Study provides easier path for asthma research in horses

A strategy for making asthma research in horses easier by using cells obtained using a nasal brush as surrogates for bronchial epithelial cells has been described by researchers in Britain.

Equine asthma is common in horses and is among the most common causes of training interruption and poor performance, particularly in racing Thoroughbreds and endurance horses.

Its prevalence in racehorses ranges from 13 to 22%, and has been found to affect nearly a third of sport horses, resulting in significant downtime.

Diane Frances Lee and her fellow researchers, writing in the journal PLOS ONE, said research is hindered by the low numbers of horses recruited into studies, a consequence in part of the invasive nature of the sampling methods of bronchial brushing and biopsy.

Live animal studies of the disease may be considered unethical, they said, while technical difficulties can hamper other areas of asthma research.

Acquiring bronchial epithelial cells from live horses requires heavy sedation, a local anaesthetic, and a recovery period.

The study team, with the School of Veterinary Medicine at the University of Surrey and the nearby Animal and Plant Health Agency, have described another way of sampling equine airway epithelial cells, the “nasal brush method”.

Samples were obtained by light brushing of the ventral meatus, part of the main nasal airway cavity, whilst horses were under short-acting standing sedation.

The technique was well tolerated by the 31 horses who took part in the study, with 28 viable samples obtained.

To address low yields and subject numbers, they successfully cultured the cells as three-dimensional spheroids, as studied in human models.

The researchers said these upper airway cells express the same markers of differentiation as their deeper counterparts.

Grown as three-dimensional spheroids or as air-liquid interface cultures, nasal epithelial cells proved responsive to the inflammatory cytokine interleukin-13.

This reaction could be reduced by using the gamma-secretase inhibitor Semagecestat, a previously unreported finding that cements the link between equine and human asthma research.

This finding, they said, strengthens the case for a One Health approach in researching asthma and treatments.

The study team also explored the possibility of assembling a molecular-based test panel of differentially expressed genes in asthma.

“Over-diagnosis of equine asthma results in unnecessary treatment and a delay in making a correct diagnosis, whilst under-diagnosis risks serious exacerbations and lung remodelling,” they said.

“The lack of cell count data from some asthmatic horses in the current study highlights the need for better tests and biomarkers for which samples may be obtained in the field.

“Our preliminary findings were that a selection of genes commonly associated with asthma were consistently differentially expressed in asthmatic equine patients relative to total equine lung RNA, compared to healthy controls.”

They said further developments in the use of qPCR as a diagnostic tool should include bronchoalveolar lavage in healthy controls and the resulting data on total cell count, neutrophils and mast cells compared between healthy controls and asthmatic horses accordingly.

“If successful, the nasal brush method and subsequent mRNA extraction of samples would offer a viable and easily implemented alternative to bronchoalveolar lavage fluid characterisation and endoscopy.”

In conclusion, the researchers said they have presented a viable method of acquiring equine nasal epithelial cells, and propose them as a more readily available and suitable surrogate for equine bronchial epithelial cells.

“The nasal brush method shows potential for use in future studies exploring the use of human therapies in the horse (and reverse), conducive to the One Health ethos, expediting achievement of the goals of good asthma control, minimisation of symptom burden and risk of exacerbations.”

The study team comprised Diane Frances Lee and Mark Andrew Chambers, with the veterinary school at the University of Surrey; and David James Everest and William Cooley, with the Animal and Plant Health Agency in Addlestone, Surrey.

Lee DF, Everest DJ, Cooley W, Chambers MA (2023) Investigation of nasal epithelial cells as a surrogate for bronchial epithelial cells in the research of equine asthma. PLoS ONE 18(11): e0293956. https://doi.org/10.1371/journal.pone.0293956

The study, published under a Creative Commons License, can be read here.