Type VI collagen in extracellular, 100-nm periodic filaments and fibrils: identification by immunoelectron microscopy.

Abstract

Abstract. Filaments and fibrils that exhibit a 100-nm axial periodicity and occur in the medium and in the deposited extracellular matrix of chicken embryo and human fibroblast cultures have been tentatively identified with type VI collagen on the basis of their similar structural characteristics (Bruns, R. R., 1984, J. Ultrastruct. Res.,. Using indirect immunoelectron microscopy and specific monoclonal and polyclonal antibodies, we now report their positive : identification with collagen VI and their distribution in fibroblast cultures and in tendon. Primary human foreskin fibroblast cultures, labeled with anti-type VI antibody and studied by fluorescence microscopy, showed a progressive increase in labeling and changes in distribution with time up to 8 d in culture. With immunoelectron microscopy and monoclonal antibodies to human type VI collagen followed by goat antimouse IgG coupled to colloidal gold, they showed in thin sections specific 100-nm periodic labeling on extracellular filaments and fibrils: one monoclonal antibody (3C4) attached to the band region and another (4B10) to the interband region of the filaments and fibrils. Rabbit antiserum to type VI collagen also localized on the band region, but the staining was less well defined. Control experiments with antibodies to fibronectin and to procollagen types I and IU labeled other filaments and fibrils, but not those with a 100-nm period. Heavy metal-stained fibrils with the same periodic and structural characteristics also have been found in both adult rat taft tendon and embryonic chicken tendon subjected to prolonged incubation in culture medium or treatment with adenosine 5'-triphosphate at pH 4.6. We conclude that the 100-nm periodic filaments and fibrils represent the native aggregate form of type VI collagen. It is likely that banded fibrils of the same periodicity and appearance, reported by many observers over the years in a wide range of normal and pathological tissues, are at least in part, type VI collagen. WITH the discovery of the genetic heterogeneity of collagen (38), it became apparent that the composition and organization of the extracellular matrices were far more complex than were ever anticipated. To date there are at least 10 known, distinct collagen gene products, not including non-matrix collagen sequences such as those in Clq (47, 48), acetylcholine esterase (50), and surfactant (60). The molecular structure and tissue supramolecular aggregates of most of these are established. For several, however, the forms in which they exist in situ and their relations with other matrix components are not yet known. Type VI collagen is an example of the latter.Extracellular filaments and fibrils that have a 100-nm periodic cross-banding have been observed in chicken embryo fibroblast cultures (7). The basic unit, a "beaded" filament, consists of a thread measuring 2-3 nm in diameter and pairs of "beads" distributed along its length at regular intervals of 90-110 nm. In the aggregated form (i.e., bundles of ordered "beaded" filaments), the...

Extracellular matrix in the trabecular meshwork

“…4. (Bruns et al 1986;Engvall et al 1986;Ball et al 2001;Reale et al 2001;Baldock et al 2003;Ball et al 2003;Knupp et al 2006) In the TM, type VI immunostaining of both heteromorphic aggregates and interband longitudinal sheets has been observed, supporting the model in Fig. 4.…”

“…(Reale et al 2001) This may relate to the 100 nm repeat structures in the JCT, although this has not been comprehensively studied in detail. (Hessle and Engvall 1984;Bruns et al 1986;Engvall et al 1986;Knupp et al 2006) The type VI collagen N-terminal repeats bind hyaluronan and heparin, while the C-terminal domains are involved in self-assembly. (Kielty et al 1992b;Specks et al 1992;Ball et al 2001;Ball et al 2003) Decorin and biglycan associate with the N-terminal end of the central collagenous domain, affecting fibril formation.…”

Increase in types IV and VI collagen in cherry haemangiomas

“…In accordance with previous studies [4,21], we observed that, in areas of normal skin surrounding the haemangiomas, there was only weak staining for type VI collagen in the subpapillary connective tissue near the epidermaldermal junction and in a thin area around nerves and capillaries. Normally, type VI collagen seems not to be an intrinsic basement membrane component [11].…”

“…Normally, type VI collagen seems not to be an intrinsic basement membrane component [11]. Based on immunoelectron microscopic investigations it has been suggested that, in a similar manner to most extracellular matrices, type VI collagen in the skin forms a network of filaments 6-10nm thick independent of collagen type I/III fibrils [4,21]. This network seems to anchor collagen type I/III fibres or the basement membranes of large interstitial structures, such as nerves and blood vessels, into surrounding connective tissue [21].…”

“…Immunoelectron microscopic studies on the extracellular matrix of cultured fibroblasts and of rat tail tendons indicate that collagen type VI fibrils aggregate to form 100 nm 'beaded' filaments and fibrils [3,4]. Based on these findings it has been suggested that there is a close relationship between type VI collagen and broadbanded aggregates in situ with a similar periodicity of 100 nm, which have also been referred to as long-spacing collagen, zebra collagen or Luse's bodies (for review see references 36 and 45].…”