Lichen sclerosus (LS) is an acquired inflammatory condition that mainly affects anogenital skin. Evidence for serum autoantibodies to glycoprotein extracellular matrix protein 1 (ECM1) in a substantial number of patients may hold clue in understanding the pathogenic signature of LS. Indirect immunofluorescence staining on confocal laser scanning microscope using sera from LS patients (n=23; 1 male and 22 female) displayed that 9 (39.1%) of them exhibit intense immunoreactivity in the lower epidermis and dermal vessels of normal skin substrate, consistent with the staining pattern of affinity-purified IgG from LS sera and rabbit anti-ECM1 antibody. To address the relationship between in vivo ECM1 dysfunction and molecular events in the LS skin, we generated human dermal fibroblasts with siRNA-knockdown for ECM1 and analyzed transcription profiles by cDNA microarray. Comparison with siRNA-untreated fibroblasts identified 3,035 differentially expressed genes. Functional assessment assigned that 1,471 upregulated and 1,564 downregulated genes are related to proteins binding with cellular components, divalent cations, enzymes, and nucleotides. Criteria employing in vivo localization and proposed function of ECM1 in the skin narrowed to 49 upregulated genes, including COL4A, laminin A, fibronectin, MMPs, CTGF, PDGFA and its receptor, SMAD, and TGFB receptor. Realtime RT-PCR and ELISA supported the upregulation of paneled genes and corresponding proteins. Laminin 332 and type IV collagen, the representatives upregulated by ECM1 silencing, revealed unique expression pattern on immunohistochemistry using LS skin. Moreover, type VII collagen, which did not satisfy the ECM1-sliencing upregulation but showed abnormal expression pattern in the LS skin, bound to ECM1 recombinant protein. Impaired ECM1 function may thus cause increased expression and selective disassembly of basement membrane, vascular, and extracellular matrix molecules, as well as growth factors facilitating fibroblast proliferation, contributing to the LS skin pathology.

Impaired function of ECM1 underlies the pathogenic disorganization of vascular and basement membrane molecules in lichen sclerosus