Fig. 1.

Defining feather follicle-associated dermal components during feather cycling. (A) Brightfield view of a dorsal resting-phase contour feather from an adult male White Leghorn chicken. (A′) H&E staining of a contour feather follicle in early growth phase showing the difference of pulp cell density between the area adjacent to the epidermis and the central part. The dotted line separates pPP and cPP. The thickness of pPP is 50-100 μm, depending on the follicle size. Molecular marker can be seen in panels I,J. (B) Diagram of a contour feather follicle in growth and resting phases, respectively. (C-N) H&E staining (C,D) and immunostaining (E-R) of follicle at early growth phase (C,E-K), resting phase (D,L-R) showing Sox2 (E,L), TGFβ2 (F,M), SMA (G,N), NCAM (H,O), TNC (I,P), Col1 (J,Q) and vimentin (K,R). Blue arrows (I,J) indicate the pPP in early growth phase. Black arrow (K) indicates the cPP in early growth phase. Green arrows (L-N) indicate the positive signals in the resting-phase central bDP. Yellow arrow (O) indicates that NCAM is positive in the resting-phase bDP. Red arrows (P,Q) indicate that the staining is more positive in the resting-phase bDP. Dashed lines outline the DP. (S,T) Schematic summary of molecular expression in growth (S) and resting (T) phase feather follicles. aDP, apical dermal papilla; bDP, basal dermal papilla; cPP, central pulp; DP, dermal papilla; DS, dermal sheath; fe, feather epidermis; pPP, peripheral pulp.