Genome-wide Transcriptome Analysis of Laminar Tissue During the Early Stages of Experimentally Induced Equine Laminitis

Abstract

Equine laminitis is a debilitating disease that causes extreme sufferring in afflicted horses and often results in a lifetime of chronic pain. The exact sequence of pathophysiological events culminating in laminitis has not yet been characterized, and this is reflected in the lack of any consistently effective therapeutic strategy. For these reasons, we used a newly developed 21,000 element equine-specific whole-genome oligoarray to perform transcriptomic analysis on laminar tissue from horses with experimentally induced models of laminitis: carbohydrate overload (CHO), hyperinsulinaemia (HI), and oligofructose (OF). Samples were collected during the developmental (DEV) and Obel grade 1 (OG1) stages of laminitis for the CHO model. For the HI model, samples were collected at the Obel grade 2 (OG2) stage. For the OF model, samples were collected at the 12 h and 24 h time points. Appropriate control samples were obtained for all models. This is the first genome-wide transcriptome analysis of laminar tissue using an equine 21,000 70-mer long oligoarray approach in CHO, HI and OF induced laminitis. Overall, we identified the differential expression of genes encoding S100 calcium binding proteins, extracellular matrix proteins, glycoproteins, transporters, olfactory receptors, genes involved in signal transduction, body‟s homeostasis, apoptosis, and immune response. Between CHO and OF models of laminitis, there were more shared genes. We discovered several common differentially expressed genes (i.e., ADAMTS1, CYCS and CXCL14) among all three models that are likely important to the pathogenesis of equine laminitis. We also discovered what appear to be central roles of apoptosis, inflammatory response, and intracellular ion homeostasis molecular processes in CHO and OF models of laminitis. Pathway analysis detected the NOD-like receptor signaling pathway, which is involved in recognition of intracellular bacteria in both the CHO and OF models of laminitis. Genetic network analysis indicated convergent pathway core molecules present in equine acute laminitis: p38 MAPK and NF-κB. Most importantly, our results of overexpression of anti-microbial genes (i.e., DEFB4, PI3, and CXCL14) suggest the central involvement of these genes in the progression of early equine laminitis and will allow refinement of current hypotheses of disease pathogenesis