Figure 4. Taxanes induce apoptosis and mitotic defects within human hair follicle K15⁺ epithelial stem/progenitor cell niches.

• A
  Paclitaxel treatment (Ai) promotes mitotic arrest (orange arrows/pH3⁺ cells) and apoptosis (white arrows/caspase‐3⁺ cells), within the K15⁺ bulge and K15⁺ proximal bulb outer root sheath (pbORS) stem/progenitor cell compartments of the human hair follicle (HF). 20‐μm scale. (Aii) High magnification montage demonstrating mitotic arrest (orange arrow) and apoptosis/caspase‐3 positivity (white arrow) within the K15⁺ bulge. 10‐μm scale.
• B
  Representative immunofluorescence images of heightened cleaved caspase‐3 immunoreactivity (arrows) within the K15⁺ bulge following extended paclitaxel organ culture experiments (see Materials and Methods). 50‐μm scale.
• C
  Graph showing significantly (P = 0.029) increased K15/caspase‐3 double‐positive cells within the bulge following extended paclitaxel HF organ cultures. Welch's t‐test performed using N of 8–9 HFs from three patients.
• D
  K15⁺ cells of the human HF bulge express Ki‐67 during extended organ culture experiments. Paclitaxel treatment did not significantly affect the number of bulge K15/Ki‐67 double‐positive cells. Unpaired t‐test performed using N of 8–9 HFs from three patients.
• E
  Representative double immunofluorescence images of elevated γH2A.X immunoreactivity (arrows) within the K15⁺ bulge following extended paclitaxel organ culture experiments (see Materials and Methods). 50‐μm scale.
• F
  γH2A.X analysis showing a significant (P = 0.0065) increase in the number of cells with DNA double‐strand breaks in the K15⁺ bulge following extended organ culture experiments. Mann–Whitney U test performed using N of 5–6 HFs from two patients.

Data information: Values plotted represent the mean number of positive cells counted per HF analysed. Error bars are standard error of the mean. pbORS, proximal bulb outer root sheath. EC, extended cultures.Source data are available online for this figure.