Citation: PLoS ONE [Electronic Resource]. 13(2):e0192769, 2018.Journal: PloS one.Published: 2018ISSN: 1932-6203.Full author list: de Cesar Netto C; Godoy-Santos AL; Augusto Pontin P; Natalino RJM; Pereira CAM; Lima FDO; da Fonseca LF; Staggers JR; Cavinatto LM; Schon LC; de Camargo OP; Fernandes TD.UI/PMID: 29438431.Subject(s): IN PROCESS -- NOT YET INDEXEDInstitution(s): MedStar Union Memorial HospitalDepartment(s): Orthopaedic SurgeryActivity type: Journal Article.Medline article type(s): Journal ArticleOnline resources: Click here to access onlineDigital Object Identifier: https://dx.doi.org/10.1371/journal.pone.0192769 (Click here)ORCID: de Cesar Netto, Cesar http://orcid.org/0000-0001-6037-0685 (Click here)Abbreviated citation: PLoS ONE. 13(2):e0192769, 2018.Local Holdings: Available online through MWHC library: 2006 - present.Abstract: Our goal was to develop a novel technique for inducing Achilles tendinopathy in animal models which more accurately represents the progressive histological and biomechanical characteristic of chronic Achilles tendinopathy in humans. In this animal research study, forty-five rabbits were randomly assigned to three groups and given bilateral Achilles injections. Low dose (LD group) (n = 18) underwent a novel technique with three low-dose (0.1mg) injections of collagenase that were separated by two weeks, the high dose group (HD) (n = 18) underwent traditional single high-dose (0.3mg) injections, and the third group were controls (n = 9). Six rabbits were sacrificed from each experimental group (LD and HD) at 10, 12 and 16 weeks. Control animals were sacrificed after 16 weeks. Histological and biomechanical properties were then compared in all three groups. At 10 weeks, Bonar score and tendon cross sectional area was highest in HD group, with impaired biomechanical properties compared to LD group. At 12 weeks, Bonar score was higher in LD group, with similar biomechanical findings when compared to HD group. After 16 weeks, Bonar score was significantly increased for both LD group (11,8+/-2,28) and HD group (5,6+/-2,51), when compared to controls (2+/-0,76). LD group showed more pronounced histological and biomechanical findings, including cross sectional area of the tendon, Young's modulus, yield stress and ultimate tensile strength. In conclusion, Achilles tendinopathy in animal models that were induced by serial injections of low-dose collagenase showed more pronounced histological and biomechanical findings after 16 weeks than traditional techniques, mimicking better the progressive and chronic characteristic of the tendinopathy in humans.