Acute kidney injury (AKI) occurs in over 50% of critically ill patients. The poor recruitment and differentiation of regulatory T cells (Tregs) is associated with chronic kidney disease (CKD) development. Here, we develop injectable, granular ‘host’-hydrogels for avidity-controlled chemokine and cytokine delivery. We aim to prevent AKI-to-CKD progression by i) attracting CD4+ T cells to the site by rapid chemokine release and ii) inducing Treg differentiation by sustained delivery of ‘guest’-modified IL-2 (Fig 1A).
Methacrylated β-cyclodextrin and dextran (MeCD, DexMA) were co-polymerized (5mM LAP, 10mW/cm²) to yield hydrogels (G’~15kPa) with a high host concentration. MeCD/DexMA hydrogels (5%_w/v DexMA, 10%_w/v MeCD) were processed into microgels by extrusion fragmentation and jammed by centrifugation, to yield injectable, shear-thinning hydrogels (rheology, G’~15kPa, Fig 2B). Comparison of established chemokines (transwell assays) identified CCL21 as a potent chemokine for activated CD4+ T cells (Fig 1C). Guests (adamantane, Ad) were conjugated to IL-2 via NHS (5 Ad per IL-2); Ad-IL2 differentiated activated CD4+ T cells into Tregs in a dosa-dependent manner with moderate loss of bioactivity (Fig 1D). Hydrogels (50μL) loaded with CCL21 and/or Ad-IL2 were injected subq in healthy mice and T cells quantified (flow cytometry, Fig 1E). CCL21 (25µg) attracted T cells to the hydrogel within the first week (Fig 1F), while combination with Ad-IL2 (5µg) increased Treg populations over 28 days (Fig 1G) without inducing cytotoxic T cells.
In sum, we identified CCL21 as a potent driver of activated CD4+ T cell recruitment; rapid release attracted these cells to the injection site. Prolonged release of Ad-IL2 induces Treg differentiation, which in combination with CCL21 increases Treg abundance. Such controlled release is a promising approach to modulate the immune microenvironment post-AKI, preventing CKD development.

Akari Seiner

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