Platelet-rich plasma (PRP) contains growth factors involved in the tissular healing process. The aim of the study was to determine if an injection of PRP could improve the healing of sectioned Achilles tendons of rats. After surgery, rats received an injection of PRP (n = 60) or a physiological solution (n = 60) in situ. After 5, 15, and 30 days, 20 rats of both groups were euthanized and 15 collected tendons were submitted to a biomechanical test using cryo-jaws before performing transcriptomic analyses. Histological and biochemical analyses were performed on the five remaining tendons in each group. Tendons in the PRP group were more resistant to rupture at 15 and 30 days. The mechanical stress was significantly increased in tendons of the PRP group at day 30. Histological analysis showed a precocious deposition of fibrillar collagen at day 5 confirmed by a biochemical measurement. The expression of tenomodulin was significantly higher at day 5. The messenger RNA levels of type III collagen, matrix metalloproteinases 2, 3, and 9, were similar in the two groups at all time points, whereas type I collagen was significantly increased at day 30 in the PRP group. In conclusion, an injection of PRP in sectioned rat Achilles tendon influences the early phase of tendon healing and results in an ultimately stronger mechanical resistance.

BackgroundEven if eccentric exercises appear favourable in primary prevention of tendons lesions and, especially, in secondary prevention after tendinopathy, the biomechanical changes to the tissue are not yet clear.ObjectiveWe aimed to better define the biomechanical changes that affect healthy tendon after eccentric and concentric training.DesignRandomised controlled trial.SettingAnimal study.Participants18 Sprague-Dawley rats of 2 months.InterventionsThe 6 rats in the control group (U) were not subjected to physical exercise. The 12 remaining rats (6 in each group) ran on a treadmill set at a +15° incline for concentric training (C) or a −15° incline for eccentric training (E), at a speed of 17 m/min for 1 h, three times per week for 5 weeks.Main outcome measurementsThe tricipital, patellar and Achilles tendons were subsequently removed to perform a traction test until rupture, and a histological analysis was performed.ResultsThere was a significant improvement in the rupture force of the patellar and tricipital tendons between the U and E groups. The tricipital tendons in the control group presented a significantly smaller cross-section than the E- and C-trained groups, but none between E and C groups. No significant difference was observed for the mechanical stress at rupture per surface unit between the three groups for all three tendons. However, a tendency towards improvement these values was observed between the trained and the U groups for the patellar tendon. Histological studies demonstrated the tendency of the development of a greater number of blood vessels and a larger quantity of collagen in the eccentric group.ConclusionsThe mechanical properties of tendons in rats improve after specific training, especially following eccentric training. Our results partly explained how mechanical loading, especially in eccentric mode, could improve the tendon structure and perhaps prevent to tendon pathologies.

The treatment of choice for tendinopathies is eccentric reeducation. Although the clinical results appear favorable, the biomechanical changes to the tissue are not yet clear. Even if the mechanotransduction theory is commonly accepted, the physiology of tendons is not clearly understood. We aimed to better define the biomechanical and histological changes that affect healthy tendon after eccentric and concentric training. This study compared the effects of two methods of training (eccentric [E] training and concentric [C] training) with untrained (U) rats. The animals were trained over a period of 5 weeks. The tricipital, patellar, and Achilles tendons were removed, measured and a tensile test until failure was performed. A histological analysis (hematoxylin and eosin and Masson's trichrome stains) was also realized. There was a significant increase in the rupture force of the patellar and tricipital tendons between the U and E groups. The tricipital tendons in the control group presented a significantly smaller cross-sectional area than the E-and C-trained groups, but none was constated between E and C groups. No significant difference was observed for the mechanical stress between the three groups for all three tendons. Histological studies demonstrated the development of a greater number of blood vessels and a larger quantity of collagen in the E group. The mechanical properties of tendons in rats improve after specific training, especially following eccentric training. Our results partly explained how mechanical loading, especially in eccentric mode, could improve the healing of tendon. ß

a b s t r a c tThe aims of this study were to evaluate the effect of age on bronchoscopic features and bronchoalveolar lavage fluid (BALF) cellularity in dogs. Thirty healthy beagle dogs from three age groups were included: young dogs (10 months to 4.5 years of age; n = 8), middle-aged dogs (5-8 years old; n = 13) and older dogs (>8 years; n = 9). Haematology, thoracic radiography, bronchoscopy and bronchoalveolar lavage were performed; bronchoscopic findings were scored and BALF total and differential cell counts were determined. The total bronchoscopic score was higher in older dogs; these dogs had more irregular bronchial mucosa, more prominent mucosal vessels and bronchiectasis. Younger dogs had a higher percentage of neutrophils in BALF compared with middle-aged and old dogs and a higher percentage of lymphocytes in BALF compared with middle-aged dogs. The results show that age has an effect on bronchoscopic features of airways and the composition of BALF in the dog.

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