In in-situ approach to estimate the layer-specific biophysical state of aortic valve interstitial cells

While advances have been made toward the understanding of isolated aortic valve interstitial cell (AVIC) behavior ex-situ, the biomechanical state within its native extracellular matrix (ECM) remains largely unknown. An... [ view full abstract ]

While advances have been made toward the understanding of isolated aortic valve interstitial cell (AVIC) behavior ex-situ, the biomechanical state within its native extracellular matrix (ECM) remains largely unknown. An integrated numerical-experimental framework was thus developed and used to estimate AVIC biophysical state in-situ, and understand differences in AVIC contractile responses due to varied layer connectivity activation stimuli. Circumferential strips approximately 4mm wide x 14mm long were removed from the belly region of porcine aortic valves (AV) and incubated with or without TGF-β1 under standard culture conditions with fresh media exchanges every 48 hours. After five days of incubation, tissue strips were removed from culture and immediately tested under flexure deformation under three activation levels: inactive (cytochalasinD), normal (5mM KCl) and hypertensive (90mM KCl). A novel macro-micro numerical model was then used to inversely compute AVIC contraction under each activation level from the acquired tissue level flexure measurements (Fig 1a-d). The estimated contractile force for AVICs in the control tissue at hypertensive conditions was approximately 26E-5 1/K (Fig. 1e). This value was significantly lower than the estimated contractile parameter for AVICs within the TGF-β1 treated tissue of approximately 35E-5 (Fig. 1f). The contractility of AVICs in control tissue increased 1.39-fold from normal to hyper, contrasted with an increase of 2.05 from AVIC contractility in TGF-β1 treated tissue; a nearly 50% upon activation with TGF-β1. In summary, the study revealed a significant increase in stiffness of the fibrosa layer with exogenous TGF-β1 treatment.