Implantation represents a critical step for embryonic development and pregnancy. Its success depends on the complex interplay between a receptive endometrium and a competent embryo. Implantation-related events remain hardly accessible, making implantation a true "black box" in developmental biology. Improved in vitro models are becoming useful experimental tools, as they are considerably more accessible than in vivo models, easier to manipulate, and permit the use of human cells or tissues, thus increasing the translational value of the studies. In this Review, we briefly summarize the relevant cell types and structures involved into the process of implantation, in order to outline which compartments are indispensable for creating the perfect in vitro model. We also critically address advantages and limitations of available models and assess their application potential. Moreover, we examine the chances and challenges brought by the latest approaches to recapitulate the endometrial compartment, as well as by peri-implantational embryoids.

中文翻译：

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让光线进入黑匣子：用于研究植入的体外系统的进步。

植入是胚胎发育和怀孕的关键步骤。它的成功取决于接受子宫内膜和感受态胚胎之间的复杂相互作用。与植入有关的事件仍然很难获得，这使植入成为发展生物学中真正的“黑匣子”。改进的体外模型正成为有用的实验工具，因为它们比体内模型更容易获得，更易于操作，并允许使用人类细胞或组织，从而提高了研究的翻译价值。在这篇综述中，我们简要总结了植入过程中涉及的相关细胞类型和结构，以概述哪些隔室对于创建理想的体外模型是必不可少的。我们还将严格解决可用模型的优势和局限性，并评估其应用潜力。此外，我们研究了通过最新方法重现子宫内膜区室以及植入前围植入类胚体带来的机遇和挑战。