Limited Regeneration of Adult Salivary Glands after Severe Injury Involves Cellular Plasticity  Pei-Lun Weng, Marit H. Aure, Takamitsu Maruyama, Catherine E. Ovitt  Cell Reports  Volume 24, Issue 6, Pages 1464-1470.e3 (August 2018) DOI: 10.1016/j.celrep.2018.07.016 Copyright © 2018 The Author(s) Terms and Conditions

Cell Reports 2018 24, 1464-1470.e3DOI: (10.1016/j.celrep.2018.07.016) Copyright © 2018 The Author(s) Terms and Conditions

Figure 1 K5-Expressing Cells Generate Duct but Not Acinar Cells in the Female SMG under Homeostatic Conditions (A) KRT5CreER was crossed with the R26tdTomato reporter strain. LoxP sites are marked by black triangles. (B) Experimental timeline of tamoxifen (TAM) induction and tissue harvest. (C–G) After a 3-day chase, RFP-labeled cells in female SMGs are co-localized with K5 (C) and K7 (D) within the intercalated ducts, and with Sma in myoepithelial cells (G). RFP+ cells are not co-localized with acinar cells marked by Mist1 (E) or Nkcc1 (F). (H–Q) After 90-day (H–L) and 180-day (M–Q) chase periods, the expanded number of RFP-labeled cells in female SMGs remain co-localized with specific duct or myoepithelial cell markers, but not with acinar cell markers. Nuclei are stained with DAPI (blue). Scale bars: 25 μm. Cell Reports 2018 24, 1464-1470.e3DOI: (10.1016/j.celrep.2018.07.016) Copyright © 2018 The Author(s) Terms and Conditions

Figure 2 Axin2-Expressing Cells Generate Duct but Not Acinar Cells in Female SMGs under Homeostatic Conditions (A) Axin2CreERT2 was crossed with the R26tdTomato reporter strain. LoxP sites are marked by black triangles. (B) Experimental timeline of TAM induction and tissue harvest. (C and D) After a 3-day chase, RFP-labeled cells in female SMG are co-localized with K5 (C) and K7 (D) in intercalated ducts. (E–G) RFP-labeled cells do not co-localize with acinar cells marked by Mist1 (E) or Nkcc1 (F), or the myoepithelial cell marker Sma (G). (H–Q) After 90-day (H–L) and 180-day (M–Q) chase periods, the RFP-labeled cells are co-localized with duct (H, I, M, and N), but not acinar (J, K, O, and P) or myoepithelial (L and Q) markers. Nuclei are stained with DAPI (blue). Scale bars: 25 μm. Cell Reports 2018 24, 1464-1470.e3DOI: (10.1016/j.celrep.2018.07.016) Copyright © 2018 The Author(s) Terms and Conditions

Figure 3 K5-Expressing Cells Generate Only Duct but Not Acinar Cells following Duct Ligation Injury (A and B) Experimental model (A) and timeline of TAM induction (B), duct ligation, and de-ligation. (C) H&E staining of sections from control (left) and ligated SMG (middle) at 14 days after ligation, and of ligated SMG (right) at 14 days after de-ligation following regeneration. Scale bars: 100 μm. (D–K) Confocal images of control (D–G) and ligated (H–K) SMG sections at 14 days after ligation stained with antibodies to RFP, duct cell markers, K5 (D and H) and K7 (E and I), or acinar cell markers Mist1 (F and J) and Aqp5 (G and K). (L–O) Confocal images of ligated SMG sections at 14 days after deligation show RFP expression co-localized with K5 (L) and K7 (M), but not with Mist1 (N) and Aqp5 (O) acinar cell markers. Enclosed boxes show enlarged images to emphasize the absence of co-localization between Mist1+ nuclei and surrounding RFP+ cells. Nuclei are stained with DAPI (blue). Scale bars: 25 μm. Cell Reports 2018 24, 1464-1470.e3DOI: (10.1016/j.celrep.2018.07.016) Copyright © 2018 The Author(s) Terms and Conditions

Figure 4 Both Duct and Acinar Cells Regenerate Acinar Cells after Radiation-Induced Injury (A) Experimental model and timeline of TAM induction, irradiation, and tissue harvest using KRT5CreER;R26tdTomato mice. (B) H&E staining of SMG sections at 2 and 30 days after a single dose (15 Gy) of radiation shows altered morphology, but acinar cells are still present. After 90 days, cell clusters are present (encircled by dotted line). Scale bars: 100 μm. (C1–C3) At 2 days after irradiation, images of sections stained with antibodies to RFP and cell type-specific markers K7 (C1), Mist1 (C2), and Nkcc1 (C3) show that RFP+ cells are located in intercalated ducts. (D1–D3) At 30 days, RFP+ cells are co-localized with duct cell markers (D1), but not acinar cell markers (D2 and D3). (E1–E3) At 90 days after irradiation, antibodies to RFP stain clusters of cells that co-localize with both duct (E1) and acinar cell markers (E2 and E3). (F and G) At 90 days after irradiation, clusters of RFP+ cells co-localize with acinar cell markers Aqp5 (F) and IP3R3 (G). (H) At 90 days after irradiation, Ki67+ cells (arrowheads) within the RFP+ Nkcc1+ clusters show that acinar cells in the cluster continue to proliferate. (I) Experimental model and timeline of TAM administration, irradiation, and tissue harvest using Mist1CreERT2;R26tdTomato mice. (J) H&E staining of SMG at 2 and 30 days after irradiation shows altered morphology, but acinar cells are still present. At 90 days after irradiation, cell clusters are observed (encircled with dotted line). Scale bars: 100 μm. (K–L) At 2 (K1–K3) and 30 days (L1–L3) after irradiation, SMG sections from Mist1CreERT2;R26tdTomato mice were stained with antibodies to RFP and K7 (K1 and L1), Mist1 (K2 and L2), and Nkcc1 (K3 and L3). (M1) At 90 days after irradiation, colocalization of RFP and K7 (arrowheads) suggests that Mist1+ acinar cells undergo acinar-to-ductal transition. (M2–O) Large clusters of RFP+ cells co-localized with acinar cell markers Mist1 (M2), Nkcc1 (M3), Aqp5 (N), and IP3R3 (O). (P) Ki67+ cells (arrowheads) show that the RFP+ Nkcc1+ cell clusters derived from Mist1-expressing cells continue to proliferate. Nuclei are stained with DAPI (blue). Scale bars: 25 μm. Cell Reports 2018 24, 1464-1470.e3DOI: (10.1016/j.celrep.2018.07.016) Copyright © 2018 The Author(s) Terms and Conditions