title: Quantification of cell density in rat Achilles tendon: development and application of a new method.
abstract: Increased tendon cell nuclei density (TCND) has been proposed to induce tendon mechanical adaptations. However, it is unknown whether TCND is increased in tendon tissue after mechanical loading and whether such an increase can be quantified in a reliable manner. The aim of this study was to develop a reliable method for quantification of TCND and to investigate potential changes in TCND in rat Achilles tendons in response to 12 weeks of running. Eight adult male Sprague-Dawley rats ran (RUN) on a treadmill with 10° incline, 1 h/day, 5 days/wk (17-20 m/min) for 12 weeks (which improved tendon mechanical properties) and were compared with 11 control rats (SED). Tissue-Tek-embedded cryosections (10 µm) from the mid region of the Achilles tendon were cut longitudinally on a cryostat. Sections were stained with alcian blue and picrosirius red. One blinded investigator counted the number of tendon cell nuclei 2-3 times in three separate regions of the mid longitudinal tendon sections with fields of 390 μm × 280 μm. Unpaired t tests were used for the statistical analysis (mean ± SE). Typical Error % for replicate counts was 5.5 and 14 % coefficient of variation for the three regions. There was no difference in TCND between running rats versus control rats (nuclei per image (≈105μm2): RUN, 152 ± 9; SED, 146 ± 8, p = 0.642). This new method provided reproducible quantification of TCND. There was no difference in TCND despite improvements in tendon mechanics, which suggests that cell number is not a major cause for altered tendon mechanical properties with loading.
authors: IOC Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Building 8, Bispebjerg Bakke 23, 2400, Copenhagen NV, Denmark. ccouppe@gmail.com.|Musculoskeletal Rehabilitation Research Unit, Department of Physical Therapy, Bispebjerg Hospital, Copenhagen, Denmark. ccouppe@gmail.com.
authors: Christian
authors: C
authors: Couppé
authors: IOC Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Building 8, Bispebjerg Bakke 23, 2400, Copenhagen NV, Denmark.
authors: René B
authors: RB
authors: Svensson
authors: IOC Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Building 8, Bispebjerg Bakke 23, 2400, Copenhagen NV, Denmark.|Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors: Katja M
authors: KM
authors: Heinemeier
authors: IOC Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Building 8, Bispebjerg Bakke 23, 2400, Copenhagen NV, Denmark.
authors: Emilie Wøjdemann
authors: EW
authors: Thomsen
authors: IOC Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Building 8, Bispebjerg Bakke 23, 2400, Copenhagen NV, Denmark.
authors: Monika Lucia
authors: ML
authors: Bayer
authors: Department of Pathology, Herlev Hospital, Copenhagen, Denmark.
authors: Lise
authors: L
authors: Christensen
authors: IOC Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Building 8, Bispebjerg Bakke 23, 2400, Copenhagen NV, Denmark.
authors: Michael
authors: M
authors: Kjær
authors: IOC Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Building 8, Bispebjerg Bakke 23, 2400, Copenhagen NV, Denmark.|Musculoskeletal Rehabilitation Research Unit, Department of Physical Therapy, Bispebjerg Hospital, Copenhagen, Denmark.
authors: S Peter
authors: SP
authors: Magnusson
authors: IOC Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Building 8, Bispebjerg Bakke 23, 2400, Copenhagen NV, Denmark.
authors: Peter
authors: P
authors: Schjerling
mesh_terms: D000125:Achilles Tendon / Q000166:cytology*; D000818:Animals; D002452:Cell Count; D002467:Cell Nucleus; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D016610:Tissue Embedding
keywords: 12 weeks uphill running; Achilles tendon mechanics; Tendon cell nuclei