Fig 1.
Light microscopy of bone-tendon junction of the calcaneal tendon of adults Wistar rats (A, B, C, D, E, C’, D’, and E’) and elderly Wistar rats (F, G, H, I, J, H’, I’, and J’). (A, B, C, D) Calcaneal tendon (T), periosteal fibrocartilage (PF), trabecular space (*), trabecular bone (arrows). Stain: Fig A: Picro-Sirius. Fig C: Picro-Sirius under polarized light. Bars: 50 μm, x100. (C’) Calcified fibrocartilage (CF), rows of cells (arrows), bone (B). Stain: Picro-Sirius. Bar: 20 μm, x200. (D’) Calcified fibrocartilage (CF), rows of cells (arrows), bone (B), division between the collagen fibers of the tendon and bone (dashed line). Stain: Picro-Sirius under polarized light. Bar: 20 μm, x200. (E) Uncalcified fibrocartilage (UF), calcified fibrocartilage (CF), tidemark (dashed ellipse), trabecular space (*), trabecular bone (arrow). Stain: Hematoxylin–eosin. Bar: 50 μm, x100. (E’) Fibrocartilage cells in the uncalcified fibrocartilage (arrowhead), fibrocartilage cells in the calcified fibrocartilage (larger arrows), tidemark (small arrows). Stain: Hematoxylin–eosin. Bar: 20 μm, x200. (F, H) Calcaneal tendon (T), trabecular space (arrowhead), trabecular bone (arrow), periosteal fibrocartilage (PF). Stain: Picro-Sirius. Bar: 50 μm, x100. (G, I) Calcaneal tendon (T), trabecular bone (arrows), periosteal fibrocartilage (PF). Stain: Picro-Sirius under polarized light. Bar: 50 μm, x100. (H’) Calcified fibrocartilage (CF), rows of cells (arrows), bone (B). Stain: Picro-Sirius. Bar: 20 μm, x200. (I’) Calcified fibrocartilage (CF), bone (B), division between the collagen fibers of the tendon and bone (dashed line). Stain: Picro-Sirius under polarized light. Bar: 20 μm, x200. (J) Uncalcified fibrocartilage (UF), calcified fibrocartilage (CF), tidemark (dashed ellipse), bone (*). Stain: Hematoxylin–eosin. Bar: 50 μm, x100. (J’) Fibrocartilage cells in the uncalcified fibrocartilage (arrowhead), fibrocartilage cells in the calcified fibrocartilage (larger arrows), tidemark (small arrows). Stain: Hematoxylin–eosin. Bar: 20 μm, x200.
Fig 2.
Scanning electron microscopy of bone-tendon junction of the calcaneal tendon of adults Wistar rats (A, C, E) and elderly Wistar rats (B, D, F). (A, B) Calcaneal tendon (T) and bone (B). Bar: 50 and 100 μm, magnification x200 and x160 respectively. (C) Collagen fiber of the tendon (small arrow), lacuna of fibrocartilage cell in the tendon tissue (larger arrow), lacuna of fibrocartilage cell in the bone (arrowheads), bone (B). Bar: 10 μm, x1,000. (D) Collagen fiber of the tendon (**) and bone (B). Bar: 10 μm, x1,000. (E) Lipid droplets (arrowheads), collagen fibers of the tendon tissue (arrows). Bar: 2 μm, x3,000. (F) Lipid droplets (arrowheads), bundles of collagen fibers of the tendon tissue (*). Bar: 2 μm, x3,000.
Fig 3.
Scanning electron microscopy of bone-tendon junction of the calcaneal tendon of adults Wistar rats (A, C) and elderly Wistar rats (B, D). (A, B) Lacuna of fibrocartilage cell fibrocartilage (**), territorial matrix (*). Bar: 1 μm, x7,500 and x10,000. (C, D) Lacuna of fibrocartilage cell (**), territorial matrix (*). Bar: 2 μm, x5,000.
Fig 4.
Transmission electron microscopy of bone-tendon junction of the calcaneal tendon of adults Wistar rats.
(A) Collagen fibers of the tendon (arrows), calcified fibrocartilage (*). Bar: 0.2 μm, x15,000. (B) Collagen fibers (**), osteocyte nucleus (N), lacuna (*), cellular process (arrow), canaliculus (arrowhead), bone (B). Bar: 0.5 μm, x6,000. (C) Nucleus of fibrocartilage cell (N), territorial matrix (*), inter-territorial matrix (**). Bar: 0.5 μm, x6,000. (D) Nucleus of fibrocartilage cell (N), rough endoplasmic reticulum (small arrows), lacuna (larger arrow), cytoplasmic processes (arrowheads), territorial matrix (*). Bar: 0.4 μm, x10,000. (E) Bands of collagen fibers of the tendon tissue (*), tenocytes (arrowheads), cytoplasmic prolongation (arrows). Bar: 0.5 μm, x6,000. (F) Striations of the collagen fibrils of the tendon, overlap (arrow), gap (arrowhead) and overlap plus gap called the D-period (*). Bar: 0.2 μm, x94,000.
Fig 5.
Transmission electron microscopy of bone-tendon junction of the calcaneal tendon of elderly Wistar rats.
(A) Collagen fibers of the tendon (arrows), calcified fibrocartilage (*). Bar: 0.5 μm, x5,000. (B) Osteocyte nucleus (white asterisk), lacuna (black asterisk), cellular process (arrows), bone (B). Bar: 0.5 μm, x5,000. (C) Nucleus of fibrocartilage cell (N), rough endoplasmic reticulum (arrow), territorial matrix (*), inter-territorial matrix (**). Bar: 0.5 μm, x5,000. (D) Nucleus of fibrocartilage cell (N), nucleolus (small arrow), mitochondria (arrowheads), cytoplasmic processes (larger arrow), territorial matrix (*), inter-territorial matrix (**). Bar: 0.5 μm, x5,000. (E) Bands of collagen fibers of the tendon tissue (*). Bar: 1 μm, x3,000. (F) Striations of the collagen fibrils of the tendon, overlap (arrow), gap (arrowhead). Bar: 0.2 μm, x75,000.
Fig 6.
Quantitative analysis of collagen type I and III, D-period of the collagen fibers, fibrocartilage cells and insertion thickness of the calcaneal tendon into the bone.
(A) Graph of collagen type I and III in the adult and elderly groups. (B) Graph D-period length of the collagen fibers. (C) Graph of fibrocartilage cells in uncalcified and calcified fibrocartilage region in the adult and elderly groups. (D) Graph of insertion thickness of the calcaneal tendon into bone tissue. In all graphs horizontal lines indicates statistical difference. Horizontal lines represent statistical difference.