Dressed in Collagen: 2D and 3D Cardiac Fibrosis Models

Figure 3. Advantages and limitations of 2D and 3D models in fibrosis studies. This figure provides a comparative overview of 2D and 3D in vitro models of cardiac fibrosis, highlighting their ability to mimic the features of an ideal fibrosis model. The “+” symbols denote the extent of representation, with “+” indicating minimal resemblance and “+++” indicating a higher degree of biomimicry. The key aspects of an ideal fibrosis model represented include: Relevant cell types (cardiac fibroblasts (CF), cardiomyocytes (CM), endothelial cells, and immune cells), Hallmarks of Fibrosis (myofibroblast activation, collagen deposition, altered electrical coupling, and inflammation), Biochemical and Biomechanical Cues, Clear and Measurable Readouts, and High-throughput Efficiency. In the image, figures/drawings within each of the features of an ideal model positioned further to the right indicate greater biomimicry and often involve the incorporation of the foundational components shown to their left. Created in BioRender. Cardona, M. (2025) https://BioRender.com/v55r799 (accessed on 22 March 2025).

Figure 1. Features of cardiac fibrosis models and insights from other organs. The inner circle represents key features that cardiac fibrosis models include, encompassing simplicity and cost-effectiveness, biochemical and biomechanical cues, measurable readouts, biological relevance, tissue organization, enhanced cell–cell interactions, and high-throughput capabilities. Below each attribute, the most suitable model type is indicated. The outer circle highlights fibrosis models from other organs, emphasizing features that could be learned from them and incorporated into cardiovascular research to further refine in vitro cardiac fibrosis models. Created in BioRender. Cardona, M. (2025) https://BioRender.com/r40s644 (accessed on 22 March 2025).

Figure 2. Cardiac myofibroblast activation and regulation in fibrosis. Myofibroblasts originate from various cellular sources, primarily cardiac fibroblasts, but also from other cell types such as endothelial cells undergoing endothelial-to-myofibroblast transition (EndMT). Following cardiac injury, additional cells within the myocardial parenchyma, including cardiomyocytes (CM) and immune cells, contribute to myofibroblast activation through signaling molecules such as transforming growth factor-beta (TGF-β), angiotensin II (Ang-II), and brain natriuretic peptide (BNP), as well as pro-inflammatory cytokines, including interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), matrix metalloproteinases (MMPs), and endothelin-1. Notably, myofibroblasts also secrete some of these signaling molecules, reinforcing a positive feedback loop that sustains their activation. Once activated, myofibroblasts play a central role in cardiac fibrosis by producing and depositing excessive extracellular matrix (ECM) proteins, leading to increased matrix stiffness and structural disorganization. Additionally, ECM remodeling releases sequestered signaling molecules, further amplifying fibrotic signaling and…

Figure 4. Engineering cardiac fibrosis models. This figure illustrates the pipeline to create an in vitro model for cardiac fibrosis. It begins with the selection of cells, which include cardiac fibroblasts, cardiomyocytes, endothelial cells, and immune cells. The cells can be obtained from primary sources, established cell lines, or induced pluripotent stem cells (iPSCs)/embryonic stem cells (ESCs). These cells are then incorporated into the chosen platform, which can range from simple cell culture plates and patterned substrates to more advanced 3D scaffolds, hydrogels, organoids/spheroids, bioprinted models, or microfluidic chips. The fibrotic model is then subjected to one or more profibrotic stimuli, and both the healthy and fibrotic models are characterized by assessing features such as myofibroblast activation, ECM deposition, altered coupling, and abnormal contraction. At this stage, the model can be used to investigate fundamental aspects of the pathology or serve as a platform to assess the antifibrotic potential of therapeutic candidates. In the latter case, some characterization parameters are re-evaluated (for example, by fluorescence imaging, quantitative PCR (qPCR), wire…