Transcriptional responses consistent with perturbation in dermo-epidermal homeostasis in septic sole ulceration

Authors: REEDER, T.L. - University Of Delaware; ZARLENGA, D.S. - Former ARS Employee; ZIEGLER, A.L. - North Carolina State University College Of Veterinary Medicine; DYER, R.M. - University Of Delaware

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2024
Publication Date: 5/31/2024
Citation: Reeder, T., Zarlenga, D., Ziegler, A., Dyer, R. 2024. Transcriptional responses consistent with perturbation in dermo-epidermal homeostasis in septic sole ulceration. Journal of Dairy Science. 107(10):8432-8451. https://doi.org/10.3168/jds.2023-24578.
DOI: https://doi.org/10.3168/jds.2023-24578

Interpretive Summary: Infections and inflammation may appear locally, but they have a detrimental effect on the way a host responds to distal infections and invading pathogens. A common and overlooked infection of dairy cows is ulcers of the claw. Sole ulcers with breaches in the horn of lateral claws exist in a state of nonhealing wound repair. Large amounts of inflammation are associated with reductions in growth factors, growth factor receptors and signal pathways orchestrating corium tissue regeneration, claw horn synthesis and ulcer repair. Gaps exist in our knowledge of biologic events that orchestrate normal growth, differentiation and maturation of hoof horn tissue because epidemiologic evidence links dietary and housing factors to claw horn lesions but the pathophysiology underlying these associations has been poorly investigated. The purpose of this investigation was to address issues relating immune responses, inflammation and wound repair to growth factors and receptors present in the claw and determine the disease state affects gene expression levels throughout the claw. This was accomplished by examining the differential regulation of a collection of genes associated with pro-inflammation, growth factors, growth factor receptors, cell cycle elements, lateral cell-to-cell signaling elements and structures of early and late keratinocyte differentiation. Our results showed that growth factor and cytokines regulating tissue growth and differentiation were expressed in horn producing tissues of the claw where inflammation, bleeding and local tissue damage disturbed expression of immune related genes and growth factors throughout the entire claw. The success in answering the above questions generated important information on early detection signs of lameness and established a model to study methods of treating this debilitating disease among dairy cows. Further it provided anecdotal evidence that host responses to cell damage and infection are not relegated to the damaged tissue but extend to normal tissues in the surrounding areas.

Technical Abstract: The aim of this study was to evaluate transcriptional changes in the sole epidermis and dermis of bovine claws with septic sole ulceration of the lateral claw. Assessment included changes in transcripts orchestrating epidermal homeostatic processes, including epidermal proliferation, differentiation, inflammation, and cell signaling. Sole epidermis and dermis samples were removed from region 4 of lesion-bearing lateral and lesion-free medial claws of pelvic limbs in multiparous, lactating Holstein cows. Control sole epidermis and dermis samples were obtained from region 4 of lateral claws of normal pelvic limbs. Transcript abundances were evaluated by real-time PCR, and relative expression analyzed by ANOVA. Relative to normal lateral claws, sole epidermis and dermis in ulcer-bearing claws exhibited downregulation of genes associated with growth factors, growth factor receptors, activator protein 1 (AP-1) and proto-oncogene (CMYC) transcription components, cell cycle elements, lateral cell-to-cell signaling elements, and structures of early and late keratinocyte differentiation. These changes were accompanied by upregulation of proinflammatory transcripts interleukin 1 a (IL1A), interleukin1 ß (IL1B), interleukin 1 receptor 1 (IL1R1), inducible nitric oxide synthase (NOS2), the inflammasome components NOD-like receptor protein 3 (NLRP3), pyrin and caspase recruitment domain (PYCARD), caspase-1 interleukin converting enzyme (CASPASE), the matrix metalloproteinases (MMP2 and MMP9), and the anti-inflammatory genes interleukin 1 receptor antagonist (IL1RN) and interleukin1 receptor 2 (IL1R2). Transcript abundance varied across epidermis and dermis from the ulcer center, margin, and epidermis and dermis adjacent to the lesion. Sole epidermis and dermis of lesion-free medial claws exhibited changes paralleling those in the adjacent lateral claws in an environment lacking inflammatory transcripts and downregulated IL1A, interleukin 18 (IL18), tumor necrosis factor a (TNFA), and NOS2. These data imply perturbations in signal pathways driving epidermal proliferation and differentiation are associated with, but not inevitably linked to epidermis and dermis inflammation. Further work is warranted to better define the role of crushing tissue injury, sepsis, metalloproteinase activity, and inflammation in sole ulceration.