Figure 2. Polarized niche confers a structurally robust architecture despite the loss of its constituent cells.

A. The same unpolarized and polarized dermal papillae (DPs, dash-lined) longitudinally imaged before and after diphtheria toxin (DTA) induced fibroblast ablation. Ablation is achieved by tamoxifen activated Cre in fibroblasts (Pdgfrα-CreER) and LSL-DTA. Fibroblast nuclei are labeled in green (Pdgfrα-H2BGFP) and cell membranes are in red (membrane-tdTomato).

B. The number of fibroblasts that remain enclosed within the hair follicle (HF) epithelium after DTA-induced fibroblast ablation. Fibroblast number is counted based on green fibroblast nuclear signal labeled by Pdgfrα-H2BGFP. For unpolarized DPs at mid-growth, n=41 (Day0–1), 53 (Day4–5), and 60 (Day6–7) from 3 mice; for polarized DPs at late-growth, n=72 (Day0–1), 78 (Day4–5), and 71 (Day6–7) from 3 mice.

C. Length of entire DPs that remain enclosed after ablation. Based on the reported critical threshold of DP fibroblast number,¹¹ we classified DP as either with abundant (14 to 32) or few (0 to 13) enclosed fibroblasts. For unpolarized DPs, n=42 HFs (14–32 fibroblasts) and 99 HFs (0–13 fibroblasts) from 3 mice; For polarized DPs, n=77 HFs (14–32 fibroblasts) and 110 HFs (0–13 fibroblasts) from 3 mice.

D. Percentage of HFs that remain enclosed DPs after fibroblast ablation. For HFs with unpolarized DPs, n=3 mice (68 HFs at Day0–1, 68 HFs at Day4–5, and 66 HFs at Day6–7); for HFs with polarized DPs, n=3 mice (102 HFs at Day0–1, 108 HFs at Day4–5, and 89 HFs at Day6–7).

E. Schematic of forming a polarized DP niche architecture that is structurally more robust even after fibroblast ablation. Green indicates DP fibroblast nuclei and red indicates their membranes.

All data are presented as mean ± S.D. Mixed-effects analysis is used in Fig.2B. Tukey’s multiple comparisons test is used in Fig.2C, D. See also Figure S1.