Elastic protein-based polymers in soft tissue augmentation and generation

Abstract

Five elastic protein-based polymers, designed as variations of polymer I, (GVGVP)251, elicited different responses when injected as subcutaneous implants in the guinea pig, a preclinical test used to evaluate materials for soft tissue augmentation and specifically for correction of urinary incontinence. All six polymers, prepared using recombinant DNA technology, expressed at good levels using transformed E. coli fermentation. These E. coli-produced polymers were purified for the first time to the exacting levels required for use as biomaterials where a large quantity could disperse into the tissues in a few days. Time periods of 2 and 4 weeks were used. Polymer I functioned as a bulking agent around which a fine fibrous capsule formed. Inclusion of (GVGVAP)8, a chemoattractant toward monocytes and elastin-synthesizing fibroblasts in the sequence of polymer I, resulted in an appropriate tissue response of invasion of macrophages. Inclusion of lysine residues, for lysyl oxidase cross-linking, suggested a possible remodeling of the implant toward fibers. Most promising however, when the cell attachment sequence, GRGDSP, was added to polymer I, the implant elicited tissue generation with a normal complement of collagen and elastic fibers, spindle-shaped histiocytes and angiogenesis. If this response is retained over time, the desired soft tissue augmentation and generation will have been achieved. Our working hypothesis is that on formation of elastin, with a half-life of the order of 70 years, a long lasting soft tissue augmentation would result rather than scar tissue as occurs with Contigen, the currently approved injectable implant for soft tissue augmentation.

Peptide-based biopolymers in biomedicine and biotechnology

“…Biological materials such as elastin-based polypeptides, collagens derived from extracellular matrices, fibrins, and spider silk proteins [59,62,153,[183][184][185][186][187] are useful for tissue engineering because they have good chemical compatibility in aqueous solutions, good in vivo biocompatibility, a controllable degradation rate in vivo, the ability to break down into natural amino acids that can be metabolized by the body, and minimal cytotoxicity, immune response, and inflammation [174,[188][189][190][191][192][193][194]. In addition, biopolymers can be easily functionalized to enhance their interactions with cells and provide an optimal platform for cellular activities and tissue functions.…”

“…Multiple physical or chemical crosslinking sites can be genetically encoded so that the ELPs form networks, and reactive sites can be incorporated for controlled degradation. Specific ligands can also be added to impart functionality for cell adhesion and tissue growth [168,180,189,[195][196][197], and initial work by Urry et al demonstrated that ELPs cause minimal cytotoxicity and immune response when implanted [189,190].…”

Rapid Cross-Linking of Elastin-like Polypeptides with (Hydroxymethyl)phosphines in Aqueous Solution

“…[24][25][26][27][28][29] ELPs are also promising scaffold materials for musculoskeletal and cardiovascular tissue engineering, as their peptide sequences are native to smooth and skeletal muscle, ligaments and other muscularskeletal tissues, and they show low cytotoxicity and no antigenic response in vivo. 11,19 In addition, ELPs may confer some benefits for cartilage tissue engineering application, as we have shown that the thermally-induced aggregated, "coacervate" phase of ELPs allows encapsulation of chondrocytes and human adipose derived stem cells while promoting a chondrogenic phenotype and cartilage matrix synthesis. 14,17 Although these studies have indicated the promise of ELPs for cartilage tissue engineering, these materials exhibited a narrow range of mechanical properties, which may limit their utility as scaffolds for cell-assisted regeneration, and provides the rationale for the development of crosslinking strategies.…”

Biomimetic Regeneration of Elastin Matrices Using Hyaluronan and Copper Ion Cues

“…In this context, implantation of synthetic elastomers or assembly of elastin peptides can replicate the mechanics of native elastin, but the absence of associated cell-signaling proteins (e.g., fibrillin) prevents the constructs from eliciting native responses from vascular smooth muscle cells (SMCs). [5][6][7][8] An alternative approach is to actively regenerate elastin structures in vivo and within tissueengineered constructs although the current unavailability of scaffolds that can provide cellular cues necessary to upregulate elastin synthesis and regenerate faithful mimics of native elastin limits this approach. 9,10 As mentioned above, elastic fibers are among the most difficult matrix structures to repair or regenerate because they contain other non-elastin protein components (e.g., fibrillin, elaunin) and have a highly regulated recruitment and deposition pattern and a multi-step hierarchical assembly process.…”