国产多孔钽材料修复兔胫骨缺损的实验研究

摘要 目的：研究国产多孔钽材料能否在兔胫骨缺损模型中顺利实现骨长入,用于修复胫骨缺损。方法：在36只新西兰大白兔双侧胫骨骨干处建立骨缺损模型,每只动物左右侧缺损随机分组,分别进入实验组(植入多孔坦材料)和对照组（不植入多孔坦材料）。植入后4周、8周和12周取材,通过X线检测以及硬组织切片苏木精伊红染色,检测多孔钽材料与骨界面的骨整合情况。采用推出实验检测多孔钽材料与骨界面的结合强度。结果：将术后不同时间点取得的胫骨标本作X射线拍片分析,4周时,骨缺损端与材料结合部位有骨质生成,在8周时材料表面有骨形成现象,逐渐完全覆盖材料表面,在12周时骨量继续增加,形成覆盖材料并桥接骨缺损断端的骨痂。样本行硬组织切片并行HE染色后检测,植入4周后实验组材料两端被新生骨所覆盖,材料深部的孔隙中也可见少量骨组织长入;植入8周后发现实验组材料与骨组织生长良好,多孔钽材料表面和两端材料孔隙内均有骨组织长入,材料孔隙与组织紧密连接,有骨小梁长入;植入12周时两端骨组织长入深度没有明显变化,但材料表面骨组织继续长入,并完全嵌入圆柱体材料内。材料植入后4周与8周比较差异无统计学意义（P＞0.05）,材料植入后8周与12周比较差异有统计学意义（P<0.05）。将植入4周、8周和12周后含材料样本置于动态疲劳试验机上进行推出实验,随时间延长所需推出力明显增加,植入后4周和8周相比,虽然后者所需推力较大,但两者比较差异无统计学意义（P＞0.05）,而8周和12周比较则差异有统计学意义（P<0.05）。结论：国产多孔坦材料能在胫骨缺损中实现与骨整合,能用于皮质骨缺损修复。     

Development of a Novel Model for the Assessment of Dead-Space Management in Soft Tissue

Following extensive surgical debridement in the treatment of infection, a “dead space” can result following surgical closure that can fill with hematoma, an environment conducive to bacterial growth. The eradication of dead space is essential in order to prevent recurrent infection. This study describes a novel small animal model to investigate dead-space management in muscle tissue. Two absorbable test materials were implanted in each animal; beads of calcium sulfate alone, and beads loaded with vancomycin and tobramycin. In-life blood samples and radiographs were taken from each animal following implantation. Animals were sacrificed at 1, 7, 21, 42, and 63 days post-operatively (n = 4), and implant sites were analysed by micro-computed tomography, histology and immunohistochemistry. Complete resorption was confirmed radiographically at 3 weeks post-implantation. Histologically, the host tissue response to both materials was identical, and subsequent healing at the implant sites was observed with no dead space remaining. Vancomycin was not detected in blood serum. However, peak tobramycin levels were detected in all animals at 6 hours post-implantation with no detectable levels in any animals at 72 hours post implantation. Serological inflammatory cytokine expression for IL-6, TNF-α and IL-1β indicated no unusual inflammatory response to the implanted materials or surgical procedure. The model was found to be convenient and effective for the assessment of implant materials for management of dead space in muscle tissue. The two materials tested were effective in resolving the surgically created dead space, and did not elicit any unexpected adverse host response.     

多孔自凝固磷酸钙/纤维蛋白1：1比例血管化的分析研究

目的：观察复合纤维蛋白的多孔自凝固磷酸钙的理学性能及体内血管化情况,探讨其各组份对材料生物学特性的影响,为其临床应用提供实验数据。方法：1）采用凝固时间测定和电镜观察材料表面和断面等方法对复合支架材料构造和理学性能进行分析;2）将24只新西兰白兔随机分为3组,每组8只,分别在每只实验兔腰背筋膜下植入1：1、CPC两种比例材料各一枚。术后2、4、8周进行取材,对材料及其周围组织进行组织学观察、微血管情况定量分析。结果：1）CPC/FG复合支架材料以1：1（g/ml）混合后,与单纯的CPC相比,初凝时间延长,而终凝时间没有明显的统计学差异;电镜观察发现多孔自凝固磷酸钙复合了纤维蛋白胶之后,纤维蛋白胶分布均匀贯穿多孔自凝固磷酸钙晶体之间,并将其紧密相连;2）术后2周材料外周可见幼稚的微血管。1：1组高于CPC组（P〈0.05）。4周微血管密度达到高峰,相对于2周时有明显差异。1：1组高于CPC组（P〈0.05）。8周时微血管密度相对4周没有显著差异。各组微血管密度与4周时没有明显变化（P〉0.05）。结论：复合支架材料具有合适的凝固时间和较好的结构,纤维蛋白胶及其降解产物影响复合材料在体内的微血管密度,使复合材料血管化能力提高,其可作为细胞载体和骨缺损修复支架材料应用于临床和实验中。     

