Regulation of hypoxia-inducible factor-1α and related genes in equine digital lamellae and in cultured keratinocytes.

The research article focuses on the role of the Hypoxia-inducible factor-1α (HIF-1A) protein in inflammation and hypoxia in horses. The study explores the regulation of HIF-1A and related genes in equine keratinocytes and in lamellar tissue affected by a type of lameness called laminitis.

Study Objective and Methodology

• The primary goal of the study was to understand the function of HIF-1A and related genes in the equine keratinocyte, a skin cell type, and in lamellar tissue from horses suffering from sepsis-related laminitis. Laminitis is a serious disease in horses causing lameness due to the inflammation of sensitive structures inside the hooves.
• Both in vivo and in vitro experiments were used to achieve this objective. Real-time quantitative PCR (RT-qPCR) and immunoblotting were performed to evaluate mRNA and protein levels of HIF-1A and HIF-1A-related genes. Additional tests included indirect immunofluorescence to localize HIF-1A in frozen lamellar tissue sections.

Results and Findings

• The results established that HIF-1A could be regulated primarily at the post-transcriptional level in equine keratinocytes, leading to increased HIF-1A responses to hypoxia but not to lipopolysaccharide exposure.
• HIF-1A was observed at high concentrations in normal equine lamina and was found to increase in early stage laminitis (Obel grade 1 or OG1) using the carbohydrate overload (CHO) model.
• mRNA concentrations of genes cyclo-oxygenase-2 and inducible nitric oxide synthase were elevated in equine keratinocytes exposed to hypoxia and lipopolysaccharide, and in lamellar tissue from induced laminitis models. However, no increase was seen in the glucose transporter-1 gene.

Conclusions

• The findings suggest that the normal equine lamellae or hoof layers are profoundly hypoxic, or lacking sufficient oxygen, compared with other tissues. This condition might contribute to the development of laminitis.
• The increase in inflammatory genes in equine keratinocytes exposed to hypoxia and lipopolysaccharide, and in lamellar tissue in laminitis, points to a possible interaction between high levels of HIF-1A signaling in lamellar keratinocytes and inflammatory signaling, likely induced by circulating inflammatory mediators.
• These results underline the potential importance of HIF-1A in the pathological mechanisms involved in laminitis, providing a new perspective on this widespread equine disease.