The Harry M. Zweig Memorial Fund for Equine Research

Regenerative Approach to Recurrent Laryngeal Neuropathy

Principal Investigator:    Jon Cheetham
Contact Information:  Email:; Phone: 607-253-3100
Project Costs: $92,029
Project Period:    1/1/2017-12/31/2018

CheethamDr. Jon Cheetham

Recurrent laryngeal neuropathy (RLN) or “Roaring” is a major cause of poor athletic performance affecting 8% of racehorses and a higher percentage of sport horses. The disease affects the ability of the nerve to conduct a signal from the brain to the muscle that opens the larynx or voice box at exercise -the CAD muscle. This CAD muscle is the only muscle that opens the larynx during exercise. In affected horses the impulses carrying this signal down the nerve travel more slowly and do not reach the muscles as effectively as in normal horses. This leads to a reduction in the size and strength of the CAD muscle causing collapse of the larynx with reduced airflow and abnormal noise production.

Currently current standard of care for RLN is the placement of a fixed and permanent laryngoplasty suture – a “tie-back”. While this method is relatively successful in the treatment of airway obstruction in RLN affected horses, it does not restore function to the airway and can be associated with risks such as coughing and failure of the suture to hold the airway open. At the Equine Performance Clinic we see a large number of cases each year that show early signs of RLN but are not yet sufficiently affected to warrant the cost or potential risks of surgery. Here, we propose a regenerative approach to restore normal laryngeal function in horses affected by RLN using an enhanced nerve graft. 

Over the last three years and with support from the Harry M. Zweig Memorial Fund and the National Institutes of Health we have begun to understand the basic mechanisms behind the role of a particular type of immune cell – the macrophage - in peripheral nerve repair. These cells are the major cell type migrating to the repair site and are the ‘conductors of the orchestra’, laying down tiny capillary networks along which other cell types can migrate.  We have developed a sophisticated technique to isolate macrophages from the site of peripheral nerve injury, evaluated how changes in genes expressed by these macrophages change over time after injury and how genes that control the types of macrophages at the injury site affect repair after nerve graft.