ABSTRACT
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 werefully recovered. Remodeling of collagen fibers was more obvious in the experimental and positive control groups than in thenegative 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 tissueengineered epidermis, in which PHEMA may be a feasible drug-delivery carrier.
ABSTRACT
The involution of female Swiss mouse thymus induced by estradiol (Es_2) were studied by morphological methods.The involuting thymuses of 2-month-old mice increased greatly in weight after ovariectomy. Treated with Es_2, the thymuses of immature mice not only stopped growing, and also involuted apparently. The regeneration of thymuses was impeded in the mice whose thymuses had already involuted induced by hydrocortisone when treated with Es_2. These results proved the obvious inhibiting and involution-inducing effects of Es_2 on thymus. The pattern of the thymus involution induced by Es_2 was different from that by hydrocortisone. Es_2 had no lethal effect on thymocytes either in vivo or in vitro, but it reduced the proliferative rate of thymocytes slowly and caused the thymus involution gradually. Es_2 made no remarkable changes in weight and histology of adrenal glands. Thymus involution induced by Es_2 was also detected in adrenalectomized mice. These results indicated that thymus involution induced by Es_2 was adrenal independent. Accompanying the thymus involution, the number of type Ⅰ thymic epithelial cells decreased, which were considered to produce thymic hormones actively, and the structure of thymic epithelial cells denatured. These morphological degenerative alterations suggest that Es_2 can result in some changes or decline of the hormone secretory activity of thymic epithelial cells, and then the proliferation of thymocytes will reduce and thymus involution will take place.
ABSTRACT
Objective To Study if aortic smooth muscle cells(ASMC) can produce elastic fibers in three-dimensional culture imitating the dermis substitute. Methods Primary culture of ASMCs were obtained by explanting of thoracic aortae from one-week old SD rats. ?-actin immunocytochemistry was used to approve the smooth muscle cells. After subculture, ASMCs were mixed with gels composed of collagen, chitin and glucosaminoglycans, then, three-dimensional culture was carried out. After 1 week and 2 weeks, Gomori aldehyde fuchsin staining and elastin immunocytochemistry were applied to detect the elastic fibers in the ASMC-collagen gels. Results More than 98% of the cultured cells were approved as smooth muscle cells by ?-actin immunocytochemistry. After both 1 and 2 weeks of three-dimentional culture, elastic fibers were detected in the ASMC-collagen gels by both stainings.Conclusion ASMCs can synthesize elastin and produce elastic fiber in three-dimentional culture imitating the dermis substitute.
ABSTRACT
Objective To investigate if aortic smooth muscle cells (ASMCs) cultured three-dimentionally with collagen gel can still produce elastic fibers and the acceptance of hosts after transplantated in subcutaneous of rats. Methods AMSC-collagen gels that had been cultured for 2 weeks by three-dimentionally imitating the dermis substitute were transplanted to rats subscutaneous. After 4,7,10,14 and 28 days, the transplantations were examined via HE staining, Gomori aldehyde fuchsin staining, ?-actin immunohistochemistry and elastin immunohistochemistry. Results The amount of elastic fibers increased significantly in the week, whereas on the 28th day, no elastic fibers were detected.There was no remarkable leucocyte infiltration around the ASMC-collagen gel during 28 days.Conclusion Further studies are needed to explore the ASMC-collagen gels as a kind of elastic dermis substitute.