Abstract
Apicobasal polarization is crucial for tissue organization during in vivo development and in human organoid models. Extracellular matrix (ECM) signaling typically provides a basal cue, and intestinal and lung organoids reverse polarity from apical-in to apical-out after ECM removal. However, ECM-free brain organoids maintain apical-in polarity, suggesting that media components may influence polarity. Exposing brain organoids to serum induced apical-out orientation. Lysophosphatidic acid (LPA), present in the medium of prior apical-out techniques, was identified as the causative factor. LPA-induced apical-out orientation in brain organoids occurred within 1 day, lasted at least 1 month, and was optimal at human cerebrospinal fluid LPA concentrations. Sphingosine-1-phosphate (S1P) induced similar apical-out polarization. Pharmacological studies revealed that LPA/S1P act via a G-protein coupled receptor/RhoA pathway. Finally, LPA induced apical-out polarity in patient-derived human lung and intestinal organoids, iPSC spheres, and multilineage iPSC-derived intestinal organoids. These findings indicate that LPA signaling is a critical apical polarity cue in multiple tissues.