Basement Membrane Reconstruction in Human Skin Equivalents Is Regulated by Fibroblasts and/or Exogenously Activated Keratinocytes

This study was undertaken to examine the role fibroblasts play in the formation of the basement membrane (BM) in human skin equivalents. For this purpose, keratinocytes were seeded on top of fibroblast-free or fibroblast-populated collagen matrix or de-epidermized dermis and cultured in the absence of serum and exogenous growth factors. The expression of various BM components was analyzed on the protein and mRNA level. Irrespective of the presence or absence of fibroblasts, keratin 14, hemidesmosomal proteins plectin, BP230 and BP180, and integrins α1β1, α2β1, α3β1, and α6β4 were expressed but laminin 1 was absent. Only in the presence of fibroblasts or of various growth factors, laminin 5 and laminin 10/11, nidogen, uncein, type IV and type VII collagen were decorating the dermal/epidermal junction. These findings indicate that the attachment of basal keratinocytes to the dermal matrix is most likely mediated by integrins α1β1 and α2β1, and not by laminins that bind to integrin α6β4 and that the epithelial-mesenchymal cross-talk plays an important role in synthesis and deposition of various BM components.