Liquid Crystalline Human Recombinant Collagen: The Challenge and the Opportunity

Abstract

Collagen is a key component of the extracellular matrix, and by far the most prominent constituent of all load-bearing tissues. Its abundance and self-assembly capacities render it a practical scaffold material for tissue repair and regeneration applications. However, some difficulties exist in artificially regenerating functional collagen structures to match native tissues and their respective performances. There are two major limitations of existing collagen-based scaffolds: The first one is poor mechanical performance, and the second one is the failure to closely mimic natural tissues as to provide the necessary topographic and mechanical cues required for cell propagation and differentiation. The complexity of inducing sufficient order and alignment stands at the base of the impediments to successful formation of artificial collagen scaffolds, which closely match native tissue strength and morphology. Recombinant human collagen produced in transgenic tobacco plants has the capacity of forming highly concentrated liquid crystalline dope that can be aligned by application of shear force. Leveraging shear alignment of liquid crystalline recombinant human collagen opens new possibilities toward obtaining scaffolds that may be able to provide the necessary mechanical support, while closely mimicking the molecular signals and mechanical cues displayed to natural cell milieu. Such scaffolds may prove advantageous in the development of improved medical devices in fields, such as ophthalmology, neurology, and orthopedics.

Human collagen produced in plants

“…The extracted protein is a pure, heterotrimeric atellocollagen, free of high molecular weight contaminants and decorated with a degree of hydroxylated proline and lysine residues similar to that of human collagen. 28 Similarly, membranes formed under shear force featured orderly, crimp-like organization of parallel, well separated fibrils. Moreover, rhCOL1 fibrils exhibit D-band striations, characteristic of natural collagen fibers (Fig.…”

Engineered proteins as multifunctional materials

“…22 Critically, the recombinant collagen retained the native trihelical structure essential for self-assembling the higher-order fibrillar structure typical of extracellular collagen and also displayed increased hydrophilicity compared to native collagen enabling high concentrations potentially useful for shear-force-based fibril alignment to more closely mimic the environment and mechanics of the extracellular matrix. 23 An important benefit of recombinant production is the relative ease with which protein sequence can be altered, with chimeric fusion proteins and site-specific variants being two common techniques to expand functionality and alter materials properties. 6 Such approaches are particularly useful in the design of highly mutable proteins such as elastin-like polypeptides where repeat motifs contain customizable residues that modulate protein properties such as phase-transition temperature allowing the creation of thermally responsive biomaterials.…”

Collagen and Elastin Biomaterials for the Fabrication of Engineered Living Tissues

“…68−70 Despite the advantages of rhCol, including control over amino acid sequence, chain length, and addition of cross-linking groups, 71,72 applications have been limited due to the high cost of protein expression. 63,73 4.2. Elastin Sources.…”