不同扩张方案下离体皮肤的生物力学特性比较

整形外科中，人们希望用快速扩张来代替常规扩张，因为这样可以大大缩短扩张时间。然而快速扩张后的皮肤特性是否接近于常规扩张，这是人们所关切的问题。据此本研究进行了快速和常规扩张的离体皮肤生物力学特性的比较。离体生物力学各参数，如强度、应力一应变、应力松弛、蠕变等参数在Instron实验机上的测定和计算结果表明：扩张后的短时期内，扩张皮肤的力学性能相对于其对照组发生较大的偏离；但随着维持时间的增加，扩张皮肤的力学性能又逐渐接近其对照组。对于同样的维持时间，快速扩张和常规扩张对生物力学性质影响区别不大。因此可以得出结论：快速扩张组的生物力学特性十分接近于常规扩张组；延长维持时间可以改变皮肤的生物力学性质，使之与对照组接近。因此，临床上可以采取缩短扩张期，延长维持期的方法来提高疗效。     

皮肤扩张粘弹性实用分析

皮肤创伤修复中,需要移植自身扩张的皮肤.随着医学的发展,现在快速扩张法已逐渐代替常规扩张,因为这样可以大大缩短扩张时间.扩张皮肤的粘弹性分析,将从力学角度确定快速扩张是否可以取代常规扩张.以往包括应力松弛和蠕变的粘弹性分析等是用复杂的连续谱来描述,临床医学接受较为困难.本文采用反映应力松弛和蠕变的速度和程度,即斜率和最终应力松弛和蠕变量作标准,易于临床上采用.并证明快速扩张粘弹性十分接近常规扩张,延长维持时间可以改变皮肤的粘弹性性质,使之与对照组接近,因此临床上可以采取缩短扩张期和延长维持期的方法来提高扩张效果.     

反复快速皮肤扩张可促进皮瓣表皮生长因子及增殖细胞核抗原的表达

背景：针对目前临床常用的常规扩张法与快速扩张法的不足,提出了反复快速皮肤扩张法。 目的：观察反复快速皮肤扩张对皮瓣表皮生长因子、增殖细胞核抗原表达的影响。 方法：雄性新西兰大白兔随机分为3组：反复快速扩张组、快速扩张组、常规扩张组。 结果与结论：扩张维持第2,3周,反复快速扩张组皮瓣表皮生长因子表达显著高于快速扩张组、常规扩张组 (P < 0.05)。除扩张维持第3周外,其余各时间段,反复快速扩张组成纤维细胞增殖细胞核抗原染色阳性率均显著高于其他两组 (P < 0.05)。扩张维持第4周,反复快速扩张组表皮细胞增殖细胞核抗原染色阳性率显著高于其他组(P < 0.05)。提示反复快速皮肤扩张可能通过促进组织细胞合成与分泌皮瓣表皮生长因子,促进了扩张皮肤中成纤维细胞及表皮细胞的增殖。     

扩张皮肤移植后的生物力学特性

对狗背部扩张后和相应对照侧的皮肤软组织在移植后的不同阶段 ,分别进行应力 应变、应力松弛特性和极限抗拉强度实验。在移植后的短时期内 ,扩张组的力学性能相对于其对照组发生较大的偏离 ;但随着移植后恢复时间的增加 ,扩张组的力学性能又逐渐接近其对照组。扩张试件在移植后 2 4周的生物力学性能基本恢复。     

常规与快速扩张后狗皮肤组织形态学的研究

对常规与快速扩张后的狗皮肤进行了形态结构的观察和分析。结果显示：常规扩张后的皮肤与正常皮肤相比较，其表皮细胞间隙轻度增宽。其厚度，ＤＮＡ积分光密度及平均光密度无显著差异。     

