Effects of exercise on tenocyte cellularity and tenocyte nuclear morphology in immature and mature equine digital tendons.

This study examined the effects of different types of exercise on the cells (tenocytes) in tendons of older and younger horses, in particular the superficial digital flexor tendon which is prone to injury. Despite different exercise regimens observed, the research found no significant changes in cell density or composition, suggesting that exercise might not affect tendon cell health or activity in the short term.

Study Objectives and Methodology

• The study aimed to measure the densities and types of tenocytes in two types of tendons in horses: the often injured superficial digital flexor tendon (SDFT) and the less injury-prone common digital extensor tendon (CDET). The study included horses enrolled in long-term, short-term, and foal exercise studies.
• Specimens were collected from the middle segment of the CDET and SDFT from each horse and prepared for histological analysis. This is a microscopic examination of cells and tissues to study their structure and function.
• The areas observed from the SDFT were divided into central (SDFTc) and peripheral (SDFTp) regions.
• Tenocyte nuclei were counted in a total area of 1.59 mm square for each tendon part in each horse. Each nucleus was classified into three types: type 1 (thin and elongated), type 2 (plump and ovoid), or type 3 (similar to cartilage cells – chondrocytes). The study’s hypothesis proposed that type 1 cells are less actively producing substances than type 2 cells.

Study Results

• With the exception of a decrease in the proportion of type 1 tenocytes found in the long-term exercise group, no significant differences were identified between the exercise groups and control groups.
• The study revealed variations in cell densities and proportions of cell types depending on the specific tendon and site within the tendon being evaluated.

Study Conclusions

• No evidence was found to suggest that exercise increases the density of tenocytes or the number of potentially more active type 2 cells in young horses participating in short-term or foal exercise studies.
• The authors posited that the training regimens might not have reached certain strain levels required to observe changes in cell density and composition.
• Even though there were no significant changes observed, the authors viewed the results as positive evidence that the training regimens did not induce hidden (subclinical) damage in foal studies.