Abstract
Introduction
Metabolic disorders are among known risk factors for tendinopathies or spontaneous tendon ruptures. However, the underlying cellular and molecular mechanisms remain unclear. We have previously shown that human and rat tendon cells produce and secrete insulin upon glucose stimulation. Therefore, we hypothesize that nutritional glucose uptake affects tendon healing in a rat model.
Materials and Methods
Unilateral full-thickness Achilles tendon defects were created in 60 female rats. Animals were randomly assigned to three groups receiving different diets for 2 weeks (high glucose diet, low glucose/high fat diet, control diet). Gait analysis was performed at three time points (n=20/group). In addition, tendon thickness, biomechanical (n=14/group), and histological and immunohistochemical analysis was conducted. Subsequently, a subtractive-suppression-hybridization (SSH) screen comparing cDNA pools (n=5) prepared from repair tissues of the high glucose and the control diet group was conducted to identify differentially expressed genes.
Results
Newly formed repair tissue of the high-glucose and high-fat group was significantly thicker compared to the control group (p<0.001). Gait analysis revealed a significantly increased Intermediate Toe Spread for animals receiving high glucose diet one week p.o. compared to the control and high fat diet group (p<0.01). Maximum tensile load was significantly reduced in the control diet and the fat diet group, compared to intact tendons (p<0.05). Interestingly, there was no reduction evident for the glucose diet group. A similar trend was observed for tendon stiffness, with glucose diet repair tissue being significantly stiffer compared to the control diet (p<0.05). The proportion of Ki67+ cells in the repair tissue was 3,3% in the control, 9,8% in the glucose and 8,4% in the fat diet group, indicating an increased cell proliferation rate for the glucose and fat diet groups (p<0.001). Finally, the SSH screen revealed 48 candidate genes to be differentially expressed among the diet groups.
Discussion
Tendon repair tissue quality is moderately affected by nutritional glucose. The molecular mechanisms underlying these effects on cells and matrix are currently under investigation and may be helpful in developing a dietary intervention scheme to support tendon regeneration after trauma or tendon disease.
