Single-cell transcriptomics of cultured human amniotic fluid cells from the second trimester reveals their heterogeneity

Amniotic fluid has been proposed as an easily available source of cells for numerous applications in regenerative medicine and tissue engineering. The use of amniotic fluid cells in biomedical applications necessitates their unequivocal characterization; however, the exact cellular composition of amniotic fluid and the precise tissue origins of these cells remain largely unclear. Using cells cultured from human amniotic fluid of the second trimester from a healthy fetus and fetuses with spina bifida aperta, we have performed single-cell RNA sequencing to characterize the tissue origin and marker expression of cultured amniotic fluid cells at the single-cell level. Our analysis identified nine different cell types of stromal, epithelial and immune cell phenotype, and from various fetal tissue origins, demonstrating the heterogeneity of the cultured amniotic fluid cell population at single-cell resolution. Further, our data question the presence of pluripotent stem cell populations in cultured AF, and provide a comprehensive list of markers for the characterization of its various progenitor and terminally differentiated cell types. Our study highlights the relevance of single-cell analysis approaches for the characterization of amniotic fluid cells in order to harness their full potential in biomedical research and clinical applications. Overall design: 1. Single cell RNA sequencing of cultured human amniotic fluid cells from the 2nd trimester