Collagen fibril formation

Abstract

Collagen is most abundant in animal tissues as very long fibrils with a characteristic axial periodic structure. The fibrils provide the major biomechanical scaffold for cell attachment and anchorage of macromolecules, allowing the shape and form of tissues to be defined and maintained. How the fibrils are formed from their monomeric precursors is the primary concern of this review. Collagen fibril formation is basically a self-assembly process (i.e. one which is to a large extent determined by the intrinsic properties of the collagen molecules themselves) but it is also sensitive to cell-mediated regulation, particularly in young or healing tissues. Recent attention has been focused on "early fibrils' or "fibril segments' of approximately 10 microns in length which appear to be intermediates in the formation of mature fibrils that can grow to be hundreds of micrometers in length. Data from several laboratories indicate that these early fibrils can be unipolar (with all molecules pointing in the same direction) or bipolar (in which the orientation of collagen molecules reverses at a single location along the fibril). The occurrence of such early fibrils has major implications for tissue morphogenesis and repair. In this article we review the current understanding of the origin of unipolar and bipolar fibrils, and how mature fibrils are assembled from early fibrils. We include preliminary evidence from invertebrates which suggests that the principles for bipolar fibril assembly were established at least 500 million years ago.

On the effect of X-ray irradiation on the deformation and fracture behavior of human cortical bone

“…The nanoropes are stabilized by hydrogen bonding between residues [67][68][69]; every third residue in each of the molecules is the amino acid glycine (GLY) and about one fourth of the TC molecule consists of proline and hydroxyproline [70,71]. At this length-scale, bone deforms by stretching and unwinding of individual collagen molecules due first to entropic and then energetic mechanisms that involve H-bond breaking [39,40].…”

Articular cartilage tensile integrity: Modulation by matrix depletion is maturation-dependent

“…These findings suggest that a decrease in certain extrafibrillar molecules is necessary to permit the association of collagen segments. In corollary, binding of collagen-binding molecules to the collagen fibrils competitively inhibits the accretion of additional collagen segments and, in this way, regulates the growth of collagen fibrils during development [39,41,42]. A similar mechanism may be responsible for controlling the restraining function of the collagen network during cartilage growth and maturation.…”

Tissue engineering with nano-fibrous scaffolds

“…Found throughout biology, self-assembly of biomolecules, such as peptides and proteins, to well-defined architectures perform a variety of functions 55 . A good example is the self-assembly of collagen molecules to collagen fibrils, and the collagen fibrils are further packed side-by-side in parallel bundles to form collagen fibers with diameter ranged from 50 to 500 nm 56 . Inspired by nature, several groups have designed and synthesized polypeptides or oligopeptides molecules to selfassemble into nano-fibrous structures under suitable conditions 53,[57][58][59] .…”