Equine exuberant granulation tissue and human keloids: a comparative histopathologic study.

This research paper compares the histopathologic features of a fibroproliferative disorder in horses (exuberant granulation tissue-EGT) and humans (keloids), noting the similarities and differences, and suggesting the need for further research to develop common treatment strategies for these conditions.

Research Methodology

• The study uses archival tissue samples of EGT from 8 horses and keloid from 12 humans.
• These tissue sections underwent automated hematoxylin and eosin staining, a common procedure used to highlight structures in biological tissues for viewing under a microscope.
• Additionally, histopathological examination was carried out using Gomori trichrome, Verhoeff-van Gieson elastin, and immunohistochemical stainings.
• The tissue samples were then evaluated using a semi-quantitative grading scale, looking for the presence or absence of various factors, such as ulceration, myofibroblasts, elastic fibers, and inflammation among others.

Findings

• The study discovered that both superficial and deep dermis in both horses and humans have increased numbers of haphazardly oriented thickened collagen fibers. Nonetheless, only keloids were found to contain “keloidal” collagen.
• There was a marked increase in fibroblasts (a type of cell that synthesizes the extracellular matrix and collagen) in both groups, but only EGT had myofibroblasts.
• There was minimal vascularity (presence of blood vessels) observed in the deep dermis of both groups, but the superficial dermis in EGT was characterized by small vessels within the immature granulation tissue.
• Different types of immune cells such as macrophages and mast cells were infrequently found in both groups. However, polymorphonuclear cells (a type of immune cell) were markedly increased in EGT.
• The study concludes that the inflammatory response may contribute to the observed differences in the cellular populations, with EGT showing more acute inflammatory cells compared to keloids.

Conclusion

• This research provides an in-depth comparative study between EGT in horses and keloids in humans—conditions marked by excessive granulation during wound healing.
• It highlights the similarities and differences between them at a cellular level, suggesting that the pathogenesis of these conditions could be somewhat similar.
• The paper concludes with the recommendation that more investigation is needed into these fibroproliferative conditions to develop common treatment strategies.