CAR-T cells inhibit vascular smooth muscle phenotypic switching and reduce intimal hyperplasia in vein grafts

Abstract Background Intimal hyperplasia (IH) is a prevalent cause of vein graft stenosis after coronary artery bypass grafting (CABG) in the middle and long term. Vascular smooth muscle cell (VSMC) phenotypic switching from a contractile phenotype to a synthetic phenotype is a hallmark of this process, along with the degradation of extracellular matrix (ECM) and smooth muscle migration. Chimeric antigen receptor (CAR)-T cell therapy is a targeted cellular immunotherapy that uses genetically engineered T cells to specifically eliminate the antigen-bearing cells. There is a potential to apply CAR-T therapy to cardiovascular diseases. Purpose In this study, we aim to design a novel CAR-T cell therapy to eliminate synthetic vascular smooth muscle cells in intimal hyperplasia, inhibit phenotypic switching, in order to reduce vein graft stenosis. Methods and results Using bulk RNA-seq dataset from the GEO database, we have identified human organic cation transporter (OCT1) as a key marker for synthetic vascular smooth muscle cell in vein grafts (Fig.1A, B). We then engineered switchable fourth-generation CAR-T cells incorporating CD28 and CD3 ζ costimulatory domains (Fig.1C, E). In addition, these CAR-T cells secrete tissue inhibitor of metalloproteinase-3 (TIMP3), a protein that had been shown to inhibit matrix metalloproteinases (MMPs) activity and the ERK1/2 pathway (Fig. 1F). Targeting FITC instead of OCT1 itself allows a controllable and switchable working process for the CAR-T cells, as they only start to identify synthetic VSMCs in combination with a FITC-conjugated OCT1 antibody (Fig.1D). Immunostaining of PDGF-induced synthetic VSMCs co-cultured with CAR-T cells and FITC-conjugated OCT1 antibody revealed increased expression of contractile markers, and reduced expression of synthetic markers (Fig1.G), along with decreased mitochondrial membrane potentials, which could be reverted after pre-treatment with a pan caspase inhibitor (Fig.1H),. In vivo studies using mice vein graft model showed reduced intimal thickness, increased intimal/medial ratio in cross-sections, in addition to increased peak velocity and inner wall diameter on ultrasound after CAR-T cell therapy (Fig.2). Conclusion Switchable CAR-T cell therapy targeting synthetic vascular smooth muscle cells might be a promising approach to alleviate intimal hyperplasia in vein graft stenosis.