Background: Keloids are recognized as benign dermal fibroproliferative tumors that result from aberrant wound healing in susceptible individuals. Nevertheless, the etiology and pathophysiology of keloids is not fully elucidated yet. A protein that has been implicated in the wound healing process, conversion of fibroblasts into myofibroblasts and production of ECM components, inflammation, and generation of galectin-glycan complexes, is galectin-1 (Gal-1). However, its presence as well as its implications in benign dermal fibroproliferative tumors such as keloids, has not been considered. Therefore, the aim of this study is to ascertain whether Gal-1 is present in keloid tissues. Methods: Seven biopsies from patients diagnosed with keloid were selected. Four normal skin specimens were obtained from patients undergoing aesthetic surgery procedures. To identification of collagen bundles, some histological sections were stained following the Mason´s trichrome protocol. The presence of Gal-1 was assessed by immunofluorescence staining using confocal laser scanning microscopy. Results: Immunostaining revealed that Gal-1 was present in the uppermost cell layers of the thickened epidermis with a gradient of expression that seems to increase from basal layer to suprabasal layers. Surprisingly, Gal-1 was particularly found outlining the cellular margin and intercellular bridges of the upper-spinous and granular keratinocytes and was absent in the epidermal keratinocytes of normal adult human skin. Interestingly, in the reticular dermis the presence of Gal-1 was noticeable in the cytoplasm of elongated fibroblasts that were forming cellular bundles of collagen and along the thick and compact collagen bundles, whereas in the dermis of normal skin, Gal-1 immunoreactivity was weak in some fibroblasts. Conclusions: Our findings suggest that in keloid tissues Gal-1 would not only be regulating the dermal fibroblast proliferation, ECM production, particularly collagen, and abnormal vascularization, but would also be contributing to the altered stratification and terminal keratinocyte differentiation and importantly, to epidermal thickening.
Collagen bundles; epidermal thickening; fibroblasts; galectin-1; keloid