Effects of Collagenase Preconditioning on Partially Incised Rat Tendon Treated with Light-Emitting Diodes and Platelet-Rich Plasma.

Background: Tendinopathy is a challenging condition associated with high treatment costs, prolonged dysfunction, and lower quality of life. Current treatment strategies aim to accelerate healing by modulating the healing phases. Phototherapy and growth factor-based modalities have shown promising outcomes in promoting tendon healing. A two-factor experimental design investigates the therapeutic efficacy of conditioning a partially tenotomized rat Achilles tendon model with low concentrations of collagenase, followed by platelet-rich plasma and/or light-emitting diode treatments. Methods: Forty-six adult male Wistar rats (284.8g ± 6.8) were randomly assigned to nine groups (G1 (n = 6), G2-G9; n = 5 per group) based on the treatment applied upon a partially incised rat's hind-limb Achilles tendon model for three weeks. On day 21, blood samples were collected for hematological and biochemical analyses and tendon explants were harvested and subjected to histology. Results: Observational findings support the safety and validity of the model with insignificant weight gain. Hematological measures revealed no significant differences, except WBC, which was affected by phototherapy (p = 0.037). Blood biochemical measures of creatinine and AST levels were significantly affected by collagenase, while both treatments significantly influence CPK levels (p < 0.001). Histological scores revealed no significant main or interaction effect of both treatment modalities. Effect size estimates for biochemical variables were strong effects while hematological and histological variables demonstrated weak effects. Conclusions: Preconditioning a partially incised tendon with low collagenase and combined with PRP and/or LED therapy may offer therapeutic benefits by enhancing the remodeling phase of tendon repair. Study results validated the rat model, which could be a reliable model for future research to refine treatment as well as the investigational tools protocols.