Advances in tenascin-C biology

Tenascin-C is an extracellular matrix glycoprotein that is specifically and transiently expressed upon tissue injury. Upon tissue damage, tenascin-C plays a multitude of different roles that mediate both inflammatory and fibrotic processes to enable effective tissue repair. In the last decade, emerging evidence has demonstrated a vital role for tenascin-C in cardiac and arterial injury, tumor angiogenesis and metastasis, as well as in modulating stem cell behavior. Here we highlight the molecular mechanisms by which tenascin-C mediates these effects and discuss the implications of mis-regulated tenascin-C expression in driving disease pathology

The role of tenascin-C in tissue injury and tumorigenesis

The extracellular matrix molecule tenascin-C is highly expressed during embryonic development, tissue repair and in pathological situations such as chronic inflammation and cancer. Tenascin-C interacts with several other extracellular matrix molecules and cell-surface receptors, thus affecting tissue architecture, tissue resilience and cell responses. Tenascin-C modulates cell migration, proliferation and cellular signaling through induction of pro-inflammatory cytokines and oncogenic signaling molecules amongst other mechanisms. Given the causal role of inflammation in cancer progression, common mechanisms might be controlled by tenascin-C during both events. Drugs targeting the expression or function of tenascin-C or the tenascin-C protein itself are currently being developed and some drugs have already reached advanced clinical trials. This generates hope that increased knowledge about tenascin-C will further improve management of diseases with high tenascin-C expression such as chronic inflammation, heart failure, artheriosclerosis and cancer

Cutaneous basement membrane formation in organotypic culture

The cutaneous basement membrane (BM) consists mainly of polymeric collagen-IV and laminin-10 and associated mono-/oligomeric laminin-5, nidogen, and perlecan. Since BM-defects in transgenic or knockout mice are mostly lethal at early developmental stages, we have studied the role of nidogen specifically in 3D-cocultures of human keratinocytes (HK) and fibroblasts (human/mouse, HF/MF) by either blocking interactions or implementing molecular deficiencies. HK or HaCaT cells were grown on collagen gels harboring HF or MF from normal or ko-mice. Nidogen-laminin interaction was blocked by the laminin-fragment (gamma-1-III3-5, L-gamma-f) binding nidogen. BM-formation was surveyed by immunofluorescence (IF), regular (EM), immuno-electron microscopy (IEM), and Western blots of protein extracts of separated epithelial and 'dermal' tissue. In 3D-cocultures of HK and HF L-gamma-f blocked mainly deposition of nidogen, laminin-10, and perlecan. Whereas the hemidesmosomal/BM components laminin-5, BP180, and integrin alpha6beta4 were still detectable (IF), by EM and IEM any BM-structures or hemidesmosomes (insertion of keratins) were absent. The fibroblast-made nidogen was eliminated by employing MF from nidogen-1/-2 ko-mice. In 3D-cocultures with HaCaT cells nidogen1/2 (--/++)-MF abolished nidogen-1 staining, but (--/+-)-MF reduced additionally nidogen-2, collagen-IV, and laminin-10. Absence of nidogens (--/--) further abolished collagen-IV and laminin-5; integrins such as alpha6beta4 appear normal (IIF). BM-formation could be reinstalled with recombinant nidogen-1 or -2. BM-perlecan, for comparison, is apparently synthesized also by keratinocytes. Thus, deficiency in either cell type did not affect BM-formation, demonstrated by growing perlecan (-/-)-MF or HaCaT antisense-perlecan cells with normal keratinocytes or fibroblasts, respectively. Accordingly, BM-components are efficiently recruited for ultrastructural assembly in this skin model

Control of basement membrane formation in skin-organotypic 3d-coculture

Basement membrane (BM) formation was functionally dissected in 3d-cocultures of human keratinocytes (HK) and fibroblasts (human/mouse, HF/MFf) by either blocking interactions or implementing molecular deficiencies. This was supposed to complement knockout mouse studies, where loss or functional defects of collagen-IV, laminins, nidogen, or perlecan are causing embryonic or neonatal death. HK or HaCaT cells were grown on collagen gels harboring hf or mf from normal or ko-mice. To block nidogen-binding to laminin-10 the corresponding laminin-fragment (gamma1-iii3-5, L-gamma-f) was applied. BM-formation was surveyed by immunofluorescence (IF), regular (EM) and immuno-electron microscopy (IEM). In 3d-cocultures of HK and HF L-gamma-f blocked deposition of nidogen, laminin-10, and perlecan, while collagen-IV appeared normal. Although the hemidesmosome components laminin-5, BP180, and integrin alpha6beta4 were only mildly affected, EM and IEM revealed complete absence of BM, hemidesmosomes, and basal insertion of keratin filaments. To eliminate nidogen, made by fibroblasts, MF from nidogen1/nidogen2 ko-mice or crossbreds were employed. In 3d-cocultures with HaCaT cells nidogen1/2 (??/++)-MF abolished nidogen1-staining, but (??/+?)-mf reduced also largely nidogen2, collagen-IV, and drastically laminin-10. Total absence of nidogen (??/??) also deleted collagen-IV & laminin-5, integrins e.g. alpha6beta4 appearing still normal (IF). BM-formation could be entirely rescued by applying recombinant nidogens. In skin, perlecan can be apparently synthesized by both keratinocytes & fibroblasts. Accordingly, deficiency in either cell type did not affect BM-formation, demonstrated by combining either perlecan (?/?)-mf or HaCaT anti-sense-perlecan cells with respective normal partner cells. Thus, in this skin model BM-components are efficiently transported to their actual assembly site

Isolation and characterization of human repetin, a member of the fused gene family of the epidermal differentiation complex

The human repetin gene is a member of the "fused" gene family and localized in the epidermal differentiation complex on chromosome 1q21. The "fused" gene family comprises profilaggrin, trichohyalin, repetin, hornerin, the profilaggrin-related protein and a protein encoded by c1orf10. Functionally, these proteins are associated with keratin intermediate filaments and partially crosslinked to the cell envelope (CE). Here, we report the isolation and characterization of the human repetin gene and of its protein product. The repetin protein of 784 amino acids contains EF (a structure resembling the E helix-calcium-binding loop-F helix domain of parvalbumin) hands of the S100 type and internal tandem repeats typical for CE precursor proteins, a combination which is characteristic for "fused" proteins. Repetin expression is scattered in the normal epidermis but strong in the acrosyringium, the inner hair root sheat and in the filiform papilli of the tongue. Ultrastructurally, repetin is a component of cytoplasmic non-membrane "keratohyalin" F-granules in the stratum granulosum of normal epidermis, similar to profilaggrin. Finally, we show that EF hands are functional and reversibly bind Ca(2+). Our results indicate that repetin is indeed a member of the fused gene family similar to the prototypical members profilaggrin and trichohyalin