Increasing the volume of vascularized tissue formation in engineered constructs: an experimental study in rats

The authors have previously described a model of in vivo tissue generation based on an implanted, microsurgically created vessel loop in a plastic chamber (volume, 0.45 ml) containing a poly(DL-lactic-co-glycolic acid) (PLGA) scaffold. Tissue grew spontaneously in association with an intense angiogenic sprouting from the loop and almost filled the chamber, resulting in a mean amount of tissue in chambers of 0.23 g with no added matrix scaffold and 0.33 g of tissue in PLGA-filled chambers after 4 weeks of incubation. The aim of the present study was to investigate whether a greater volume of tissue could be generated when the same-size vessel loop was inserted into a larger (1.9 ml) chamber. In four groups of five rats, an arteriovenous shunt sandwiched between two disks of PLGA, used as a scaffold for structural support, was placed inside a large polycarbonate growth chamber. Tissue and PLGA weight and volume, as well as histological characteristics of the newly formed tissue, were assessed at 2, 4, 6, and 8 weeks. Tissue weight and volume showed a strong linear correlation. Tissue weight increased progressively from 0.13 +/- 0.04 g at 2 weeks to 0.57 +/- 0.06 g at 6 weeks (p < 0.0005). PLGA weight decreased progressively from 0.89 +/- 0.07 g at 2 weeks to 0.20 +/- 0.09 g at 8 weeks (p < 0.0005). Histological examination of the specimens confirmed increased tissue growth and maturation over time. It is concluded that larger quantities of tissue can be grown over a longer period of time by using larger-size growth chambers.     

石墨化炭/炭复合材料＋羟基磷灰石涂层（C/C＋HA）复合骨植入材料研究

目的：通过建立兔股骨缺损的动物实验模型,对采用等温化学气相沉积法和等离子喷涂技术所制备的石墨化炭/炭复合材料＋羟基磷灰石涂层（C/C＋HA）复合骨植入材料进行骨植入实验的的生物相容性进行评价,探索该复合材料作为植入机体骨组织的可行性依据。方法：采用骨科钻在实验动物股骨髁上钻孔的方法建立骨缺损的动物实验模型,将待研究比较的实验材料分别植入实验动物的股骨髁内,持续观察8周,在术后第2、4、8周时应用X线照片、组织学染色和扫描电镜技术,分别观察所研究材料在机体内对骨缺损愈合及其对机体的影响,进行组间比较和相关性分析。结果：石墨化炭/炭复合材料＋羟基磷灰石涂层（C/C＋HA）复合骨植入材料的骨植入实验生物相容性良好,材料与骨组织结合牢固,界面中成骨细胞生长明显,且炭颗粒脱落现象少,未见炎症细胞浸润。植入动物体内的材料在植入期未引起机体局部的炎症浸润反应且表面脱落的碳颗粒在机体组织中也未引起局部严重的炎症反应。在实验动物植入材料后的连续8周观察期中,组织学观察显示：表面涂有HA的炭/炭复合材料对骨组织形态改建上表现良好,其与骨组织接界处所形成的纤维结缔组织膜层厚度明显比未涂HA的材料要小,与骨组织结合更为紧密和牢固;碳颗粒出现脱落游离的现象明显减少。结论：在炭/炭复合材料表面涂以HA生物涂层对骨的形态改建和促进骨小梁生长等方面具有良好的作用,是一种具有发展潜力的骨修复材料。     

