Local immunomodulation using a microneedle patch for the management of skin transplant

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ABSTRACT Skin allograft transplantation is a lifesaving approach for the management of severe burn patients when skin autografts or artificial substitutes are not available due to the severity of the wound. However, their ultimate rejection increases patient morbidity and mortality and requires regrafting. Clinically-used systemic immunosuppression, while useful in other organ transplants, cannot be prescribed for this patient cohort as they present a high risk of life-threatening infections. Therefore, new strategies that can generate donor-specific tolerance, while preserving other protective immune functions through local immunoregulation, are needed. We recently demonstrated that hydrogel-based microneedle (MN) patches can be used to promote proliferation of regulatory T cells (Tregs) in skin allografts, by locally delivering immunomodulators (CCL22 and IL-2) at the transplant site. The MNs also facilitate the monitoring of the Treg homing process via skin interstitial fluid (ISF) sampling (Artzi, azzi, et al, Advanced Materials, 2021). Here, we will develop a novel family of hydrogel-based MNs that will be chemically functionalized to tailor the release kinetic profile of the immunomodulators to identify the optimal Treg recruitment to the allograft to sustain a local, immunosuppressive effect and to restore allo- tolerance. We will study the immunomodulatory role of the top CCL22/IL-2-doped MN platform in prolonging long-term skin allograft while providing mechanistic insight into the biological processes driving local immune regulation and Treg homeostasis in the allograft via ISF sampling in both an immunocompetent- and a humanized-skin transplant murine model. Specifically, we aim to define the optimal dose of CCL22 and IL-2 needed to maximize Treg recruitment and Treg proliferation respectively, and to assess the role of supplementary cytokines such as IL-7 in supporting Treg homeostasis (based on our previous data, Azzi et al, Science Translational Medicine, 2020) when co-delivered with our MN platform. Moreover, we will gain mechanistic insight into Treg stability, function and alloantigen specificity following MN-based therapy using a transgenic mouse model, which allows tracing the genetic lineage of Tregs. Also, we will validate the diagnostic ability of the MN-platform for in situ monitoring of the response to therapy. Finally, we will test the therapeutic and diagnostic merit of the MN platform in a humanized mouse model when delivering the optimal therapeutic combination of cytokines/chemokines and its capacity to induce long-term allograft survival. Our study will provide the foundation to develop safer technologies for enhancing skin transplant survival in a local, minimally-invasive way without compromising the regulatory arm of the immune system of burn patients while offering an opportunity to continuously monitor the response to the therapy.