| Background: Polyacrylamide hydrogel(PAHG) is an atoxic, stable, non- resorbable watery gel consisting of approximately 2.5% cross-linked polyacrylamide and nonpyrogenic water. PAHG is widely used in ophthalmic operations, food packaging products, and water purification. In Ukraine, the largest producing area in the world, PAHG has been applied in plastic and aesthetic surgery for more than 10 years since 1987, and mostly, in breast augmentation, as well as in soft tissue reparation. PAHG, an injectable alloplastic biomaterial, imported from the Ukraine has been used for augmentation mammaplasty in China since 1997. More than 100 thousand person-times received PAHG injection within later 6 years in China, therefore, china becomes the biggest user in the world.Simultaneously, former injectable filling materials, represented by liquid paraffin and liquid silicone, was refused because of their high complication rates.The main complication after PAHG injection is induration,other complications including hematome, asepsis imflammation, pectoralis major imflammation and material displacement. Most complications are caused by inappropriate manipulation and poor asepsis condition.Our department performed PAHG injection since 2000 and complications are only found in individual patients. Most of them suffer from induration, while victims of material displacement, pectoris inflammation is hardly found.Fibrous capsules form around PAHG after injection, highly resembled the capsules commonly found around breast implants. Induration formation is similar to capsule contraction process. Material displacement happens as in each direction of the galactophore, the tissue density varies. At the same time, fibrous capsule formation is another crucial cause never should be ignored. To some extent, the process of biomaterial implantation could be considered as a injury and foreign body invading. In general, wound healing is a complex pathological process based on a series activities of immune cells and repairing cells. Immune cells mainly include macrophages, T lymphocytes and mast cells, while repairing cells generally are fibroblasts, vascular endothelial cells and epithelial cells, etc. Local tissue reaction and immunity stimulation have been proved the most important procedure between biomaterial and organism in vivo study. Current studies are mostly based on experiments performed in vitro, nevertheless, the local tissue reaction after PAHG injection and mechanism of fibrous capsule formation have never been adequately studied by far.Objective: In this study, the local soft tissue reaction, fibrous capsule formation, and its relationship with inflammatory cells infiltration and distributing are evaluated after three different materials are implanted underneath the skin of SD rats respectively. The effect of inflammatory cells and its secrete cytokins on fibrous capsule formation are observed in order to control fibrous capsule formation and reduce complication rate.Methods: PAHG is injected in underneath the skins of SD rats, and liquid silicone(LS) is used for the positive control and expanded polytetrafluoroethylene(ePTFE) for negative control. At 1 week, 2 weeks, 1 month, 2 months, 3 months, 6 months after the injection, observe the massive morphological characters of the tissues with naked eye respectively. Meanwhile, take the materials and surrounding tissues for HE staining, studying local fibrous capsule formation and inflammatory cells infiltration, plus to measuring fibrous capsule thickness with biology image analyses software. All the tissue-covered implants collected at 6 different periods are processed into paraffin sections for histological analysis. In order to assess the infiltration and distribution status of macrophages, T lymphocytes and B lymphocytes, immunohistochemistry SABC method are adopted, by evaluating the expression of CD4, CD8, CD20, CD68 in tissues enveloping the implants. Treated with collagenase, tissue specimens are processed into cell suspension, then the flow cytometry is applied t...
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