The Roles of the Extracellular Matrix in Cardiac Structure and Function: A Commemorative Issue in Honor of Dr. Thomas K. Borg

A special issue of Cells (ISSN 2073-4409). This special issue belongs to the section "Cell Microenvironment".

Deadline for manuscript submissions: 30 January 2026 | Viewed by 1789

Special Issue Editors


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Guest Editor
Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, SC 29209, USA
Interests: fibrosis; extracellular matrix; fibroblast activation; integrins; cardiovascular disease; alcohol abuse; decellularization; tissue engineering
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Guest Editor
Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, 6439 Garners Ferry Rd., Columbia, SC 29209, USA
Interests: fibroblast; myofibroblast; extracellular matrix

Special Issue Information

Dear Colleagues,

This Special Issue is dedicated to Dr. Thomas K. Borg for his substantial contributions to our understanding of the structure–function relationships of the heart, particularly the contributions of the extracellular matrix (ECM).

Dr. Borg was a passionate scientist, energetic collaborator and insightful mentor. He began his illustrious career by receiving his Ph.D. in entomology, utilizing electron microscopy to study the ultrastructure of neurosecretory cells and sensory receptors in insects. Because of his expertise in microscopy, Tom was recruited to Columbia, S.C., in the 1970s to direct the microscopy facility at the new School of Medicine of the University of South Carolina. It was there that he began over four decades of research focused largely on the structure and function of the heart. This began with seminal studies in collaboration with Dr. James Caulfield that characterized the organization and development of the collagen network in the heart. Studies by Tom and others subsequently illustrated that collagen deposition and crosslinking are critical to the mechanical properties, structural integrity, and physiology of the myocardium. Ultrastructural images of the myocardium led to speculation that cardiomyocytes physically interact with ECM components. Collaborations with Drs. Kristofer Rubin, Björn Öbrink, Evy Lundgren, and others from the University of Uppsala and long-time colleague Dr. Louis Terracio provided a foundation for defining how cardiomyocytes interact with components of the extracellular matrix. This group took advantage of the, then relatively novel, use of cultured heart myocytes to identify integrins as the primary ECM receptors in these cells and begin to elucidate the roles of these proteins in the physiology of myocytes and other heart cells. Research such as this by many investigators worldwide has demonstrated the essential role of cell–ECM interactions in cell motility, proliferation, differentiation, and even survival. Dr. Borg had a strong interest in bioengineering, playing an instrumental role in creation of the biomedical engineering program at the University of South Carolina. Some of his later research applied his knowledge of cardiac ECM to engineer model systems that more closely simulated in vivo cardiac biology to advance our understanding of cardiac development and disease.

Dr. Borg’s broad interests and creative insight helped enhance our understanding of heart structure–function relationships, and his collegiality and outgoing nature helped advance the careers of many young scientists. The aim of this Special Issue of Cells is to recognize the impact that Dr. Borg had in advancing our understanding of the structure–function relationships of the heart at the cellular level. In this Special Issue, we invite contributions in the form of original articles and reviews broadly related to the cellular biology of cardiac structure and function.

Prof. Dr. Wayne Carver
Prof. Dr. Edie Goldsmith
Guest Editors

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Keywords

  • collagen
  • integrin
  • extracellular matrix
  • cardiomyocyte
  • fibroblast
  • heart bioengineering

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Published Papers (3 papers)

