Abstract
Cardiomyocytes branch and interconnect with one another, providing important redundancy for propagation of electro-chemical signals. Despite this, cardiomyocyte branching structure remains poorly understood. Herein, myocardium from spontaneously hypertensive rats (SHR) was imaged using extended volume confocal microscopy. Samples from untreated SHRs (\(n = 2\)) were compared with SHRs undergoing ACE inhibitor treatment (\(n = 2\)). From these image-stacks the cardiomyocyte network (center-lines and branches) were manually tracked. The frequency of cardiomyocyte branching was calculated and these branching frequencies were compared according to spatial position within a myocardial sheetlet. ACE inhibitor treatment resulted in significantly reduced total cardiomyocyte branching compared with untreated SHR myocardium at 24 mo (0.49 ± 0.04 vs 1.07 ± 0.15 branches per 100 \(\upmu \)m, \(P = 0.020\)). Cardiomyocytes on the sheetlet-surface branched more frequently within their respective cell-layer (0.59 ± 0.07 branches per 100 \(\upmu \)m) compared with cardiomyocytes in the sheetlet interior (0.29 ± 0.12 branches per 100 \(\upmu \)m). The cardiomyocytes in the sheetlet interior exhibited more frequent between-layer branching (0.56 ± 0.06 branches per 100 \(\upmu \)m) compared to sheetlet-surface cardiomyocytes (0.17 ± 0.03 branches per 100 \(\upmu \)m). The ratio of within-layer to between-layer branching was significantly greater at the surface layer compared with the interior layer (3.93 ± 1.06 vs 0.47 ± 0.16, \(P=0.018\)). This proof-of-concept study demonstrates an approach to measuring branching cardiomyocyte networks and shows the spatial heterogeneity of cardiomyocyte branching.
Supported by funding from the American Heart Association.
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Acknowledgements
We thank Linley Nisbet for assistance with the animal experiments and Dane Gerneke for support with confocal imaging.
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This work was supported by funding from the American Heart Association (19IPLOI34760294 to DBE), the Marsden Fund administered by the Royal Society of New Zealand, and the Health Research Council of New Zealand.
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This study was approved by the Animal Ethics Committee of the University of Auckland (Ref: 001119).
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Wilson, A.J., Sands, G.B., Ennis, D.B. (2021). Analysis of Location-Dependent Cardiomyocyte Branching. In: Ennis, D.B., Perotti, L.E., Wang, V.Y. (eds) Functional Imaging and Modeling of the Heart. FIMH 2021. Lecture Notes in Computer Science(), vol 12738. Springer, Cham. https://doi.org/10.1007/978-3-030-78710-3_19
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DOI: https://doi.org/10.1007/978-3-030-78710-3_19
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