Abstract
Tendons are hypocellular and hypovascular tissues, and thus, their natural healing capacity is low. In this study, we sought to evaluate the efficacy of platelet-rich fibrin (PRF) to serve as a bioactive scaffold in promoting the healing of rabbit Achilles tendon injury. For in vitro study, the essence portion of PRF was determined through bioluminescent assay. Furthermore, we analyzed the time-sequential cytokines-release kinetics of PRF and evaluated their effects on tenocytes proliferation and tenogenic gene expressions. In animal study, the rabbit Achilles tendon defect was left untreated or implanted with normal/heat-denatured PRF scaffolds. Six weeks postoperatively, the specimens were evaluated through sonographic imaging and histological analysis. The results revealed significantly more activated platelets on bottom half of the PRF scaffold. Cytokine concentrations released from PRF could be detected from the first hour to six days. For the in vitro study, PRF enhanced cell viability and collagen I, collagen III, tenomodulin, and tenascin gene expression compared to the standard culture medium. For in vivo study, sonographic images revealed significantly better tendon healing in the PRF group in terms of tissue echogenicity and homogeneity. The histological analysis showed that the healing tissues in the PRF group had more organized collagen fiber, less vascularity, and minimal cartilage formation. In conclusion, bioactive PRF promotes in vitro tenocytes viability and tenogenic phenotypic differentiation. Administration of a PRF scaffold at the tendon defect promotes tissue healing as evidenced by imaging and histological outcomes.
Highlights
The Achilles tendon is the largest and strongest tendon in the human body and helps to transmit forces from the calf muscles to the calcaneus during motion [1]
The bioactivity of platelet-rich fibrin (PRF) was determined through determining local adenosine triphosphate (ATP) released from activated platelets
We found that PRF-conditioned medium (PRFM) could stimulate tenocytes proliferation and tenogenic matrix production
Summary
The Achilles tendon is the largest and strongest tendon in the human body and helps to transmit forces from the calf muscles to the calcaneus during motion [1]. Achilles tendon injuries are common in athletes and in non-athlete adults. The treatment of acute Achilles tendon injuries can be categorized into operative and non-operative. Regardless of the treatment method, the primary goal of management of acute Achilles tendon injuries is to ensure a rapid return to full function. Tendon healing usually results in the formation of fibrovascular scar or granulation tissue. This discrepancy in the microstructure and biomechanical properties of scar tissues often makes the tissue more susceptible to re-injury or even re-rupture [2,3,4,5]
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