Augmentation of tendon healing with an injectable tendon hydrogel in a rat Achilles tendon model.
BACKGROUND
Many unsolved problems in plastic and hand surgery are related to poor healing of acute and chronic tendon injuries. The authors hypothesized that tendon healing could be augmented by the addition of a tendon-derived, extracellular matrix hydrogel that would guide tissue regeneration.


METHODS
Both Achilles tendons of 36 Wistar rats were given full-thickness injuries approximately 5 mm long and 0.5 mm wide from the tendon insertion at the calcaneus to the midsubstance. The hydrogel was injected into the injury site of one leg and compared with control saline in the other. The ultimate failure load, ultimate tensile stress, and stiffness were evaluated at 2, 4, and 8 weeks. Tendon cross-sections underwent histologic analysis (hematoxylin and eosin and picrosirius red) after the animals were killed. Statistical analysis of biomechanical data was performed using a paired t test.


RESULTS
There was no significant difference in strength between gel and saline injections in ultimate failure load (p = 0.15), ultimate tensile stress (p = 0.42), or stiffness (p = 0.76) at 2 weeks. However, there was a significant difference in ultimate failure load (74.8 ± 11.6 N versus 58.4 ± 14.2 N; p = 0.02) at 4 weeks. The difference in ultimate tensile stress (p = 0.63) and stiffness (p = 0.08) remained insignificant. By 8 weeks, there was no significant difference in strength in ultimate failure load (p = 0.15), ultimate tensile stress (p = 0.39), or stiffness (p = 0.75).


CONCLUSIONS
Treatment with the tendon hydrogel significantly increases the ultimate failure load of tendons at the critical 4-week time point, and is a promising method for augmentation of tendon healing.
Stanford and Palo Alto, Calif. From the Division of Plastic and Reconstructive Surgery, Stanford University Medical Center; and the Section of Plastic Surgery, VA Palo Alto Health Care System.
Maxwell Y
MY
Kim
Simon
S
Farnebo
Colin Y L
CYL
Woon
Taliah
T
Schmitt
Hung
H
Pham
James
J
Chang
D000125:Achilles Tendon / Q000187:drug effects* / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena / Q000187:drug effects; D002102:Cadaver; D002111:Calcaneus / Q000502:physiology; D004195:Disease Models, Animal; D005109:Extracellular Matrix; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013708:Tendon Injuries / Q000188:drug therapy* / Q000503:physiopathology*; D013718:Tensile Strength / Q000187:drug effects / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology; D014945:Wound Healing / Q000187:drug effects*
D020136:Hydrogel, Polyethylene Glycol Dimethacrylate