Matthew Worssam

All Publications

• Network-based prioritization and validation of regulators of vascular smooth muscle cell proliferation in disease. Nature cardiovascular research Lambert, J., Oc, S., Worssam, M. D., Häußler, D., Solomon, C. U., Figg, N. L., Baxter, R., Imaz, M., Taylor, J. C., Foote, K., Finigan, A., Mahbubani, K. T., Webb, T. R., Ye, S., Bennett, M. R., Krüger, A., Spivakov, M., Jørgensen, H. F. 2024; 3 (6): 714-733

  Abstract

  Aberrant vascular smooth muscle cell (VSMC) homeostasis and proliferation characterize vascular diseases causing heart attack and stroke. Here we elucidate molecular determinants governing VSMC proliferation by reconstructing gene regulatory networks from single-cell transcriptomics and epigenetic profiling. We detect widespread activation of enhancers at disease-relevant loci in proliferation-predisposed VSMCs. We compared gene regulatory network rewiring between injury-responsive and nonresponsive VSMCs, which suggested shared transcription factors but differing target loci between VSMC states. Through in silico perturbation analysis, we identified and prioritized previously unrecognized regulators of proliferation, including RUNX1 and TIMP1. Moreover, we showed that the pioneer transcription factor RUNX1 increased VSMC responsiveness and that TIMP1 feeds back to promote VSMC proliferation through CD74-mediated STAT3 signaling. Both RUNX1 and the TIMP1-CD74 axis were expressed in human VSMCs, showing low levels in normal arteries and increased expression in disease, suggesting clinical relevance and potential as vascular disease targets.

  View details for DOI 10.1038/s44161-024-00474-4

  View details for PubMedID 38898928

  View details for PubMedCentralID PMC11182749

• Network-based prioritization and validation of regulators of vascular smooth muscle cell proliferation in disease. Nature cardiovascular research Lambert, J., Oc, S., Worssam, M. D., Häußler, D., Solomon, C. U., Figg, N. L., Baxter, R., Imaz, M., Taylor, J. C., Foote, K., Finigan, A., Mahbubani, K. T., Webb, T. R., Ye, S., Bennett, M. R., Krüger, A., Spivakov, M., Jørgensen, H. F. 2024; 3 (6): 714-733

  Abstract

  Aberrant vascular smooth muscle cell (VSMC) homeostasis and proliferation characterize vascular diseases causing heart attack and stroke. Here we elucidate molecular determinants governing VSMC proliferation by reconstructing gene regulatory networks from single-cell transcriptomics and epigenetic profiling. We detect widespread activation of enhancers at disease-relevant loci in proliferation-predisposed VSMCs. We compared gene regulatory network rewiring between injury-responsive and nonresponsive VSMCs, which suggested shared transcription factors but differing target loci between VSMC states. Through in silico perturbation analysis, we identified and prioritized previously unrecognized regulators of proliferation, including RUNX1 and TIMP1. Moreover, we showed that the pioneer transcription factor RUNX1 increased VSMC responsiveness and that TIMP1 feeds back to promote VSMC proliferation through CD74-mediated STAT3 signaling. Both RUNX1 and the TIMP1-CD74 axis were expressed in human VSMCs, showing low levels in normal arteries and increased expression in disease, suggesting clinical relevance and potential as vascular disease targets.

  View details for DOI 10.1038/s44161-024-00474-4

  View details for PubMedID 39215134

  View details for PubMedCentralID 8260472

• Genome-Wide Genetic Associations Prioritize Evaluation of Causal Mechanisms of Atherosclerotic Disease Risk. Arteriosclerosis, thrombosis, and vascular biology Quertermous, T., Li, D. Y., Weldy, C. S., Ramste, M., Sharma, D., Monteiro, J. P., Gu, W., Worssam, M. D., Palmisano, B. T., Park, C. Y., Cheng, P. 2024; 44 (2): 323-327

  Abstract

  The goal of this review is to discuss the implementation of genome-wide association studies to identify causal mechanisms of vascular disease risk.The history of genome-wide association studies is described, the use of imputation and the creation of consortia to conduct meta-analyses with sufficient power to arrive at consistent associated loci for vascular disease. Genomic methods are described that allow the identification of causal variants and causal genes and how they impact the disease process. The power of single-cell analyses to promote genome-wide association studies of causal gene function is described.Genome-wide association studies represent a paradigm shift in the study of cardiovascular disease, providing identification of genes, cellular phenotypes, and disease pathways that empower the future of targeted drug development.

