Liver disease is a leading cause of mortality worldwide, resulting in 1.3 million deaths annually. The vast majority of liver disease is caused by metabolic disease (i.e., NASH) and alcohol-induced hepatitis, and to a lesser extent by acute and chronic viral infection. Furthermore, multiple insults to the liver is becoming common due to the prevalence of metabolic and alcohol-related liver diseases. Despite this rising prevalence of liver disease, there are few treatment options: there are treatments for viral hepatitis C and there is vaccination for hepatitis B. Aside from the management of metabolic syndrome, no direct liver therapy has shown clinical efficacy for metabolic liver disease, there is very little for acute alcohol-induced liver disease, and liver transplantation remains the only effective treatment for late-stage liver disease. Traditional pharmacologic interventions have failed to appreciably impact the pathophysiology of alcohol-related liver disease or end-stage liver disease. The difficulties associated with developing liver-specific therapies result from three factors that are common to late-stage liver disease arising from any cause: hepatocyte injury, inflammation, and aberrant tissue healing. Hepatocyte injury results in tissue damage with inflammation, which sensitizes the liver to additional hepatocyte injury and stimulates hepatic stellate cells and aberrant tissue healing responses. In the setting of chronic liver insults, there is progressive scarring, the loss of hepatocyte function, and hemodynamic dysregulation. Regenerative strategies using hepatocyte-like cells that are manufactured from mesenchymal stromal cells may be able to correct this pathophysiology through multiple mechanisms of action. Preclinical studies support their effectiveness and recent clinical studies suggest that cell replacement therapy can be safe and effective in patients with liver disease for whom there is no other option.

Epigenetic dysregulation of long noncoding RNA H19 was recently found to be associated with calcific aortic valve disease (CAVD) in humans by repressing NOTCH1 transcription. This finding offers a possible epigenetic explanation for the abundance of cases of CAVD that are not explained by any clear genetic mutation. In this study, we examined the effect of age and sex on epigenetic dysregulation of H19 and subsequent aortic stenosis. Cohorts of littermate, wild‐type C57BL/6 mice were studied at developmental ages analogous to human middle age through advanced age. Cardiac and aortic valve function were assessed with M‐mode echocardiography and pulsed wave Doppler ultrasound, respectively. Bisulfite sequencing was used to determine methylation‐based epigenetic regulation of H19, and RT‐PCR was used to determine changes in gene expression profiles. Male mice were found to have higher peak systolic velocities than females, with several of the oldest mice showing signs of early aortic stenosis. The imprinting control region of H19 was not hypomethylated with age, and H19 expression was lower in the aortic valves of older mice than in the youngest group. These results suggest that age‐related upregulation of H19 is not observed in murine aortic valves and that other factors may initiate H19‐related CAVD in humans.

Objectives: Specialized endocardial cells are responsible for the development of heart valves in utero . During a highly regulated morphogenetic process, these endocardial cells undergo endothelial-to-mesenchymal transformation (EMT) to become valve interstitial cells (VICs) and reorganize the extracellular matrix to form the structure of the valves. Potentially, induced pluripotent stem cells (iPSCs) may be coaxed into endocardial cells, then to VICs, to yield a suitable cell source for tissue engineered heart valves. Unfortunately, no method to generate iPSC derived endocardial cells exists. Current biochemical strategies utilize static culture, which does not represent the dynamic mechanical environment of the developing heart, which is known to affect differentiation and function of endocardial cells. Methods and Results: Human iPSCs were differentiated and purified to endothelial progenitors (CD34+), seeded onto collagen IV coated plates, and grown to confluency. Using a FlexCell system and a custom-built fluid shear device (A,B) , mechanical strain and shear stress were administered to the maturing cells independently, which were then assayed via qPCR for changes to endocardial and EMT markers. Bidirectional shear stress (C) was found to downregulate endothelial markers CD31, VE-cadherin and VEGFR2, as well as endocardial specific gene Nfatc1, yet increased expression of EMT markers BMP2 and Snai2. Conversely, unidirectional shear (D) increased Nfatc1 while causing lower expression of BMP2 and Snai2 than bidirectional shear. Cyclic strain decreased both endocardial and EMT markers (E) . Conclusions: These data suggest that unidirectional shear stress maintains an endocardial phenotype, while bidirectional shear stress induces EMT, promoting an interstitial cell phenotype. These stimuli may be utilized to maintain and expand patient-specific endocardial and valve interstitial cells for the creation of tissue engineered heart valves.