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Research

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15 pages, 7207 KB  
Article
Collagen Fiber Maturity and Architecture in MVP-Associated Fibrosis Quantified by Digital Pathology
by Ranan Phookan, Jordan E. Morningstar, Brian Loizzi, Antonia Van Kampen, Cortney Gensemer, Maja-Theresa Dieterlen, Ricardo Spampinato, Louis Petitjean, Mathieu Petitjean, Taylor Petrucci, Roman Fenner, Jake Griner, Kathryn Byerly, Robert A. Levine, Michael A. Borger and Russell A. Norris
Cells 2025, 14(19), 1536; https://doi.org/10.3390/cells14191536 (registering DOI) - 30 Sep 2025
Abstract
Recent evidence demonstrates that mitral valve prolapse (MVP) increases mechanical stress on the subvalvular apparatus and is linked to regional myocardial fibrosis and life-threatening ventricular arrhythmias. However, current surgical guidelines do not account for the extent of myocardial fibrosis or the severity of [...] Read more.
Recent evidence demonstrates that mitral valve prolapse (MVP) increases mechanical stress on the subvalvular apparatus and is linked to regional myocardial fibrosis and life-threatening ventricular arrhythmias. However, current surgical guidelines do not account for the extent of myocardial fibrosis or the severity of leaflet involvement, both key features of arrhythmogenic MVP. To address this gap, we conducted histopathological analysis of endomyocardial biopsies from patients with MVP and regionalized myocardial fibrosis (n = 6) who underwent mitral valve repair. Using digital pathology-based quantitative image analysis (QIA), we found that fibrosis in peri-papillary biopsies exhibited a significantly higher Morphometric Composite Score compared with remote biopsies (5.68 ± 0.69 vs. 3.71 ± 0.49, p = 0.042), reflecting larger, more branched, and more assembled collagen fibers, indicative of a mature and persistent fibrotic phenotype. These findings suggest that myocardial scarring in MVP is well-established by the time of surgery and underscore the potential value of earlier surgical intervention to reduce the risk of arrhythmia and preserve post-operative left ventricular function. Full article
14 pages, 2406 KB  
Article
Dynamic Expression and Functional Implications of the Cell Polarity Gene, Dchs1, During Cardiac Development
by Kathryn Byerly, Cayla Wolfe, Hannah Parris, Charlotte Griggs, Emily Wilson, Matthew Huff, Molly Griggs, Jordan Morningstar, Lilong Guo, Fulei Tang, Jan Guz, Taylor Petrucci, Ranan Phookan, Brian Loizzi, Cortney Gensemer and Russell A. Norris
Cells 2025, 14(11), 774; https://doi.org/10.3390/cells14110774 - 24 May 2025
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Abstract
Intercellular interactions among cardiac cell populations are essential for cardiac morphogenesis, yet the molecular mechanisms orchestrating these events remain incompletely understood. Dachsous1 (Dchs1), an atypical cadherin linked to mitral valve prolapse, is a core planar cell polarity protein whose function in the developing [...] Read more.
Intercellular interactions among cardiac cell populations are essential for cardiac morphogenesis, yet the molecular mechanisms orchestrating these events remain incompletely understood. Dachsous1 (Dchs1), an atypical cadherin linked to mitral valve prolapse, is a core planar cell polarity protein whose function in the developing heart has not been fully elucidated. To address this, we generated a Dchs1-HA knock-in mouse model to define its spatial, temporal, and cellular expression patterns. Using immunohistochemistry, western blotting, and single-cell transcriptomics across developmental stages, we demonstrate that cardiac Dchs1 expression is restricted to non-cardiomyocyte lineages. DCHS1 displays dynamic subcellular localization and tissue organization depending on the developmental timepoint, with staining being found in epicardial and endocardial surfaces at earlier embryonic stages and in the compact myocardium in later fetal and neonatal stages. During fetal and neonatal stages, DCHS1-positive non-myocyte, non-endothelial cells form polarized extensions that bridge endothelial and non-myocyte, non-endothelial cells, suggesting direct heterotypic and homotypic interactions. Western blotting revealed evidence of DCHS1 proteolytic cleavage, with intracellular C-terminal fragments. RNA co-expression with its binding partner FAT4 supports a conserved, non-myocyte-specific DCHS1-FAT4 signaling axis. These findings identify DCHS1 as a potential molecular tether that is utilized in intercellular communications during cardiac development, with implications for congenital and acquired heart disease. Full article
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Review

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26 pages, 1238 KB  
Review
Temporal Dynamics of Extracellular Matrix Remodeling in Anthracycline-Induced Cardiotoxicity
by Fibi Meshrkey, Somaya Y. Ibrahim, Rushita A. Bagchi and William J. Richardson
Cells 2025, 14(18), 1471; https://doi.org/10.3390/cells14181471 - 20 Sep 2025
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Abstract
Anthracyclines are widely used chemotherapeutic agents with proven efficacy against a broad range of malignancies, but their clinical utility is limited by a well-documented, dose-dependent cardiotoxicity. While this toxicity has traditionally been attributed to direct cardiomyocyte injury, emerging evidence highlights the pivotal role [...] Read more.
Anthracyclines are widely used chemotherapeutic agents with proven efficacy against a broad range of malignancies, but their clinical utility is limited by a well-documented, dose-dependent cardiotoxicity. While this toxicity has traditionally been attributed to direct cardiomyocyte injury, emerging evidence highlights the pivotal role of cardiac fibroblasts (CFs) in the development and progression of anthracycline-induced cardiotoxicity. This review examines the diverse effects of anthracycline focusing on doxorubicin (DOX) and CFs across the temporal phases of cardiac injury. DOX activates fibroblast-driven extracellular matrix remodeling and promotes fibrosis through enhanced collagen production and the induction of cellular senescence, thereby exacerbating early myocardial inflammation and dysfunction. Clinically, anthracycline cardiotoxicity may present as acute (within days), subacute (within weeks), or chronic progressive forms manifesting either early (within one year) or late (up to decades post-treatment). While early manifestations may be reversible with timely detection and management, late-phase cardiotoxicity is often irreversible, characterized by declining left ventricular ejection fraction and heart failure. A deeper understanding of the molecular and cellular contributions of CFs may uncover novel therapeutic targets to prevent or attenuate anthracycline-related cardiac damage. Full article
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