Multi-scale Extracellular Matrix Mechanics and Mechanobiology by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9783030201821
Publisher: Springer International Publishing

3 Hierarchical Design of Collagen In Vivo

Understanding the unique hierarchical organization of type I collagen and its associated physical properties, interactions with other biomolecules, and metabolism (turnover) is fundamental to its use in the fabrication of next-generation biomaterials and tissue-engineered medical products. As the most prevalent protein, collagen is widely distributed throughout the body, where it is found in load-bearing tissues (e.g., skin, bone, tendon, cartilage, and blood vessels), organs (e.g., bladder, stomach, and intestine), and other connective tissues (e.g., pericardium, fat, and placenta). Collagen molecules are produced by cells and deposited within the extracellular space, where they self-assemble in a multi-scale fashion to give rise to the fibrillar scaffold of the tissue ECM. As shown in Fig. 2, this supramolecular assembly involves several aggregation steps: first from single polypeptide chains to a stable triple helical molecule, then to microfibrils, fibrils, and fibers, and finally to macro-scale tissues. Although its primary sequence is identical across tissues, post-translational modifications and formation of intermolecular crosslinks contribute to diversification of collagen building blocks, ECM collagen-fibril networks, and therefore tissue-specific form and function [61, 109].

Fig. 2Multi-scale synthesis and assembly of collagen as occurs in vivo. (A) Collagen genes are transcribed from DNA into RNA. (B) Translation of component polypeptide alpha chains by ribosomes and translocation into the rough endoplasmic reticulum. (C) Hydroxylation of alpha chains by lysyl hydroxylases. (D) Folding of trimeric procollagen molecule. (E) Transfer of procollagen to Golgi for additional post-translational modification and packaging for exocytosis. (F) Enzymatic cleavage of propeptide ends yielding tropocollagen molecules. (G) Crosslinking of tropocollagen molecules by lysyl oxidases to form oligomers. (H) Self-assembly of collagen molecules into D-banded fibrils. (I) Fibrils merge to form fibers and networks, giving rise to complex tissue architecture

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