Collagen oligomers modulate physical and biological properties of three‐dimensional self‐assembled matrices

Abstract

Elucidation of mechanisms underlying collagen fibril assembly and matrix-induced guidance of cell fate will contribute to the design and expanded use of this biopolymer for research and clinical applications. Here, we define how Type I collagen oligomers affect in-vitro polymerization kinetics as well as fibril microstructure and mechanical properties of formed matrices. Monomers and oligomers were fractionated from acid-solubilized pig skin collagen and used to generate formulations varying in monomer/oligomer content or average polymer molecular weight (AMW). Polymerization half-times decreased with increasing collagen AMW and closely paralleled lag times, indicating that oligomers effectively served as nucleation sites. Furthermore, increasing AMW yielded matrices with increased interfibril branching and had no correlative effect on fibril density or diameter. These microstructure changes increased the stiffness of matrices as evidenced by increases in both shear storage and compressive moduli. Finally, the biological relevance of modulating collagen AMW was evidenced by the ability of cultured endothelial colony forming cells to sense associated changes in matrix physical properties and alter vacuole and capillary-like network formation. This work documents the importance of oligomers as another physiologically-relevant design parameter for development and standardization of polymerizable collagen formulations to be used for cell culture, regenerative medicine, and engineered tissue applications.

Review of Collagen I Hydrogels for Bioengineered Tissue Microenvironments: Characterization of Mechanics, Structure, and Transport

“…12 All studies that investigate the effect of collagen concentration on hydrogel elastic and shear moduli demonstrate positive correlation. 12,41,44,60,76,77 Similarly, increasing pH increases all metrics of collagen hydrogel modulus. 13,34,35,60 The relationship between ionic strength and compression modulus is less straightforward, and appears to be interdependent with pH and temperature.…”

“…Reported values using such recipes fall within the range 130-300 mM. 12,21,34,47,54,60,70,76,79 Finer control of ionic strength has been achieved by adjusting the concentration of phosphate in the buffer or adding sodium chloride (NaCl) to the hydrogel. 35,50,79 Ionic strength is seldom measured directly for collagen hydrogels, but rather it is calculated from known or estimated concentrations of all ionic compounds present in solution.…”

“…Although many researchers have investigated collagen hydrogel network structure, no standard automated image analysis technique has yet emerged and therefore wide variation exists in published structural characteristics. Approaches in recent publications utilize algorithms exploiting a wide range of image segmentation and thresholding techniques, 12,21,26,27,34,41,44,47,49,64,76 grid-based estimation, 27,40,49 and even Fourier transforms and autocorrelation. 34,40,68 Further, manual estimation of dimensions of user-identified fibers and pores is not uncommon.…”

Preparation and Characterization Urea-Solubilized Sol-Gel Type I Collagen and Its Possible Use in Applications

“…Later many groups modified the methods to improve the quality of the isolated collagens and to reduce the working time [Miller, & Rhodes, 1982;Miller, & Gay, 1987;Bailey, et al, 2011]. Briefly, different tissues such as rat tail tendons, skin from human, porcine and bovine sources are defatted and disinfected to germ free (e.g.…”

“…Several other problems with the AC, such as the pH adjustment prior to usage in cell culture with medium and buffers, which is also batch-dependent, makes the application of such collagen very time-and laborconsuming. most importantly, this reduced the reproducibility of the collagen based experiments as indeed, the collagens produced from the neutral salt or acidic procedure are mixture from differentially hydrolyzed/degraded collagen peptides and intact collagen Chandrakasan, et al, 1976;Bailey, et al, 2011;Bann, et al, 2003;Mizuno, et al, 2004;Rajan, et al, 2006]. In Fig.…”