Mathieu C, Chen G, Chevrier A, Marchand C, Sun J, Rivard GE and Hoemann CD
Posters: J Cell Sci Ther
Bone marrow stimulation in combination with chitosan-GP/blood implant increases the quality of the repair cartilage, through mechanisms involving transient subchondral angiogenesis [1,2]. Although in situ solidifi cation of the implant can be accelerated using clotting factors , their eff ect on early osteochondral repair is unknown. Th e purpose of this study was to test the hypothesis that clotting factors, including thrombin (IIa), tissue factor (TF) and recombinant human factor rhFVIIa, would enhance implant-induced subchondral angiogenesis in repairing drilled defects. Full-thickness cartilage defects were created bilaterally in 12 skeletally mature NZW rabbits, and microdrilled to ~4mm deep. N=6 defects served as drill-only controls. Other defects were treated with implant solidifi ed without (N=6) or with distinct clotting factors (N=4 per factor), resulting in total of N=24 defects. A quantitative stereology method was used to evaluate new blood vessel length (Lv), surface (Sv), and volume density (Vv) formed 3 weeks post-operative in repairing microdrill holes. Gomori-stained cryosections were generated through two distal 1.0 mm diameter drill holes, and 4 digital 40x magnifi cation images acquired at 4 systematic depths in each repairing drill hole. For all stereological parameters, blood vessel density increased in a depth-dependent manner (p<0.001). Between treatment groups, blood vessel Lv was not signifi cantly diff erent whereas Sv was signifi cantly higher for Implant-rhFVIIa vs drill-only controls (Sv=269mm -1 treated vs Sv=165mm -1 drill-only). For the volume density, signifi cant diff erences were found for Implant-rhFVIIa and Implant-IIa (Implant-rhFVIIa Vv=11.6%; Implant-IIa Vv=10.1%; control Vv=3.7%). Despite some variability in the defect morphology (hole depth, sectioning angle), signifi cant diff erences could be obtained in the center of repairing drill holes treated with rhFVIIa for Sv and Vv and with thrombin for Vv. Th us, blood vessel stereology revealed those clot factor implants stimulated the formation of larger blood vessels rather than stimulating formation of more blood vessels compared to drill-only controls.
C. Mathieu has completed a bachelor in chemical engineering at Ecole Polytechnique de MontrEal and is now a M.Sc.A. candidate at Ecole Polytechnique under the supervision of Prof. C. Hoemann.