VX2肿瘤侵犯兔下腔静脉的生物学行为观察

目的建立VX2肿瘤侵犯新西兰兔下腔静脉(IVC)的动物模型,并观察相应的生物学行为。方法经腹直视下,将VX2肿瘤组织块分别种植在28只兔肾以下IVC附近的软组织内,然后随机分为A、B两组。A组术后每周在超声下观察肿瘤的大小、IVC和腹主动脉(AA)管径大小;DSA观察侧支循环建立。B组每周随机解剖4只,取IVC和AA做病理和免疫组化(PCNA)检查,并观察转移情况。结果 1.超声显示:所有肿瘤均种植成功,肿瘤面积大小与生长时间呈明显正相关(r=0.879),IVC管径与肿瘤面积大小显著负相关(r=-0.8295);4周时25%的IVC管腔闭塞,5周时达到91.7%。2.病理和免疫组化显示:3周时IVC管壁中见大量肿瘤细胞;5周时AA管壁中未见肿瘤细胞。3.DSA显示:IVC慢性受侵犯过程中侧枝循环建立良好。4.解剖观察:模型动物在第4周开始出现肝、肺和腹腔转移。结论 VX2肿瘤成瘤率高,其生长变化、对IVC的侵犯和远处器官转移均随生长时间而变化明显。     

Bone regeneration potential of allogeneic or autogeneic mesenchymal stem cells loaded onto cancellous bone granules in a rabbit radial defect model

For developing a clinically effective bone regeneration strategy, we compare the bone regeneration potential of cultured allogeneic bone marrow-derived mesenchymal stem cells (BM-MSCs) and of autologous BM-MSCs loaded onto allogeneic cancellous bone granule scaffolds. A critical-sized segmental bone defect was made at the mid-shaft of both radiuses in 19 New Zealand White rabbits (NWRs). In the experimental group, allogeneic BM-MSCs loaded onto small-sized allogeneic cancellous bone granules (300~700 um in diameter) were implanted in one side of a bone defect. In the control group, autologous BM-MSCs loaded onto allogeneic cancellous granules were grafted in the other side. Bone regeneration was assessed by radiographic evaluation at 4, 8, 12 and 16 weeks post-implantation and by micro-computed tomography (micro-CT) and histological evaluation at 8 and 16 weeks. The experimental groups showed lower bone quantity indices (BQIs) than the control groups at 12 and 16 weeks (p?<?0.05), although no significant difference was observed at 4 and 8 weeks (p?>?0.05). Micro-CT analysis revealed that both groups had similar mean total bone volume and other parameters including trabecular thickness, number and separation at either 8 or 16 weeks. Only bone surface area revealed less area in the experimental group at 16 weeks. Histological evaluation of 8-week and 16-week specimens showed similar biologic processes of new bone formation and maturation. There was no inflammatory reaction indicating an adverse immune response in both allogeneic and autologous MSC groups. In conclusion, allogeneic BM-MSCs loaded onto allogeneic cancellous bone granules had comparable bone regeneration potential to autologous BM-MSCs in a rabbit radial defect model.     

玉米醇溶蛋白动物体内植入后的免疫学分析方法初探

目的：为了考察玉米醇溶蛋白作为生物医用材料的应用前景,需要检测玉米醇溶蛋白植入后的免疫反应。本实验中我们将玉米醇溶蛋白管植入SD（Sprague Dawley）大鼠皮下,流式细胞仪检测植入后大鼠外周血中CD4^＋和CD8^＋T淋巴细胞含量的变化;对不同部位植入材料的组织学切片方法进行改进,用于后续机体免疫反应分析。方法：雄性SD大鼠八只,随机分成两组：空白对照组、材料植入组。分别于植入后一、二和四周对实验大鼠进行眼眶取血,并用流式细胞仪检测外周血中CD4^＋和CD8^＋T淋巴细胞的含量。皮下或肌袋植入材料四周后,将玉米醇溶蛋白管或三维多孔支架连同周围组织一起取出,用改进的石蜡切片方法制备组织切片,HE染色后观察。结果：玉米醇溶蛋白管植入后一周,蛋白管植入组CD4^＋（T—test,P〈0．01）和CD8^＋（T-test,P〈0．05）T淋巴细胞的含量下降。植入后两周和四周,蛋白管植入组CD4^＋和CD8^＋T淋巴细胞的含量（T—test,P〉0．05）均无明显变化。植入后一、二和四周,与空白对照组相比,蛋白管植入组CD4^＋／CD8^＋的比值（T—Test,P〉0．05）均无显著差异。改进后的切片方法可以制备出完整的、并且耐HE（hematoxylin—eosin）和免疫组化染色处理的组织学切片。结论：利用流式细胞仪检测出了大鼠皮下植入玉米蛋白管后外周血中CD4^＋、CD8^＋T淋巴细胞的含量变化。并且,克服了切片制备过程中材料的脆性问题和贴片不牢固问题,可以进行HE和免疫组化染色处理,为进一步深入地分析玉米醇溶蛋白植入机体后的免疫反应打下了基础。     

