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Introduction: Microphysiological systems (MPS) offer simulation of (patho)physiological parameters. Investigation includes items which lead to fibrosis and calcification in development and progress of calcific aortic valve disease, based e.g. on culturing of isolated valvular interstitial cells (VICs). Hypoxia regulated by hypoxia inducible factors impacts pathological differentiation in aortic valve (AV) disease. This is mimicked via an MPS implemented oxygenator in combination with calcification inducing medium supplementation. Methods: Human valvular interstitial cells were isolated and dynamically cultured in MPS at hypoxic, normoxic, arterial blood oxygen concentration and cell incubator condition. Expression profile of fibrosis and calcification markers was monitored and calcification was quantified in induction and control media with and without hypoxia and in comparison to statically cultured counterparts. Results: Hypoxic 24-hour culture of human VICs leads to HIF1α nuclear localization and induction of EGLN1, EGLN3 and LDHA mRNA expression but does not directly impact expression of fibrosis and calcification markers. Dependent on medium formulation, induction medium induces monolayer calcification and elevates RUNX2, ACTA2 and FN1 but reduces SOX9 mRNA expression in dynamic and static MPS culture. But combining hypoxic oxygen concentration leads to higher calcification potential of human VICs in calcification and standard medium formulation dynamically cultured for 96 h. Conclusion: In hypoxic oxygen concentration an increased human VIC calcification in 2D VIC culture in an oxygenator assisted MPS was detected. Oxygen regulation therefore can be combined with calcification induction media to monitor additional effects of pathological marker expression. Validation of oxygenator dependent VIC behavior envisions future advancement and transfer to long term aortic valve tissue culture MPS. [ABSTRACT FROM AUTHOR]

Background: Calcific aortic valve disease (CAVD) causes an increasing health burden in the 21st century due to aging population. The complex pathophysiology remains to be understood to develop novel prevention and treatment strategies. Microphysiological systems (MPSs), also known as organ-on-chip or lab-on-a-chip systems, proved promising in bridging in vitro and in vivo approaches by applying integer AV tissue and modelling biomechanical microenvironment. This study introduces a novel MPS comprising different micropumps in conjunction with a tissue-incubation-chamber (TIC) for long-term porcine and human AV incubation (pAV, hAV). Results: Tissue cultures in two different MPS setups were compared and validated by a bimodal viability analysis and extracellular matrix transformation assessment. The MPS-TIC conjunction proved applicable for incubation periods of 14–26 days. An increased metabolic rate was detected for pulsatile dynamic MPS culture compared to static condition indicated by increased LDH intensity. ECM changes such as an increase of collagen fibre content in line with tissue contraction and mass reduction, also observed in early CAVD, were detected in MPS-TIC culture, as well as an increase of collagen fibre content. Glycosaminoglycans remained stable, no significant alterations of α-SMA or CD31 epitopes and no accumulation of calciumhydroxyapatite were observed after 14 days of incubation. Conclusions: The presented ex vivo MPS allows long-term AV tissue incubation and will be adopted for future investigation of CAVD pathophysiology, also implementing human tissues. The bimodal viability assessment and ECM analyses approve reliability of ex vivo CAVD investigation and comparability of parallel tissue segments with different treatment strategies regarding the AV (patho)physiology. [ABSTRACT FROM AUTHOR]