Background: Early detection of stress fractures can be difficult using clinical imaging techniques. MicroRNAs (miRNA) could be used as potential diagnostic biomarkers. Objectives: To establish a miRNA profile associated with increased risk of stress fractures in Thoroughbred racehorses in training. Study design: Prospective case-controlled study. Methods: Residue blood samples from lame Thoroughbreds referred for nuclear scintigraphy and divided into lame stress fracture (5 horses) or lame non-stress fracture (5 horses) groups. A second control group consisted of non-lame Thoroughbreds presenting for blood sampling (5 horses). Next generation sequencing of miRNA profiles was compared between the three groups. The effects of selected stress fracture-related miRNAs on equine bone marrow derived mesenchymal stem cells (BMMSCs) were investigated. BMMSCs were transfected using miRNA-486-5p mimic or inhibitor and a lipofectamine control from three donors. Results: No miRNA profile was identified for potential usage as a biomarker for differentiating stress fracture from lame cases. However, the miRNA profiles of lame cases and non-lame control horses were significantly different. RNA-sequencing showed three miRNAs (eca-miR-486-5p, eca-miR-26a and eca-miR-23a) were differentially expressed (p value <0.05) between lame cases and non-lame controls, which was validated by qPCR. Of these, eca-miR-486-5p demonstrated the most abundant change. Cell transfection experiments using the miR-486-5p mimic treatment in equine BMMSCs showed upregulation of the osteogenic transcription factor, Runt-related transcription factor 2 (RUNX2) and insulin-like growth factor type 1 (IGF1). A significant decrease of miR-133a in the miR-486-5p mimic treated cells was also demonstrated. Main limitations: Small sample size. Exercise can influence miRNA expression was not controlled for between groups. Conclusions: Since RUNX2 is the known target of miR-133a, miR-486-5p together with miR-133a would suggest the biological importance of bone turnover and osteogenesis in equine BMMSCs, but further investigation of role of miR-486-5p and miR-133a in equine bone biology is warranted.

Background Cone beam computed tomography (CBCT) and magnetic resonance imaging (MRI) of the equine foot under standing sedation are increasingly available yet there is little published information to guide veterinarians on how both modalities compare to optimise horse management. Objective To describe dual modality CBCT and MRI findings in the equine foot of images acquired in the standing sedated horse on the same day for clinical purposes. Study design Retrospective descriptive study Methods Clinical records, CBCT and MRI DICOM images of patients that underwent advanced imaging with both modalities on the same day (April 2024-April 2025) were reviewed. Key imaging findings were categorised to allow comparison of CBCT and MRI findings. Results Imaging studies of 85 horses met the inclusion criteria resulting in imaging of 120 foot and 38 pastern regions. Twenty-four of 85 horses had a primary soft tissue injury that was detected on MRI but not visible on CBCT. Forty-four horses had increased STIR signal on MRI within the phalanges or navicular bone. CBCT identified small sequestration of the distal phalanx that was identified on MRI retrospectively subsequent to CBCT evaluation. CBCT allowed clearer evaluation of cortical bone specifically at the margins of the flexor cortex of the navicular bone and the articular surfaces of the phalanges. Main limitations Imaging findings were not verified by a gold standard and are subjective and descriptive. Categorical representation of primary diagnosis was difficult for some horses. The horses evaluated are limited to a mixed referral population of horses in Scotland. ConclusionsThe primary diagnosis was provided by MRI in more horses than CBCT due to the ability of MRI to identify soft tissue injury. Combined MRI and CBCT imaging of the foot can provide additional information in horses of solar penetration or where careful evaluation of cortical bone is needed.