Development of Tissue Engineered Tregs as a Treatment for Acute Ischemic Stroke

ABSTRACT In the U.S., nearly 800,000 individuals experience a stroke each year, predominantly ischemic strokes. The economic burden of stroke is staggering, with projected stroke-related medical costs in the U.S. expected to surpass $94 billion by 2035. This underscores the urgent need for effective therapies to address this significant public health challenge. While the potential of regulatory T cells (Tregs) in promoting stroke recovery has been recognized, translating this promise into clinical success has been hampered by several obstacles. Traditional Treg therapies face challenges in manufacturing, phenotypic instability, and a lack of tissue specificity. This proposal focuses on the development of allogeneic engineered tissue Tregs (EngTregs) as a novel off-the-shelf therapeutic approach for stroke. Overexpression of ST2, the receptor for the alarmin IL-33, enhances the ability of EngTregs to: (i) sense and respond to tissue damage (ST2-expressing EngTregs efficiently migrate to sites of inflammation and injury); (ii) suppress excessive inflammation (EngTregs exert potent anti-inflammatory effects through multiple mechanisms, including direct suppression of immune cells and modulation of the inflammatory environment); and (iii) actively participate in tissue repair (EngTregs produce growth factors and interact with other cells to promote tissue regeneration). Overexpression of FOXP3 ensures a stable and suppressive Treg phenotype, crucial for long-term therapeutic efficacy. A chemically induced signaling complex (CISC) enables tunable IL-2 signaling, promoting Treg survival and function while facilitating scalable manufacturing. These innovations culminate in a first-in-class allogeneic tissue EngTreg product with advantages in manufacturing scalability, cost-effectiveness, and therapeutic potential compared to conventional Treg therapies. Preliminary studies demonstrate the ability of allogeneic EngTregs to accumulate in the injured brain and improve motor skills, sensory function, learning, and memory following ischemic injury induced in the transient middle cerebral artery occlusion (tMCAO) mouse model of stroke. This proposal outlines three aims to further advance the preclinical development of EngTregs for stroke: Aim 1: Evaluate the therapeutic efficacy of EngTregs in two preclinical stroke models (permanent middle cerebral artery occlusion and photothrombosis) in both adult and aged mice, assessing a comprehensive range of functional and histological outcomes. Aim 2: Characterize the mechanism of action and define a comprehensive in vitro profile of the human EngTreg drug product, including assessment of cytokine sequestration, T cell suppression, macrophage polarization, and transcriptomic analysis. Aim 3: Assess the immunotoxicity and immunogenicity of human EngTregs to ensure clinical safety, including evaluation of cytokine release syndrome and allo-immunogenicity. Successful completion of these aims will provide critical preclinical data supporting the clinical translation of EngTregs as a novel and promising therapeutic strategy for stroke, addressing a significant unmet medical need.