DNA microbeads for spatio-temporally controlled morphogen release within organoids [Research data]

Organoids have proven to be powerful in vitro model systems that mimic features of the corresponding tissue in vivo. However, across tissue types and species, organoids still often fail to reach full maturity and function because biochemical cues cannot be provided from within the organoid to guide their development. The establishment of such tools has been identified as a major goal of the field. Here, we introduce DNA microbeads as a novel tool for implementing spatio-temporally controlled morphogen gradients inside of organoids at any point in their life cycle. The DNA microbeads are formed in a simple one-pot process, they can be stored for a year and their stiffness and surface modification is tunable to mimic the corresponding tissue. Employing medaka retinal organoids and early embryos, we show that DNA microbeads can be integrated into embryos and organoids by microinjection and erased in a non-invasive manner with light. Coupling a recombinant surrogate Wnt to the DNA microbeads, we demonstrate the spatio-temporally controlled release of the morphogen from the microinjection site, which leads to morphogen gradients resulting in the formation of retinal pigmented epithelium (RPE) while maintaining retinal ganglion cells. The spatial localization of the induced RPE was shown to directly correlate with the DNA microbeads’ position. We were thus able to bioengineer retinal organoids to more closely mirror the cell type diversity of in vivo retinae. The DNA microbead technology can easily be adapted to other organoid applications for improved tissue mimicry.

类器官（Organoids）已被证实为一类性能优异的体外模型系统，可模拟体内对应组织的各项特征。然而，在不同组织类型与物种中，类器官往往仍无法达到完全成熟的状态与生理功能，这是因为无法从类器官内部提供生化信号以指导其发育。开发这类工具已被该领域确立为核心研究目标之一。本研究中，我们引入DNA微珠（DNA microbeads）作为一种新型工具，可在类器官生命周期的任意节点，于其内部构建时空可控的形态发生素（morphogen）梯度。该DNA微珠可通过简便的一锅法制备，能够保存长达一年，且其刚度与表面修饰可调节，以匹配对应组织的特性。我们利用青鳉（medaka）视网膜类器官与早期胚胎开展实验，证实DNA微珠可通过显微注射（microinjection）整合至胚胎与类器官内部，并可通过光照以无创方式清除。我们将重组替代型Wnt偶联至DNA微珠，证实可从显微注射位点时空可控地释放形态发生素，进而形成形态发生素梯度，诱导视网膜色素上皮（retinal pigmented epithelium, RPE）生成的同时，保留视网膜神经节细胞（retinal ganglion cells）。实验表明，诱导生成的RPE的空间定位与DNA微珠的位置直接相关。由此，我们可通过生物工程手段改造视网膜类器官，使其更贴近体内视网膜的细胞类型多样性。该DNA微珠技术可轻松适配其他类器官相关应用，以进一步提升组织模拟效果。