Treg-recruiting microspheres prevent inflammation in a murine model of dry eye disease.

Dry eye disease (DED) is a common ocular disorder affecting millions of individuals worldwide. The pathology of DED involves the infiltration of CD4+ lymphocytes, leading to tear film instability and destructive inflammation. In the healthy steady state, a population of immunosuppressive T-cells called regulatory T-cells (Treg) regulates proliferation of immune cells that would otherwise lead to a disruption of immunological homeostasis. For this reason, it has been suggested that Tregs could restore the immunological imbalance in DED. To this end, one possible approach would be to recruit the body's own, endogenous Tregs in order to enrich them at the site of inflammation and tissue destruction. Previously, we have demonstrated a reduction of inflammation and disease symptoms in models of periodontitis corresponding to recruitment of endogenous Tregs, which was accomplished by local placement of controlled release systems that sustain a gradient of the chemokine CCL22, referred to here as Treg-recruiting microspheres. Given that DED is characterized by a pro-inflammatory environment resulting in local tissue destruction, we hypothesized that the controlled release of CCL22 could also recruit Tregs to the ocular surface potentially mediating inflammation and symptoms of DED. Indeed, data suggest that Treg-recruiting microspheres are capable of overcoming the immunological imbalance of Tregs and CD4+ IFN-γ+ cells in the lacrimal gland. Administration of Treg-recruiting microspheres effectively mitigated the symptoms of DED as measured through a number of outcomes such as tear clearance, goblet cells density and corneal epithelial integrity, suggesting that recruitment of endogenous Treg can mitigate inflammation associated with DED.

Prevention of inflammation-mediated bone loss in murine and canine periodontal disease via recruitment of regulatory lymphocytes.

The hallmark of periodontal disease is the progressive destruction of gingival soft tissue and alveolar bone, which is initiated by inflammation in response to an invasive and persistent bacterial insult. In recent years, it has become apparent that this tissue destruction is associated with a decrease in local regulatory processes, including a decrease of forkhead box P3-expressing regulatory lymphocytes. Accordingly, we developed a controlled release system capable of generating a steady release of a known chemoattractant for regulatory lymphocytes, C-C motif chemokine ligand 22 (CCL22), composed of a degradable polymer with a proven track record of clinical translation, poly(lactic-co-glycolic) acid. We have previously shown that this sustained presentation of CCL22 from a point source effectively recruits regulatory T cells (Tregs) to the site of injection. Following administration of the Treg-recruiting formulation to the gingivae in murine experimental periodontitis, we observed increases in hallmark Treg-associated anti-inflammatory molecules, a decrease of proinflammatory cytokines, and a marked reduction in alveolar bone resorption. Furthermore, application of the Treg-recruiting formulation (fabricated with human CCL22) in ligature-induced periodontitis in beagle dogs leads to reduced clinical measures of inflammation and less alveolar bone loss under severe inflammatory conditions in the presence of a diverse periodontopathogen milieu.