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Macroscopic Banding Pattern of Collagen Gel Formed by a Diffusion-Reaction Process.

ABSTRACT: Shapes and patterns observed in internal organs and tissues are reproducibly and robustly produced over a long distance (up to millimeters in length). The most fundamental remaining question is how these long geometries of shape and pattern form arise from the genetic message. Recent studies have demonstrated that extracellular matrix (ECM) critically participates as a structural foundation on which cells can organize and communicate. ECMs may be a key to understanding the underlying mechanisms of long-distance patterning and morphogenesis. However, previous studies in this field mainly focused on the complexes and interaction of cells and ECM. This paper pays particular attention to ECM and demonstrates that collagen, a major ECM component, natively possesses the reproducible and definite patterning ability reaching centimeter-scale length. The macroscopic pattern consists of striped transparent layers. The observation under crossed Nicols demonstrates that the layers consist of alternately arranged polarized and unpolarized parts. Confocal fluorescence microscopy studies revealed that the polarized and unpolarized segments include collagen-rich and -poor regions, respectively. The patterning process was proposed based on the Liesegang banding formation, which are mineral precipitation bands formed in hydrogel matrixes. These findings will give hints to the questions about long-distance cell alignment and provide new clues to artificially control cell placement over micron size in the field of regenerative medicine.

SUBMITTER: Narita T

PROVIDER: S-EPMC8756805 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Collagen is heavily hydroxylated. Experiments show that proline hydroxylation is important to triple helix (monomer) stability, fibril assembly, and interaction of fibrils with other molecules. Nevertheless, experiments also show that even without hydroxylation, type I collagen does assemble into its native D-banded fibrillar structure. This raises two questions. Firstly, even though hydroxylation removal marginally affects macroscopic structure, how does such an extensive chemical change, which is expected to substantially reduce hydrogen bonding capacity, affect local structure? Secondly, how does such a chemical perturbation, which is expected to substantially decrease electrostatic attraction between monomers, affect collagen's mechanical properties? To address these issues, we conduct a benchmarked molecular dynamics study of rat type I fibrils in the presence and absence of hydroxylation. Our simulations reproduce the experimental observation that hydroxylation removal has a minimal effect on collagen's D-band length. We also find that the gap-overlap ratio, monomer width and monomer length are minimally affected. Surprisingly, we find that de-hydroxylation also has a minor effect on the fibril's Young's modulus, and elastic stress build up is also accompanied by tightening of triple-helix windings. In terms of local structure, de-hydroxylation does result in a substantial drop (23%) in inter-monomer hydrogen bonding. However, at the same time, the local structures and inter-monomer hydrogen bonding networks of non-hydroxylated amino acids are also affected. It seems that it is this intrinsic plasticity in inter-monomer interactions that preclude fibrils from undergoing any large changes in macroscopic properties. Nevertheless, changes in local structure can be expected to directly impact collagen's interaction with extra-cellular matrix proteins. In general, this study highlights a key challenge in tissue engineering and medicine related to mapping collagen chemistry to macroscopic properties but suggests a path forward to address it using molecular dynamics simulations.

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Macroscopic Banding Pattern of Collagen Gel Formed by a Diffusion-Reaction Process.

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