Role of Embedded Pure Xenogenous Bovine Platelet Gel on Experimental Tendon Healing, Modelling and Remodelling

Background and Objectives Surgical reconstruction of large tendon defects is technically demanding. In addition, tendon healing has poor quality and is associated with development of peritendinous adhesions. Tissue engineering and regenerative medicine is an option. A combination of scaffolds and factors that promote healing, such as a bioactive graft, could be a valuable strategy for treatment of the injured tendons. Different forms of platelets have been used for tendon healing. Since the availability and cost effectiveness of biomaterials are important in tissue engineering, bovine platelets could be a valuable alternative option for the autograft platelets. We investigated whether bovine platelet gel embedded within an artificial tendon could be effective in tendon healing and regeneration, in vivo. Methods After in vitro evaluations, a large tendon defect model was produced in rabbits and the defect maintained align using Kessler suture. The animals were divided into four groups of control (no implant), treatment with collagen implant, collagen implant-polydioxanone sheath, and collagen implant-polydioxanone sheet-bovine platelet gel. The healing and regeneration were assessed by gross- micro- and nano-morphologic analyses, biomechanical testing, biochemistry, bioelectricity, and clinical evaluations at 60 and 120 days after injury. Results Bovine platelet gel induced cellular proliferation and enhanced cell viability in vitro. In vivo, it significantly increased inflammation in the short term, enhanced cellular distribution, proliferation, migration, differentiation and matrix production at mid-term and finally it facilitated graft degradation, incorporation and acceptance in the newly regenerated tendon. Compared with the control groups, the platelet-treated neotendon had significantly higher mechanical strength which was due to the collagen fibril's better density, diameter, number, differentiation and distribution, collagen fibril to fiber and fiber bundle differentiation and lower peritendinous adhesion, muscle fibrosis and atrophy. Conclusion Bovine platelet gel-embedded artificial tendon could be considered as a new option in reconstruction and healing of large tendon defects.