Tissue Engineering, VA Boston Healthcare System, Boston, MA 02130, USA.
Biomaterials. 2012 May;33(15):3835-45. doi: 10.1016/j.biomaterials.2012.01.065. Epub 2012 Feb 25.
An injectable and biodegradable hydrogel system comprising hyaluronic acid-tyramine (HA-Tyr) conjugates can safely undergo covalent cross-linking in vivo by the addition of small amounts of peroxidase and hydrogen peroxide (H(2)O(2)), with the independent tuning of the gelation rate and degree of cross-linking. Such hydrogel networks with tunable mechanical and degradation properties may provide the additional level of control needed to enhance chondrogenesis and overall cartilage tissue formation in vitro and in vivo. In this study, HA-Tyr hydrogels were explored as biomimetic matrices for caprine mesenchymal stem cells (MSCs) in cartilage tissue engineering. The compressive modulus, equilibrium swelling and degradation rate could be controlled by varying the concentration of H(2)O(2) as the oxidant in the oxidative coupling reaction. Cellular condensation reflected by the increase in effective number density of rounded cells in lacunae was greater in softer hydrogel matrices with lower cross-linking that displayed enhanced scaffold contracture. Conversely, within higher cross-linked matrices, cells adopted a more elongated morphology, with a reduced degree of cellular condensation. Furthermore, the degree of hydrogel cross-linking also modulated matrix biosynthesis and cartilage tissue histogenesis. Lower cross-linked matrix enhanced chondrogenesis with increases in the percentage of cells with chondrocytic morphology; biosynthetic rates of glycosaminoglycan and type II collagen; and hyaline cartilage tissue formation. With increasing cross-linking degree and matrix stiffness, a shift in MSC differentiation toward fibrous phenotypes with the formation of fibrocartilage and fibrous tissues was observed. These findings suggest that the tunable three-dimensional microenvironment of the HA-Tyr hydrogels modulates cellular condensation during chondrogenesis and has a dramatic impact on spatial organization of cells, matrix biosynthesis, and overall cartilage tissue histogenesis.
一种包含透明质酸-酪胺（HA-Tyr）缀合物的可注射和可生物降解的水凝胶系统可以通过添加少量过氧化物酶和过氧化氢（H2O2）在体内安全地进行共价交联，并且可以独立调节凝胶速率和交联程度。具有可调节机械性能和降解特性的这种水凝胶网络可能提供了增强体外和体内软骨形成所需要的额外控制水平。在这项研究中，HA-Tyr 水凝胶被探索作为山羊间充质干细胞（MSCs）在软骨组织工程中的仿生基质。通过改变 H2O2 的浓度作为氧化偶联反应中的氧化剂，可以控制压缩模量、平衡溶胀和降解速率。细胞浓缩反映为陷窝中圆形细胞的有效数密度增加，在交联较低的较软水凝胶基质中更大，显示出增强的支架收缩。相反，在较高交联的基质中，细胞采用更细长的形态，细胞浓缩程度降低。此外，水凝胶交联程度也调节基质生物合成和软骨组织发生。较低交联基质增强软骨形成，增加具有软骨细胞形态的细胞百分比；糖胺聚糖和 II 型胶原的生物合成率；以及透明软骨组织的形成。随着交联程度和基质硬度的增加，MSC 分化向纤维表型转变，形成纤维软骨和纤维组织。这些发现表明，HA-Tyr 水凝胶的可调三维微环境调节软骨形成过程中的细胞浓缩，并对细胞、基质生物合成和整体软骨组织发生的空间组织产生巨大影响。
