Lamellation in Fibrous Dysplasia: a Clinicopathologic Study

Abstract

Despite advances in regenerative medicine and tissue engineering, human skin substitutes remain a clear goal to achieve. Autografts remain the principal clinical option. The long-term changes in dermis, as well as its response after injuries, are not well known. Research in this field has been hindered by a lack of experimental animal models. This study analyzes the architectural dermal scaffold (collagen and elastin fibers plus fibrillin-microfibrils) changes in a model of human skin pressure ulcers in mice. Immunosuppressed NOD/Scid mice (n=10) were engrafted with human skin of dimensions 4x3 cm. After 60 days as a permanent graft, a pressure ulcer (PU) was created in the human skin using a compression device. Three study groups were established: full-thickness skin graft before (hFTSG) and after applying mechanical pressure (hFTSG-PU). Native human skin was used as control group. Evaluations were conducted with visual and histological assessment. Scaffold components from each group were compared by immunohistochemical staining (tropoelastin, collagen I and III, metalloproteins (MMP), fibulins, and lysil oxidases (LOX) among others). The long-term engrafted skin showed a certain degradative state of dermis scaffold, as noticed by the active expression of MMPs and tropoelastin compared to native skin. However, a great reparative response after pressure ulcer onto the engrafted skin was observed. A significant increase of fibrillin microfibrils components (TGF-β, MAGP-1 and fibrillin-1), and matrix suprastructures of collagen I, III and LOX lead to an active restructuration of dermal tissue. Our human skin model in mice revealed the important role of the dermal scaffold component to reach skin stability and its capability to react to mechanical pressure injuries. These results showed the important role of dermal scaffold to support the histoarchitecture and mechanosensation of the human skin.