Mesenchymal Stem Cell Therapy Regenerates the Native Bone-Tendon Junction after Surgical Repair in a Degenerative Rat Model

BACKGROUND: The enthesis, which attaches the tendon to the bone, naturally disappears with aging, thus limiting joint mobility. Surgery is frequently needed but the clinical outcome is often poor due to the decreased natural healing capacity of the elderly. This study explored the benefits of a treatment based on injecting chondrocyte and mesenchymal stem cells (MSC) in a new rat model of degenerative enthesis repair. METHODOLOGY: The Achilles' tendon was cut and the enthesis destroyed. The damage was repaired by classical surgery without cell injection (group G1, n = 52) and with chondrocyte (group G2, n = 51) or MSC injection (group G3, n = 39). The healing rate was determined macroscopically 15, 30 and 45 days later. The production and organization of a new enthesis was assessed by histological scoring of collagen II immunostaining, glycoaminoglycan production and the presence of columnar chondrocytes. The biomechanical load required to rupture the bone-tendon junction was determined. PRINCIPAL FINDINGS: The spontaneous healing rate in the G1 control group was 40%, close to those observed in humans. Cell injection significantly improved healing (69%, p = 0.0028 for G2 and p = 0.006 for G3) and the load-to-failure after 45 days (p<0.05) over controls. A new enthesis was clearly produced in cell-injected G2 and G3 rats, but not in the controls. Only the MSC-injected G3 rats had an organized enthesis with columnar chondrocytes as in a native enthesis 45 days after surgery. CONCLUSIONS: Cell therapy is an efficient procedure for reconstructing degenerative entheses. MSC treatment produced better organ regeneration than chondrocyte treatment. The morphological and biomechanical properties were similar to those of a native enthesis

Etude des effets de la compression sur le métabolisme des osteoblasts: un nouveau modèle 3D de compression in vitro

peer reviewe

Histological scale used to assess the tissue engineering of the enthesis.

<p>The first 3 columns are visual grades assigned by examining x 25 images of the bone-tendon junction. The last 2 columns are assessments of x 100 images. The first column uses sections stained with H&E and the second immunostained for type II collagen. The third column sections were stained with Alcian Blue. Columns 1 to 3 were used to define the production of an enthesis. Columns 2 to 5 were used to rank the organization of the neo-enthesis (16-point scale). The native enthesis always scored 16 points in double blind trials (SD = 0).</p

Improvement by cell therapy of the load-to-failure after repair of Achilles tendons.

<p>We determined the Load-to-failure of Achilles tendons taken from control (G1), chondrocyte- (G2) and MSC-injected (G3) rats 15, 30 and 45 days after repair and compared them to those of a native enthesis (74.4±10.9 N, white box). There was a statistically significant difference between the value for the native entheses and those for other populations at 15 days post-repair. There was a statistically significant difference between the values for the native enthesis and those of G1 and G3 30 days post-repair, and a statistically significant difference between G1 and G2 and G3, 45 days post-repair. * p<0.05, ** p<0.01 and *** p<0.001.</p

Enthesis structure and healing ratse after repair.

<p>The enthesis is the area of bone-tendon junction. A) Wistar rat Achilles tendon-bone junction. B) Higher magnification of the delimited area shown in (A). T, tendon; Bo, bone. C and D) Type II collagen immunostaining of a native (C) and a destroyed enthesis (D). Native enthesis shows two positive areas of collagen II staining: E1, the insertion of the tendon (T) into the bone (Bo) and E2, the sliding zone of the tendon. Note the absence of the tendon and the E1 area just after destruction of the enthesis (D). (C and D, scale  = 200μm). E and F) Healing failure after repair was evaluated by suture breakage (E) and a distance between the bone and the tendon of greater than 1 cm (F) (E and F, scale  = 1 cm). G) Healing rate was evaluated at sacrifice for the three groups of rats and expressed as a percentage. * p<0.05 and ** p 0.01.</p

MSC and chondrocyte immuno-characterization.

<p>Fluorescent immunostaining. A: type II collagen around chondrocytes and its negative control: B. C: Type I collagen of rat MSCs. D: Fibronectin in rat MSCs. E: Integrin β1 in rat MSCs. F: CD54 in rat MSCs. G: CD45 negative immunostaining of rat MSCs. H: CD14 negative immunostaining of rat MSCs. Scale is 100 µm.</p