Figure 1.

Characterization of human PF tested by SEM ((a)–(f)), H&E staining ((g)–(l)), and Safranin O and Fast Green ((m)–(r)). SEM results show that horizontal and cross sections of whole human PF tissue ((a) and (d), respectively) have a sheath region outlined by a blue box and a core region outlined by a yellow box, each characterized by distinct qualities. An enlarged image of the sheath ((b), (e)) region shows a crosslinked collagen network, while an enlarged image of the core ((c), (f)) displays well-organized collagen bundles. H&E staining confirmed SEM findings ((g)–(l)). Enlarged images of the blue (sheath tissue) and yellow (core tissue) box areas in (g) and (j) show sheath tissue with crosslinked network of collagen fibers with many blood vessels (red arrows in (h), (k)) and elongated cells (yellow arrows in (i)) in the core tissue with well-organized collagen fibers. Enlarged image of yellow box area in (j) shows that core tissue has collagen bundle (l). Safranin O and Fast Green staining ((m)–(r)) shows the same results. Both horizontal and cross tissue sections ((m), (p)) show sheath (blue box) and core parts (yellow box). Enlarged image of the blue box area in (m) shows that sheath tissue has a crosslink network of collagen with many blood vessels (red arrows in (n)). Enlarged image of the yellow box area in (m) shows elongated cells (yellow arrows in (o)) stay in the core part with well-organized collagen fibers. Enlarged image of the blue box area in (p) shows sheath with crosslinks of collagen and blood vessels (red arrows in (q)) and some mucin-like tissues (green arrow in (q)). Enlarged image of yellow box area in (p) shows that core tissue has collagen bundle ((r), red arrow). Black bars: 500 µm, yellow bars: 125 µm.