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Int J Clin Exp Pathol 2011;4(7):683-691

Original Article
Achilles tendinosis - a morphometrical study in a rat model

Rafael Duarte Silva, Mark Anthony Glazebrook, Vinicius Castro Campos, Anilton Cesar Vasconcelos

Departament of General Pathology, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil; Division of Orthopedic Surgery, Dalhousie
University, Halifax, Canada ; Departament of Physiotherapy, Medical Science Faculty of Minas Gerais, Belo Horizonte, Brazil

Received September 3, 2011; accepted October 5, 2011; Epub October 12, 2011; Published October 31, 2011

Abstract: This study addresses the morphopathogenesis of Achilles tendinosis, using a rat model and presenting quantitative analysis of
time-dependent histological changes. Thirty Wistar rats were used, randomly split in experimental and control groups. Animals of the
experimental group were submitted to a treadmill running scheme. Five animals of each group were euthanized at four, eight and sixteen
weeks. Achilles tendons were collected and processed routinely for histopath sections. Slides were stained by Hematoxylin-Eosin, Picrosirius
Red, Alcian Blue, AgNOR, TUNEL and evaluated morphometrically. Cellular density decreased slightly along the time and was higher in the
experimental group than in controls at fourth, eighth and sixteenth weeks. Fiber microtearing, percentual of reticular fibers and
glycosaminoglycans content increased along the time and were higher in experimental group than in controls at all-time intervals. AgNOR
labeling here interpreted as a marker of transcription activity was higher in the experimental groups than in controls at all-time intervals.
Apoptotic cells were more frequent and diffusely distributed in tendinosis samples than in control groups. These results suggest that as
mechanical overload is becoming chronic, cellular turnover and matrix deposition increases leading to tendinosis. The combination of staining
techniques and morphometry used here to describe the evolution of lesions occurring in a rat model system has proved to be suited for the
study of induced Achilles tendinosis.

Keywords: Tendinosis, achilles tendon, animal model, overuse, morphometry

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Address all correspondence to:
Dr. A.C. Vasconcelos
Laboratório de Apoptose, Departamento de Patologia Geral
Instituto de Ciências Biológicas da Universidade Federal de Minas Gerais
Caixa Postal 2486, 31270010, Belo Horizonte, Minas Gerais, Brasil.
Tel: +553134092887; Fax: +553134092879
E-mail: anilton@icb.ufmg.br