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Equine deep stromal abscesses (51 cases – 2004–2009) – Part 2: the histopathology and immunohistochemical aspect with attention to the histopathologic diagnosis, vascular response, and infectious agents

Authors

  • Michala de Linde Henriksen,

    1. Faculty of Health and Medical Sciences, Department of Veterinary Clinical and Animal Sciences, University of Copenhagen, Frederiksberg, Denmark
    2. Departments of Large and Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
    3. Department of Veterinary Clinical Sciences, Comparative Ophthalmology, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN, USA
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    • This study is a part of the first author's PhD study performed and sponsored by the University of Copenhagen, Denmark (2008–2013). The cases in the study were collected during the first author's residency in comparative ophthalmology at the University of Florida, USA (2009–2012). The first author is now a faculty member at the University of Minnesota (2013-present).
  • Pia Haubro Andersen,

    1. Faculty of Veterinary Medicine and Animal Science, Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden
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  • Kristy Mietelka,

    1. Diagnostic Center for Population and Animal Health, College of Veterinary Medicine, Michigan State University, Lansing, MI, USA
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  • Lisa Farina,

    1. Department of Infectious diseases & Pathology, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
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  • Preben D. Thomsen,

    1. Faculty of Health and Medical Sciences, Department of Veterinary Clinical and Animal Sciences, University of Copenhagen, Frederiksberg, Denmark
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  • Caryn E Plummer,

    1. Departments of Large and Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
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  • Brendan G Mangan,

    1. Departments of Large and Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
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  • Steffen Heegaard,

    1. Department of Ophthalmology, Glostrup Hospital, University of Copenhagen, Frederiksberg, Denmark
    2. Department of Neuroscience and Pharmacology, Eye Pathology Institute, University of Copenhagen, Frederiksberg, Denmark
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  • James K Coleman,

    1. Department of Infectious diseases & Pathology, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
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  • Nils Toft,

    1. Faculty of Health and Medical Sciences, Department of Large Animal Sciences, University of Copenhagen, Frederiksberg, Denmark
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  • Dennis E. Brooks

    Corresponding author
    1. Departments of Large and Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
    • Address communications to:

      D. E. Brooks

      Tel.: +1 (352) 392 2229

      Fax: +1 (352) 392 6125

      e-mail: brooksd@ufl.edu

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Abstract

Purpose

To investigate histopathologic and immunohistochemical aspects of equine deep stromal abscesses (DSA) with a focus on the histopathologic diagnosis, presumptive etiology, and the immunohistochemical expression of three angiogenesis-related factors: vascular endothelial growth factor-A (VEGF-A), pigment epithelium-derived factor (PEDF), and interleukin-1 receptor antagonist (IL-1ra).

Sample population

Paraffin-embedded biopsy samples from 51 DSA. The biopsies were collected from full-thickness penetrating keratoplasty or split-thickness lamellar keratoplasty surgeries at the University of Florida Veterinary Medical Center in the period from 2004 to 2009.

Procedure

The histopathologic and immunohistochemical findings were tested for association between each other. Prevalence calculation and test for association with qualitative data analysis was used for data evaluation.

Results

Fungal hyphae were found histologically in 47.1% (n = 24) of the DSA cases. Histopathologically, most fungal DSA showed suppurative keratitis (n = 34; 66.7%) and little to no stromal vascularization infiltrating the abscess (negative association, P = 0.005). All three angiogenesis-related factors were expressed to some degree in DSA tissue. A negative association between VEGF-A and PEDF when compared to the presence of fungal hyphae (P < 0.001, P = 0.023) indicated that cases positive for these two factors will most probably not have fungal hyphae present.

Conclusion

Abnormally decreased VEGF-A expression is suggested as the reason for the slow vascularization and delayed resolution of fungal DSA, whereas PEDF and IL-ra did not seem to have any influence on the vascularization process. Clinical and histopathologic characteristics of DSA make it possible to suggest an etiology for an equine DSA with an unknown etiology.

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