扩张皮肤的生物力学和组织化学研究

采用人体皮肤扩张的最佳动物模型,进行模拟临床皮肤扩张的研究。最后一次注水后的第1、2、3天,在扩张和正常皮肤上切取纵横两个方向的样条进行皮肤生物力学的研究。同时在扩张皮肤的中心、中部和边缘取小块标本,在临近周围取小块正常皮肤标本,观察和测定其胶原纤维、弹性纤维、琥珀酸脱氢酶(SDH)和酸性磷酸酶(ACP)。扩张后第1、2天的应力一应变曲线,有明显的变化,但第3天的曲线逐渐恢复至正常状态。组织化学的平均密度变化与生物力学特性的变化具有相同的趋势。     

扩张皮肤移植后的生物力学变化

背景：应用皮肤软组织扩张器植入正常的皮肤软组织下,通过增加扩张器内的容量,对皮肤表面软组织产生压力,使其扩张产生“额外”的皮肤软组织,已成为皮肤组织工程研究领域的基本技术手段。 目的：通过狗皮肤扩张移植模型了解扩张皮肤在移植后的近期和远期的变化规律。 方法：随机抽取12只成年狗,在其背部置入150 mL的4个扩张器,其中2个不扩张进行对照。测试扩张不同时间后皮肤应力-应变、应力松弛、极限抗拉强度的结果,并对比分析测定结果。 结果与结论：经过扩张,皮肤的黏弹性、强度发生明显降低,黏弹性可在移植后6个月恢复,强度恢复较慢。在行皮肤移植后,生物力学的变化仅为暂时现象,可以恢复至正常,临床应给予关注。     

药物辅助扩张皮瓣的本构关系及其临床意义

研究药物辅助扩张皮瓣的本构关系以及对其生物力学特性进行数学描述，探讨其临床意义，为应用和推广药物辅助组织扩张技术提供理论基础。以小型猪为实验动物，分为用药扩张组和常规扩张组，用药扩张组在组织扩张过程中外用罂粟碱霜，两组均在扩张过程中取皮瓣试件，进行应力-应变测定，并拟合出试件的应力-应变理论曲线和本构方程。结果表明，药物辅助扩张皮瓣和常规扩张皮瓣的本构关系均可用指数函数形式的本构方程和应力-应变理论曲线描述，药物辅助扩张皮瓣的粘弹性较常规扩张皮瓣有提高和增强的趋势。表明移植时扩张皮瓣，选择药物辅助扩张皮瓣可减缓组织张力的增加，有利于创面愈合和扩大修复范围。     

抚平岁月皱纹 绽放青春光彩

每个女士都希望永远拥有年轻美丽的肌肤，永不衰老。然而，匆匆岁月总是无情，许多大龄女士都希望找到一种灵丹妙药，可以帮助他们消除面容上的皱纹、色斑、白发，令容颜重新焕发青春。如何才能延长我们的青春呢?先让我们来科学地认识一下皮肤衰老的过程。     

同种小鼠皮肤移植时的肿瘤坏死因子水平

ｐ＜０．０１二、红毛五加水提物对血清ＴＮＦ－α的影响ＡＨ各组在延长皮片存活时间同时，血清中ＴＮＦ－α水平随剂量增加而升高，在１．５、３．０、６．０ｇ／ｋｇ剂量时，ＴＮＦ－α水平与ＮＳ组比较，未见显著性差异（ｐ＞０．０５），但是，ＡＨ各组血清ＴＮＦ－α水平与Ａｚａ组比较，有显著性差异（ｐ＜０．０１），结果见表２。表２ＤＢＡ／２受体小鼠血清肿瘤坏死因子变化（ｎｇ／ｍｌ）注：与Ａｚａ组比较，＊ｐ＜０．０１，与ＮＳ组比较ｐ＞０．０５讨论肿瘤坏死因子（ＴＮＦ－α）是一种重要的免疫调节因子，可由巨噬细胞、单核细胞、ＮＫ细胞等非特异性免疫细胞产生，个有广泛的生物学效应，并且在器官移植中已开始引起人们的注意［３］。对中药进行筛选，发掘具有免疫抑制作用的药物用于临床，减少器官移植排斥反应是器官移植领域的重要研究内容之一。实验动物皮肤移植模型操作简便，易于观察，是初筛免疫排斥抑制剂的有效方法。Ａｚａ在延长移植皮片存活时间时，血清中ＴＮＦ－α水平明显低于ＮＳ组（ｐ＜０．０１），可见，降低血清ＴＮＦ－α水平与延长皮片存活时间有关。然而，在本实验中，ＡＨ各组在延长皮片存活时间时，一方面，ＴＮＦ－α水平未见降低，另一方面，从ＡＨ量──     

