With knowledge about the molecular mechanisms of chronic laminitis (founder), the biology of PRP (Platelet Rich Plasma), and evidence that PRP helps to heal tendons, ligaments, and wounds, researchers at the Universidad de Caldas in Manizales Columbia describe why they think that PRP (platelet-rich plasma) might be a useful therapy for laminitis.

In their paper, Could Platelet-Rich Plasma be a Clinical Treatment for Horse with Laminitis? the researchers describe five horses that showed new hoof growth and improved hoof horn quality after a course of PRP injections. These horses, which had chronic laminitis after episodes of tying up, colic and traumatic hoof damage, all showed visible improvement after treatment with PRP.

With these encouraging results and a detailed examination of the molecular picture in laminitis, the authors examine the possible ways that the PRP could help tamp down the various cell mediators that contribute to the inflammatory response in chronic laminitis.

Chronic Laminitis

The authors observe that the chronic laminitis is similar to other types of inflammatory responses. The trouble starts when some metabolic disturbance – colic, grain overfeeding, Cushing’s disease, “tying up” (rhabdomyolysis), triggers a series of events that result in inflammation of the sensitive structures (lamellae) that lie between the pedal bone and the inner wall of the hoof. As the disease process progresses, the connection between the coffin bone and the hoof wall deteriorates, leaving the horse with weakened suspensory apparatus of the distal phalanx (SADP); the structures that buffer the daily pounding of the foot on the ground. 

Inflammation’s Effects

Chronic inflammation has several stages that involve mediators (cytokines, proteins, and enzymes) that act on cells in tendons, ligaments, and bone. In chronic inflammation, an initial inflammatory response kicks off a secondary one that releases matrix metalloproteinases (MMPs), enzymes that break down components of collagen. Also present in inflammation are peptides that control blood vessel constriction, molecules that contribute to neuropathic pain, and other mediators that increase levels of cytokines that act on important structures like collagen, and the molecules that absorb and maintain water in the tissue.

Possibly, according to the authors, the molecular pathways in chronic inflammation could be the same events that cause deterioration and ultimately, separation of the lamellae and hoof wall in laminitis.

Why could PRP Help?

PRP (platelet rich plasma) is a formulation of blood platelets and plasma (usually from the patient). It is prepared with a centrifuge that separates the components of the blood. An anticoagulant is added so that the liquid does not clot. Platelets produce growth factors and proteins that are known to participate in essential biologic activities including collagen deposition, bone formation, and blood vessel formation.

Growth Factors and Cytokines

Seven growth factors produced by platelets have an effect on some of the molecular actors in chronic inflammation.  PRP is reported to have helped heal equine tendons and ligaments and is currently used in human sports medicine as an aid healing after tendon and ligament injuries. Knowing their general biological actions, and citing the current literature, the authors discuss the potential actions of these on the mechanisms of laminitis.

After describing encouraging results with five horses treated with PRP, the authors have considered why the growth factors released by platelets might help stop the inflammatory cycle that leads to chronic laminitis. “However,” they write, “additional basic and clinical research is necessary to determine the exact role of PRP as treatment of horses with chronic laminitis.” The next step, according to the authors, is more research to examine the specific actions of PRP on inflammation mediators in equine lamellae – specifically, the cell mediators that might be affected by PRP grown factors, and the genes that control them.

References

1. Dhurat, Rachita, and MS Sukesh. “Principles and Methods of Preparation of Platelet-Rich Plasma: A Review and Author’s Perspective.” Journal of Cutaneous and Aesthetic Surgery 7, no. 4 (2014): 189–97. https://doi.org/10.4103/0974-2077.150734.
2. “Laminitis.pdf.” Accessed April 26, 2018. https://vet.osu.edu/vmc/sites/default/files/import/assets/pdf/hospital/equineFarmAnimals/equine/articles/2008/laminitis.pdf.
3. Libby, Peter. “Inflammatory Mechanisms: The Molecular Basis of Inflammation and Disease.” Nutrition Reviews 65, no. 12 Pt 2 (December 2007): S140-146.
4. Pollitt, Christopher C. “The Anatomy and Physiology of the Suspensory Apparatus of the Distal Phalanx.” Veterinary Clinics of North America: Equine Practice 26, no. 1 (April 2010): 29–49. https://doi.org/10.1016/j.cveq.2010.01.005.
5. “PRP Information.pdf.” Accessed April 26, 2018. http://www.newenglandequine.com/Articles/PRP%20information.pdf.

Show season is here! You and your horse will travel to a local show, perhaps to another state, or even across the country. Your horse is vaccinated, registered, and ready to go. You know there is a potential for exposure to disease, so at the show, you try to limit his contact with other horses. If you could see the pattern of potential contacts at the horse show, what would it look like?

Using network analysis, a method from social media research, researchers at the Ontario Veterinary College, University of Guelph described the network of contacts between horses at a 2-day dressage show in Ontario Canada.

Ninety-six competitors kept their horses in three different locations at the show – an outside covered arena (cover all), a barn, or a trailer in a field. Show attendees completed a questionnaire about contacts with other horses. Using the answers from the competitors, the researchers developed a network graph (see figure). The figure shows the relationships between the three locations at the fairgrounds, the horses attending the show (primary contacts), and the horses stabled at the home facility (secondary contacts). The lines represent connections between horses and locations.

From: Descriptive and network analyses of the equine contact network at an equestrian show in Ontario, Canada and implications for disease spread. BMC Veterinary Research. Authors: Kelsey L. Spence, Terri L. O’Sullivan, Zvonimir Poljak and Amy L. Greer. Ontario Veterinary College, University of Guelph.

The graph shows a high degree of connectivity from horses from the home location (the black dots). The horses attending the show (blue dots) have a less dense pattern. “Only 8% (69/820) of the nodes in the network represented horses that were competing at the show, while 87% (710/820) represented horses stabled at individual home facilities,” according to the authors. The “home barn” contacts represent additional opportunities for contact, in addition to the relatively sparse connection density of horses at the show.

This, according to the researchers, is something to keep in mind when considering strategies for disease intervention and biosecurity. “Simply planning disease intervention strategies based on the horses that attended the show without explicit consideration of secondary contacts would severely underestimate the resources required to control a potential outbreak,” say the authors.

Visualizing equine contact patterns the same way we visualize social media contacts or computer local area networks could be helpful in determining biosecurity policies and heading off disease outbreaks.

The paper is freely available on the BMC Veterinary Research website. You can read it here.
Descriptive and network analyses of the equine contact network at an equestrian show in Ontario, Canada and implications for disease spread.