Embryoid body arrays: Parallel cryosectioning of spheroid/embryoid body samples for medium through-put analysis

Three dimensional (3D) culture of mammalian cells is emerging as a powerful new tool to understand organogenesis as well as serve as models for diseases with implications for therapeutic evaluation. 3D cultures are referred to variously as spheroid, organoids or embryoid bodies. While many methods exist for large scale production of embryoid bodies or other spheroid cell aggregates, either at controlled sizes using microwell/micropatterned plates or uncontrolled sizes in suspension dishes, very few protocols exist for medium throughput analysis of differentiation at the histological level. We have developed a method which allows for parallel processing, sectioning and analysis of multiple 3D samples (e.g. fixed at different time points, treated with different drugs/growth factors, generated from different cell lines etc.) by double-embedding blocks in a larger array format. Our protocol has few barriers for use and requires only materials commonly found in any lab currently using embedding materials for cryosectioning. Sectioning in parallel allows histological techniques (such as histochemistry, immunostaining or in situ hybridisation) to be performed simultaneously on many samples on a single slide. This reduces slide to slide variation as well as requiring less reagents, fewer consumables with lower time and labour requirements when compared to individually embedded samples.