Diffusion limits of an in vitro thick prevascularized tissue
Diffusion limits of an in vitro thick prevascularized tissue
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DOI：
10.1089/ten.2005.11.257
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发表时间：
2005-01-01
影响因子：
--
通讯作者：
George, SC
中科院分区：
文献类型：
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作者：
Griffith, CK;Miller, C;George, SC
尽管组织工程学承诺替换或恢复人体内几乎每一个组织失去的功能，但目前成功的应用仅限于厚度小于2毫米的组织。体内毛细血管网络将氧气和营养物质输送到较厚(2毫米)的组织中，这表明引入预制的体外血管网络可能是工程组织的有用策略。本文描述了一种在厚厚的纤维蛋白基质中生成毛细血管样网络的系统。生长在微载体珠表面的人脐静脉内皮细胞被嵌入纤维蛋白凝胶中，距离人皮肤成纤维细胞的单层已知距离(Delta=1.8-4.5 mm)。含有血管内皮生长因子和碱性成纤维细胞生长因子的生长介质与微珠C的距离为2.7~7.2 mm。可见管腔的毛细血管在2-3天内萌发，6-8天内长度超过500微米。在第7天，毛细血管网络的形成基本上与C无关，但与Delta呈强烈的负相关，在Delta=1.8 mm时网络形成最大。令人惊讶的是，凝胶的厚度并不是氧气扩散的限制因素，因为这些组织结构保持了相对较高的氧分压>；125 mmHg。我们得出的结论是，氧气在体外的扩散是不受限制的，允许组织结构在厘米量级上的发展。此外，成纤维细胞来源的可溶性介质的扩散对于稳定的毛细血管形成是必要的，但相对于培养液中存在的营养物质，扩散是显著受阻的。
Although tissue engineering promises to replace or restore lost function to nearly every tissue in the body, successful applications are currently limited to tissue less than 2 mm in thickness. In vivo capillary networks deliver oxygen and nutrients to thicker (>2 mm) tissues, suggesting that introduction of a preformed in vitro vascular network may be a useful strategy for engineered tissues. This article describes a system for generating capillary-like networks within a thick fibrin matrix. Human umbilical vein endothelial cells, growing on the surface of microcarrier beads, were embedded in fibrin gels a known distance ( Delta = 1.8 - 4.5 mm) from a monolayer of human dermal fibroblasts. The distance of the growth medium, which contained vascular endothelial growth factor and basic fibroblast growth factor, from the beads, C, was varied from 2.7 to 7.2 mm. Capillaries with visible lumens sprouted in 2 - 3 days, reaching lengths that exceeded 500 mu m within 6 - 8 days. On day 7, capillary network formation was largely independent of C; however, a strong inverse correlation with Delta was observed, with the maximum network formation at Delta = 1.8 mm. Surprisingly, the thickness of the gel was not a limiting factor for oxygen diffusion as these tissue constructs retained a relatively high oxygen tension of > 125 mmHg. We conclude that diffusion of oxygen in vitro is not limiting, allowing the development of tissue constructs on the order of centimeters in thickness. In addition, diffusion of fibroblast-derived soluble mediators is necessary for stable capillary formation, but is significantly impeded relative to that of nutrients present in the medium.