Photocrosslinkable laminin-functionalized polyethylene glycol hydrogel for intervertebral disc regeneration

Abstract

Intervertebral disc (IVD) disorders and age-related degeneration are believed to contribute to low back pain. There is significant interest in cell-based strategies for regenerating the nucleus pulposus (NP) region of the disc; however, few scaffolds have been evaluated for their ability to promote or maintain an immature NP cell phenotype. Previous studies have shown that NP cell-laminin interactions promote cell adhesion and biosynthesis, which suggests a laminin-functionalized biomaterial may be useful for promoting or maintaining the NP cell phenotype. Here, a photocrosslinkable poly(ethylene glycol)-laminin 111 (PEG-LM111) hydrogel was developed. PEG-LM111 hydrogel mechanical properties could be tuned within the range of dynamic shear moduli values previously reported for human NP. When primary immature porcine NP cells were seeded onto PEG-LM111 hydrogels of varying stiffnesses, LM111 presenting hydrogels were found to promote cell clustering and increased levels of sGAG production as compared to stiffer LM111 presenting and PEG-only gels. When cells were encapsulated in 3D gels, hydrogel formulation was found to influence NP cell metabolism and expression of proposed NP phenotypic markers, with higher expression of N-cadherin and cytokeratin 8 observed for cells cultured in softer (<1 kPa) PEG-LM111 hydrogels. Overall, these findings suggest that soft, LM111 functionalized hydrogels may promote or maintain the expression of specific markers characteristic of an immature NP cell phenotype.

Laminin Enriched Scaffolds for Tissue Engineering Applications

“…PEG-LM111 hydrogels were synthesized by reacting them with PEG-diacrylate (PEGDA) in the presence of irgacure as an initiator. 45 In contrast to findings reported by other studies, 46 the hydrogel stiffness decreased with increasing concentrations of PEG-LM111 conjugates. Hydrogel encapsulated dorsal root ganglion exhibited longer neurite extensions with increasing LM111 concentration (0-100µg/ml).…”

“…In a subsequent study, Fransisco et al 46 synthesized photocrosslinkablePEG-LM111 hydrogels for IVD regeneration. Increasing the degree of LM modification was found to alter LM bioactivity and inhibit immature NP cell adhesion.…”

Cell therapy for the degenerating intervertebral disc

“…(84) We have further tested a tripleinterpenetrating-network (TIN) hydrogel that enhances biomechanical properties of the repaired IVD and supports cell delivery. (85) Other natural and synthetic scaffold materials, including laminin,(86) pig bone gelatin and cartilage extracellular matrix,(87) collagen,(88) composite of collagen with alginate,(89) and carboxymethylcellulose (90) have been tested for engineering IVD by seeding with cells in vitro, followed by implantation into the disc space. All the above scaffolds could be modified into injectable form and used in minimally invasive cell therapy.…”

Biomechanics and mechanobiology in functional tissue engineering

“…Biomaterials that undergo phase transition from liquid to solid through exposure to light, temperature changes, or chemical crosslinking/degradation can provide versatile environments for controlling cell behavior while defining the mechanical environment and functional properties of the scaffold (Betre et al, 2006; Chao et al, 2010; Cuchiara et al, 2012; Dankers et al, 2005; Sharma et al, 2013). Furthermore, chemical functionalization of such materials with proteins or gene delivery systems has been shown to provide an additional level of design capability for scaffold function (DeLong et al, 2005; Francisco et al, 2014; Glass et al, 2014; Hume et al, 2011; Kisiel et al, 2013; Salimath and Garcia, 2014). …”