Equine exuberant granulation tissue and human keloids: a comparative histopathologic study.
Authors: Theoret Christine L, Olutoye Oluyinka O, Parnell Laura K S, Hicks John
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Equine Exuberant Granulation Tissue and Human Keloids Horses and humans are uniquely susceptible among mammals to excessive fibroproliferative scarring during wound healing—equine exuberant granulation tissue (EGT) and human keloids respectively—yet their cellular and structural similarities remain poorly characterised. Theoret and colleagues conducted a detailed histopathologic comparison of archival tissue samples (8 EGT cases, 12 keloid cases) using conventional staining alongside immunohistochemistry to identify key cell populations and tissue architecture. Both conditions featured haphazardly organised, thickened collagen bundles with markedly elevated fibroblast numbers in the superficial and deep dermis; however, only human keloids displayed the distinctive "keloidal" collagen pattern, whilst myofibroblasts were abundant exclusively in equine tissue. The inflammatory profile differed notably between species: EGT showed significantly increased polymorphonuclear cells, small immature vessels, and myofibroblasts, whereas keloids displayed minimal vascularity and sparse acute inflammatory infiltrate. These findings suggest that the acute inflammatory response—more pronounced in horses—may fundamentally drive the cellular differences observed between conditions, with implications for species-specific treatment approaches; however, the authors emphasise that comparative investigation of common therapeutic strategies remains warranted to leverage insights from one species to benefit the other.
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Practical Takeaways
- •EGT and human keloids share fundamental fibroproliferative mechanisms but differ in inflammatory response patterns—EGT shows much more acute inflammation and vessel proliferation, which may inform treatment strategy selection
- •The marked increase in myofibroblasts and acute inflammatory cells in EGT suggests anti-inflammatory and anti-angiogenic interventions may be more effective than collagen-modulating approaches alone
- •Cross-species comparison reveals potential common treatment strategies for these problematic wound complications, warranting collaborative research between equine and human medicine
Key Findings
- •Both EGT and keloids showed increased haphazardly oriented thickened collagen fibers in superficial and deep dermis, but only keloids contained keloidal collagen
- •EGT uniquely demonstrated markedly increased myofibroblasts, small vessels in immature granulation tissue, and acute inflammatory cells (polymorphonuclear cells) compared to keloids
- •Humans and horses are the only mammals known to naturally develop excessive granulation during wound healing
- •Fibroblast numbers were markedly increased in both EGT and keloids, while macrophages and mast cells were infrequently found in both groups