(483c) Engineering Immunoinstructive Cryogel Scaffolds to Induce Regulatory T-Cells

Regulatory T-cells (Tregs), mediators of immune tolerance, can prevent aberrant immune responses that lead to autoimmune diseases. Treatments using patients’ own Tregs have shown some clinical benefit. Yet, low availability of Tregs in combination with their laborious and costly ex vivo manipulation have hindered their widespread application.¹ Therefore, there is a pressing need to develop therapies that can locally generate Tregs directly in the body. Engineering immunomodulatory biomaterials to manipulate immune cells could provide a promising strategy to weaken effector T-cell responses while inducing Tregs. Cryogels are advanced hydrogels polymerized at subzero temperatures,^2,3 resulting in an interconnected macroporous network that promotes immune cell infiltration.⁴ Here, immunoinstructive cryogels were engineered to induce and expand Tregs (Fig. 1A).

Syringe-injectable cryogel scaffolds were fabricated from hyaluronic acid (HA) and heparin. Stimulating antibodies against murine CD3 and CD28 were effectively conjugated to cryogels via bioorthogonal click reactions. These functionalized cryogels induced cytokine secretion from T-cells when infused within the scaffolds. Additionally, cryogels were effectively loaded with T-cell modulating cytokines (TGFβ and IL-2), leading to their release in a controlled and sustained fashion. Increasing the heparin fraction in cryogels helped promote cytokine loading and slow down their subsequent release rates. Compared to cytokine-free cryogels and cryogels in cytokine-supplemented medium, the stimulation of T-cells within cytokine-loaded cryogels resulted in reduced secretion of inflammatory cytokines and increased numbers of Tregs (Fig. 1B). Heparin, antibody and cytokine concentrations within the immunomodulatory cryogels were optimized to boost Treg induction while preventing proliferation of conventional T-cells. Collectively, our data demonstrate that immunoinstructive cryogel scaffolds can effectively reinforce Treg induction and hold great potential for the rational design of effective therapies to promote immunological tolerance. Directing in situ immunomodulation using injectable cryogels to locally induce large numbers of Tregs may pave the way for basic research and translational medicine to treat autoimmune and inflammatory disorders.

References

1. 1. C. Raffin et al., Nature Reviews Immunology, 2020.
2. 2. S.A. Bencherif et al., PNAS, 2012.
3. 3. L.J. Eggermont et al., Trends. Biotechnol., 2020.
4. 4. S.A. Bencherif et al., Nat. Commun., 2015.