Lamellar cell death and proliferation are associated with restricted ambulation and preferential weight bearing in a model relevant to supporting-limb laminitis.

The research investigated the effects of limited movement and increased weight bearing on hoof health in horses. Specifically, it showed that restricting a horse’s movement and increasing the weight it carries can lead to hoof damage, even if the weight increase is not painful.

Experimental Design

• A total of 12 healthy Standardbred horses were used in the study. These horses were kept stationary for 92 hours.
• A platform shoe was fitted to one forelimb of each horse in the Preferential Weight Bearing (PWB) group (6 horses), which increased the load on the horse’s supporting limb by about 10% of its bodyweight. The other 6 horses, referred to as the Reduced Ambulation (RA) group, bore the normal weight.
• The researchers also used samples from 8 healthy horses as a control group.
• The effects on the hoof lamellae were determined through histomorphometry and histochemistry.

Findings

• Both the PWB and RA groups developed lesions in multiple limbs, including elongation of the secondary epidermal lamellae, cell death (primarily TUNEL-positive, caspase-3-negative parabasal keratinocytes), and increased proliferation of the basal cells (TPX-2 positive).
• These effects were significantly more pronounced in the PWB group’s supporting limbs. Comparing to the control group, these horses saw increases in the length of the primary epidermal lamella, length of the secondary epidermal lamellae, the number of TUNEL-positive cells (indicative of cell death), and the number of TPX-2-positive cells (indicative of cell proliferation).
• The RA group also had increased TUNEL- and TPX-2-positive cell counts in their forelimbs when compared to the controls.

Implications

• The research showed that restricting a horse’s movement, even if it does not have to bear more weight, can still result in cell death in the parabasal keratinocytes of the hoof lamellae and structural disorganization of the lamellae.
• This study’s findings support the notion that encouraging movement, not merely relieving the load on the limb, is key in preventing supporting-limb laminitis in horses.