Low levels of microRNA-21 in neutrophil-derived exosomes may contribute to airway smooth muscle hyperproliferation in horses with severe asthma.

This study reveals a possible link between a decrease in microRNA-21 in neutrophil-derived exosomes and hyperproliferation of airway smooth muscle (ASM) cells in horses with severe equine asthma (SEA). This could potentially contribute to the thickening of the bronchial wall in SEA, shedding light on the disease’s pathogenesis.

Objective and Background

• The overarching objective of this research was to improve our understanding of severe equine asthma (SEA) by investigating the role of neutrophil-derived exosomes, and a particular type of miRNA called miR-21, on airway smooth muscle (ASM) cell proliferation and bronchial remodeling.
• Taking into account earlier findings connoting a potential link between neutrophilic inflammation and the degree of airway obstruction in SEA, this study aimed to scrutinize this further.

Methods

• The scientists began by selecting six horses identified with SEA and six healthy horses as their controls.
• Using quantitative PCR, they observed the expression of selected miRNAs within peripheral neutrophil-derived exosomes.
• Following this, they transfected miR-21 into ASM cells and assessed its effects through gene expression analysis and proliferation studies.

Findings

• The team discovered that miR-21 was indeed downregulated in the neutrophil-derived exosomes of SEA-affected horses – essentially, there was less of it.
• It was concluded that miR-21 had the capability to attenuate the proliferation of ASM cells stimulated with lipopolysaccharide – a common component of the cell wall of gram-negative bacteria.
• This led the researchers to posit that a reduced level of miR-21 in these exosomes could be leading to an over-proliferation of ASM cells (hyperproliferation).

Conclusions and Implications

• The study concluded that the low level of miR-21 could contribute to over-proliferation of airway smooth muscle cells, which could, in turn, cause thickening of the bronchial wall in SEA – a common marker of asthma.
• This finding could have significant implications in the understanding of SEA pathogenesis and open new avenues for therapeutic interventions targeting the regulation of miR-21.