An in vivo and in vitro spatiotemporal atlas of human fetal midbrain development

The dopaminergic system has key roles in human physiology and is implicated in a broad range of neurological and neuropsychiatric conditions that are increasingly investigated using induced pluripotent stem cell-derived midbrain models. To determine the similarity of such models to human systems, we undertook single cell and spatial profiling of first and second trimester fetal midbrain and compared it to in vitro midbrain models. Our initial histological analysis of second trimester fetal midbrain revealed structural complexity already similar to that of adult tissue, although this similarity did not fully extend to transcriptional activity. Moreover, we show that in vitro models recapitulate the transcriptional activity of late first trimester fetal midbrain, while 3D models replicate the spatial organization and cellular microenvironments of first and second trimester fetal midbrain. Understanding the extent of human tissue recapitulation in midbrain laboratory models is essential to justify their use as biological proxies.