Spatial transcriptomics reveals molecular programs linked to heart-transplant rejection
A landmark study published in Nature Cardiovascular Research uses image-based spatial transcriptomics on biopsies from 62 adult and pediatric heart transplant recipients to map acute rejection at subcellular resolution. The resulting molecular atlas reveals that patients with identical histological biopsy grades run fundamentally different molecular programs. These hidden variations predict who will respond to immunomodulatory therapies and identify key pathways, such as IL-6/JAK-STAT3, that drive chronic cardiac allograft vasculopathy.
Spatial transcriptomics molecular atlas
▪Researchers at Vanderbilt Health and the Translational Genomics Research Institute used image-based spatial transcriptomics to construct a high-resolution longitudinal molecular atlas of acute heart transplant rejection.
▪The spatial transcriptomics study analyzed longitudinal endomyocardial biopsy samples from 49 adult and 13 pediatric heart transplant recipients collected between December 2017 and January 2023.
▪Standard clinical diagnosis of acute heart transplant rejection relies on invasive endomyocardial biopsies and histologic grading, which are subject to interobserver variability and potential over- or under-immunosuppression.
▪Repeated endomyocardial biopsies over years of post-transplant surveillance carry a documented risk of damage to the tricuspid valve, leading to significant valve regurgitation in a substantial proportion of recipients.
▪Solid organ transplant rejection occurs in up to 40% of organ recipients within one year of transplantation, potentially causing long-term organ failure and death.
Molecular heterogeneity in rejection phenotypes
▪The spatial transcriptomics study revealed substantial molecular heterogeneity across rejection types and within identical histologic rejection grades that is not apparent by standard histology alone.
▪The molecular heterogeneity within identical histologic grades may explain why clinical presentations of heart transplant rejection range from a complete lack of symptoms to cardiogenic shock.
▪In acute cellular rejection, T-cell aggregates co-localized with dendritic cells, whereas in antibody-mediated rejection, the dominant spatial pattern involved macrophages and fibroblasts clustering together.
Treatment response prediction markers
▪An ongoing randomized multicenter clinical trial (NCT03644667) since 2018 is testing whether tocilizumab, an anti-IL-6 receptor monoclonal antibody, reduces rejection-associated injury in 200 heart transplant recipients.
▪Baseline rejection biopsies from patients who respond to immunomodulatory therapies have distinct transcriptomic profiles compared to biopsies from patients who do not respond.
▪The transcriptomic differences between treatment responders and non-responders spanned 216 genes across 6 cell types, with non-responders showing activation in IL-6/JAK-STAT3, IFNα/IFNγ, and TNFα signaling pathways.
▪The spatial transcriptomics study linked cell-specific gene expression patterns during acute rejection to the development of cardiac allograft vasculopathy, a chronic rejection form limiting long-term survival.
▪According to 2019 ISHLT registry data, cardiac allograft vasculopathy affects 8% of heart transplant recipients at one year, rising to 29% at five years and 47% at ten years post-transplant.
▪A May 2026 study by Owen and colleagues found that the JAK1/2 inhibitor ruxolitinib significantly reduced cardiac allograft vasculopathy and prolonged survival in a mouse model.
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