骨髓间充质干细胞源神经细胞移植治疗帕金森病大鼠模型

目的探讨骨髓间充质干细胞（mesenchymal stemcells,MSCs）源神经细胞脑内移植对帕金森病（Parkinson s disease,PD）大鼠的治疗作用。方法贴壁培养法分离、培养大鼠骨髓MSCs,脑匀浆上清诱导第3代MSCs向神经细胞分化,采用免疫细胞化学法鉴定诱导分化后细胞的性质,激光共聚焦显微镜检测诱导前后细胞Ca2＋浓度变化,6只PD大鼠行纹状体内MSCs源神经细胞移植作为细胞移植组,6只PD大鼠作为对照组。细胞移植术后4周检测PD大鼠的行为变化,观察移植细胞在脑内的分布情况。结果倒置显微镜下可见MSCs呈纺锤形和多角形,有1～2个核仁,MSCs经脑匀浆上清诱导后其胞体折光性增强,发出数个细长突起,互相交织成网,有的似轴突。诱导后细胞表达神经元特异性标志物神经元特异性烯醇化酶（NSE）和神经丝蛋白（NF）,胞质Ca2＋荧光强度显著增强,可推测诱导后的细胞为MSCs源神经细胞,将BrdU标记的MSCs源神经细胞移植到PD大鼠纹状体治疗4周后,可见细胞散在分布于注射侧脑组织,有少量细胞可迁移到对侧脑组织,PD大鼠的旋转行为得到显著改善。结论MSCs源神经细胞移植治疗帕金森病大鼠可使其旋转行为得到改善。     

植入了骨修复材料的小型猪腰椎椎体不脱钙病理组织切片制备方法

摘要 目的：建立植入了骨修复材料小型猪腰椎椎体骨组织标本的不脱钙病理组织切片制备方法。方法：将含骨修复材料的腰椎椎体骨组织标本进行分割暴露组织切面,梯度浓度乙醇脱水后经Technovit 7200 VLC光聚树脂浸润,经黄蓝光共同辐照进行光聚合包埋,借助硬组织病理切磨系统制备含骨修复材料不脱钙病理组织切片。结果：结果显示通过上述方法制备的病理组织切片,经苏木精-伊红（HE）染色及甲苯胺蓝染色后光学显微镜下观察能较好地显示骨的各种组织细胞结构,可清晰的观察到骨小梁的走向及连接情况。结论：研究建立了含骨修复材料骨组织标本病理组织切片制备方法,实现了含骨修复材料不脱钙骨组织病理切片的制备,经病理染色后实现了带植入物的组织学观察,为生物材料及医疗器械动物试验研究提供了新的病理检测手段及组织学评价途径。     

Accelerating tissue expansion by application of topical papaverine cream

The rate of tissue expansion can be accelerated by papaverine through a special delivery system, according to an early report. Because the delivery system was complex and inconvenient, another means of administrating papaverine was tested to observe the rate of tissue expansion. In this study, 24 miniature pigs were divided equally into three groups. Four 150-ml silicone expanders were implanted into each pig in groups A and C. Four modified rectangular silicone expanders were also implanted into each animal in group B. During the expansion process, 1 g of 2% hydrochloride papaverine cream was applied topically onto the surface of each pig's expanding skin in group A two times daily, and hydrochloride papaverine solution was injected into the outer shell of each modified expander in group B weekly. Group C acted as the control group. The mean sum of the first four times of saline water volume that was injected into the expanders was 142.42 +/- 5.6 ml in group A, 128.72+/-4.8 ml in group B, and 106.38+/-3.28 in group C. There were statistical differences among the three groups. The mean sum of volume saline water that was injected into hind expanders was 137.51 +/- 5.1 ml in group A, 120.35 +/- 3.6 ml in group B, and 102.63 +/- 4.76 ml in group C, and there was a statistical difference among the three groups as well. There was no statistically significant difference in the thickness of fibrous capsules among the three groups. This study shows that the rate of tissue expansion can be accelerated by topical application of papaverine cream, and the rate is better than the rate of tissue expansion induced by the special drug delivery system.     

