Department of Bioengineering, University of Washington, Seattle, WA 98195, USA.
Tissue Eng Part A. 2013 Apr;19(7-8):967-77. doi: 10.1089/ten.tea.2012.0286. Epub 2013 Jan 14.
Myocardial infarction (MI) causes significant cell loss and damage to myocardium. Cell-based therapies for treatment of MI aim to remuscularize the resultant scar tissue, but the majority of transplanted cells do not survive or integrate with the host tissue. Scaffolds can improve cell retention following construct implantation, but often do little to enhance host-graft integration and/or show limited biodegradation. Fibrin is an ideal biomaterial for cardiac tissue engineering as it is a natural, biodegradable polymer that can induce neovascularization, promote cell attachment, and has tunable mechanical properties. Here we describe a novel, high-density microtemplated fibrin scaffold seeded with a tri-cell mixture of cardiomyocytes, endothelial cells (ECs), and fibroblasts to mimic native cardiac tissue in structure and cellular composition to improve cell retention and promote integration with the host tissue. Scaffolds were designed with uniform architecture of parallel 60 μm microchannels surrounded by an interconnected microporous network of 27-μm-diameter pores and mechanical stiffness comparable to native cardiac tissues (70-90kPa). Scaffold degradation was controlled with the addition of Factor XIII (FXIII) and/or protease inhibitor (aprotinin). Unmodified scaffolds had a fast degradation profile both in vitro (19.9%±3.9% stiffness retention after 10 days) and in vivo. Scaffolds treated with FXIII showed an intermediate degradation profile in vitro (45.8%±5.9%), while scaffolds treated with aprotinin or both FXIII and aprotinin showed significantly slowed degradation in vitro (60.9%±5.2% and 76.4%±7.6%, respectively, p<0.05). Acellular aprotinin scaffold myocardial implants showed decreased collagen deposition after 7 days. Unmodified and aprotinin implants could not be located by 14 days, while 2 of 8 FXIII implants were found, but were significantly degraded. Constructs supported seeded cell survival and organization in vitro, promoting EC-lined lumen structure formation in construct channels and colocalization of viable ECs and cardiomyocytes. In addition, constructs promoted extracellular matrix deposition by seeded cells, as shown by collagen staining within construct channels and by significant increases in construct stiffness over 10 days in vitro (209%±32%, p<0.05). The data suggest our fibrin scaffolds are ideally designed to promote graft cell survival and organization, thus improving chances of promoting construct integration with the host tissue upon implantation.
心肌梗死（MI）会导致心肌大量细胞丧失和损伤。用于 MI 治疗的基于细胞的疗法旨在使梗死部位的瘢痕组织再肌化，但大多数移植细胞不能存活或与宿主组织整合。支架可以提高构建体植入后的细胞保留率，但通常对增强宿主-移植物整合作用不大，或者显示出有限的生物降解性。纤维蛋白是心脏组织工程的理想生物材料，因为它是一种天然的、可生物降解的聚合物，可以诱导新血管生成、促进细胞附着，并且具有可调节的机械性能。在这里，我们描述了一种新型的、高密度的微模板纤维蛋白支架，该支架种有由心肌细胞、内皮细胞（EC）和成纤维细胞组成的三细胞混合物，以在结构和细胞组成上模拟天然心脏组织，从而提高细胞保留率并促进与宿主组织的整合。支架的设计具有均匀的结构，由 60μm 的平行微通道组成，周围是 27μm 直径的相互连接的微孔网络，机械刚度与天然心脏组织相当（70-90kPa）。通过添加因子 XIII（FXIII）和/或蛋白酶抑制剂（抑肽酶）来控制支架的降解。未修饰的支架在体外（10 天后刚度保留率为 19.9%±3.9%）和体内均具有快速降解的特征。在体外，用 FXIII 处理的支架表现出中间降解谱（45.8%±5.9%），而用抑肽酶或 FXIII 和抑肽酶处理的支架在体外的降解速度明显减慢（分别为 60.9%±5.2%和 76.4%±7.6%，p<0.05）。无细胞抑肽酶支架心肌植入物在 7 天后胶原沉积减少。14 天后无法定位未修饰和抑肽酶植入物，而 8 个 FXIII 植入物中有 2 个被发现，但降解明显。构建物支持种子细胞的存活和组织，促进了构建物通道中 EC 衬里管腔结构的形成，并使存活的 ECs 和心肌细胞共定位。此外，构建物促进了种子细胞的细胞外基质沉积，如在构建物通道内的胶原染色以及体外 10 天内构建物刚度的显著增加（209%±32%，p<0.05）所示。数据表明，我们的纤维蛋白支架的设计理想，可促进移植物细胞的存活和组织，从而提高移植物与宿主组织整合的机会。
