Molecular evidence of sterile tissue damage during pathogenesis of the pododermatitis aseptica hemorrhagica circumscripta is associated with disturbed epidermal-dermal homeostasis

Authors: REEDER, T.L. - University Of Delaware; ZARLENGA, D.S. - Former ARS Employee; 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., Dyer, R. 2024. Molecular evidence of sterile tissue damage during pathogenesis of the pododermatitis aseptica hemorrhagica circumscripta is associated with disturbed epidermal-dermal homeostasis. Journal of Dairy Science. 107(10):8413-8431. https://doi.org/10.3168/jds.2023-24577.
DOI: https://doi.org/10.3168/jds.2023-24577

Interpretive Summary: Ulceration is a periparturient claw horn disorder resulting in lowered resistance to stress and strain. Ulceration and inflammation may surface locally, but they can affect the way a host responds to distal infections and invading pathogens. Herein, we examined changes in target genes of inflammation, signal elements, and other genes that support epidermal proliferation and differentiation in the claws of dairy cows. Results of this investigation indicated regions of the claw with damage to horn producing tissue but in the absence of a breached sole horn, develop sterile inflammatory responses. Alterations to gene expression supporting epithelial proliferation and differentiation and that infer disruption in wound repair accompany this inflammation. Surprisingly, normal lesion-free claw sole exhibited similar changes in gene expression for proliferative and differentiating functions in the absence of sterile inflammation or damage. These data indicate that repair to tissue damage from infection is not locally confined but can permeate local, normal tissues as well. These data are applicable to studying the effects of tissue damage from injury or infection not only on the damaged tissues but also on tissue which are normal but proximal to the damaged site.

Technical Abstract: Pododermatitis aseptica hemorrhagica circumscripta is associated with metalloproteinase 2 weakening of distal phalangeal suspensory structures and sinkage of the distal phalanx in the claw capsule. Pressure from the tuberculum flexorium on the sole epidermis and dermis produces hemorrhagic tissue injury and defective horn production appearing as yellow-red, softened claw horn in region 4 of the sole. A model of the MAPK/ERK signal cascade orchestrating epidermal-dermal homeostasis was employed to determine if sterile inflammatory responses are linked to disturbed signal transduction for epidermal homeostasis in sole epidermis and dermis. The objective was to assess shifts in target genes of inflammation, up- and downstream MAPK/ERK signal elements, and targeted genes supporting epidermal proliferation and differentiation. Sole epidermis and dermis were removed from lateral claws bearing lesions of PAHC, medial claws from the same limb and lateral claws from completely normal limbs of multiparous, lactating Holstein cows. The abundance levels of targeted transcripts were evaluated by real-time PCR. Lesion effects were assessed by ANOVA, and mean comparisons were performed with t-tests to assess variations between mean expression in ulcer-bearing or medial claw dermis and epidermis and completely normal lateral claw dermis and epidermis or between ulcer-bearing dermis and epidermis and medial claw dermis and epidermis. The lesions were sterile and showed losses across multiple growth factors, their receptors, several downstream AP1 transcription components, CMYC, multiple cell-cycle and terminal differentiation elements conducted by MAPK/ERK signals and ß 4, a 6, and collagen 17A hemidesmosome components. These losses coincided with increased cytokeratin 6, ß 1 integrin, proinflammatory metalloproteinases 2 and 9, IL1B and physiologic inhibitors of IL1B, the decoy receptor, and receptor antagonist. Medial claw epidermis and dermis from limbs with lateral claws bearing PAHC showed reductions in upstream MAPK/ERK signal elements and downstream targets that paralleled those in hemorrhagic lesions. Inhibitors of IL1B increased in the absence of real increases in inflammatory targets in the medial claw dermis and epidermis. Losses across multiple signal path elements and downstream targets were associated with negative effects on targeted transcripts supporting claw horn production and wound repair across lesion-bearing lateral claws and lesion-free medial claw dermis and epidermis. It was unclear if the sterile inflammation was causative or a consequence of these perturbations.