Biocompatibility Studies of a New Biosynthetic Dermal Substitute Based on Collagen/Hyaluronan Conjugate

The use of glycosaminoglycans (GAGs) as the second macromolecular component with collagen for the membrane preparation is based on the idea to create a biodegradable scaffold for new tissue. A hybrid collagen/hyaluronan membrane with specific bubble macrostructure was designed to serve as a synthetic dermal substitute. The objectives were to explain the two questions: what is the local biological response to the implanted membrane, and what is its reconstruction rate in tissue. The histological study proved low irritability, good compatibility, ingrowth of autologous tissue starting on day 7 post implantation, and resorption within four weeks. The major part of the implant was replaced by autologous tissue at the end of three weeks post implantation. The overall local biological response to implant was very good.     

Use of hydrogel coating to improve the performance of implanted glucose sensors

In order to protect implanted glucose sensors from biofouling, novel hydrogels (146-217% water by mass) were developed based on a copolymer of hydroxyethyl methacrylate (HEMA) and 2,3-dihydroxypropyl methacrylate (DHPMA). The porosity and mechanical properties of the hydrogels were improved using N-vinyl-2-pyrrolidinone (VP) and ethyleneglycol dimethacrylate (EGDMA). The results of SEM and DSC FT-IT analyses showed that the hydrogel (VP30) produced from a monomeric mixture of 34.5% HEMA, 34.5% DHPMA, 30% VP and 1% EDGMA (mol%) had an excellent pore structure, high water content at swelling equilibrium (W eq=166% by mass) and acceptable mechanical properties. Two kinds of VP30-coated sensors, Pt/GOx/VP30 and Pt/GOx/epoxy-polyurethane (EPU)/VP30 sensors were examined in glucose solutions during a period of 4 weeks. The Pt/GOx/VP30 sensors produced large response currents but the response linearity was poor. Therefore, further studies were focused on the Pt/GOx/EPU/VP30 sensors. With a diffusion-limiting epoxy-polyurethane membrane, the linearity was improved (2-30 mM) and the response time was within 5 min. Eight Pt/GOx/EPU/VP30 sensors were subcutaneously implanted in rats and tested once per week over 4 weeks. All of the implanted sensors kept functioning for at least 21 days and 3 out of 8 sensors still functioned at day 28. Histology revealed that the fibrous capsules surrounding hydrogel-coated sensors were thinner than those surrounding Pt/GOx/EPU sensors after 28 days of implantation.     

Pulpal regeneration and root development after subcutaneous transplantation of cryopreserved immature teeth in rats

The purpose of this in vivo study was to investigate revascularization and root growth after autotransplantation of cryopreserved immature teeth. Immature molar teeth were extracted in 4-week-old Wistar rats. In the test group, teeth were cryopreserved for 1 week and transplanted subcutaneously to the abdomen. In the control group, teeth were transplanted subcutaneously immediately after extraction. Material was collected in test and control animals at intervals of 1, 2, 4 and 10 weeks post-transplantation and histological and microradiographical examination was performed. Results showed that during the first weeks after transplantation, pulpal repair was similar in both groups although degenerated pulpal tissue was replaced slower in cryopreserved teeth and some differences in types of hard tissue formation were found between test and control teeth. After 10 weeks, the differences in the regenerated pulpal tissue between cryopreserved and control teeth observed during the first weeks were no longer detectable. No root growth was detected microradiographically 10 weeks after transplantation in any of the transplanted teeth. The presence of dentin-like tissue in the pulp cavity of some autotransplanted cryopreserved teeth, suggests survival of pulpal tissue after cryopreservation.     

Gradual Thawing Improves the Preservation of Cryopreserved Arteries

This study was designed to test a slow, controlled, automated process for the thawing of cryopreserved arteries, whereby specimen warming is synchronized with the warming of its environment. Segments of minipig iliac artery, 4-5 cm in length, were subjected to controlled, automated cryopreservation in a biological freezer at a cooling rate of 1 degrees C/min to -120 degrees C, followed by storage in liquid nitrogen at -196 degrees C for 30 days. Following storage, the arterial segments were subjected to rapid (warming rate of approximately 100 degrees C/min) or gradual (1 degrees C/min) thawing. Thawed specimens were processed for light microscopy and for scanning and transmission electron microscopy, Cell death was determined by the TUNEL method. Metalloproteinase (MMP) expression was estimated by immunohistochemical analysis. Most of the cryopreserved vessels subjected to rapid thawing showed spontaneous fractures, mainly microfractures, whereas these were absent in slowly thawed specimens. In rapidly thawed vessels, the proportion of damaged cells was double that observed in those thawed more gradually. Increased intensity and extent of MMP-2 expression was shown by rapidly thawed specimens. The slow-thawing protocol tested avoids the formation of spontaneous fractures and microfractures and the accumulation of fluid within the arterial wall tissue. This results in improved tissue preservation.     