Bioreactor maintained living skin matrix

Numerous reconstructive procedures result in wounds that require skin grafting. Often, the amount of tissue available from donor sites is limited. In vivo tissue expanders have been used clinically to generate larger sections of skin, and other methods exist to cover large wounds, but all have significant limitations. We investigated whether these difficulties could be overcome by increasing the surface area of skin in vitro while maintaining tissue viability. Human foreskin was incrementally expanded in a computer-controlled bioreactor system over 6 days to increase its surface dimensions under culture conditions. Morphological, ultrastructural, and mechanical properties of the foreskin were evaluated before and after expansion using histology, scanning electron microscopy, mercury porosimetry, and tensile testing. The surface area of the tissue was 110.7% +/- 12.2% greater, with maintenance of cell viability and proliferative potential. Histomorphological and ultrastructural analyses showed that dermal structural integrity was preserved. The pore diameter of the expanded skin was 64.49% +/- 32.8% greater. The mechanical properties were not adversely affected. These findings show that expansion of living skin matrices can be achieved using a computer-controlled bioreactor system. This technique provides an opportunity to generate large amounts of skin for reconstructive procedures.     

Epithelial and stromal developmental patterns in a novel substitute of the human skin generated with fibrin-agarose biomaterials

Development of human skin substitutes by tissue engineering may offer new therapeutic alternatives to the use of autologous tissue grafts. For that reason, it is necessary to investigate and develop new biocompatible biomaterials that support the generation of a proper human skin construct. In this study, we generated a novel model of bioengineered human skin substitute using human cells obtained from skin biopsies and fibrin-agarose biomaterials and we evaluated this model both at the ex vivo and the in vivo levels. Once the dermal fibroblasts and the epithelial keratinocytes were isolated and expanded in culture, we used fibrin-agarose scaffolds for the development of a full-thickness human skin construct, which was evaluated after 1, 2, 3 and 4 weeks of development ex vivo. The skin substitutes were then grafted onto immune-deficient nude mice and analyzed at days 10, 20, 30 and 40 postimplantation using transmission electron microscopy, histochemistry and immunofluorescence. The results demonstrated that the fibrin-agarose artificial skin had adequate biocompatibility and proper biomechanical properties. A proper development of both the bioengineered dermis and epidermis was found after 30 days in vivo, although the tissues kept ex vivo and those implanted in the animal model for 10 or 20 days showed lower levels of differentiation. In summary, our model of fibrin-agarose skin equivalent was able to reproduce the structure and histological architecture of the native human skin, especially after long-term in vivo implantation, suggesting that these tissues could reproduce the native skin.     

Measurement of skin stretch via light reflection

A noninvasive technique for measuring the stretch of skin is described. The technique utilizes changes in the reflectivity of polarized light intensity as a monitor of skin stretch. Measurements of in vitro pigskin and in vivo human skin show that the reflectivity of polarized light intensity increases linearly with stretch. The changes in diffusive reflectivity properties of skin result from the alterations that take place in the roughness across the thickness of the skin layers due to stretch. Conceptually, as the roughness of a layer decreases with stretch, a smoother reflecting media is produced, resulting in a proportional increase in the specular reflection. Results can be easily extended to a real-time stretch analysis of large tissue areas that would be applicable for mapping the stretch of skin.