背景:作者在对人发角蛋白的机制研究和临床应用中提出了一个伞新的组织工程学概念--在体,原位组织工程.在该理论的指导下,拟以人发角蚩白-胶原海绵为支架,复合一种可作为药物缓释载体的聚甲基丙烯酸羟乙酯,探讨其在体内原位诱导周围组织细胞构建真皮的可行性.目的:以人发角蛋白胶原海绵为敷料内层,复合包裹药物虎杖的聚甲基丙烯酸羟乙酯载体,制各一种双层复合生物材料,观察其对烧伤创面的促愈合作用.设计、时间及地点:随机对照动物实验,于2005-03/12在南方医科大学组胚教研室完成.材料:选用雄性SD大鼠15只制备烧伤动物模型,将模型鼠完全随机分为3组:实验组,阳性对照组及阴性对照组.方法:①将在体内具有慢、中、快3种吸收速度的人发角蛋白组分材料编织成网孔为1 mm×1 mm的网格,与从牛跟腱中抽提Ⅰ型胶原溶液混合后放入模具,经真空冷冻干燥后制成海绵状膜(作复合内层敷料).②用聚合法制备聚甲基丙烯酸羟乙酯,再与药物虎杖一同成膜,制备药物缓释载体膜(作复合外层敷料).③用SD大鼠制备深Ⅱ度烧伤动物模型,烧伤后3 d做清创处理,清创后实验组用与创面相同大小的人发角蛋白胶原海绵-聚甲基丙烯酸羟乙酯复合敷料覆盖创面,阳性对照组用戊二醛猪皮覆盖创面.阴性对照组为单纯无菌纱布覆盖.主要观察指标:①术后以创面完全上皮化为标准,记录创面愈合时间并分别计算7,14,21 d愈合率.②于覆敷料后1,2,4,6,8周切取整个刨面及其周围组织,光学显微镜观察肉牙组织生长情况和免疫组织化学染色观察新生组织中的胶原纤维和弹性纤维形态.结果:①实验组创面覆盖后渗出明显减少且保持一定湿度,而阳性对照组创面较干燥:实验组及阳性对照组的创面愈合时间较阴性对照组提前(P=0.000);创面在7,14,21 d的愈合率均较阴性对照组高(P=0.000),且实验组在14 d的愈合率较阳性对照组高(P＜0.05).②覆敷料后2周,光镜下观察可见创面肉芽组织中有较细小的胶原纤维填充创面.实验组较其他2组明显.胶原蛋白及弹性蛋白的免疫组织化学染色显示:第2周,实验组创面真皮基质中,Ⅰ型胶原呈棕黄色细密条带状;且有少量破染成棕黄色细丝状的弹性纤维,阳性对照组不明显,而阴性对照组中弹性蛋白无阳情表达.第8周,3组创面均愈合良好.实验组及阳性对照组胶原纤维束改造塑形,无瘢痕形成趋势.阴性对照组真皮层组织排列紊乱.结论:人发角蛋白-胶原海绵聚甲基内烯酸羟乙酯/虎杖复合生物敷料可促进深Ⅱ度烧伤实验大鼠创面的愈合.%BACKGROUND: Based on our previous researches in mechanism studies and clinical applications of human hair keratin (HHK), a new concept "in vivol in situ tissue engineering" has been proposed. Under the guidance of this theory, a scaffold of HHK-collagan sponge (inner layer) combined with poly (2-hydroxyethyl methacrylate) (PHEMA) (outer layer as a drug delivery carrier) would be developed to investigate its feasibility to be as a dermal dressing. OBJECTIVE: To develop a scaffold composed of HHK-collagan sponge (inner layer) combined with PHEMA film containing polydatin(PD)(outer layer as a drug delivery carrier) and to evaluate the therapeutic efficacy of the HHK-collagen sponge-PHEMA/PD complex on burn wound healing. DESIGN, TIME AND SETTING: A randomized controlled animal experiment was performed at the Department of Histology and Embryology, Southern Medical University between March and December 2005. MATERIALS: Burn was induced in 15 male Sprague-Dawiey (SD) rats, Rat models of burn were evenly randomized to 3 groups: experimental, positive control, and negative control. METHODS: ①HHK-collagen sponge was prepared through combination of a HHK meshwork (1mm × 1 mm in size for each grid) made up of three components (determined according to biochemical procedures of various degrees, i.e., light, medial, and severe) at a ratio of 4:3:3 with primary collagen sponge extracted from bovine tendons in a mould. Sponge film (used as inner layer dressing) was made by vacuum freeze-drying. ② PHEMA was prepared by polymerization. Than PD was added to prepare PHEMNPD film (used as outer layer dressing).③ Degree Ⅱ burn wound models were established in SD rats by scalding, Superficial necrotic tissue was removed from burn wounds at postnatal 3 days and leave the denatured dermis remained. The wounds were either covered with human HHK-collagen- PHEMNPD complex in the experimental group, or with glutaraldehyde-treated porcine skin in the positive control group, and sterile absorbent gauze was used in the negative control group. MAIN OUTCOME MEASURES: ① Complete epithelization was taken as the standards, and at postoperative 7, 14, and 21 days, wound healing was respectively calculated. ② At postoperative 1, 2, 4, 6, and 8 weeks, the whole wound surface and its peripheral tissue were dissected for observing granulation tissue growing under an optical microscope and detecting the collagen fiber and elastic fiber in the newly formed tissue by immunohistochemical staining. RESULTS: ① Gross observation results revealed that in the experimental group, the volume of the diffusate under the ideal moisture was less compared with the positive control group; the healing time was slightly shorter in both the experimental group and the positive control group than in the negative control group (P= 0.000); At postoperative 7, 14, and 21 days, the healing rate was higher in the experimental and positive control groups than in the negative control group (P=0.000), in addition, the experimental group exhibited higher healing rate than the positive control group at postoperative 14 days ( P ＜ 0.05). ②Optical microscope results showed that at postoperative 2 weeks, a small quantity of collagen fibers were found in the wound granulation tissue in all 3 groups, in particular in the experimental group. Immunohistochemical staining results regarding collagen protein and elastin revealed that at postoperative 2 weeks, both the fine strip-like type Ⅰ collagen fibers and a few silk-like elastic fibers were stained yellowish-brown in the dermal matrix in the experimental group, which were weakly positive in the positive control group, while there was no elastin detectable in the negative control group; at postoperative 8 weeks, burn wounds in all the 3 groups were fully recovered. Remodeling of collagen fibers was more obvious in the experimental and positive control groups than in the negative control group, while the tendency to scar formation with derangement of epithelial cells and collagen fibers in dermis was more prominent in the negative control group than in the remaining two groups. CONCLUSION: HHK-collagen sponge-PHEMA/PD complex may be a new burn dressing via in vivo construction of tissue engineered epidermis, in which PHEMA may be a feasible drug-delivery carrier.
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