Background: There is limited information relating bronchoalveolar lavage (BAL) cytology and cytokine messenger ribonucleic acid (mRNA) expression in racehorses with inflammatory airway disease (IAD).Hypothesis and Objective: We hypothesize that cytokine expression in BAL cells would correlate with cytology. Thus, we evaluated the mRNA expression of selected cytokines in BAL cells in racehorses with exercise intolerance and lower airway inflammation.Animals: Thirty-one client-owned Standardbred racehorses with exercise intolerance. Methods: Prospective, observational study. Cells were obtained by BAL, and mRNA expression of interleukin (IL)-1b, IL-4, IL-8, tumor necrosis factor (TNF)-a, and interferon (IFN)-g was determined by reverse transcription quantitative polymerase chain reaction (RT-qPCR).Results: Nine horses had normal BAL cell differential cytology (Controls), while 22 horses had evidence of IAD based on BAL fluid cytology. Relative expressions of TNF-a/glyceraldehyde 3-phosphate dehydrogenase (GAPDH; 0.0092 AE 0.010 versus 0.0045 AE 0.005, P 5 .034), IL-4/GAPDH (0.001 AE 0.002 versus 0.0003 AE 0.0003, P 5 .029), and IFN-g/GAPDH (0.0027 AE 0.003 versus 0.0009 AE 0.001, P 5 .028) were greater in horses with IAD compared with controls. Furthermore, IL-4/GAPDH (0.001 AE 0.002 versus 0.0002 AE 0.0003, P o .0001) and IFN-g/GAPDH (0.003 AE 0.003 versus 0.001 AE 0.001, P 5 .002) mRNA expression was increased in horses with increased metachromatic cell counts compared with horses with normal metachromatic cell counts. Only the mRNA expression of IL-1b/GAPDH (1.1 AE 0.7 versus 0.3 AE 0.3, P 5 .045) was increased with airway neutrophilia.Conclusions and Clinical Importance: Differences in gene expression were associated with the presence of IAD and with specific cell types present in airway secretions of Standardbred racehorses with poor performance. These findings suggest that different pathophysiological pathways are implicated in IAD.
The etiology and pathophysiology of osteochondrosis remain poorly understood because it is difficult to obtain material from lesions in the early stage of this disease and because there is no satisfactory experimental animal model. We wished to determine whether there are changes in articular cartilage turnover in equine osteochondrosis, which closely resembles the human disease, by assaying cartilage matrix molecules in synovial fluids. We used immunoassays that measure a keratan sulfate epitope and the epitope 846 on the cartilage proteoglycan aggrecan and the C-propeptide of cartilage type-II procollagen, which is released following the synthesis of this molecule, to analyse synovial fluids from equine tarsocrural joints with and without osteochondrosis. In young horses with osteochondrosis, there was a significant increase of C-propeptide of type-II procollagen accompanied by a decrease in the 846 and keratan sulfate epitopes. The results identify differential alterations in aggrecan and type-II collagen turnover in the cartilage matrix in young animals with osteochondrosis that may contribute to the pathological degeneration of articular cartilage in this disease.
In vivo the effects of intra-articular (IA) corticosteroids on articular cartilage remain controversial. This study was designed to examine this issue using synovial fluid (SF) markers of cartilage metabolism. Paired radiocarpal joints, without clinical or radiographic signs of joint disease, were studied in 10 adult horses. Aseptic arthrocentesis was performed weekly for 13 weeks. IA injections of methylprednisolone acetate (MPA) into the treatment joint and the vehicle into the control joint were performed at weeks 3, 5 and 7. We used radioimmunoassays on SF samples which measure a keratan sulfate epitope (KS) and the 846 epitope on cartilage aggrecan (PG) and the C-propeptide (CPII) of cartilage type I1 procollagen which is released following synthesis of this molecule. Gel chromatography was performed on selected SF samples to evaluate the sizes of SF PG molecules. The total joint KS and the 846 epitopes were both present on a heterogeneous population of mainly molecules which, from chromotographic analysis, appeared to be mainly fragments of the articular cartilage aggrecan. They were significantly elevated in MPA joints whereas CPII was significantly reduced compared to the control during the treatment period. These results indicate that the repeated use of IA MPA leads to a potentially harmful inhibition of procollagen I1 synthesis and an increased release of degradation products of the PG aggrecan from articular cartilage.
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