Lineage tracing studies suggest that the placenta is not a de novo source of hematopoietic stem cells
Fig 5
Timed Cdh5-CreERT2 lineage tracing of HSPCs in the mouse placenta.
(A) Tamoxifen administration strategy for timed Cdh5-CreERT2 lineage tracing studies. Pregnant dams were orally gavaged with 4-OHT at E7.5 or E10.5 and tissues harvested at E12.5. Anticipated sites of maximal labeling (YS vs. AGM + Placenta) at each time point are indicated. (B) Representative images of Endomucin (green) and TdT (red) immunostaining of E12.5 yolk sac (YS, upper) and labyrinth from a Cdh5-CreERT2; Ai14 conceptus treated with 4-OHT at E7.5. White arrows indicate rare, TdT + placental ECs. (C) Immunofluorescence staining for TdT (red), Sox17 (green) and Endomucin (magenta) on E12.5 mouse AGM sections following Hoxa13Cre induction at E7.5 (N = 3 placentas). DA, dorsal aorta. White arrows indicate rare TdT + arterial ECs. (D) Immunofluorescence staining for TdT (red), RUNX (green) and c-Kit (magenta) on E12.5 mouse placenta sections of Ai14 control (upper panel, N = 4 placentas) and Cdh5-CreERT2; Ai14 (lower panel, N = 3 placentas) following induction with 4-OHT at E7.5. White arrows indicate RUNX + c-Kit + cells. Red arrows indicate other RUNX + hematopoietic cells. (E) Quantification of TdT + RUNX + c-Kit + cells (HSPCs) in the placenta following lineage tracing at E7.5. The absolute numbers of TdT + placental RUNX + c-Kit + cells out of the total number of placental RUNX + c-Kit + cells counted are shown. (F) Immunofluorescence staining for TdT (red), Sox17 (green) and Endomucin (magenta) on E12.5 mouse AGM sections following induction at E10.5 (N = 3 placentas). (G) Representative images of Endomucin (green) and TdT (red) immunostaining on E12.5 placenta chorioallantoic region (upper) and labyrinth (lower) from a Cdh5-CreERT2 Ai14 conceptus treated with 4-OHT at E10.5. White arrows indicate larger vessels in the chorioallantoic region (top) or placental labyrinth ECs (bottom) that were labeled. The dotted line denotes the border between the labyrinth and chorioallantoic region of the fetal placenta. (H) Immunofluorescence staining for TdT (red), RUNX (green) and c-Kit (magenta) on E12.5 mouse placenta sections of a Cdh5-CreERT2; Ai14 (N = 3 placentas) conceptus treated with 4-OHT at E10.5. White arrows indicate RUNX + c-Kit + cells in the placenta. (I) Quantification of TdT + RUNX + c-Kit + cells in the placenta following lineage tracing at E10.5. 163/231 indicates the number of TdT + cells per number of RUNX + c-Kit + cells counted. Scale bars: 100 μm (B, D and H), 50 μm (C, F and G). The data underlying this figure can be found in S1 Data.