Reconstructing AF-Associated Atrial Fibrosis: Patient-Specific iPSC Models, Fit-for-Purpose Atrial Microphysiological Systems, and Nanomedicine

Figures

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  Fig. 1. Overall evidence framework for AF-associated atrial fibrosis modeling and therapeutic evaluation. The diagram links clinical atrial cardiomyopathy, three evidence paths (direct atrial/AF-specific, cardiac non-atrial, and extrapolated non-cardiac evidence), proposed fit-for-purpose human atrial microphysiological-system construction, high-content evaluation, nanomedicine transport/exposure assessment, and bounded translation outputs. Evidence codes apply to individual studies or claims rather than assigning a fixed rank to an entire model class. The proposed integration and decision gate require validation, and complementary in vivo and clinical confirmation remain necessary. Representative evidence is discussed in Refs. [1,[3], [4], [5],[31], [32], [33], [34], [35], [36], [37], [38], [39]].

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  Fig. 2. Multiscale regulatory network and evidence boundaries in AF-associated atrial fibrosis. Clinical inputs are connected to fibroblast state and signaling, ECM synthesis and organization, interstitial/reactive or replacement fibrosis, and functional consequences. Solid arrows denote supported directional relationships, double arrows supported feedback, and dashed arrows context-dependent or hypothesized relationships. Evidence codes identify the dominant source for each claim, whereas the right-hand panel separately distinguishes directly measured endpoints, operational readouts, and clinical inferences requiring validation. Replacement fibrosis is shown as a context-dependent and less typical AF phenotype rather than a universal endpoint. Representative evidence is discussed in Refs. [1,[41], [42], [43], [44], [45], [46], [47], [48], [49], [50], [51], [52], [53], [54], [55], [56], [57], [58]].

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  Fig. 3. Context-of-use capability matrix and translation-gap map for atrial fibrosis models. Animal/in vivo models, two-dimensional cellular assays, three-dimensional engineered tissues, and proposed human atrial microphysiological systems are compared across six design-dependent capability domains. Strong, conditional, limited, and not-primary categories are qualitative and are not numerical scores or universal model rankings. The translation map distinguishes mechanism, endpoint, and exposure/safety mismatches, while the complementary evidence stack shows why human atrial evidence, controlled MPS studies, in vivo pharmacokinetics/safety, and clinical confirmation are jointly required. Source-evidence categories remain study- and claim-specific. Representative evidence is discussed in Refs. [1,[3], [4], [5],39,[63], [64], [65], [66], [67], [68], [69], [70]] and summarized in Table 1 and Supplementary Table S1.

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  Fig. 4. Fit-for-purpose design and harmonization framework for donor-informed atrial fibrosis microphysiological systems. Context of use and upstream requirements guide biological specification, fibroblast provenance, atrial differentiation, mechanical and microenvironmental inputs, modular engineering, shared QC, and intended use. Adult primary atrial, iPSC-derived cardiac, and commercial primary cardiac fibroblasts are not interchangeable; patient matching denotes a paired study design and must be documented rather than treated as a distinct lineage. The integrated platform and closed-loop connections are proposed and require validation. Acceptance domains include donor/clone metadata, atrial identity and maturity, intra- and interbatch variability, device geometry/materials, reference compounds, actual exposure, and data traceability. The platform is not a direct in vivo substitute. Supporting evidence is summarized in Refs. [[2], [3], [4], [5],7,36,39,68,[70], [71], [72], [73], [74], [75], [76], [77], [78], [79], [80], [81], [82], [83], [84], [85], [86], [87], [88], [89], [90], [91], [92], [93], [94], [95], [96], [97], [98], [99], [100], [101], [102]], Table 1, and Supplementary…

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  Fig. 5. From target engagement to tiered high-content phenotype evaluation in atrial microphysiological systems. Direct measurements progress from target/pathway engagement through cellular response, ECM/structure, electrophysiology, mechanics, perfusion, and safety. Inferred constructs, including rhythm instability, reentry susceptibility, long-term remodeling, and clinical reversibility, are shown separately and require validation. M denotes a directly measured endpoint and IC an inferred construct; these labels are distinct from the source-evidence tier. Decisions are routed to Prioritize, Refine, or Stop/De-prioritize using prespecified, assay-specific criteria rather than fixed universal thresholds. Refinement and redesign routes are developed in Fig. 7. Shared QC includes exposure verification, reference compounds, batch variability, blinding, dose-response assessment, and traceability. Representative evidence and endpoint boundaries are discussed in Refs. [1,[4], [5], [6], [7],44,92,[110], [111], [112], [113], [114], [115], [116], [117], [118], [119], [120], [121], [122], [123], [124], [125], [126], [127]] and Table 2.

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  Fig. 6. Barriers to atrial-targeted nanomedicine: route, transport, exposure, and validation boundaries. Route-dependent delivery is followed through blood or local distribution, endothelial passage, ECM transport, atrial-cell uptake, endosomal escape, intracellular release, and retention/remodeling. Intravenous, intracoronary/selective, intracardiac/direct atrial, and epicardial/pericardial routes are distinguished. Device adsorption, nonspecific retention, payload leakage, off-target distribution, complement, thrombogenicity, and manufacturing variability are explicit failure modes. Actual exposure and mass balance should account for fluid, device, tissue, and cellular compartments. Most quantitative transport and design evidence is cardiac non-atrial or extrapolated; the atrial MPS can measure device-level transport and uptake but cannot alone establish whole-body biodistribution, systemic clearance, or immune toxicity. No validated atrial nanoparticle specification is implied. Details are provided in Table 3 and references [[8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23],37,38,128,129].

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  Fig. 7. Evidence-integrated closed-loop evaluation of nanomedicine in atrial fibrosis microphysiological systems. The proposed sequence links formulation and route, measured transport and actual exposure, target engagement, cellular/ECM responses, structure and function, safety, and an evidence-integrated decision. M denotes measured endpoints, IC inferred constructs requiring validation, and P proposed workflow elements; source evidence and inference status are not interchangeable. Failure-source feedback directs redesign toward formulation, transport, target/model selection, structure/function, or safety rather than repeating an undifferentiated loop. The traceable evidence package records raw data, QC, metadata, uncertainty, and decision rationale. This complete workflow remains prospective and requires complementary in vivo pharmacokinetic/safety testing and clinical confirmation. Representative evidence is discussed in Refs. [[4], [5], [6], [7],[20], [21], [22], [23],92,[110], [111], [112], [113], [114], [115], [116], [117], [118], [119], [120], [121], [122], [123], [124], [125], [126], [127],[131], [132], [133], [134], [135], [136], [137], [138], [139],[142], [143], [144]], [[145],…