Figure 1.
Tendons have a cell-retentive barrier.
A. Ex vivo mouse flexor tendon embedded in a fibrin gel. B. Ex vivo tendons were briefly subjected to enzymatic treatment (trypsin) and imaged 5 days later. Cells were labeled with Calcein AM (green, living cells) and propidium iodide (red, dead cells).
Figure 2.
Identification of an epithelium at the surface of tendon.
Immunofluorescence detection of ZO-1 (A) and claudin-1 (B) in transverse sections of day 13 embryonic chick metatarsal tendon; keratin 1 (C) and keratin 10 (D) in longitudinal sections of postnatal mouse flexor digitorum superficialis. Blue, DAPI staining.
Figure 3.
Characterisation of the basement membrane in postnatal mouse and rat tendon.
(A–B) TEM of mouse and rat tail tendon showing the presence of flat epithelial cells adjacent to a thin BM (arrowheads). (C) Immunofluorescence detection of α2(IV) chain of type IV collagen (Col4a2), α3(IV) chain of type IV collagen (Col4a3), and α6(IV) chain of type IV collagen (Col4a6), laminin, nidogen, and perlecan in longitudinal sections of P28 mouse tail tendon.
Figure 4.
Separation of laminin-expressing cells from the surfaces of tendon.
Cells were released from the surface of tendon by limited trypsin digestion. Cells from the central core of the tendon were released by further digestion in trypsin and bacterial collagenase. The presence of laminin β1 was determined by the polymerase chain reaction. The surface (Surf) cells express laminin β1 (lam β1) whereas the endotendon (Endo) cells do not. L, ladder.
Figure 5.
Tail and flexor tendons of the col4+/SVC mouse have a disrupted and interrupted basement membrane.
A, C and E, Col4a1+/Svc mouse samples. B, D and F, wild-type littermate mouse samples. Immunofluoresence detection of collagen IV using an anti-α2(IV) antibody (A, B) and laminin (C, D) in longitudinal sections of postnatal mouse tail. (E, F) Immunolocalisation of lamining in the flexor digitorum profundus in wild-type and Col4a1+/Svc mice. T, tendon. S, synovial space. Blue, DAPI. White arrows, tendon epithelium. Red arrow, discontinuous basement membrane. (G), western blot analysis for laminin from the EHS tumor (used as control), and flexor tendons of wild-type (WT) and Col4a1+/Sv c mice (Svc).
Figure 6.
The Col4a1+/Svc mice have spontaneous tendon adhesions.
H & E staining of longitudinal sections through a wild-type (A) and Col4a1+/Svc (B) mouse hind limb. Insert shows the absence of a synovial space and hyperplasia (H) of the tendon synovium. Blue, DAPI. S, synovial space.
Figure 7.
Immunofluorescence detection of laminin (red) in mouse flexor digitorum profundus 3 days (A) and (B) 21 days post injury in vivo. Blue, DAPI. Arrow, laminin expression at the site of the tenotomy. FDP, flexor digitorum profundus.