Heart failure, predominately caused by myocardial infarction (MI), is the leading cause of death in the United States. Currently the only treatment for heart failure is cardiac transplantation, but studies show that progenitor cell, biomaterial, or combined therapies have improved cardiac function post-MI. The endogenous environment of CPCs is drastically different from commonly used culture conditions. Further the endogenous environment changes with age and disease state. We evaluated the behavior of CPCs cultured on a naturally-derived, cardiac extracellular matrix (cECM) as compared to the standard culture coating collagen I, that also mimics fibrotic tissue. In this study, CPCs cultured on cECM had improved cell numbers and cardiomyogenic maturation. However, the microenvironmental cues responsible for stimulating CPC activation are largely unknown. During development, aging and disease the myocardium changes in matrix composition and stiffness exposing endogenous cells to a wide variety of stimuli. In a combinatorial study, we evaluated the effect of cyclic strain and extracellular matrix composition on CPC behavior. The response of CPCs to signals from the microenvironment is complex, with more matrix-dependency observed at lower strains. Alignment, cell division and paracrine signaling are extracellular matrix and strain dependent. Extracellular matrix conditions affect CPC maturation and calcium signaling. Mechanotransduction pathways, including focal adhesion kinase and extracellular signal-regulated kinase, are activated through adhesion and maintained under cyclic strain. Insights from this work will advance pragmatic cell therapy attempts to regenerate healthy myocardium post-MI.

Recreating organ-specific microenvironments of the extracellular matrix (ECM) in vitro has been an ongoing challenge in biofabrication. In this study, I present a biofunctional ECM-mimicking protein scaffold with tunable biochemical, mechanical and topographical properties. This scaffold, formed by microfibres, displays three favorable characteristics as a cell culture platform: high-loading of key ECM proteins, single-layered mesh membrane with controllable mesh size, and flexibility for supporting a range of cell culture configurations. Decellularized extracellular matrix (dECM) powder was used to fabricate this protein scaffold, as a close replicate of the chemical composition of physiological ECM. The highest dECM concentration in the solidified protein scaffold was 50 wt%, with gelatin consisting the rest. In practice, a high density of dECM-laden nano- to microfibres was directly patterned on a variety of substrates to form a single layer of mesh membrane, using the low-voltage electrospinning patterning (LEP) method. The smallest fibre diameter was measured at 450 nm, the smallest mesh size of the membrane was below 1 μm, and the thickness of the membrane was estimated to be less than 2 μm. This fabrication method demonstrated a good preservation of the key ECM proteins and growth factors, including collagen IV, laminin, fibronectin, VEGF and b-FGF. The integrated fibrous mesh exhibited robust mechanical properties, with tunable fibril Young’s modulus for over two orders of magnitude in the physiological range (depending on the dECM concentration). Combining this mesh membrane with 3D printing, a cell culture device was constructed. Co-culture of human glomerulus endothelial cells and podocytes was performed on this device, to simulate the blood-to-urine interface in vitro. Good cell attachment and viability were demonstrated, and specific cell differentiation and fibronectin secretion were observed. This dECM-laden protein scaffold sees the potential to be incorporated into a glomerulus-on-chip model, to further improve the physiological relevance of in vitro pathological models.

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