The development of the human olfactory epithelium (OE) and the whole olfactory system is complex in nature and until now poorly understood, due to its challenging accessibility. The embryonic induction and development of the olfactory placode (OP), which gives rise to the OE, is dependent on complex multilateral tissue interactions, limiting the modeling capacity of classical adherent cell culture. Here, we report first evidence of a human induced pluripotent stem cell (hiPSC) derived olfactory organoid, co-inducing forebrain neuroectoderm, non-neural ectoderm, olfactory placode, and nasal mesenchyme. These structures develop and appear similar to their in vivo counterparts. The organoids were generated from hiPSC in suspension culture using our optimized differentiation protocol from earlier adherent studies. Directed differentiation towards an olfactory fate was achieved by temporal manipulation of FGF, WNT, BMP, TGFβ, and SSH signaling pathways, mimicking the in vivo situation. Organoids were analyzed using immunostainings as well as qPCR and showed faithful marker expression with a high level of morphological organization. They present with forebrain-vesicle-like structures inside and a surface-like ectoderm on the outside. This surface-like ectoderm is enriched for pre-placodal-region-like cells, which later form thickened placodal patches and invaginate into the bona fide nasal mesenchyme between the surface-like-ectoderm and the telencephalic tissue. We can report the successful and robust differentiation of iPSC into olfactory organoids and further insights into the development of the human OE. Our findings show the possibility to generate organoids with developing OP and possibly even an OE in vitro. Further efforts will need to be made in the future with the goal to generate a functioning in vitro model of the human OE, which will open new possibilities for disease modeling and drug testing.
All funding was granted by the University of Tübingen.