MCC950-loaded silk microgel-hydrogel composite scaffolds effectively modulate inflammation for improving tissue
Kieran Lau1, Angus Grant2, Alex H P Chan2
1School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia; Sydney Biomanufacturing Incubator, University of Sydney, Sydney, NSW 2006, Australia; Charles Perkins Centre, University of Sydney, Sydney, NSW 2006, Australia.
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Hydrogels are an attractive biomaterial for use in soft tissue engineering applications but fall short when used in large volume applications, exhibiting limited cellular infiltration and exaggerated fibrotic capsule responses. Embedding microgels within bulk hydrogels to generate microporosity enables greater cellular infiltration and provides more control over cell fate. Microgels can be further encapsulated with therapeutics to provide bioactive cues to the surrounding local microenvironment, synergistically complementing their intrinsic physical properties. MCC950, a NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome inhibitor, has been previously shown to selectively halt foreign body driven inflammation while preserving inflammation beneficial to minimizing the fibrotic capsule response and promoting tissue repair within implanted biomaterials. Here, we fabricated a silk fibroin-based hydrogel construct composed of MCC950-encapsulated microgels encased within a bulk hydrogel filler. While the encapsulation of MCC950 into silk constructs resulted in few changes in mechanical properties, the eluted drug retained bioactivity in vitro against human THP-1 cells. In vivo implantation of MCC950-encapsulated microgel-hydrogel constructs in a subcutaneous mouse model over 2 weeks showed synergistic effects between the physical and biological cues, resulting in a decrease in fibrous capsule formation and increase in cellular infiltration, attributed to the decrease in NLRP3 expression around the scaffold. Together, these results demonstrate the potential of MCC950-encapsulated silk microgel-hydrogel constructs for soft tissue engineering applications. Furthermore, these findings highlight a synergistic interplay between targeted NLRP3 inhibition and the microporous scaffold architecture that collectively drives reduced fibrosis and a more pro-regenerative immune microenvironment conducive to positive tissue remodeling. STATEMENT OF SIGNIFICANCE: Hydrogels are promising for soft tissue engineering but often lack cell infiltration at larger volumes. Embedding microgels within bulk hydrogels creates a microporous structure that enhances cellular infiltration. Therapeutics can also be encapsulated to provide bioactive cues to synergistically complement the physical architecture. In this study, silk-based microgel-hydrogel constructs were encapsulated with MCC950, a selective immunomodulatory drug, to minimize the fibrotic response and promoting tissue repair. Scaffolds were optimized for mechanical strength, drug release with eluted MCC950 retaining bioactivity against human THP-1 cells. 2-week mouse subcutaneous implantations demonstrated effects between architectural and bioactive cues, decreasing capsule thickness and increasing cell infiltration. These findings highlight the synergistic between physical and bioactive cues towards creating a pro-regenerative microenvironment conducive to tissue remodeling.