Inertia effects on characterization of dynamic response of brain tissue

Modeling and simulation of traumatic brain injury (TBI) resulted from collision or blast loading requires characterization of mechanical response over a wide range of loading rates under valid testing conditions. In this study, mechanical response of fresh bovine brain tissue was studied using the two modified Kolsky bar techniques. Radial deformation behavior of annular specimens, which are typically used to characterize the dynamic uniaxial compressive response of biological tissues, was examined using a modified Kolsky bar and a high speed camera to collect images while the specimen deforms at an axial strain rate of 2000s(-1). The high-speed images revealed inhomogeneous specimen deformation possibly brought about by radial inertia and causing a multi-axial stress state. To acquire valid stress-strain results that can be used to produce constitutive behavior of the soft materials, a novel torsion technique was developed to obtain pure shear response at dynamic loading rates. Experimental results show clear differences in the material response using the two methods. These results indicate that the previously demonstrated annular specimen geometry aimed at reducing inertia induced stress components for high rate soft materials uniaxial-compressive testing may still possess a significant component of radial inertia induced radial stress which consequently caused the observed inhomogeneous deformation in brain tissue test samples.     

Cerebrovascular response after interstitial irradiation.

To characterize the role of the cerebrovascular response in the development of brain injury after focal irradiation, 125I sources were implanted in frontal white matter of the brain of normal dogs; dose was 20 Gy, 7.5 mm from the source. Cerebral blood flow, vascular volume and mean transit time of blood were quantified in irradiated tissues relative to tissues in the contralateral hemisphere and analyzed with respect to previously determined volumetric measurements of damage and the blood-to-brain transfer constant. Blood flow and vascular volume within the radiation-induced focal lesion were maximally reduced 3 weeks after implant, when necrosis volume was maximal. By 6 weeks, vascular volume and mean transit time were increased, suggesting a strong neovascular response. In tissues surrounding the lesion, blood flow and vascular volume were reduced 1-4 weeks after irradiation and approached normal at 6 weeks; average mean transit time was not altered significantly. Alterations in blood flow and mean transit time were significantly related to edema volume and transfer constant, but alterations in vascular volume were not, suggesting that edema-induced vascular compression was not responsible for changes in blood flow. Reductions of radiation-induced permeability of the blood-brain barrier and/or edema might limit radiation-induced changes in blood flow and the extent of tissue injury.     

Increased matrix metalloproteinase-3 mRNA expression in visceral fat in mice implanted with cultured preadipocytes

Using preadipocyte implantation methods, we recently demonstrated that adipocytes in the visceral area change their function, as the expression of tumor necrosis factor-alpha (TNF-alpha) increases, thereby causing insulin resistance. In order to clarify the mechanism for changes in the function of adipocytes in visceral area, we examined the mRNA expression profiles in visceral fat tissue specimens. Four weeks after cell implantation, we performed a microarray analysis using the RNA of fat tissue specimens implanted either with 3T3-L1 cells or PBS alone. Sixty-three genes were thus isolated and the expression of matrix metalloproteinase-3 (MMP-3) mRNA was found to dramatically increase in the fat tissue specimens. The neutralization of MMP-3 protein inhibited adipogenesis and the free fatty acid-induced TNF-alpha secretion in 3T3-L1 adipocytes. These results suggest a potential role of MMP-3, which promotes the TNF-alpha secretion, thus contributing to the disturbance of the functions in the adipocytes which accumulate in the visceral area.     

Biorheological characteristics of skin after expansion

This study investigated the changes in biorheological characteristics of skin after expansion. Expanders were implanted into the back of eight adult dogs, and after an eight-week expansion the expanded and the non-expanded control skins were transferred to an adjacent site. The expanded specimens and their controls were obtained at 3, 6, 12 and 24 weeks after transfer, and their biorheological characteristics and histological changes were studied. The characteristics of the stress-relaxation, the stress-strain relationship and tensile strength of the expanded and control specimens were measured. The tests demonstrated that during the initial stage after transfer, the biorheological properties of experimental specimens differed significantly from those of their controls. However, the differences between expanded and control specimens began to lessen gradually with increasing recovery time. When the recovery time reached 24 weeks or longer, the experimental skin exhibited the same mechanical properties as the control skin. Histological examination of expanded specimens showed thickened epidermis and thinned dermis. But there were no significant histological differences between expanded skins and their controls after 24 weeks.