not come from flexible stretch, mechanical creep and shift of surrounding skins, but also partly from biological hyperplasia. The traction power can make spring maintain mild tension is enough and traction times of 8w to 12w are appropriate, which can avoid damage of inner tissues of nipples and reduce the occurrence of retraction.