Bioinspired Oligo-Urethane Nanoparticles for Delivering Exogenous C-Type Natriuretic Peptide: Synthetic Biomaterial Nanocarrier Complexes and Their Interactions with Cardiac Myofibroblasts.

In a healthy heart, cells naturally secrete C-type natriuretic peptide (CNP), a cytokine that protects against myofibroblast differentiation of cardiac fibroblasts and extracellular matrix deposition leading to fibrosis. CNP availability during myocardial remodeling is important to prevent cardiac fibrosis, but CNP is limited after an injury because of the loss of cardiomyocytes and the activation of cardiac fibroblasts to myofibroblasts. We hypothesized that the sustained release of exogenous CNP from oligo-urethane nanoparticles (NPs) would reduce differentiation of human cardiac fibroblasts toward a myofibrogenic phenotype. Our work used a modified form of a degradable polar hydrophobic ionic (D-PHI) oligo-urethane, which has shown the ability to self-assemble into NPs for the delivery of peptide and oligonucleotide biomolecules. The CNP-loaded NPs (NPCNP) were characterized for a diameter of 129 ± 1.4 nm and a ζ potential of -46 ± 7.8 mV. Treatment of cardiac fibroblasts with NPCNP increased cyclic guanosine-monophosphate (cGMP) synthesis, confirming that exogenous CNP delivered via oligo-urethane NPs is bioactive and can induce downstream signaling that has been implicated in antagonizing transforming growth factor-ß1 (TGF-ß1)-induced myofibrogenic differentiation. It is also shown that treatment with NPCNP attenuated contraction of collagen gels by cardiac myofibroblasts stimulated with TGF-ß1. Coating with heparin on the NPCNP (HEP-NPCNP) exemplified an approach to extend the release of CNP from the NPs. Both HEP-NPCNP and NPCNP show minimal cell toxicity, studied up to 0.25 × 1010 NPs/mL in culture media. These findings support further investigation of CNP delivery via NPs as a future therapy for suppressing cardiac fibrosis.

Assessment of fibrin-collagen co-gels for generating microvesselsex vivousing endothelial cell-lined microfluidics and multipotent stromal cell (MSC)-induced capillary morphogenesis.

One aspect of the challenge of engineering viable tissuesex vivois the generation of perfusable microvessels of varying diameters. In this work, we take the approach of using hydrogel-based microfluidics seeded with endothelial cells (ECs) to form small artery/vein-like vessels, in conjunction with using the self-assembly behavior of ECs to form capillary-like vessels when co-cultured with multipotent stromal cells (MSCs). In exploring this approach, we focused on investigating collagen, fibrin, and various collagen-fibrin co-gel formulations for their potential suitability as serving as scaffold materials by surveying their angiogencity and mechanical properties. Fibrin and co-gels successfully facilitated multicellular EC sprouting, whereas collagen elicited a migration response of individual ECs, unless supplemented with the protein kinase C (PKC)-activator, phorbol 12-myristate 13-acetate. Collagen scaffolds were also found to severely contract when embedded with mesenchymal cells, but this contraction could be abrogated with the addition of fibrin. Increasing collagen content within co-gel formulations, however, imparted a higher compressive modulus and allowed for the reliable formation of intact hydrogel-based microchannels which could then be perfused. Given the bioactivity and mechanical benefits of fibrin and collagen, respectively, collagen-fibrin co-gels are a promising scaffold option for generating vascularized tissue constructs.

The Roles of Matrix Stiffness and ß-Catenin Signaling in Endothelial-to-Mesenchymal Transition of Aortic Valve Endothelial Cells.

Valve stiffening is a hallmark of aortic valve stenosis caused by excess extracellular matrix accumulation by myofibroblasts. We aimed to elucidate whether matrix stiffness regulates endothelial-to-mesenchymal transition (EndMT) of adult valvular endothelial cells (VECs) to myofibroblasts as a mechanism to further promote valve fibrosis. In addition, we specifically examined the role of the Wnt/ß-catenin signaling pathway in the development of myofibroblasts during EndMT, as Wnt/ß-catenin signaling has been implicated in EndMT during heart development, is reactivated in valve disease, and is required for mechanically-regulated myofibrogenesis of valve interstitial cells. Clonally derived porcine VECs were cultured on soft (5 kPa) or stiff (50 kPa) silicone Sylgard 527 substrates and treated with transforming growth factor (TGF)-ß1 to induce EndMT. Immunofluorescent staining revealed that TGF-ß1 preferentially promoted EndMT in VECs on stiffer substrates, evidenced by a decrease in the endothelial marker VE-cadherin and an increase in the myofibroblast marker α-smooth muscle actin (α-SMA). These changes were accompanied by ß-catenin nuclear localization both in vitro and in vivo, assessed by immunostaining. Degradation of ß-catenin with endostatin reduced VEC myofibroblast transition, as indicated by decreased α-SMA fiber expression. We conclude that TGF-ß1-induced EndMT in aortic VECs is dependent on matrix stiffness and Wnt/ß-catenin signaling promotes myofibrogenesis during EndMT.