Biomimetic sulphated alginate hydrogels suppress IL-1β-induced inflammatory responses in human chondrocytes

Abstract

Loss of articular cartilage from ageing, injury or degenerative disease is commonly associated with inflammation, causing pain and accelerating degradation of the cartilage matrix. Sulphated glycosaminoglycans (GAGs) are involved in the regulation of immune responses in vivo, and analogous polysaccharides are currently being evaluated for tissue engineering matrices to form a biomimetic environment promoting tissue growth while suppressing inflammatory and catabolic activities. Here, we characterise physical properties of sulphated alginate (S-Alg) gels for use in cartilage engineering scaffolds, and study their anti-inflammatory effects on encapsulated chondrocytes stimulated with IL-1β. Sulphation resulted in decreased storage modulus and increased swelling of alginate gels, whereas mixing highly sulphated alginate with unmodified alginate resulted in improved mechanical properties compared to gels from pure S-Alg. S-Alg gels showed extensive anti-inflammatory and anti-catabolic effects on encapsulated chondrocytes induced by IL-1β. Cytokine-stimulated gene expression of pro-inflammatory markers IL-6, IL-8, COX-2 and aggrecanase ADAMTS-5 were significantly lower in the sulphated gels compared to unmodified alginate gels. Moreover, sulphation of the microenvironment suppressed the protein expression of COX-2 and NF-κB as well as the activation of NF-κB and p38-MAPK. The sulphated alginate matrices were found to interact with IL-1β, and proposed to inhibit inflammatory induction by sequestering cytokines from their receptors. This study shows promising potential for sulphated alginates in biomimetic tissue engineering scaffolds, by reducing cytokine-mediated inflammation and providing a protective microenvironment for encapsulated cells.

Development of 3D Biofabricated Cell Laden Hydrogel Vessels and a Low‐Cost Desktop Printed Perfusion Chamber for In Vitro Vessel Maturation

“…It has to be mentioned that these results were obtained in 2D, and comparison with 3D encapsulated NHDF in the ADA‐GEL, as performed in this study, must be considered with care. A high retention of barium inside alginate based hydrogels was described previously, while the crosslinking of alginate based hydrogels with 60 m m BaCl 2 to increase hydrogel stability has been also described before . U87‐MG cells were not compromised in viability .…”

“…A high viability of NHDF cells embedded in ADA‐GEL when crosslinked with 60 m m BaCl 2 for 10 min was confirmed, showing no toxic effect of Ba 2+ on the encapsulated cells. Moreover, the applied molarity of Ba 2+ is considerably higher compared to the already successfully reported BaCl 2 crosslinking, while, for example, Arlov et al showed high viability of cells inside alginate‐based hydrogels crosslinked with 1 m m BaCl 2 combined with 50 m m CaCl 2 . Due to the positive viability results of NHDF in 60 m m BaCl 2 crosslinked ADA‐GEL, it is confirmed that the modification of alginate to ADA may not change its capability for barium retention, allowing successful cell encapsulation using Ba 2+ as a crosslinker for oxidized alginate.…”

Inflammation-Modulating Hydrogels for Osteoarthritis Cartilage Tissue Engineering

“…Some existing biomaterials exhibit limited anti-inflammatory properties. For example, low molecular weight xanthan gum downregulates caspase 3 [77], and heparin/heparin sulfate [78,79] and sulfated alginate can capture free IL-1β, suppressing IL1β-mediated inflammation [80,81]. Carboxymethylated chitin was reported to reduce MMP-1 expression in the rabbit OA model [82].…”

Sulfated Alginates as Heparin Analogues: A Review of Chemical and Functional Properties

“…In a recent study, we characterized gels made exclusively from sulfated alginates with varying sulfation degrees, as well as the effect of combining highly sulfated alginate (DS = 1) in unmodified alginate gels at various proportions. Sulfated alginate alone (150 kDa) was found to form stabile gels with calcium up to a sulfation degree of approximately 0.4, whereas increasing the sulfation level required either the inclusion of unmodified alginate or utilization of gelling ions with a higher affinity for alginate (e.g., barium, strontium) [ 58 ]. An alternative strategy that has not yet been explored to the authors’ knowledge is covalent cross-linking between sulfated alginates, or to unmodified alginates, which can be a feasible approach where a higher gel stiffness is required.…”