Department of Chemical and Biological Engineering, University of Colorado, 3415 Colorado Avenue, Boulder, Colorado, 80303.
Biotechnol Bioeng. 2014 May;111(5):1028-37. doi: 10.1002/bit.25153. Epub 2013 Dec 6.
Multi-cellular aggregates are found in healthy and diseased tissues, and while cell-cell contact is important for regulating many cell functions, cells also interact, to varying degrees, with extra-cellular matrix (ECM) proteins. Islets of Langerhans are one such example of cell aggregates in contact with ECM, both at the periphery of the cluster and dispersed throughout. While several studies have investigated the effect of reintroducing contact with ECM proteins on islet cell survival and function, the majority of these experiments only allow contact with the exterior cells. Thus, cell-culture platforms that enable the study of ECM-cell interactions throughout multi-cellular aggregates are of interest. Here, local presentation of ECM proteins was achieved using hydrogel microwell arrays to incorporate protein-laden microparticles during formation of MIN6 β-cell aggregates. Varying the microparticle seeding density reproducibly controlled the number of microparticles incorporated within three-dimensional aggregates (i.e., total amount of protein). Further, a relatively uniform spatial distribution of laminin- and fibronectin-coated microparticles was achieved throughout the x-, y-, and z-directions. Multiple ECM proteins were presented to β-cells in concert by incorporating two distinct populations of microparticles throughout the aggregates. Finally, scaling the microwell device dimensions allowed for the formation of two different sized cell-particle aggregates, ∼80 and 160 µm in diameter. While the total number of microparticles incorporated per aggregate varied with size, the fraction of the aggregate occupied by microparticles was affected only by the microparticle seeding density, indicating that uniform local concentrations of proteins can be preserved while changing the overall aggregate dimensions.
多细胞聚集体存在于健康和患病组织中，虽然细胞间的接触对于调节许多细胞功能很重要，但细胞也在不同程度上与细胞外基质（ECM）蛋白相互作用。胰岛是与 ECM 接触的细胞聚集体的一个例子，无论是在簇的外围还是分散在其中。虽然有几项研究调查了重新引入与 ECM 蛋白接触对胰岛细胞存活和功能的影响，但这些实验中的大多数仅允许与外部细胞接触。因此，能够研究整个多细胞聚集体中 ECM-细胞相互作用的细胞培养平台很有意义。在这里，通过使用水凝胶微井阵列在 MIN6 β 细胞聚集体形成过程中纳入载有蛋白质的微颗粒来实现 ECM 蛋白的局部呈现。通过改变微颗粒接种密度，可重复性地控制三维聚集体中纳入的微颗粒数量（即蛋白质总量）。此外，通过在 x、y 和 z 方向上实现了纤连蛋白包被的微颗粒的相对均匀的空间分布。通过在聚集体中纳入两种不同群体的微颗粒，将多种 ECM 蛋白同时呈递给 β 细胞。最后，扩展微井装置的尺寸允许形成两种不同大小的细胞-颗粒聚集体，直径分别约为 80 和 160μm。虽然每个聚集体中纳入的微颗粒总数随尺寸而变化，但微颗粒占据聚集体的比例仅受微颗粒接种密度的影响，这表明在改变总体聚集体尺寸的同时，可以保持蛋白质的均匀局部浓度。
