Optimization of an Injectable Tendon Hydrogel: The Effects of Platelet-Rich Plasma and Adipose-Derived Stem Cells on Tendon Healing In Vivo

Introduction: Acute and chronic tendon injuries would benefit from stronger and more expeditious healing. We hypothesize that supplementation of a biocompatible tendon hydrogel with platelet-rich plasma (PRP) and adipose-derived stem cells (ASCs) would augment the tendon healing process. Materials and Methods: Using 55 Wistar rats, a full-thickness defect was created within the midsubstance of each Achilles tendon with the addition of one of five experimental conditions: (i) saline control (50-μL), (ii) tendon hydrogel (50-μL), (iii) tendon hydrogel (45-μL)+PRP (5-μL), (iv) tendon hydrogel (45-μL)+2×10 6 -ASCs/mL in phosphate buffered saline (5-μL), and (v) tendon hydrogel (45-μL)+2×10 6 -ASCs/mL in PRP (5-μL). Hydrogel was developed from decellularized, human cadaveric tendons. Fresh rat PRP was obtained per Amable et al.'s technique, and green fluorescent protein/luciferase-positive rat ASCs were utilized. Rats were sacrificed at weeks 1, 2, 4, and 8 after injury. Real-time in vivo bioluminescence imaging of groups with ASCs was performed. Upon sacrifice, Achilles tendons underwent biomechanical and histological evaluation. Comparisons across groups were analyzed using the two-sample Z -test for proportions and the Student's t -test for independent samples. Significance was set at p