Napolitano Anthony P, Chai Peter, Dean Dylan M, Morgan Jeffrey R
Department of Molecular Pharmacology, Physiology, and Biotechnology, Center for Biomedical Engineering, Brown University, Providence, Rhode Island, USA.
Tissue Eng. 2007 Aug;13(8):2087-94. doi: 10.1089/ten.2006.0190.
The process by which cells self-assemble to form three-dimensional (3D) structures is central to morphogenesis and development of living tissues and hence is of growing interest to the field of tissue engineering. Using rapid prototyping technology we made micromolded nonadhesive hydrogels to study the dynamics of self-assembly in a low-shear environment with simple spherical geometries as well as more complex geometries such as a toroid. Aggregate size, shape, and composition were easily controlled; aggregates were easily retrieved; and the dynamics of the assembly process were readily observed by time-lapse microscopy. When two cell types, normal human fibroblasts (NHFs) and human umbilical vein endothelial cells (HUVECs), were seeded together, they self-segregated into multilayered spherical microtissues with a core of NHFs enveloped by a layer of HUVECs. Surprisingly, when a single cell suspension of NHFs was added to 7-day-old HUVEC spheroids, the HUVEC spheroid reorganized such that NHFs occupied the center and HUVECs coated the outside, demonstrating that self-assembly is not terminal and that spheroids are fluid structures that retain the ability to reassemble. We also showed that cells can self-assemble to form a complex toroid shape, and we observed several phenomena indicating that cellular contraction and tension play a significant role in the assembly process of complex shapes.
细胞自我组装形成三维（3D）结构的过程是生物组织形态发生和发育的核心，因此在组织工程领域越来越受到关注。我们使用快速成型技术制作了微模制非粘性水凝胶，以研究在低剪切环境中具有简单球形几何形状以及更复杂几何形状（如环形）的自我组装动力学。聚集体的大小、形状和组成易于控制；聚集体易于获取；并且通过延时显微镜可以很容易地观察到组装过程的动力学。当将两种细胞类型，即正常人成纤维细胞（NHF）和人脐静脉内皮细胞（HUVEC）一起接种时，它们会自我分离成多层球形微组织，其核心是被一层HUVEC包裹的NHF。令人惊讶的是，当将NHF的单细胞悬液添加到7天大的HUVEC球体中时，HUVEC球体重新组织，使得NHF占据中心而HUVEC覆盖在外部，这表明自我组装不是终点，并且球体是具有重新组装能力的流体结构。我们还表明细胞可以自我组装形成复杂的环形形状，并且我们观察到了几种现象，表明细胞收缩和张力在复杂形状的组装过程中起着重要作用。
