Heterogeneous engineered cartilage growth results from gradients of media-supplemented active TGF-β and is ameliorated by the alternative supplementation of latent TGF-β.
Heterogeneous engineered cartilage growth results from gradients of media-supplemented active TGF-β and is ameliorated by the alternative supplementation of latent TGF-β.
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DOI：
10.1016/j.biomaterials.2015.10.018
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发表时间：
2016-01
期刊：
影响因子：
14
通讯作者：
Ateshian GA
中科院分区：
文献类型：
--
作者：
Albro MB;Nims RJ;Durney KM;Cigan AD;Shim JJ;Vunjak-Novakovic G;Hung CT;Ateshian GA
转化生长因子β（TGF-β）已成为工程软骨生长中使用最广泛的介质之一。它通常以其活性形式外源地补充在培养基中，期望它能够通过被动扩散容易地转运到组织构建体中并均匀地影响细胞生物合成。这项研究的结果提出了关于 TGF-β 在软骨组织工程中的作用的三个新概念，这些概念对组织发育具有重要意义。首先，通过对 TGF-β 浓度分布的实验和计算分析，我们证明，与传统预期相反，补充培养基的外源活性 TGF-β 在组织结构中表现出明显的浓度梯度，这是由高亲和力结合相互作用和高细胞内化率相结合造成的。这些梯度在整个培养期间持续存在，导致高度异质的组织生长；生化和组织学测量结果表明，虽然构建体外围的生化含量增强了 4 倍，但构建体表面 1 毫米以外的区域完全没有增强。其次，构建体封装的软骨细胞持续分泌大量潜在形式的内源性TGF-β，其中一部分经历细胞介导的激活并在整个组织中均匀地增强生物合成。最后，受这些先前见解的启发，我们证明额外的外源性潜在 TGF-β 的替代补充可以增强整个组织结构的生物合成，从而导致增强但均匀的组织生长。这一新颖的论证表明，潜在的 TGF-β 补充剂可用作大型软骨结构转化工程的重要工具，而大型软骨结构是修复临床观察到的大型骨关节炎缺陷所必需的。
Transforming growth factor beta (TGF-β) has become one of the most widely utilized mediators of engineered cartilage growth. It is typically exogenously supplemented in the culture medium in its active form, with the expectation that it will readily transport into tissue constructs through passive diffusion and influence cellular biosynthesis uniformly. The results of this investigation advance three novel concepts regarding the role of TGF-β in cartilage tissue engineering that have important implications for tissue development. First, through the experimental and computational analysis of TGF-β concentration distributions, we demonstrate that, contrary to conventional expectations, media-supplemented exogenous active TGF-β exhibits a pronounced concentration gradient in tissue constructs, resulting from a combination of high-affinity binding interactions and a high cellular internalization rate. These gradients are sustained throughout the entire culture duration, leading to highly heterogeneous tissue growth; biochemical and histological measurements support that while biochemical content is enhanced up to 4-fold at the construct periphery, enhancements are entirely absent beyond 1 mm from the construct surface. Second, construct-encapsulated chondrocytes continuously secrete large amounts of endogenous TGF-β in its latent form, a portion of which undergoes cell-mediated activation and enhances biosynthesis uniformly throughout the tissue. Finally, motivated by these prior insights, we demonstrate that the alternative supplementation of additional exogenous latent TGF-β enhances biosynthesis uniformly throughout tissue constructs, leading to enhanced but homogeneous tissue growth. This novel demonstration suggests that latent TGF-β supplementation may be utilized as an important tool for the translational engineering of large cartilage constructs that will be required to repair the large osteoarthritic defects observed clinically.