  View details for DOI 10.1161/ATVBAHA.123.319480

  View details for PubMedID 38266112

• Comprehensive Integration of Multiple Single-Cell Transcriptomic Datasets Defines Distinct Cell Populations and Their Phenotypic Changes in Murine Atherosclerosis. Arteriosclerosis, thrombosis, and vascular biology Sharma, D., DeForest Worssam, M., Pedroza, A. J., Dalal, A. R., Alemany, H., Kim, H. J., Kundu, R., Fischbein, M., Cheng, P., Wirka, R., Quertermous, T. 2023

  Abstract

  The application of single-cell transcriptomic (single-cell RNA sequencing) analysis to the study of atherosclerosis has provided unique insights into the molecular and genetic mechanisms that mediate disease risk and pathophysiology. However, nonstandardized methodologies and relatively high costs associated with the technique have limited the size and replication of existing data sets and created disparate or contradictory findings that have fostered misunderstanding and controversy.To address these uncertainties, we have performed a conservative integration of multiple published single-cell RNA sequencing data sets into a single meta-analysis, performed extended analysis of native resident vascular cells, and used in situ hybridization to map the disease anatomic location of the identified cluster cells. To investigate the transdifferentiation of smooth muscle cells to macrophage phenotype, we have developed a classifying algorithm based on the quantification of reporter transgene expression.The reporter gene expression tool indicates that within the experimental limits of the examined studies, transdifferentiation of smooth muscle cell to the macrophage lineage is extremely rare. Validated transition smooth muscle cell phenotypes were defined by clustering, and the location of these cells was mapped to lesion anatomy with in situ hybridization. We have also characterized 5 endothelial cell phenotypes and linked these cellular species to different vascular structures and functions. Finally, we have identified a transcriptomically unique cellular phenotype that constitutes the aortic valve.Taken together, these analyses resolve a number of outstanding issues related to differing results reported with vascular disease single-cell RNA sequencing studies, and significantly extend our understanding of the role of resident vascular cells in anatomy and disease.

  View details for DOI 10.1161/ATVBAHA.123.320030

  View details for PubMedID 38152886

• Cellular mechanisms of oligoclonal vascular smooth muscle cell expansion in cardiovascular disease CARDIOVASCULAR RESEARCH Worssam, M. D., Lambert, J., Oc, S., Taylor, J. K., Taylor, A. L., Dobnikar, L., Chappell, J., Harman, J. L., Figg, N. L., Finigan, A., Foote, K., Uryga, A. K., Bennett, M. R., Spivakov, M., Jorgensen, H. F. 2023; 119 (5): 1279-1294

