Cysteine-rich matricellular protein improves callus regenerate in a rabbit trauma model

Open fractures with severe soft-tissue trauma are predisposed to poor bone healing. The vital coupling between osteo- and angiogenesis is disturbed. Cysteine-rich protein 61 (CYR61) is an angiogenic inducer promoting vascularisation. However, little is known about the effect of CYR61 on the callus regenerate after acute musculoskeletal trauma. Therefore, our aim was to determine whether local administration of CYR61: (1) has an influence on callus formation and remodelling, (2) increases bone volume and (3) partially restores callus stability.

A musculoskeletal trauma was created in 20 rabbits. To simulate fracture-site debridement, the limb was shortened. In the test group, a CYR61-coated collagen matrix was locally applied around the osteotomy. After ten days, gradual distraction was commenced (0.5 mm/12 h) to restore the original length. New bone formation was evaluated histomorphometrically, radiographically and biomechanically.

Osseus consolidation occured in all animals. Average maximum callus diameter was higher in the test group [1.39 mm; standard deviation (SD) = 0.078 vs 1.26 mm (SD = 0.14); p = 0.096]. In addition, bone volume was higher (p = 0.11) in the test group, with a mean value of 49.73 % (SD = 13.68) compared with 37.6 % (SD = 5.91). Torsional strength was significantly higher (p = 0.005) in the test group [105.43 % (SD = 31.68 %) vs. 52.57 % (SD = 24.39)]. Instead, stiffness of the newly reconstructed callus decreased (64.21 % (SD = 11.52) vs. 71.30 % (SD = 32.25) (p = 0.81)).

CYR61 positively influences callus regenerate after acute trauma, not only histologically and radiographically but also biomechanically, most probably by a CYR61-associated pathway.