Department of Materials Science and Engineering, Ohio State University, Columbus, OH 43210, USA.
Biomaterials. 2011 Apr;32(12):3220-32. doi: 10.1016/j.biomaterials.2011.01.050. Epub 2011 Feb 5.
A family of injectable and thermosensitive hydrogels suitable for myocardial injection was developed to deliver cardiosphere-derived cells (CDCs), an emerging and promising cell type for cardiac cell therapy. The hydrogels were based on polycaprolactone, N-isopropylacrylamide, 2-hydroxyethyl methacrylate and dimethyl-γ-butyrolactone acrylate. Atom transfer radical polymerization was used to synthesize hydrogels with a well-defined structure and well-controlled properties. The hydrogel solutions possessed thermal transition temperatures around room temperature and exhibited injectability suitable for myocardial injection. At 37 °C, the hydrogel solutions were capable of forming solid gels within 5s. This would allow the hydrogels to largely retain in the heart during injection. The hydrogels were highly flexible at body temperature with moduli matching those of the rat and human myocardium, and breaking strains higher than those of the myocardium, enabling them to respond synchronically with heart motion. The well-controlled polymer structure allowed for precisely controlling and decoupling water content and stiffness that affect cell differentiation. DNA assay demonstrated that CDCs proliferated in the 3D hydrogels during a 2-week culture period. CDCs maintained their colony formation capability in the hydrogel. Interestingly, hydrogels directed CDCs differentiation into mature cardiac lineage. At mRNA level, the mature cardiac specific transcript factors cardiac troponin T (cTnT) and cardiac myosin heavy chain (MYH6) were up-regulated, while the pre-mature cardiac marker GATA4 was down-regulated even after 1 day of encapsulation. CDC differentiation was interplayed by hydrogel stiffness and collagen in the hydrogel. Hydrogel with modulus ∼31 kPa was found to more significantly up-regulate cardiac expression than that with modulus ∼5 or ∼63 kPa. cTnT expression was largely regulated by both stiffness and collagen while MYH6 was mainly regulated by stiffness. Immunohistochemistry study showed that CDCs expressed cardiac troponin I and MYH6 proteins after 2 weeks of culture. These results demonstrate that the thermosensitive hydrogels not only possess physical properties suitable for myocardial injection, but also promote CDC proliferation and cardiac differentiation. These hydrogels represent potential candidates for delivery of CDCs into infarcted hearts.
一种适用于心肌内注射的可注射和温敏水凝胶家族被开发出来，用于递送心脏球源性细胞（CDC），这是一种新兴的、有前途的心脏细胞治疗细胞类型。该水凝胶基于聚己内酯、N-异丙基丙烯酰胺、2-羟乙基甲基丙烯酸酯和二甲基-γ-丁内酯丙烯酸酯。原子转移自由基聚合被用于合成具有明确定义结构和良好控制性能的水凝胶。水凝胶溶液具有接近室温的热转变温度，并表现出适合心肌内注射的可注射性。在 37°C 下，水凝胶溶液在 5s 内能够形成固体凝胶。这将使水凝胶在注射过程中大部分保留在心脏内。水凝胶在体温下具有高度的柔韧性，其模量与大鼠和人心肌相匹配，断裂应变高于心肌，使其能够与心脏运动同步响应。良好控制的聚合物结构允许精确控制和解耦影响细胞分化的水含量和刚度。DNA 分析表明，CDC 在为期 2 周的培养过程中在 3D 水凝胶中增殖。CDC 在水凝胶中保持其集落形成能力。有趣的是，水凝胶指导 CDC 分化为成熟的心脏谱系。在 mRNA 水平上，成熟的心脏特异性转录因子肌钙蛋白 T（cTnT）和心脏肌球蛋白重链（MYH6）上调，而早期心脏标志物 GATA4 即使在包封 1 天后也下调。CDC 分化受到水凝胶刚度和水凝胶中胶原的相互作用。发现模量约为 31kPa 的水凝胶比模量约为 5kPa 或 63kPa 的水凝胶更显著地上调心脏表达。cTnT 表达主要受刚度和胶原调节，而 MYH6 主要受刚度调节。免疫组织化学研究表明，CDC 在培养 2 周后表达心脏肌钙蛋白 I 和 MYH6 蛋白。这些结果表明，温敏水凝胶不仅具有适合心肌内注射的物理性质，而且还促进了 CDC 的增殖和心脏分化。这些水凝胶代表了将 CDC 递送到梗死心脏的潜在候选物。