  Abstract

  Quiescent, differentiated adult vascular smooth muscle cells (VSMCs) can be induced to proliferate and switch phenotype. Such plasticity underlies blood vessel homeostasis and contributes to vascular disease development. Oligoclonal VSMC contribution is a hallmark of end-stage vascular disease. Here, we aim to understand cellular mechanisms underpinning generation of this VSMC oligoclonality.We investigate the dynamics of VSMC clone formation using confocal microscopy and single-cell transcriptomics in VSMC-lineage-traced animal models. We find that activation of medial VSMC proliferation occurs at low frequency after vascular injury and that only a subset of expanding clones migrate, which together drives formation of oligoclonal neointimal lesions. VSMC contribution in small atherosclerotic lesions is typically from one or two clones, similar to observations in mature lesions. Low frequency (<0.1%) of clonal VSMC proliferation is also observed in vitro. Single-cell RNA-sequencing revealed progressive cell state changes across a contiguous VSMC population at onset of injury-induced proliferation. Proliferating VSMCs mapped selectively to one of two distinct trajectories and were associated with cells showing extensive phenotypic switching. A proliferation-associated transitory state shared pronounced similarities with atypical SCA1+ VSMCs from uninjured mouse arteries and VSMCs in healthy human aorta. We show functionally that clonal expansion of SCA1+ VSMCs from healthy arteries occurs at higher rate and frequency compared with SCA1- cells.Our data suggest that activation of proliferation at low frequency is a general, cell-intrinsic feature of VSMCs. We show that rare VSMCs in healthy arteries display VSMC phenotypic switching akin to that observed in pathological vessel remodelling and that this is a conserved feature of mouse and human healthy arteries. The increased proliferation of modulated VSMCs from healthy arteries suggests that these cells respond more readily to disease-inducing cues and could drive oligoclonal VSMC expansion.

  View details for DOI 10.1093/cvr/cvac138

  View details for Web of Science ID 000853175400001

  View details for PubMedID 35994249

  View details for PubMedCentralID PMC10202649

• Epigenetic Regulation of Vascular Smooth Muscle Cells by Histone H3 Lysine 9 Dimethylation Attenuates Target Gene-Induction by Inflammatory Signaling ARTERIOSCLEROSIS THROMBOSIS AND VASCULAR BIOLOGY Harman, J. L., Dobnikar, L., Chappell, J., Stokell, B. G., Dalby, A., Foote, K., Finigan, A., Freire-Pritchett, P., Taylor, A. L., Worssam, M. D., Madsen, R. R., Loche, E., Uryga, A., Bennett, M. R., Jorgensen, H. F. 2019; 39 (11): 2289-2302

  Abstract

  Vascular inflammation underlies cardiovascular disease. Vascular smooth muscle cells (VSMCs) upregulate selective genes, including MMPs (matrix metalloproteinases) and proinflammatory cytokines upon local inflammation, which directly contribute to vascular disease and adverse clinical outcome. Identification of factors controlling VSMC responses to inflammation is therefore of considerable therapeutic importance. Here, we determine the role of Histone H3 lysine 9 di-methylation (H3K9me2), a repressive epigenetic mark that is reduced in atherosclerotic lesions, in regulating the VSMC inflammatory response. Approach and Results: We used VSMC-lineage tracing to reveal reduced H3K9me2 levels in VSMCs of arteries after injury and in atherosclerotic lesions compared with control vessels. Intriguingly, chromatin immunoprecipitation showed H3K9me2 enrichment at a subset of inflammation-responsive gene promoters, including MMP3, MMP9, MMP12, and IL6, in mouse and human VSMCs. Inhibition of G9A/GLP (G9A-like protein), the primary enzymes responsible for H3K9me2, significantly potentiated inflammation-induced gene induction in vitro and in vivo without altering NFκB (nuclear factor kappa-light-chain-enhancer of activated B cell) and MAPK (mitogen-activated protein kinase) signaling. Rather, reduced G9A/GLP activity enhanced inflammation-induced binding of transcription factors NFκB-p65 and cJUN to H3K9me2 target gene promoters MMP3 and IL6. Taken together, these results suggest that promoter-associated H3K9me2 directly attenuates the induction of target genes in response to inflammation in human VSMCs.This study implicates H3K9me2 in regulating the proinflammatory VSMC phenotype. Our findings suggest that reduced H3K9me2 in disease enhance binding of NFκB and AP-1 (activator protein-1) transcription factors at specific inflammation-responsive genes to augment proinflammatory stimuli in VSMC. Therefore, H3K9me2-regulation could be targeted clinically to limit expression of MMPs and IL6, which are induced in vascular disease.

  View details for DOI 10.1161/ATVBAHA.119.312765

  View details for Web of Science ID 000494483700016

  View details for PubMedID 31434493

  View details for PubMedCentralID PMC6818986