Abstract 18758: Hypertrophy of Neonatal Cardiomyocytes in 3D Engineered Cardiac Tissue Induced by Activation of mTOR Signaling
Introduction: An in vitro system inducing robust hypertrophy of neonatal cardiomyocytes (CM) is highly useful for studying cardiac development and improving function of engineered cardiac tissues. Our objective was to establish a methodologically simple way to hypertrophy CMs in densely-packed engineered 3D tissues, and to identify signaling pathways involved.
Hypothesis: We hypothesized that hypertrophy could be induced by enhancing mass transport of nutrients to CMs in degradable hydrogel, and this effect would act through mTOR signaling pathway.
Methods: Neonatal rat CMs were embedded in fibrin-based hydrogel to form cardiac microbundles, which were cultured for 2 weeks on either a static or dynamic platform.
Results: Dynamic culture increases the volume occupied by CMs (Fig 1A), quantified as 2.3-fold increase in CM cross-sectional area (Fig 1B). The amount of sarcomeric proteins was increased by 2.4 to 4.6 fold in dynamically cultured tissues (Fig 1C). mTOR phosphorylation was increased by 51% upon transfer to dynamic culture, and decreased by 42% upon transfer to static culture (Fig 1D). Dynamic cultures generated higher contractile force (2.09 +/- 0.10 mN vs. 0.65 +/- 0.11 mN), and inhibition of mTOR with rapamycin attenuated the effect (1.27 +/- 0.07 mN, Fig 1E, n=12). Conduction velocity of action potentials was increased from 38.1 +/- 2.2 cm/s in static cultures to 51.7 +/- 2.8 cm/s in dynamic cultures (n=19).
Conclusions: Dynamic culture of 3D cardiac microtissues results in significant mTOR-mediated CM hypertrophy and contractile force increase without the need for biophysical or growth factor stimulation. For the first time, we show optimized cardiac microtissues with diameter and specific contractile forces similar to trabecular muscle of the adult myocardium (~200 um diameter, 61.5 mN/mm2).
Author Disclosures: C. Jackman: None. N. Bursac: None.
- © 2015 by American Heart Association, Inc.