Researcher(s)
- Tarun Ravichandar, Biomedical Engineering, University of Delaware
Faculty Mentor(s)
- Brian Kwee, Biomedical Engineering, University of Delaware
Abstract
Prolonged inflammation following severe ischemic muscle injuries disrupts tissue repair by increasing pro-inflammatory cytokines, leading to fibrosis. While inflammation is initially necessary to clear tissue debris, a transition to anti-inflammatory signaling post-injury is critical to permit regeneration. Regulatory T cells (Tregs) are anti-inflammatory immune cells that promote tissue regeneration. However, the persistent inflammation of severe ischemic injuries limits Treg recruitment. Interleukin-33(-IL-33) is a cytokine that can recruit Tregs to sites of injury. Delivering IL-33 using hydrogels is advantageous to free drugs because hydrogels protect IL-33 from rapid degradation and provide localized release. Thus, we have developed an IL-33-releasing hydrogel to provide sustained and localized delivery at sites of severe ischemic inflammation to enhance repair.
Hydrogels were prepared from ultrapure alginate crosslinked with calcium. Laponite-RD (L-RD), nanoparticles with negatively charged surfaces and positively charged edges, were incorporated into the hydrogel to enhance controlled cytokine release. The viscoelastic character of hydrogels containing different L-RD concentrations was measured using oscillatory shear rheology with a 12 mm parallel plate. Representative cross sections of ischemic thigh muscles treated with a blank hydrogel or IL-33-hydrogel were stained for CD31 (a marker for blood vessels) to evaluate blood vessel regeneration within the injury site.
Over one week, hydrogels with 0 mg/mL L-RD exhibited minimal release of IL-33, with only 5% of its dose, as compared to 0.1 mg/mL L-RD with 50% release. However, gels with 1 mg/mL L-RD only released 20% of the loaded dose. For rheological assessment, we expect Laponite to increase hydrogel stiffness. Previous work demonstrated increased blood perfusion in ischemic limbs of BALB/c mice treated with IL-33-loaded hydrogel. From histology, we expect an increase in CD31 staining in IL-33-treated mice compared to blank mice.
Overall, IL-33-loaded alginate hydrogels with laponite present a promising therapeutic strategy to enhance muscle regeneration following severe ischemic injuries.